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de-linting of .s files
remove inlines,some other files
@@ -18,624 +18,1285 @@
*
* CDDL HEADER END
*/
/*
* Copyright (c) 2004, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright 2019 Joyent, Inc.
* Copyright (c) 2016 by Delphix. All rights reserved.
*/
-/* Copyright (c) 1990, 1991 UNIX System Laboratories, Inc. */
-/* Copyright (c) 1984, 1986, 1987, 1988, 1989, 1990 AT&T */
-/* All Rights Reserved */
-
-/* Copyright (c) 1987, 1988 Microsoft Corporation */
-/* All Rights Reserved */
-
#include <sys/asm_linkage.h>
#include <sys/asm_misc.h>
#include <sys/regset.h>
+#include <sys/privregs.h>
#include <sys/psw.h>
-#include <sys/x86_archext.h>
#include <sys/machbrand.h>
-#include <sys/privregs.h>
-#if defined(__lint)
-
-#include <sys/types.h>
-#include <sys/thread.h>
-#include <sys/systm.h>
-
-#else /* __lint */
-
#include <sys/segments.h>
#include <sys/pcb.h>
#include <sys/trap.h>
#include <sys/ftrace.h>
#include <sys/traptrace.h>
#include <sys/clock.h>
+#include <sys/model.h>
#include <sys/panic.h>
-#include "assym.h"
-#endif /* __lint */
+#if defined(__xpv)
+#include <sys/hypervisor.h>
+#endif
+#include "assym.h"
+
/*
- * We implement two flavours of system call entry points
+ * We implement five flavours of system call entry points
*
- * - {int,lcall}/iret (i386)
- * - sysenter/sysexit (Pentium II and beyond)
+ * - syscall/sysretq (amd64 generic)
+ * - syscall/sysretl (i386 plus SYSC bit)
+ * - sysenter/sysexit (i386 plus SEP bit)
+ * - int/iret (i386 generic)
+ * - lcall/iret (i386 generic)
*
- * The basic pattern used in the handlers is to check to see if we can
- * do fast (simple) version of the system call; if we can't we use various
- * C routines that handle corner cases and debugging.
+ * The current libc included in Solaris uses int/iret as the base unoptimized
+ * kernel entry method. Older libc implementations and legacy binaries may use
+ * the lcall call gate, so it must continue to be supported.
*
- * To reduce the amount of assembler replication, yet keep the system call
- * implementations vaguely comprehensible, the common code in the body
- * of the handlers is broken up into a set of preprocessor definitions
- * below.
+ * System calls that use an lcall call gate are processed in trap() via a
+ * segment-not-present trap, i.e. lcalls are extremely slow(!).
+ *
+ * The basic pattern used in the 32-bit SYSC handler at this point in time is
+ * to have the bare minimum of assembler, and get to the C handlers as
+ * quickly as possible.
+ *
+ * The 64-bit handler is much closer to the sparcv9 handler; that's
+ * because of passing arguments in registers. The 32-bit world still
+ * passes arguments on the stack -- that makes that handler substantially
+ * more complex.
+ *
+ * The two handlers share a few code fragments which are broken
+ * out into preprocessor macros below.
+ *
+ * XX64 come back and speed all this up later. The 32-bit stuff looks
+ * especially easy to speed up the argument copying part ..
+ *
+ *
+ * Notes about segment register usage (c.f. the 32-bit kernel)
+ *
+ * In the 32-bit kernel, segment registers are dutifully saved and
+ * restored on all mode transitions because the kernel uses them directly.
+ * When the processor is running in 64-bit mode, segment registers are
+ * largely ignored.
+ *
+ * %cs and %ss
+ * controlled by the hardware mechanisms that make mode transitions
+ *
+ * The remaining segment registers have to either be pointing at a valid
+ * descriptor i.e. with the 'present' bit set, or they can NULL descriptors
+ *
+ * %ds and %es
+ * always ignored
+ *
+ * %fs and %gs
+ * fsbase and gsbase are used to control the place they really point at.
+ * The kernel only depends on %gs, and controls its own gsbase via swapgs
+ *
+ * Note that loading segment registers is still costly because the GDT
+ * lookup still happens (this is because the hardware can't know that we're
+ * not setting up these segment registers for a 32-bit program). Thus we
+ * avoid doing this in the syscall path, and defer them to lwp context switch
+ * handlers, so the register values remain virtualized to the lwp.
*/
-/*
- * When we have SYSCALLTRACE defined, we sneak an extra
- * predicate into a couple of tests.
- */
#if defined(SYSCALLTRACE)
#define ORL_SYSCALLTRACE(r32) \
- orl syscalltrace, r32
+ orl syscalltrace(%rip), r32
#else
#define ORL_SYSCALLTRACE(r32)
#endif
/*
- * This check is false whenever we want to go fast i.e.
+ * In the 32-bit kernel, we do absolutely nothing before getting into the
+ * brand callback checks. In 64-bit land, we do swapgs and then come here.
+ * We assume that the %rsp- and %r15-stashing fields in the CPU structure
+ * are still unused.
*
- * if (code >= NSYSCALL ||
- * t->t_pre_sys || (t->t_proc_flag & TP_WATCHPT) != 0)
- * do full version
- * #ifdef SYSCALLTRACE
- * if (syscalltrace)
- * do full version
- * #endif
- *
- * Preconditions:
- * - t curthread
- * - code contains the syscall number
- * Postconditions:
- * - %ecx and %edi are smashed
- * - condition code flag ZF is cleared if pre-sys is too complex
- */
-#define CHECK_PRESYS_NE(t, code) \
- movzbl T_PRE_SYS(t), %edi; \
- movzwl T_PROC_FLAG(t), %ecx; \
- andl $TP_WATCHPT, %ecx; \
- orl %ecx, %edi; \
- cmpl $NSYSCALL, code; \
- setae %cl; \
- movzbl %cl, %ecx; \
- orl %ecx, %edi; \
- ORL_SYSCALLTRACE(%edi)
-
-/*
* Check if a brand_mach_ops callback is defined for the specified callback_id
- * type. If so invoke it with the user's %gs value loaded and the following
+ * type. If so invoke it with the kernel's %gs value loaded and the following
* data on the stack:
+ *
+ * stack: --------------------------------------
+ * 32 | callback pointer |
+ * | 24 | user (or interrupt) stack pointer |
+ * | 16 | lwp pointer |
+ * v 8 | userland return address |
+ * 0 | callback wrapper return addr |
* --------------------------------------
- * | user's %ss |
+ *
+ * Since we're pushing the userland return address onto the kernel stack
+ * we need to get that address without accessing the user's stack (since we
+ * can't trust that data). There are different ways to get the userland
+ * return address depending on how the syscall trap was made:
+ *
+ * a) For sys_syscall and sys_syscall32 the return address is in %rcx.
+ * b) For sys_sysenter the return address is in %rdx.
+ * c) For sys_int80 and sys_syscall_int (int91), upon entry into the macro,
+ * the stack pointer points at the state saved when we took the interrupt:
+ * ------------------------
+ * | | user's %ss |
* | | user's %esp |
* | | EFLAGS register |
- * | | user's %cs |
- * | | user's %eip (user return address) |
- * | | 'scratch space' |
- * | | user's %ebx |
- * | | user's %gs selector |
- * v | lwp pointer |
- * | callback wrapper return addr |
- * --------------------------------------
+ * v | user's %cs |
+ * | user's %eip |
+ * ------------------------
*
- * If the brand code returns, we assume that we are meant to execute the
- * normal system call path.
+ * The 2nd parameter to the BRAND_CALLBACK macro is either the
+ * BRAND_URET_FROM_REG or BRAND_URET_FROM_INTR_STACK macro. These macros are
+ * used to generate the proper code to get the userland return address for
+ * each syscall entry point.
*
- * The interface to the brand callbacks on the 32-bit kernel assumes %ebx
+ * The interface to the brand callbacks on the 64-bit kernel assumes %r15
* is available as a scratch register within the callback. If the callback
- * returns within the kernel then this macro will restore %ebx. If the
+ * returns within the kernel then this macro will restore %r15. If the
* callback is going to return directly to userland then it should restore
- * %ebx before returning to userland.
+ * %r15 before returning to userland.
*/
-#define BRAND_CALLBACK(callback_id) \
- subl $4, %esp /* save some scratch space */ ;\
- pushl %ebx /* save %ebx to use for scratch */ ;\
- pushl %gs /* save the user %gs */ ;\
- movl $KGS_SEL, %ebx ;\
- movw %bx, %gs /* switch to the kernel's %gs */ ;\
- movl %gs:CPU_THREAD, %ebx /* load the thread pointer */ ;\
- movl T_LWP(%ebx), %ebx /* load the lwp pointer */ ;\
- pushl %ebx /* push the lwp pointer */ ;\
- movl LWP_PROCP(%ebx), %ebx /* load the proc pointer */ ;\
- movl P_BRAND(%ebx), %ebx /* load the brand pointer */ ;\
- movl B_MACHOPS(%ebx), %ebx /* load the machops pointer */ ;\
- movl _CONST(_MUL(callback_id, CPTRSIZE))(%ebx), %ebx ;\
- cmpl $0, %ebx ;\
+#define BRAND_URET_FROM_REG(rip_reg) \
+ pushq rip_reg /* push the return address */
+
+/*
+ * The interrupt stack pointer we saved on entry to the BRAND_CALLBACK macro
+ * is currently pointing at the user return address (%eip).
