10908 Simplify SMAP relocations with krtld

*** 21,33 ****
  
  /*
   * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
  
- #pragma ident   "%Z%%M% %I%     %E% SMI"
- 
  /*
   * x86 relocation code.
   */
  
  #include <sys/types.h>
--- 21,34 ----
  
  /*
   * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
   */
+ /*
+  * Copyright 2019 Joyent, Inc.
+  */
  
  /*
   * x86 relocation code.
   */
  
  #include <sys/types.h>
*** 117,128 ****
                  instr[i - 1] = SDT_NOP;
  
          return (0);
  }
  
  int
- /* ARGSUSED2 */
  do_relocate(struct module *mp, char *reltbl, Word relshtype, int nreloc,
          int relocsize, Addr baseaddr)
  {
          unsigned long stndx;
          unsigned long off;      /* can't be register for tnf_reloc_resolve() */
--- 118,179 ----
                  instr[i - 1] = SDT_NOP;
  
          return (0);
  }
  
+ 
+ /*
+  * We're relying on the fact that the call we're replacing is
+  * call (e8) plus 4 bytes of address, making a 5 byte instruction
+  */
+ #define NOP_INSTR       0x90
+ #define SMAP_NOPS       5
+ 
+ /*
+  * Currently the only call replaced as a hot inline
+  * is smap_enable() and smap_disable(). If more are needed
+  * we should probably come up with an sdt probe like prefix
+  * and look for those instead of exact call names.
+  */
+ static int
+ smap_reloc_resolve(struct module *mp, char *symname, uint8_t *instr)
+ {
+         uint_t symlen;
+         hotinline_desc_t *hid;
+ 
+         if (strcmp(symname, "smap_enable") == 0 ||
+             strcmp(symname, "smap_disable") == 0) {
+ 
+ #ifdef  KOBJ_DEBUG
+                 if (kobj_debug & D_RELOCATIONS) {
+                         _kobj_printf(ops, "smap_reloc_resolve: %s relocating "
+                             "enable/disable_smap\n", mp->filename);
+                 }
+ #endif
+ 
+                 hid = kobj_alloc(sizeof (hotinline_desc_t), KM_WAIT);
+                 symlen = strlen(symname) + 1;
+                 hid->hid_symname = kobj_alloc(symlen, KM_WAIT);
+                 bcopy(symname, hid->hid_symname, symlen);
+ 
+                 /*
+                  * We backtrack one byte here to consume the call
+                  * instruction itself.
+                  */
+                 hid->hid_instr_offset = (uintptr_t)instr - 1;
+                 hid->hid_next = mp->hi_calls;
+                 mp->hi_calls = hid;
+ 
+                 memset((void *)hid->hid_instr_offset, NOP_INSTR, SMAP_NOPS);
+ 
+                 return (0);
+         }
+ 
+         return (1);
+ }
+ 
  int
  do_relocate(struct module *mp, char *reltbl, Word relshtype, int nreloc,
      int relocsize, Addr baseaddr)
  {
          unsigned long stndx;
          unsigned long off;      /* can't be register for tnf_reloc_resolve() */
*** 219,228 ****
--- 270,284 ----
                                   */
                                  if (symref->st_shndx == SHN_UNDEF &&
                                      sdt_reloc_resolve(mp, mp->strings +
                                      symref->st_name, (uint8_t *)off) == 0)
                                          continue;
+ 
+                                 if (symref->st_shndx == SHN_UNDEF &&
+                                     smap_reloc_resolve(mp, mp->strings +
+                                     symref->st_name, (uint8_t *)off) == 0)
+                                         continue;
  
                                  if (symref->st_shndx == SHN_UNDEF &&
                                      tnf_reloc_resolve(mp->strings +
                                      symref->st_name, &symref->st_value,
                                      &addend, off, &probelist, &taglist) != 0) {