elf: Add _dl_audit_symbind_alt and _dl_audit_symbind

It consolidates the code required to call la_symbind{32,64} audit
callback.

Checked on x86_64-linux-gnu, i686-linux-gnu, and aarch64-linux-gnu.

Reviewed-by: Florian Weimer <fweimer@redhat.com>

1 files changed, 122 insertions, 0 deletions

diff --git a/elf/dl-audit.c b/elf/dl-audit.c
index cb1c3de..a21530f 100644
--- a/elf/dl-audit.c
+++ b/elf/dl-audit.c
@@ -16,6 +16,7 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
+#include <assert.h>
 #include <ldsodefs.h>
 
 void
@@ -106,3 +107,124 @@ _dl_audit_objclose (struct link_map *l)
       afct = afct->next;
     }
 }
+
+void
+_dl_audit_symbind_alt (struct link_map *l, const ElfW(Sym) *ref, void **value,
+		       lookup_t result)
+{
+  if ((l->l_audit_any_plt | result->l_audit_any_plt) == 0)
+    return;
+
+  const char *strtab = (const char *) D_PTR (result, l_info[DT_STRTAB]);
+  /* Compute index of the symbol entry in the symbol table of the DSO with
+     the definition.  */
+  unsigned int ndx = (ref - (ElfW(Sym) *) D_PTR (result, l_info[DT_SYMTAB]));
+
+  unsigned int altvalue = 0;
+  /* Synthesize a symbol record where the st_value field is the result.  */
+  ElfW(Sym) sym = *ref;
+  sym.st_value = (ElfW(Addr)) *value;
+
+  struct audit_ifaces *afct = GLRO(dl_audit);
+  for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
+    {
+      struct auditstate *match_audit = link_map_audit_state (l, cnt);
+      struct auditstate *result_audit = link_map_audit_state (result, cnt);
+      if (afct->symbind != NULL
+	  && ((match_audit->bindflags & LA_FLG_BINDFROM) != 0
+	      || ((result_audit->bindflags & LA_FLG_BINDTO)
+		  != 0)))
+	{
+	  unsigned int flags = altvalue | LA_SYMB_DLSYM;
+	  uintptr_t new_value = afct->symbind (&sym, ndx,
+					       &match_audit->cookie,
+					       &result_audit->cookie,
+					       &flags, strtab + ref->st_name);
+	  if (new_value != (uintptr_t) sym.st_value)
+	    {
+	      altvalue = LA_SYMB_ALTVALUE;
+	      sym.st_value = new_value;
+	    }
+
+	  afct = afct->next;
+	}
+
+      *value = (void *) sym.st_value;
+    }
+}
+rtld_hidden_def (_dl_audit_symbind_alt)
+
+void
+_dl_audit_symbind (struct link_map *l, struct reloc_result *reloc_result,
+		   const ElfW(Sym) *defsym, DL_FIXUP_VALUE_TYPE *value,
+		   lookup_t result)
+{
+  reloc_result->bound = result;
+  /* Compute index of the symbol entry in the symbol table of the DSO with the
+     definition.  */
+  reloc_result->boundndx = (defsym - (ElfW(Sym) *) D_PTR (result,
+							  l_info[DT_SYMTAB]));
+
+  if ((l->l_audit_any_plt | result->l_audit_any_plt) == 0)
+    {
+      /* Set all bits since this symbol binding is not interesting.  */
+      reloc_result->enterexit = (1u << DL_NNS) - 1;
+      return;
+    }
+
+  /* Synthesize a symbol record where the st_value field is the result.  */
+  ElfW(Sym) sym = *defsym;
+  sym.st_value = DL_FIXUP_VALUE_ADDR (*value);
+
+  /* Keep track whether there is any interest in tracing the call in the lower
+     two bits.  */
+  assert (DL_NNS * 2 <= sizeof (reloc_result->flags) * 8);
+  assert ((LA_SYMB_NOPLTENTER | LA_SYMB_NOPLTEXIT) == 3);
+  reloc_result->enterexit = LA_SYMB_NOPLTENTER | LA_SYMB_NOPLTEXIT;
+
+  const char *strtab2 = (const void *) D_PTR (result, l_info[DT_STRTAB]);
+
+  unsigned int flags = 0;
+  struct audit_ifaces *afct = GLRO(dl_audit);
+  for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
+    {
+      /* XXX Check whether both DSOs must request action or only one */
+      struct auditstate *l_state = link_map_audit_state (l, cnt);
+      struct auditstate *result_state = link_map_audit_state (result, cnt);
+      if ((l_state->bindflags & LA_FLG_BINDFROM) != 0
+	  && (result_state->bindflags & LA_FLG_BINDTO) != 0)
+	{
+	  if (afct->symbind != NULL)
+	    {
+	      uintptr_t new_value = afct->symbind (&sym,
+						   reloc_result->boundndx,
+						   &l_state->cookie,
+						   &result_state->cookie,
+						   &flags,
+						   strtab2 + defsym->st_name);
+	      if (new_value != (uintptr_t) sym.st_value)
+		{
+		  flags |= LA_SYMB_ALTVALUE;
+		  sym.st_value = new_value;
+		}
+	    }
+
+	  /* Remember the results for every audit library and store a summary
+	     in the first two bits.  */
+	  reloc_result->enterexit &= flags & (LA_SYMB_NOPLTENTER
+					      | LA_SYMB_NOPLTEXIT);
+	  reloc_result->enterexit |= ((flags & (LA_SYMB_NOPLTENTER
+						| LA_SYMB_NOPLTEXIT))
+				      << ((cnt + 1) * 2));
+	}
+      else
+	/* If the bind flags say this auditor is not interested, set the bits
+	   manually.  */
+	reloc_result->enterexit |= ((LA_SYMB_NOPLTENTER | LA_SYMB_NOPLTEXIT)
+				    << ((cnt + 1) * 2));
+      afct = afct->next;
+    }
+
+  reloc_result->flags = flags;
+  *value = DL_FIXUP_ADDR_VALUE (sym.st_value);
+}