+ */
+#define BRAND_URET_FROM_INTR_STACK() \
+ movq %gs:CPU_RTMP_RSP, %r15 /* grab the intr. stack pointer */ ;\
+ pushq (%r15) /* push the return address */
+
+#define BRAND_CALLBACK(callback_id, push_userland_ret) \
+ movq %rsp, %gs:CPU_RTMP_RSP /* save the stack pointer */ ;\
+ movq %r15, %gs:CPU_RTMP_R15 /* save %r15 */ ;\
+ movq %gs:CPU_THREAD, %r15 /* load the thread pointer */ ;\
+ movq T_STACK(%r15), %rsp /* switch to the kernel stack */ ;\
+ subq $16, %rsp /* save space for 2 pointers */ ;\
+ pushq %r14 /* save %r14 */ ;\
+ movq %gs:CPU_RTMP_RSP, %r14 ;\
+ movq %r14, 8(%rsp) /* stash the user stack pointer */ ;\
+ popq %r14 /* restore %r14 */ ;\
+ movq T_LWP(%r15), %r15 /* load the lwp pointer */ ;\
+ pushq %r15 /* push the lwp pointer */ ;\
+ movq LWP_PROCP(%r15), %r15 /* load the proc pointer */ ;\
+ movq P_BRAND(%r15), %r15 /* load the brand pointer */ ;\
+ movq B_MACHOPS(%r15), %r15 /* load the machops pointer */ ;\
+ movq _CONST(_MUL(callback_id, CPTRSIZE))(%r15), %r15 ;\
+ cmpq $0, %r15 ;\
je 1f ;\
- movl %ebx, 12(%esp) /* save callback to scratch */ ;\
- movl 4(%esp), %ebx /* grab the user %gs */ ;\
- movw %bx, %gs /* restore the user %gs */ ;\
- call *12(%esp) /* call callback in scratch */ ;\
-1: movl 4(%esp), %ebx /* restore user %gs (re-do if */ ;\
- movw %bx, %gs /* branch due to no callback) */ ;\
- movl 8(%esp), %ebx /* restore user's %ebx */ ;\
- addl $16, %esp /* restore stack ptr */
+ movq %r15, 16(%rsp) /* save the callback pointer */ ;\
+ push_userland_ret /* push the return address */ ;\
+ movq 24(%rsp), %r15 /* load callback pointer */ ;\
+ INDIRECT_CALL_REG(r15) /* call callback */ ;\
+1: movq %gs:CPU_RTMP_R15, %r15 /* restore %r15 */ ;\
+ movq %gs:CPU_RTMP_RSP, %rsp /* restore the stack pointer */
#define MSTATE_TRANSITION(from, to) \
- pushl $to; \
- pushl $from; \
- call syscall_mstate; \
- addl $0x8, %esp
+ movl $from, %edi; \
+ movl $to, %esi; \
+ call syscall_mstate
/*
- * aka CPU_STATS_ADDQ(CPU, sys.syscall, 1)
- * This must be called with interrupts or preemption disabled.
+ * Check to see if a simple (direct) return is possible i.e.
+ *
+ * if (t->t_post_sys_ast | syscalltrace |
+ * lwp->lwp_pcb.pcb_rupdate == 1)
+ * do full version ;
+ *
+ * Preconditions:
+ * - t is curthread
+ * Postconditions:
+ * - condition code NE is set if post-sys is too complex
+ * - rtmp is zeroed if it isn't (we rely on this!)
+ * - ltmp is smashed
*/
-#define CPU_STATS_SYS_SYSCALL_INC \
- addl $1, %gs:CPU_STATS_SYS_SYSCALL; \
- adcl $0, %gs:CPU_STATS_SYS_SYSCALL+4;
+#define CHECK_POSTSYS_NE(t, ltmp, rtmp) \
+ movq T_LWP(t), ltmp; \
+ movzbl PCB_RUPDATE(ltmp), rtmp; \
+ ORL_SYSCALLTRACE(rtmp); \
+ orl T_POST_SYS_AST(t), rtmp; \
+ cmpl $0, rtmp
-#if !defined(__lint)
+/*
+ * Fix up the lwp, thread, and eflags for a successful return
+ *
+ * Preconditions:
+ * - zwreg contains zero
+ */
+#define SIMPLE_SYSCALL_POSTSYS(t, lwp, zwreg) \
+ movb $LWP_USER, LWP_STATE(lwp); \
+ movw zwreg, T_SYSNUM(t); \
+ andb $_CONST(0xffff - PS_C), REGOFF_RFL(%rsp)
/*
* ASSERT(lwptoregs(lwp) == rp);
*
- * this may seem obvious, but very odd things happen if this
+ * This may seem obvious, but very odd things happen if this
* assertion is false
*
* Preconditions:
+ * (%rsp is ready for normal call sequence)
+ * Postconditions (if assertion is true):
+ * %r11 is smashed
+ *
+ * ASSERT(rp->r_cs == descnum)
+ *
+ * The code selector is written into the regs structure when the
+ * lwp stack is created. We use this ASSERT to validate that
+ * the regs structure really matches how we came in.
+ *
+ * Preconditions:
+ * (%rsp is ready for normal call sequence)
+ * Postconditions (if assertion is true):
* -none-
+ *
+ * ASSERT(lwp->lwp_pcb.pcb_rupdate == 0);
+ *
+ * If this is false, it meant that we returned to userland without
+ * updating the segment registers as we were supposed to.
+ *
+ * Note that we must ensure no interrupts or other traps intervene
+ * between entering privileged mode and performing the assertion,
+ * otherwise we may perform a context switch on the thread, which
+ * will end up setting pcb_rupdate to 1 again.
+ *
+ * ASSERT(%cr0 & CR0_TS == 0);
+ * Preconditions:
+ * (%rsp is ready for normal call sequence)
* Postconditions (if assertion is true):
- * %esi and %edi are smashed
+ * (specified register is clobbered)
+ *
+ * Check to make sure that we are returning to user land and that CR0.TS
+ * is not set. This is required as part of the eager FPU (see
+ * uts/intel/ia32/os/fpu.c for more information).
*/
+
#if defined(DEBUG)
__lwptoregs_msg:
.string "syscall_asm.s:%d lwptoregs(%p) [%p] != rp [%p]"
-#define ASSERT_LWPTOREGS(t, rp) \
- movl T_LWP(t), %esi; \
- movl LWP_REGS(%esi), %edi; \
- cmpl rp, %edi; \
+__codesel_msg:
+ .string "syscall_asm.s:%d rp->r_cs [%ld] != %ld"
+
+__no_rupdate_msg:
+ .string "syscall_asm.s:%d lwp %p, pcb_rupdate != 0"
+
+__bad_ts_msg:
+ .string "syscall_asm.s:%d CR0.TS set on user return"
+
+#define ASSERT_LWPTOREGS(lwp, rp) \
+ movq LWP_REGS(lwp), %r11; \
+ cmpq rp, %r11; \
je 7f; \
- pushl rp; \
- pushl %edi; \
- pushl %esi; \
- pushl $__LINE__; \
- pushl $__lwptoregs_msg; \
+ leaq __lwptoregs_msg(%rip), %rdi; \
+ movl $__LINE__, %esi; \
+ movq lwp, %rdx; \
+ movq %r11, %rcx; \
+ movq rp, %r8; \
+ xorl %eax, %eax; \
call panic; \
7:
+
+#define ASSERT_NO_RUPDATE_PENDING(lwp) \
+ testb $0x1, PCB_RUPDATE(lwp); \
+ je 8f; \
+ movq lwp, %rdx; \
+ leaq __no_rupdate_msg(%rip), %rdi; \
+ movl $__LINE__, %esi; \
+ xorl %eax, %eax; \
+ call panic; \
+8:
+
+#define ASSERT_CR0TS_ZERO(reg) \
+ movq %cr0, reg; \
+ testq $CR0_TS, reg; \
+ jz 9f; \
+ leaq __bad_ts_msg(%rip), %rdi; \
+ movl $__LINE__, %esi; \
+ xorl %eax, %eax; \
+ call panic; \
+9:
+
#else
-#define ASSERT_LWPTOREGS(t, rp)
+#define ASSERT_LWPTOREGS(lwp, rp)
+#define ASSERT_NO_RUPDATE_PENDING(lwp)
+#define ASSERT_CR0TS_ZERO(reg)
#endif
-#endif /* __lint */
-
/*
- * This is an assembler version of this fragment:
- *
- * lwp->lwp_state = LWP_SYS;
- * lwp->lwp_ru.sysc++;
- * lwp->lwp_eosys = NORMALRETURN;
- * lwp->lwp_ap = argp;
- *
- * Preconditions:
- * -none-
- * Postconditions:
- * -none-
+ * Do the traptrace thing and restore any registers we used
+ * in situ. Assumes that %rsp is pointing at the base of
+ * the struct regs, obviously ..
*/
-#define SET_LWP(lwp, argp) \
- movb $LWP_SYS, LWP_STATE(lwp); \
- addl $1, LWP_RU_SYSC(lwp); \
- adcl $0, LWP_RU_SYSC+4(lwp); \
- movb $NORMALRETURN, LWP_EOSYS(lwp); \
- movl argp, LWP_AP(lwp)
+#ifdef TRAPTRACE
+#define SYSCALL_TRAPTRACE(ttype) \
+ TRACE_PTR(%rdi, %rbx, %ebx, %rcx, ttype); \
+ TRACE_REGS(%rdi, %rsp, %rbx, %rcx); \
+ TRACE_STAMP(%rdi); /* rdtsc clobbers %eax, %edx */ \
+ movq REGOFF_RAX(%rsp), %rax; \
+ movq REGOFF_RBX(%rsp), %rbx; \
+ movq REGOFF_RCX(%rsp), %rcx; \
+ movq REGOFF_RDX(%rsp), %rdx; \
+ movl %eax, TTR_SYSNUM(%rdi); \
+ movq REGOFF_RDI(%rsp), %rdi
-/*
- * Set up the thread, lwp, find the handler, and copy
- * in the arguments from userland to the kernel stack.
- *
- * Preconditions:
- * - %eax contains the syscall number
- * Postconditions:
- * - %eax contains a pointer to the sysent structure
- * - %ecx is zeroed
- * - %esi, %edi are smashed
- * - %esp is SYS_DROPped ready for the syscall
- */
-#define SIMPLE_SYSCALL_PRESYS(t, faultlabel) \
- movl T_LWP(t), %esi; \
- movw %ax, T_SYSNUM(t); \
- subl $SYS_DROP, %esp; \
- shll $SYSENT_SIZE_SHIFT, %eax; \
- SET_LWP(%esi, %esp); \
- leal sysent(%eax), %eax; \
- movzbl SY_NARG(%eax), %ecx; \
- testl %ecx, %ecx; \
- jz 4f; \
- movl %esp, %edi; \
- movl SYS_DROP + REGOFF_UESP(%esp), %esi; \
- movl $faultlabel, T_LOFAULT(t); \
- addl $4, %esi; \
- rep; \
- smovl; \
- movl %ecx, T_LOFAULT(t); \
-4:
+#define SYSCALL_TRAPTRACE32(ttype) \
+ SYSCALL_TRAPTRACE(ttype); \
+ /* paranoia: clean the top 32-bits of the registers */ \
+ orl %eax, %eax; \
+ orl %ebx, %ebx; \
+ orl %ecx, %ecx; \
+ orl %edx, %edx; \
+ orl %edi, %edi
+#else /* TRAPTRACE */
+#define SYSCALL_TRAPTRACE(ttype)
+#define SYSCALL_TRAPTRACE32(ttype)
+#endif /* TRAPTRACE */
/*
- * Check to see if a simple return is possible i.e.
+ * The 64-bit libc syscall wrapper does this:
*
- * if ((t->t_post_sys_ast | syscalltrace) != 0)
- * do full version;
+ * fn(<args>)
+ * {
+ * movq %rcx, %r10 -- because syscall smashes %rcx
+ * movl $CODE, %eax
+ * syscall
+ * <error processing>
+ * }
*
- * Preconditions:
- * - t is curthread
- * Postconditions:
- * - condition code NE is set if post-sys is too complex
- * - rtmp is zeroed if it isn't (we rely on this!)
- */
-#define CHECK_POSTSYS_NE(t, rtmp) \
- xorl rtmp, rtmp; \
- ORL_SYSCALLTRACE(rtmp); \
- orl T_POST_SYS_AST(t), rtmp; \
- cmpl $0, rtmp
-
-/*
- * Fix up the lwp, thread, and eflags for a successful return
+ * Thus when we come into the kernel:
*
- * Preconditions:
- * - zwreg contains zero
- * Postconditions:
- * - %esp has been unSYS_DROPped
- * - %esi is smashed (points to lwp)
- */
-#define SIMPLE_SYSCALL_POSTSYS(t, zwreg) \
- movl T_LWP(t), %esi; \
- addl $SYS_DROP, %esp; \
- movw zwreg, T_SYSNUM(t); \
- movb $LWP_USER, LWP_STATE(%esi); \
- andb $_CONST(0xffff - PS_C), REGOFF_EFL(%esp)
-
-/*
- * System call handler. This is the destination of both the call
- * gate (lcall 0x27) _and_ the interrupt gate (int 0x91). For our purposes,
- * there are two significant differences between an interrupt gate and a call
- * gate:
+ * %rdi, %rsi, %rdx, %r10, %r8, %r9 contain first six args
+ * %rax is the syscall number
+ * %r12-%r15 contain caller state
*
- * 1) An interrupt gate runs the handler with interrupts disabled, whereas a
- * call gate runs the handler with whatever EFLAGS settings were in effect at
- * the time of the call.
+ * The syscall instruction arranges that:
*
- * 2) An interrupt gate pushes the contents of the EFLAGS register at the time
- * of the interrupt onto the stack, whereas a call gate does not.
+ * %rcx contains the return %rip
+ * %r11d contains bottom 32-bits of %rflags
+ * %rflags is masked (as determined by the SFMASK msr)
+ * %cs is set to UCS_SEL (as determined by the STAR msr)
+ * %ss is set to UDS_SEL (as determined by the STAR msr)
+ * %rip is set to sys_syscall (as determined by the LSTAR msr)
*
- * Because we use the following code sequence to handle system calls made from
- * _both_ a call gate _and_ an interrupt gate, these two differences must be
- * respected. In regards to number 1) above, the handler must ensure that a sane
- * EFLAGS snapshot is stored on the stack so that when the kernel returns back
- * to the user via iret (which returns to user with the EFLAGS value saved on
- * the stack), interrupts are re-enabled.
+ * Or in other words, we have no registers available at all.
+ * Only swapgs can save us!
*
- * In regards to number 2) above, the handler must always put a current snapshot
- * of EFLAGS onto the stack in the appropriate place. If we came in via an
- * interrupt gate, we will be clobbering the EFLAGS value that was pushed by
- * the interrupt gate. This is OK, as the only bit that was changed by the
- * hardware was the IE (interrupt enable) bit, which for an interrupt gate is
- * now off. If we were to do nothing, the stack would contain an EFLAGS with
- * IE off, resulting in us eventually returning back to the user with interrupts
- * disabled. The solution is to turn on the IE bit in the EFLAGS value saved on
- * the stack.
+ * Under the hypervisor, the swapgs has happened already. However, the
+ * state of the world is very different from that we're familiar with.
*
- * Another subtlety which deserves mention is the difference between the two
- * descriptors. The call gate descriptor is set to instruct the hardware to copy
- * one parameter from the user stack to the kernel stack, whereas the interrupt
- * gate descriptor doesn't use the parameter passing mechanism at all. The
- * kernel doesn't actually use the parameter that is copied by the hardware; the
- * only reason it does this is so that there is a space on the stack large
- * enough to hold an EFLAGS register value, which happens to be in the correct
- * place for use by iret when we go back to userland. How convenient.
+ * In particular, we have a stack structure like that for interrupt
+ * gates, except that the %cs and %ss registers are modified for reasons
+ * that are not entirely clear. Critically, the %rcx/%r11 values do
+ * *not* reflect the usage of those registers under a 'real' syscall[1];
+ * the stack, therefore, looks like this:
*
- * Stack frame description in syscall() and callees.
+ * 0x0(rsp) potentially junk %rcx
+ * 0x8(rsp) potentially junk %r11
+ * 0x10(rsp) user %rip
+ * 0x18(rsp) modified %cs
+ * 0x20(rsp) user %rflags
+ * 0x28(rsp) user %rsp
+ * 0x30(rsp) modified %ss
*
- * |------------|
- * | regs | +(8*4)+4 registers
- * |------------|
- * | 8 args | <- %esp MAXSYSARGS (currently 8) arguments
- * |------------|
*
+ * and before continuing on, we must load the %rip into %rcx and the
+ * %rflags into %r11.
+ *
+ * [1] They used to, and we relied on it, but this was broken in 3.1.1.
+ * Sigh.
*/
-#define SYS_DROP _CONST(_MUL(MAXSYSARGS, 4))
+#if defined(__xpv)
+#define XPV_SYSCALL_PROD \
+ movq 0x10(%rsp), %rcx; \
+ movq 0x20(%rsp), %r11; \
+ movq 0x28(%rsp), %rsp
+#else
+#define XPV_SYSCALL_PROD /* nothing */
+#endif
-#if defined(__lint)
+ ENTRY_NP2(brand_sys_syscall,_allsyscalls)
+ SWAPGS /* kernel gsbase */
+ XPV_SYSCALL_PROD
+ BRAND_CALLBACK(BRAND_CB_SYSCALL, BRAND_URET_FROM_REG(%rcx))
+ jmp noprod_sys_syscall
-/*ARGSUSED*/
-void
-sys_call()
-{}
+ ALTENTRY(sys_syscall)
+ SWAPGS /* kernel gsbase */
+ XPV_SYSCALL_PROD
-void
-_allsyscalls()
-{}
+noprod_sys_syscall:
+ movq %r15, %gs:CPU_RTMP_R15
+ movq %rsp, %gs:CPU_RTMP_RSP
-size_t _allsyscalls_size;
+ movq %gs:CPU_THREAD, %r15
+ movq T_STACK(%r15), %rsp /* switch from user to kernel stack */
-#else /* __lint */
+ ASSERT_UPCALL_MASK_IS_SET
- ENTRY_NP2(brand_sys_call, _allsyscalls)
- BRAND_CALLBACK(BRAND_CB_SYSCALL)
+ movl $UCS_SEL, REGOFF_CS(%rsp)
+ movq %rcx, REGOFF_RIP(%rsp) /* syscall: %rip -> %rcx */
+ movq %r11, REGOFF_RFL(%rsp) /* syscall: %rfl -> %r11d */
+ movl $UDS_SEL, REGOFF_SS(%rsp)
- ALTENTRY(sys_call)
- / on entry eax = system call number
+ movl %eax, %eax /* wrapper: sysc# -> %eax */
+ movq %rdi, REGOFF_RDI(%rsp)
+ movq %rsi, REGOFF_RSI(%rsp)
+ movq %rdx, REGOFF_RDX(%rsp)
+ movq %r10, REGOFF_RCX(%rsp) /* wrapper: %rcx -> %r10 */
+ movq %r10, %rcx /* arg[3] for direct calls */
- / set up the stack to look as in reg.h
- subl $8, %esp / pad the stack with ERRCODE and TRAPNO
+ movq %r8, REGOFF_R8(%rsp)
+ movq %r9, REGOFF_R9(%rsp)
+ movq %rax, REGOFF_RAX(%rsp)
+ movq %rbx, REGOFF_RBX(%rsp)
- SYSCALL_PUSH
+ movq %rbp, REGOFF_RBP(%rsp)
+ movq %r10, REGOFF_R10(%rsp)
+ movq %gs:CPU_RTMP_RSP, %r11
+ movq %r11, REGOFF_RSP(%rsp)
+ movq %r12, REGOFF_R12(%rsp)
-#ifdef TRAPTRACE
- TRACE_PTR(%edi, %ebx, %ebx, %ecx, $TT_SYSCALL) / Uses labels "8" and "9"
- TRACE_REGS(%edi, %esp, %ebx, %ecx) / Uses label "9"
- pushl %eax
- TRACE_STAMP(%edi) / Clobbers %eax, %edx, uses "9"
- popl %eax
- movl %eax, TTR_SYSNUM(%edi)
+ movq %r13, REGOFF_R13(%rsp)
+ movq %r14, REGOFF_R14(%rsp)
+ movq %gs:CPU_RTMP_R15, %r10
+ movq %r10, REGOFF_R15(%rsp)
+ movq $0, REGOFF_SAVFP(%rsp)
+ movq $0, REGOFF_SAVPC(%rsp)
+
+ /*
+ * Copy these registers here in case we end up stopped with
+ * someone (like, say, /proc) messing with our register state.
+ * We don't -restore- them unless we have to in update_sregs.
+ *
+ * Since userland -can't- change fsbase or gsbase directly,
+ * and capturing them involves two serializing instructions,
+ * we don't bother to capture them here.
+ */
+ xorl %ebx, %ebx
+ movw %ds, %bx
+ movq %rbx, REGOFF_DS(%rsp)
+ movw %es, %bx
+ movq %rbx, REGOFF_ES(%rsp)
+ movw %fs, %bx
+ movq %rbx, REGOFF_FS(%rsp)
+ movw %gs, %bx
+ movq %rbx, REGOFF_GS(%rsp)
+
+ /*
+ * If we're trying to use TRAPTRACE though, I take that back: we're
+ * probably debugging some problem in the SWAPGS logic and want to know
+ * what the incoming gsbase was.
+ *
+ * Since we already did SWAPGS, record the KGSBASE.
+ */
+#if defined(DEBUG) && defined(TRAPTRACE) && !defined(__xpv)
+ movl $MSR_AMD_KGSBASE, %ecx
+ rdmsr
+ movl %eax, REGOFF_GSBASE(%rsp)
+ movl %edx, REGOFF_GSBASE+4(%rsp)
#endif
-_watch_do_syscall:
- movl %esp, %ebp
+ /*
+ * Machine state saved in the regs structure on the stack
+ * First six args in %rdi, %rsi, %rdx, %rcx, %r8, %r9
+ * %eax is the syscall number
+ * %rsp is the thread's stack, %r15 is curthread
+ * REG_RSP(%rsp) is the user's stack
+ */
- / Interrupts may be enabled here, so we must make sure this thread
- / doesn't migrate off the CPU while it updates the CPU stats.
- /
- / XXX This is only true if we got here via call gate thru the LDT for
- / old style syscalls. Perhaps this preempt++-- will go away soon?
- movl %gs:CPU_THREAD, %ebx
- addb $1, T_PREEMPT(%ebx)
- CPU_STATS_SYS_SYSCALL_INC
- subb $1, T_PREEMPT(%ebx)
+ SYSCALL_TRAPTRACE($TT_SYSC64)
+ movq %rsp, %rbp
+
+ movq T_LWP(%r15), %r14
+ ASSERT_NO_RUPDATE_PENDING(%r14)
ENABLE_INTR_FLAGS
- pushl %eax / preserve across mstate call
MSTATE_TRANSITION(LMS_USER, LMS_SYSTEM)
- popl %eax
+ movl REGOFF_RAX(%rsp), %eax /* (%rax damaged by mstate call) */
- movl %gs:CPU_THREAD, %ebx
+ ASSERT_LWPTOREGS(%r14, %rsp)
- ASSERT_LWPTOREGS(%ebx, %esp)
+ movb $LWP_SYS, LWP_STATE(%r14)
+ incq LWP_RU_SYSC(%r14)
+ movb $NORMALRETURN, LWP_EOSYS(%r14)
- CHECK_PRESYS_NE(%ebx, %eax)
- jne _full_syscall_presys
- SIMPLE_SYSCALL_PRESYS(%ebx, _syscall_fault)
+ incq %gs:CPU_STATS_SYS_SYSCALL
-_syslcall_call:
- call *SY_CALLC(%eax)
+ movw %ax, T_SYSNUM(%r15)
+ movzbl T_PRE_SYS(%r15), %ebx
+ ORL_SYSCALLTRACE(%ebx)
+ testl %ebx, %ebx
+ jne _syscall_pre
-_syslcall_done:
- CHECK_POSTSYS_NE(%ebx, %ecx)
- jne _full_syscall_postsys
- SIMPLE_SYSCALL_POSTSYS(%ebx, %cx)
- movl %eax, REGOFF_EAX(%esp)
- movl %edx, REGOFF_EDX(%esp)
+_syscall_invoke:
+ movq REGOFF_RDI(%rbp), %rdi
+ movq REGOFF_RSI(%rbp), %rsi
+ movq REGOFF_RDX(%rbp), %rdx
+ movq REGOFF_RCX(%rbp), %rcx
+ movq REGOFF_R8(%rbp), %r8
+ movq REGOFF_R9(%rbp), %r9
+ cmpl $NSYSCALL, %eax
+ jae _syscall_ill
+ shll $SYSENT_SIZE_SHIFT, %eax
+ leaq sysent(%rax), %rbx
+
+ movq SY_CALLC(%rbx), %rax
+ INDIRECT_CALL_REG(rax)
+
+ movq %rax, %r12
+ movq %rdx, %r13
+
+ /*
+ * If the handler returns two ints, then we need to split the
+ * 64-bit return value into two 32-bit values.
+ */
+ testw $SE_32RVAL2, SY_FLAGS(%rbx)
+ je 5f
+ movq %r12, %r13
+ shrq $32, %r13 /* upper 32-bits into %edx */
+ movl %r12d, %r12d /* lower 32-bits into %eax */
+5:
+ /*
+ * Optimistically assume that there's no post-syscall
+ * work to do. (This is to avoid having to call syscall_mstate()
+ * with interrupts disabled)
+ */
MSTATE_TRANSITION(LMS_SYSTEM, LMS_USER)
- /
- / get back via iret
- /
- CLI(%edx)
- jmp sys_rtt_syscall
+ /*
+ * We must protect ourselves from being descheduled here;
+ * If we were, and we ended up on another cpu, or another
+ * lwp got in ahead of us, it could change the segment
+ * registers without us noticing before we return to userland.
+ */
+ CLI(%r14)
+ CHECK_POSTSYS_NE(%r15, %r14, %ebx)
+ jne _syscall_post
-_full_syscall_presys:
- movl T_LWP(%ebx), %esi
- subl $SYS_DROP, %esp
- movb $LWP_SYS, LWP_STATE(%esi)
- pushl %esp
- pushl %ebx
- call syscall_entry
- addl $8, %esp
- jmp _syslcall_call
+ /*
+ * We need to protect ourselves against non-canonical return values
+ * because Intel doesn't check for them on sysret (AMD does). Canonical
+ * addresses on current amd64 processors only use 48-bits for VAs; an
+ * address is canonical if all upper bits (47-63) are identical. If we
+ * find a non-canonical %rip, we opt to go through the full
+ * _syscall_post path which takes us into an iretq which is not
+ * susceptible to the same problems sysret is.
+ *
+ * We're checking for a canonical address by first doing an arithmetic
+ * shift. This will fill in the remaining bits with the value of bit 63.
+ * If the address were canonical, the register would now have either all
+ * zeroes or all ones in it. Therefore we add one (inducing overflow)
+ * and compare against 1. A canonical address will either be zero or one
+ * at this point, hence the use of ja.
+ *
+ * At this point, r12 and r13 have the return value so we can't use
+ * those registers.
+ */
+ movq REGOFF_RIP(%rsp), %rcx
+ sarq $47, %rcx
+ incq %rcx
+ cmpq $1, %rcx
+ ja _syscall_post
-_full_syscall_postsys:
- addl $SYS_DROP, %esp
- pushl %edx
- pushl %eax
- pushl %ebx
- call syscall_exit
- addl $12, %esp
+
+ SIMPLE_SYSCALL_POSTSYS(%r15, %r14, %bx)
+
+ movq %r12, REGOFF_RAX(%rsp)
+ movq %r13, REGOFF_RDX(%rsp)
+
+ /*
+ * Clobber %r11 as we check CR0.TS.
+ */
+ ASSERT_CR0TS_ZERO(%r11)
+
+ /*
+ * Unlike other cases, because we need to restore the user stack pointer
+ * before exiting the kernel we must clear the microarch state before
+ * getting here. This should be safe because it means that the only
+ * values on the bus after this are based on the user's registers and
+ * potentially the addresses where we stored them. Given the constraints
+ * of sysret, that's how it has to be.
+ */
+ call x86_md_clear
+
+ /*
+ * To get back to userland, we need the return %rip in %rcx and
+ * the return %rfl in %r11d. The sysretq instruction also arranges
+ * to fix up %cs and %ss; everything else is our responsibility.
+ */
+ movq REGOFF_RDI(%rsp), %rdi
+ movq REGOFF_RSI(%rsp), %rsi
+ movq REGOFF_RDX(%rsp), %rdx
+ /* %rcx used to restore %rip value */
+
+ movq REGOFF_R8(%rsp), %r8
+ movq REGOFF_R9(%rsp), %r9
+ movq REGOFF_RAX(%rsp), %rax
+ movq REGOFF_RBX(%rsp), %rbx
+
+ movq REGOFF_RBP(%rsp), %rbp
+ movq REGOFF_R10(%rsp), %r10
+ /* %r11 used to restore %rfl value */
+ movq REGOFF_R12(%rsp), %r12
+
+ movq REGOFF_R13(%rsp), %r13
+ movq REGOFF_R14(%rsp), %r14
+ movq REGOFF_R15(%rsp), %r15
+
+ movq REGOFF_RIP(%rsp), %rcx
+ movl REGOFF_RFL(%rsp), %r11d
+
+#if defined(__xpv)
+ addq $REGOFF_RIP, %rsp
+#else
+ movq REGOFF_RSP(%rsp), %rsp
+#endif
+
+ /*
+ * There can be no instructions between the ALTENTRY below and
+ * SYSRET or we could end up breaking brand support. See label usage
+ * in sn1_brand_syscall_callback for an example.
+ */
+ ASSERT_UPCALL_MASK_IS_SET
+#if defined(__xpv)
+ SYSRETQ
+ ALTENTRY(nopop_sys_syscall_swapgs_sysretq)
+
+ /*
+ * We can only get here after executing a brand syscall
+ * interposition callback handler and simply need to
+ * "sysretq" back to userland. On the hypervisor this
+ * involves the iret hypercall which requires us to construct
+ * just enough of the stack needed for the hypercall.
+ * (rip, cs, rflags, rsp, ss).
+ */
+ movq %rsp, %gs:CPU_RTMP_RSP /* save user's rsp */
+ movq %gs:CPU_THREAD, %r11
+ movq T_STACK(%r11), %rsp
+
+ movq %rcx, REGOFF_RIP(%rsp)
+ movl $UCS_SEL, REGOFF_CS(%rsp)
+ movq %gs:CPU_RTMP_RSP, %r11
+ movq %r11, REGOFF_RSP(%rsp)
+ pushfq
+ popq %r11 /* hypercall enables ints */
+ movq %r11, REGOFF_RFL(%rsp)
+ movl $UDS_SEL, REGOFF_SS(%rsp)
+ addq $REGOFF_RIP, %rsp
+ /*
+ * XXPV: see comment in SYSRETQ definition for future optimization
+ * we could take.
+ */
+ ASSERT_UPCALL_MASK_IS_SET
+ SYSRETQ
+#else
+ ALTENTRY(nopop_sys_syscall_swapgs_sysretq)
+ jmp tr_sysretq
+#endif
+ /*NOTREACHED*/
+ SET_SIZE(nopop_sys_syscall_swapgs_sysretq)
+
+_syscall_pre:
+ call pre_syscall
+ movl %eax, %r12d
+ testl %eax, %eax
+ jne _syscall_post_call
+ /*
+ * Didn't abort, so reload the syscall args and invoke the handler.
+ */
+ movzwl T_SYSNUM(%r15), %eax
+ jmp _syscall_invoke
+
+_syscall_ill:
+ call nosys
+ movq %rax, %r12
+ movq %rdx, %r13
+ jmp _syscall_post_call
+
+_syscall_post:
+ STI
+ /*
+ * Sigh, our optimism wasn't justified, put it back to LMS_SYSTEM
+ * so that we can account for the extra work it takes us to finish.
+ */
+ MSTATE_TRANSITION(LMS_USER, LMS_SYSTEM)
+_syscall_post_call:
+ movq %r12, %rdi
+ movq %r13, %rsi
+ call post_syscall
MSTATE_TRANSITION(LMS_SYSTEM, LMS_USER)
jmp _sys_rtt
+ SET_SIZE(sys_syscall)
+ SET_SIZE(brand_sys_syscall)
-_syscall_fault:
- push $0xe / EFAULT
- call set_errno
- addl $4, %esp
- xorl %eax, %eax / fake syscall_err()
- xorl %edx, %edx
- jmp _syslcall_done
- SET_SIZE(sys_call)
- SET_SIZE(brand_sys_call)
+ ENTRY_NP(brand_sys_syscall32)
+ SWAPGS /* kernel gsbase */
+ XPV_TRAP_POP
+ BRAND_CALLBACK(BRAND_CB_SYSCALL32, BRAND_URET_FROM_REG(%rcx))
+ jmp nopop_sys_syscall32
-#endif /* __lint */
+ ALTENTRY(sys_syscall32)
+ SWAPGS /* kernel gsbase */
+ XPV_TRAP_POP
-/*
- * System call handler via the sysenter instruction
+nopop_sys_syscall32:
+ movl %esp, %r10d
+ movq %gs:CPU_THREAD, %r15
+ movq T_STACK(%r15), %rsp
+ movl %eax, %eax
+
+ movl $U32CS_SEL, REGOFF_CS(%rsp)
+ movl %ecx, REGOFF_RIP(%rsp) /* syscall: %rip -> %rcx */
+ movq %r11, REGOFF_RFL(%rsp) /* syscall: %rfl -> %r11d */
+ movq %r10, REGOFF_RSP(%rsp)
+ movl $UDS_SEL, REGOFF_SS(%rsp)
+
+_syscall32_save:
+ movl %edi, REGOFF_RDI(%rsp)
+ movl %esi, REGOFF_RSI(%rsp)
+ movl %ebp, REGOFF_RBP(%rsp)
+ movl %ebx, REGOFF_RBX(%rsp)
+ movl %edx, REGOFF_RDX(%rsp)
+ movl %ecx, REGOFF_RCX(%rsp)
+ movl %eax, REGOFF_RAX(%rsp) /* wrapper: sysc# -> %eax */
+ movq $0, REGOFF_SAVFP(%rsp)
+ movq $0, REGOFF_SAVPC(%rsp)
+
+ /*
+ * Copy these registers here in case we end up stopped with
+ * someone (like, say, /proc) messing with our register state.
+ * We don't -restore- them unless we have to in update_sregs.
*
- * Here's how syscall entry usually works (see sys_call for details).
+ * Since userland -can't- change fsbase or gsbase directly,
+ * we don't bother to capture them here.
+ */
+ xorl %ebx, %ebx
+ movw %ds, %bx
+ movq %rbx, REGOFF_DS(%rsp)
+ movw %es, %bx
+ movq %rbx, REGOFF_ES(%rsp)
+ movw %fs, %bx
+ movq %rbx, REGOFF_FS(%rsp)
+ movw %gs, %bx
+ movq %rbx, REGOFF_GS(%rsp)
+
+ /*
+ * If we're trying to use TRAPTRACE though, I take that back: we're
+ * probably debugging some problem in the SWAPGS logic and want to know
+ * what the incoming gsbase was.
*
- * There, the caller (lcall or int) in userland has arranged that:
+ * Since we already did SWAPGS, record the KGSBASE.
+ */
+#if defined(DEBUG) && defined(TRAPTRACE) && !defined(__xpv)
+ movl $MSR_AMD_KGSBASE, %ecx
+ rdmsr
+ movl %eax, REGOFF_GSBASE(%rsp)
+ movl %edx, REGOFF_GSBASE+4(%rsp)
+#endif
+
+ /*
+ * Application state saved in the regs structure on the stack
+ * %eax is the syscall number
+ * %rsp is the thread's stack, %r15 is curthread
+ * REG_RSP(%rsp) is the user's stack
+ */
+
+ SYSCALL_TRAPTRACE32($TT_SYSC)
+
+ movq %rsp, %rbp
+
+ movq T_LWP(%r15), %r14
+ ASSERT_NO_RUPDATE_PENDING(%r14)
+
+ ENABLE_INTR_FLAGS
+
+ MSTATE_TRANSITION(LMS_USER, LMS_SYSTEM)
+ movl REGOFF_RAX(%rsp), %eax /* (%rax damaged by mstate call) */
+
+ ASSERT_LWPTOREGS(%r14, %rsp)
+
+ incq %gs:CPU_STATS_SYS_SYSCALL
+
+ /*
+ * Make some space for MAXSYSARGS (currently 8) 32-bit args placed
+ * into 64-bit (long) arg slots, maintaining 16 byte alignment. Or
+ * more succinctly:
*
- * - %eax contains the syscall number
- * - the user stack contains the args to the syscall
+ * SA(MAXSYSARGS * sizeof (long)) == 64
+ */
+#define SYS_DROP 64 /* drop for args */
+ subq $SYS_DROP, %rsp
+ movb $LWP_SYS, LWP_STATE(%r14)
+ movq %r15, %rdi
+ movq %rsp, %rsi
+ call syscall_entry
+
+ /*
+ * Fetch the arguments copied onto the kernel stack and put
+ * them in the right registers to invoke a C-style syscall handler.
+ * %rax contains the handler address.
*
- * Normally the lcall instruction into the call gate causes the processor
- * to push %ss, %esp, <top-of-stack>, %cs, %eip onto the kernel stack.
- * The sys_call handler then leaves space for r_trapno and r_err, and
- * pusha's {%eax, %ecx, %edx, %ebx, %esp, %ebp, %esi, %edi}, followed
- * by %ds, %es, %fs and %gs to capture a 'struct regs' on the stack.
- * Then the kernel sets %ds, %es and %gs to kernel selectors, and finally
- * extracts %efl and puts it into r_efl (which happens to live at the offset
- * that <top-of-stack> was copied into). Note that the value in r_efl has
- * the IF (interrupt enable) flag turned on. (The int instruction into the
- * interrupt gate does essentially the same thing, only instead of
- * <top-of-stack> we get eflags - see comment above.)
+ * Ideas for making all this go faster of course include simply
+ * forcibly fetching 6 arguments from the user stack under lofault
+ * protection, reverting to copyin_args only when watchpoints
+ * are in effect.
*
- * In the sysenter case, things are a lot more primitive.
+ * (If we do this, make sure that exec and libthread leave
+ * enough space at the top of the stack to ensure that we'll
+ * never do a fetch from an invalid page.)
*
+ * Lots of ideas here, but they won't really help with bringup B-)
+ * Correctness can't wait, performance can wait a little longer ..
+ */
+
+ movq %rax, %rbx
+ movl 0(%rsp), %edi
+ movl 8(%rsp), %esi
+ movl 0x10(%rsp), %edx
+ movl 0x18(%rsp), %ecx
+ movl 0x20(%rsp), %r8d
+ movl 0x28(%rsp), %r9d
+
+ movq SY_CALLC(%rbx), %rax
+ INDIRECT_CALL_REG(rax)
+
+ movq %rbp, %rsp /* pop the args */
+
+ /*
+ * amd64 syscall handlers -always- return a 64-bit value in %rax.
+ * On the 32-bit kernel, they always return that value in %eax:%edx
+ * as required by the 32-bit ABI.
+ *
+ * Simulate the same behaviour by unconditionally splitting the
+ * return value in the same way.
+ */
+ movq %rax, %r13
+ shrq $32, %r13 /* upper 32-bits into %edx */
+ movl %eax, %r12d /* lower 32-bits into %eax */
+
+ /*
+ * Optimistically assume that there's no post-syscall
+ * work to do. (This is to avoid having to call syscall_mstate()
+ * with interrupts disabled)
+ */
+ MSTATE_TRANSITION(LMS_SYSTEM, LMS_USER)
+
+ /*
+ * We must protect ourselves from being descheduled here;
+ * If we were, and we ended up on another cpu, or another
+ * lwp got in ahead of us, it could change the segment
+ * registers without us noticing before we return to userland.
+ */
+ CLI(%r14)
+ CHECK_POSTSYS_NE(%r15, %r14, %ebx)
+ jne _full_syscall_postsys32
+ SIMPLE_SYSCALL_POSTSYS(%r15, %r14, %bx)
+
+ /*
+ * Clobber %r11 as we check CR0.TS.
+ */
+ ASSERT_CR0TS_ZERO(%r11)
+
+ /*
+ * Unlike other cases, because we need to restore the user stack pointer
+ * before exiting the kernel we must clear the microarch state before
+ * getting here. This should be safe because it means that the only
+ * values on the bus after this are based on the user's registers and
+ * potentially the addresses where we stored them. Given the constraints
+ * of sysret, that's how it has to be.
+ */
+ call x86_md_clear
+
+ /*
+ * To get back to userland, we need to put the return %rip in %rcx and
+ * the return %rfl in %r11d. The sysret instruction also arranges
+ * to fix up %cs and %ss; everything else is our responsibility.
+ */
+
+ movl %r12d, %eax /* %eax: rval1 */
+ movl REGOFF_RBX(%rsp), %ebx
+ /* %ecx used for return pointer */
+ movl %r13d, %edx /* %edx: rval2 */
+ movl REGOFF_RBP(%rsp), %ebp
+ movl REGOFF_RSI(%rsp), %esi
+ movl REGOFF_RDI(%rsp), %edi
+
+ movl REGOFF_RFL(%rsp), %r11d /* %r11 -> eflags */
+ movl REGOFF_RIP(%rsp), %ecx /* %ecx -> %eip */
+ movl REGOFF_RSP(%rsp), %esp
+
+ ASSERT_UPCALL_MASK_IS_SET
+ ALTENTRY(nopop_sys_syscall32_swapgs_sysretl)
+ jmp tr_sysretl
+ SET_SIZE(nopop_sys_syscall32_swapgs_sysretl)
+ /*NOTREACHED*/
+
+_full_syscall_postsys32:
+ STI
+ /*
+ * Sigh, our optimism wasn't justified, put it back to LMS_SYSTEM
+ * so that we can account for the extra work it takes us to finish.
+ */
+ MSTATE_TRANSITION(LMS_USER, LMS_SYSTEM)
+ movq %r15, %rdi
+ movq %r12, %rsi /* rval1 - %eax */
+ movq %r13, %rdx /* rval2 - %edx */
+ call syscall_exit
+ MSTATE_TRANSITION(LMS_SYSTEM, LMS_USER)
+ jmp _sys_rtt
+ SET_SIZE(sys_syscall32)
+ SET_SIZE(brand_sys_syscall32)
+
+/*
+ * System call handler via the sysenter instruction
+ * Used only for 32-bit system calls on the 64-bit kernel.
+ *
* The caller in userland has arranged that:
*
* - %eax contains the syscall number
* - %ecx contains the user %esp
* - %edx contains the return %eip
* - the user stack contains the args to the syscall
*
- * e.g.
- * <args on the stack>
- * mov $SYS_callnum, %eax
- * mov $1f, %edx / return %eip
- * mov %esp, %ecx / return %esp
- * sysenter
- * 1:
- *
* Hardware and (privileged) initialization code have arranged that by
* the time the sysenter instructions completes:
*
- * - %eip is pointing to sys_sysenter (below).
+ * - %rip is pointing to sys_sysenter (below).
* - %cs and %ss are set to kernel text and stack (data) selectors.
- * - %esp is pointing at the lwp's stack
- * - Interrupts have been disabled.
+ * - %rsp is pointing at the lwp's stack
+ * - interrupts have been disabled.
*
- * The task for the sysenter handler is:
+ * Note that we are unable to return both "rvals" to userland with
+ * this call, as %edx is used by the sysexit instruction.
*
- * - recreate the same regs structure on the stack and the same
- * kernel state as if we'd come in on an lcall
- * - do the normal work of a syscall
- * - execute the system call epilogue, use sysexit to return to userland.
- *
- * Note that we are unable to return both "rvals" to userland with this
- * call, as %edx is used by the sysexit instruction.
- *
* One final complication in this routine is its interaction with
- * single-stepping in a debugger. For most of the system call mechanisms,
- * the CPU automatically clears the single-step flag before we enter the
- * kernel. The sysenter mechanism does not clear the flag, so a user
- * single-stepping through a libc routine may suddenly find themself
- * single-stepping through the kernel. To detect this, kmdb compares the
- * trap %pc to the [brand_]sys_enter addresses on each single-step trap.
- * If it finds that we have single-stepped to a sysenter entry point, it
- * explicitly clears the flag and executes the sys_sysenter routine.
+ * single-stepping in a debugger. For most of the system call mechanisms, the
+ * CPU automatically clears the single-step flag before we enter the kernel.
+ * The sysenter mechanism does not clear the flag, so a user single-stepping
+ * through a libc routine may suddenly find themself single-stepping through the
+ * kernel. To detect this, kmdb and trap() both compare the trap %pc to the
+ * [brand_]sys_enter addresses on each single-step trap. If it finds that we
+ * have single-stepped to a sysenter entry point, it explicitly clears the flag
+ * and executes the sys_sysenter routine.
*
- * One final complication in this final complication is the fact that we
- * have two different entry points for sysenter: brand_sys_sysenter and
- * sys_sysenter. If we enter at brand_sys_sysenter and start single-stepping
- * through the kernel with kmdb, we will eventually hit the instruction at
- * sys_sysenter. kmdb cannot distinguish between that valid single-step
- * and the undesirable one mentioned above. To avoid this situation, we
- * simply add a jump over the instruction at sys_sysenter to make it
- * impossible to single-step to it.
+ * One final complication in this final complication is the fact that we have
+ * two different entry points for sysenter: brand_sys_sysenter and sys_sysenter.
+ * If we enter at brand_sys_sysenter and start single-stepping through the
+ * kernel with kmdb, we will eventually hit the instruction at sys_sysenter.
+ * kmdb cannot distinguish between that valid single-step and the undesirable
+ * one mentioned above. To avoid this situation, we simply add a jump over the
+ * instruction at sys_sysenter to make it impossible to single-step to it.
*/
-#if defined(__lint)
-void
-sys_sysenter()
-{}
-
-#else /* __lint */
-
ENTRY_NP(brand_sys_sysenter)
- pushl %edx
- BRAND_CALLBACK(BRAND_CB_SYSENTER)
- popl %edx
+ SWAPGS /* kernel gsbase */
+ ALTENTRY(_brand_sys_sysenter_post_swapgs)
+
+ BRAND_CALLBACK(BRAND_CB_SYSENTER, BRAND_URET_FROM_REG(%rdx))
/*
* Jump over sys_sysenter to allow single-stepping as described
* above.
*/
- ja 1f
+ jmp _sys_sysenter_post_swapgs
ALTENTRY(sys_sysenter)
- nop
-1:
- /
- / do what the call gate would've done to the stack ..
- /
- pushl $UDS_SEL / (really %ss, but it's the same ..)
- pushl %ecx / userland makes this a copy of %esp
- pushfl
- orl $PS_IE, (%esp) / turn interrupts on when we return to user
- pushl $UCS_SEL
- pushl %edx / userland makes this a copy of %eip
- /
- / done. finish building the stack frame
- /
- subl $8, %esp / leave space for ERR and TRAPNO
+ SWAPGS /* kernel gsbase */
+ ALTENTRY(_sys_sysenter_post_swapgs)
- SYSENTER_PUSH
+ movq %gs:CPU_THREAD, %r15
-#ifdef TRAPTRACE
- TRACE_PTR(%edi, %ebx, %ebx, %ecx, $TT_SYSENTER) / uses labels 8 and 9
- TRACE_REGS(%edi, %esp, %ebx, %ecx) / uses label 9
- pushl %eax
- TRACE_STAMP(%edi) / clobbers %eax, %edx, uses label 9
- popl %eax
- movl %eax, TTR_SYSNUM(%edi)
+ movl $U32CS_SEL, REGOFF_CS(%rsp)
+ movl %ecx, REGOFF_RSP(%rsp) /* wrapper: %esp -> %ecx */
+ movl %edx, REGOFF_RIP(%rsp) /* wrapper: %eip -> %edx */
+ /*
+ * NOTE: none of the instructions that run before we get here should
+ * clobber bits in (R)FLAGS! This includes the kpti trampoline.
+ */
+ pushfq
+ popq %r10
+ movl $UDS_SEL, REGOFF_SS(%rsp)
+
+ /*
+ * Set the interrupt flag before storing the flags to the
+ * flags image on the stack so we can return to user with
+ * interrupts enabled if we return via sys_rtt_syscall32
+ */
+ orq $PS_IE, %r10
+ movq %r10, REGOFF_RFL(%rsp)
+
+ movl %edi, REGOFF_RDI(%rsp)
+ movl %esi, REGOFF_RSI(%rsp)
+ movl %ebp, REGOFF_RBP(%rsp)
+ movl %ebx, REGOFF_RBX(%rsp)
+ movl %edx, REGOFF_RDX(%rsp)
+ movl %ecx, REGOFF_RCX(%rsp)
+ movl %eax, REGOFF_RAX(%rsp) /* wrapper: sysc# -> %eax */
+ movq $0, REGOFF_SAVFP(%rsp)
+ movq $0, REGOFF_SAVPC(%rsp)
+
+ /*
+ * Copy these registers here in case we end up stopped with
+ * someone (like, say, /proc) messing with our register state.
+ * We don't -restore- them unless we have to in update_sregs.
+ *
+ * Since userland -can't- change fsbase or gsbase directly,
+ * we don't bother to capture them here.
+ */
+ xorl %ebx, %ebx
+ movw %ds, %bx
+ movq %rbx, REGOFF_DS(%rsp)
+ movw %es, %bx
+ movq %rbx, REGOFF_ES(%rsp)
+ movw %fs, %bx
+ movq %rbx, REGOFF_FS(%rsp)
+ movw %gs, %bx
+ movq %rbx, REGOFF_GS(%rsp)
+
+ /*
+ * If we're trying to use TRAPTRACE though, I take that back: we're
+ * probably debugging some problem in the SWAPGS logic and want to know
+ * what the incoming gsbase was.
+ *
+ * Since we already did SWAPGS, record the KGSBASE.
+ */
+#if defined(DEBUG) && defined(TRAPTRACE) && !defined(__xpv)
+ movl $MSR_AMD_KGSBASE, %ecx
+ rdmsr
+ movl %eax, REGOFF_GSBASE(%rsp)
+ movl %edx, REGOFF_GSBASE+4(%rsp)
#endif
- movl %esp, %ebp
- CPU_STATS_SYS_SYSCALL_INC
+ /*
+ * Application state saved in the regs structure on the stack
+ * %eax is the syscall number
+ * %rsp is the thread's stack, %r15 is curthread
+ * REG_RSP(%rsp) is the user's stack
+ */
+ SYSCALL_TRAPTRACE($TT_SYSENTER)
+
+ movq %rsp, %rbp
+
+ movq T_LWP(%r15), %r14
+ ASSERT_NO_RUPDATE_PENDING(%r14)
+
ENABLE_INTR_FLAGS
- pushl %eax / preserve across mstate call
+ /*
+ * Catch 64-bit process trying to issue sysenter instruction
+ * on Nocona based systems.
+ */
+ movq LWP_PROCP(%r14), %rax
+ cmpq $DATAMODEL_ILP32, P_MODEL(%rax)
+ je 7f
+
+ /*
+ * For a non-32-bit process, simulate a #ud, since that's what
+ * native hardware does. The traptrace entry (above) will
+ * let you know what really happened.
+ */
+ movq $T_ILLINST, REGOFF_TRAPNO(%rsp)
+ movq REGOFF_CS(%rsp), %rdi
+ movq %rdi, REGOFF_ERR(%rsp)
+ movq %rsp, %rdi
+ movq REGOFF_RIP(%rsp), %rsi
+ movl %gs:CPU_ID, %edx
+ call trap
+ jmp _sys_rtt
+7:
+
MSTATE_TRANSITION(LMS_USER, LMS_SYSTEM)
- popl %eax
+ movl REGOFF_RAX(%rsp), %eax /* (%rax damaged by mstate calls) */
- movl %gs:CPU_THREAD, %ebx
+ ASSERT_LWPTOREGS(%r14, %rsp)
- ASSERT_LWPTOREGS(%ebx, %esp)
+ incq %gs:CPU_STATS_SYS_SYSCALL
- CHECK_PRESYS_NE(%ebx, %eax)
- jne _full_syscall_presys
- SIMPLE_SYSCALL_PRESYS(%ebx, _syscall_fault)
+ /*
+ * Make some space for MAXSYSARGS (currently 8) 32-bit args
+ * placed into 64-bit (long) arg slots, plus one 64-bit
+ * (long) arg count, maintaining 16 byte alignment.
+ */
+ subq $SYS_DROP, %rsp
+ movb $LWP_SYS, LWP_STATE(%r14)
+ movq %r15, %rdi
+ movq %rsp, %rsi
+ call syscall_entry
-_sysenter_call:
- call *SY_CALLC(%eax)
+ /*
+ * Fetch the arguments copied onto the kernel stack and put
+ * them in the right registers to invoke a C-style syscall handler.
+ * %rax contains the handler address.
+ */
+ movq %rax, %rbx
+ movl 0(%rsp), %edi
+ movl 8(%rsp), %esi
+ movl 0x10(%rsp), %edx
+ movl 0x18(%rsp), %ecx
+ movl 0x20(%rsp), %r8d
+ movl 0x28(%rsp), %r9d
-_sysenter_done:
- CHECK_POSTSYS_NE(%ebx, %ecx)
- jne _full_syscall_postsys
- SIMPLE_SYSCALL_POSTSYS(%ebx, %cx)
- /
- / sysexit uses %edx to restore %eip, so we can't use it
- / to return a value, sigh.
- /
- movl %eax, REGOFF_EAX(%esp)
- / movl %edx, REGOFF_EDX(%esp)
+ movq SY_CALLC(%rbx), %rax
+ INDIRECT_CALL_REG(rax)
- / Interrupts will be turned on by the 'sti' executed just before
- / sysexit. The following ensures that restoring the user's EFLAGS
- / doesn't enable interrupts too soon.
- andl $_BITNOT(PS_IE), REGOFF_EFL(%esp)
+ movq %rbp, %rsp /* pop the args */
+ /*
+ * amd64 syscall handlers -always- return a 64-bit value in %rax.
+ * On the 32-bit kernel, the always return that value in %eax:%edx
+ * as required by the 32-bit ABI.
+ *
+ * Simulate the same behaviour by unconditionally splitting the
+ * return value in the same way.
+ */
+ movq %rax, %r13
+ shrq $32, %r13 /* upper 32-bits into %edx */
+ movl %eax, %r12d /* lower 32-bits into %eax */
+
+ /*
+ * Optimistically assume that there's no post-syscall
+ * work to do. (This is to avoid having to call syscall_mstate()
+ * with interrupts disabled)
+ */
MSTATE_TRANSITION(LMS_SYSTEM, LMS_USER)
+ /*
+ * We must protect ourselves from being descheduled here;
+ * If we were, and we ended up on another cpu, or another
+ * lwp got int ahead of us, it could change the segment
+ * registers without us noticing before we return to userland.
+ *
+ * This cli is undone in the tr_sysexit trampoline code.
+ */
cli
+ CHECK_POSTSYS_NE(%r15, %r14, %ebx)
+ jne _full_syscall_postsys32
+ SIMPLE_SYSCALL_POSTSYS(%r15, %r14, %bx)
- SYSCALL_POP
+ /*
+ * To get back to userland, load up the 32-bit registers and
+ * sysexit back where we came from.
+ */
- popl %edx / sysexit: %edx -> %eip
- addl $4, %esp / get CS off the stack
- popfl / EFL
- popl %ecx / sysexit: %ecx -> %esp
- sti
- sysexit
+ /*
+ * Interrupts will be turned on by the 'sti' executed just before
+ * sysexit. The following ensures that restoring the user's rflags
+ * doesn't enable interrupts too soon.
+ */
+ andq $_BITNOT(PS_IE), REGOFF_RFL(%rsp)
+
+ /*
+ * Clobber %r11 as we check CR0.TS.
+ */
+ ASSERT_CR0TS_ZERO(%r11)
+
+ /*
+ * (There's no point in loading up %edx because the sysexit
+ * mechanism smashes it.)
+ */
+ movl %r12d, %eax
+ movl REGOFF_RBX(%rsp), %ebx
+ movl REGOFF_RBP(%rsp), %ebp
+ movl REGOFF_RSI(%rsp), %esi
+ movl REGOFF_RDI(%rsp), %edi
+
+ movl REGOFF_RIP(%rsp), %edx /* sysexit: %edx -> %eip */
+ pushq REGOFF_RFL(%rsp)
+ popfq
+ movl REGOFF_RSP(%rsp), %ecx /* sysexit: %ecx -> %esp */
+ ALTENTRY(sys_sysenter_swapgs_sysexit)
+ call x86_md_clear
+ jmp tr_sysexit
+ SET_SIZE(sys_sysenter_swapgs_sysexit)
SET_SIZE(sys_sysenter)
+ SET_SIZE(_sys_sysenter_post_swapgs)
SET_SIZE(brand_sys_sysenter)
/*
+ * This is the destination of the "int $T_SYSCALLINT" interrupt gate, used by
+ * the generic i386 libc to do system calls. We do a small amount of setup
+ * before jumping into the existing sys_syscall32 path.
+ */
+
+ ENTRY_NP(brand_sys_syscall_int)
+ SWAPGS /* kernel gsbase */
+ XPV_TRAP_POP
+ call smap_enable
+ BRAND_CALLBACK(BRAND_CB_INT91, BRAND_URET_FROM_INTR_STACK())
+ jmp nopop_syscall_int
+
+ ALTENTRY(sys_syscall_int)
+ SWAPGS /* kernel gsbase */
+ XPV_TRAP_POP
+ call smap_enable
+
+nopop_syscall_int:
+ movq %gs:CPU_THREAD, %r15
+ movq T_STACK(%r15), %rsp
+ movl %eax, %eax
+ /*
+ * Set t_post_sys on this thread to force ourselves out via the slow
+ * path. It might be possible at some later date to optimize this out
+ * and use a faster return mechanism.
+ */
+ movb $1, T_POST_SYS(%r15)
+ CLEAN_CS
+ jmp _syscall32_save
+ /*
+ * There should be no instructions between this label and SWAPGS/IRET
+ * or we could end up breaking branded zone support. See the usage of
+ * this label in lx_brand_int80_callback and sn1_brand_int91_callback
+ * for examples.
+ *
+ * We want to swapgs to maintain the invariant that all entries into
+ * tr_iret_user are done on the user gsbase.
+ */
+ ALTENTRY(sys_sysint_swapgs_iret)
+ call x86_md_clear
+ SWAPGS
+ jmp tr_iret_user
+ /*NOTREACHED*/
+ SET_SIZE(sys_sysint_swapgs_iret)
+ SET_SIZE(sys_syscall_int)
+ SET_SIZE(brand_sys_syscall_int)
+
+/*
+ * Legacy 32-bit applications and old libc implementations do lcalls;
+ * we should never get here because the LDT entry containing the syscall
+ * segment descriptor has the "segment present" bit cleared, which means
+ * we end up processing those system calls in trap() via a not-present trap.
+ *
+ * We do it this way because a call gate unhelpfully does -nothing- to the
+ * interrupt flag bit, so an interrupt can run us just after the lcall
+ * completes, but just before the swapgs takes effect. Thus the INTR_PUSH and
+ * INTR_POP paths would have to be slightly more complex to dance around
+ * this problem, and end up depending explicitly on the first
+ * instruction of this handler being either swapgs or cli.
+ */
+
+ ENTRY_NP(sys_lcall32)
+ SWAPGS /* kernel gsbase */
+ pushq $0
+ pushq %rbp
+ movq %rsp, %rbp
+ leaq __lcall_panic_str(%rip), %rdi
+ xorl %eax, %eax
+ call panic
+ SET_SIZE(sys_lcall32)
+
+__lcall_panic_str:
+ .string "sys_lcall32: shouldn't be here!"
+
+/*
* Declare a uintptr_t which covers the entire pc range of syscall
* handlers for the stack walkers that need this.
*/
.align CPTRSIZE
.globl _allsyscalls_size
@@ -642,30 +1303,14 @@
.type _allsyscalls_size, @object
_allsyscalls_size:
.NWORD . - _allsyscalls
SET_SIZE(_allsyscalls_size)
-#endif /* __lint */
-
/*
* These are the thread context handlers for lwps using sysenter/sysexit.
*/
-#if defined(__lint)
-
-/*ARGSUSED*/
-void
-sep_save(void *ksp)
-{}
-
-/*ARGSUSED*/
-void
-sep_restore(void *ksp)
-{}
-
-#else /* __lint */
-
/*
* setting this value to zero as we switch away causes the
* stack-pointer-on-sysenter to be NULL, ensuring that we
* don't silently corrupt another (preempted) thread stack
* when running an lwp that (somehow) didn't get sep_restore'd
@@ -680,35 +1325,13 @@
/*
* Update the kernel stack pointer as we resume onto this cpu.
*/
ENTRY_NP(sep_restore)
- movl 4(%esp), %eax /* per-lwp kernel sp */
- xorl %edx, %edx
+ movq %rdi, %rdx
+ shrq $32, %rdx
+ movl %edi, %eax
movl $MSR_INTC_SEP_ESP, %ecx
wrmsr
ret
SET_SIZE(sep_restore)
-#endif /* __lint */
-
-/*
- * Call syscall(). Called from trap() on watchpoint at lcall 0,7
- */
-
-#if defined(__lint)
-
-void
-watch_syscall(void)
-{}
-
-#else /* __lint */
-
- ENTRY_NP(watch_syscall)
- CLI(%eax)
- movl %gs:CPU_THREAD, %ebx
- movl T_STACK(%ebx), %esp / switch to the thread stack
- movl REGOFF_EAX(%esp), %eax / recover original syscall#
- jmp _watch_do_syscall
- SET_SIZE(watch_syscall)
-
-#endif /* __lint */