svn commit: r313504 - head/cddl/contrib/opensolaris/lib/libdtrace/common

[Mark Johnston]

Author: markj
Date: Fri Feb 10 02:01:32 2017
New Revision: 313504
URL: https://svnweb.freebsd.org/changeset/base/313504

Log:
  When patching USDT probes, use non-unique names for aliases of weak symbols.
  
  Aliases are normally given names that include a key that's unique for each
  input object file. This, for example, ensures that aliases for identically
  named local symbols in different object files don't conflict. However, in
  some cases the static linker will leave an undefined alias after merging
  identical weak symbols, resulting in a link error. A non-unique name allows
  the aliases to be merged as well.
  
  PR:		216871
  X-MFC With:	r313262

Modified:
  head/cddl/contrib/opensolaris/lib/libdtrace/common/dt_link.c

Modified: head/cddl/contrib/opensolaris/lib/libdtrace/common/dt_link.c
==============================================================================
--- head/cddl/contrib/opensolaris/lib/libdtrace/common/dt_link.c	Fri Feb 10 01:59:35 2017	(r313503)
+++ head/cddl/contrib/opensolaris/lib/libdtrace/common/dt_link.c	Fri Feb 10 02:01:32 2017	(r313504)
@@ -261,7 +261,7 @@ printf("%s:%s(%d): DOODAD\n",__FUNCTION_
 			sym->st_value = 0;
 			sym->st_size = 0;
 			sym->st_info = ELF32_ST_INFO(STB_GLOBAL, STT_FUNC);
-			sym->st_other = ELF32_ST_VISIBILITY(STV_HIDDEN);
+			sym->st_other = 0;
 			sym->st_shndx = SHN_UNDEF;
 
 			rel++;
@@ -445,7 +445,7 @@ prepare_elf64(dtrace_hdl_t *dtp, const d
 			sym->st_value = 0;
 			sym->st_size = 0;
 			sym->st_info = GELF_ST_INFO(STB_GLOBAL, STT_FUNC);
-			sym->st_other = ELF64_ST_VISIBILITY(STV_HIDDEN);
+			sym->st_other = 0;
 			sym->st_shndx = SHN_UNDEF;
 
 			rel++;
@@ -1187,6 +1187,7 @@ process_obj(dtrace_hdl_t *dtp, const cha
 	static const char dt_enabled[] = "enabled";
 	static const char dt_symprefix[] = "$dtrace";
 	static const char dt_symfmt[] = "%s%ld.%s";
+	static const char dt_weaksymfmt[] = "%s.%s";
 	char probename[DTRACE_NAMELEN];
 	int fd, i, ndx, eprobe, mod = 0;
 	Elf *elf = NULL;
@@ -1548,44 +1549,46 @@ process_obj(dtrace_hdl_t *dtp, const cha
 
 			if (dt_symtab_lookup(data_sym, osym, isym,
 			    rela.r_offset, shdr_rel.sh_info, &fsym,
-			    (emachine1 == EM_PPC64), elf) != 0 &&
-			    dt_symtab_lookup(data_sym, 0, osym,
+			    (emachine1 == EM_PPC64), elf) == 0) {
+				if (fsym.st_name > data_str->d_size)
+					goto err;
+
+				r = s = (char *) data_str->d_buf + fsym.st_name;
+				assert(strstr(s, dt_symprefix) == s);
+				s = strchr(s, '.') + 1;
+			} else if (dt_symtab_lookup(data_sym, 0, osym,
 			    rela.r_offset, shdr_rel.sh_info, &fsym,
-			    (emachine1 == EM_PPC64), elf) != 0)
-				goto err;
-
-			if (fsym.st_name > data_str->d_size)
-				goto err;
+			    (emachine1 == EM_PPC64), elf) == 0) {
+				u_int bind;
 
-			assert(GELF_ST_TYPE(fsym.st_info) == STT_FUNC);
-
-			/*
-			 * If this is our first time encountering this symbol,
-			 * emit an alias.
-			 */
-			s = (char *)data_str->d_buf + fsym.st_name;
-
-			if (strncmp(s, dt_symprefix,
-			    sizeof (dt_symprefix) - 1) != 0) {
-				u_int bind = GELF_ST_BIND(fsym.st_info);
+				bind = GELF_ST_BIND(fsym.st_info) == STB_WEAK ?
+				    STB_WEAK : STB_GLOBAL;
 
+				/*
+				 * Emit an alias for the symbol. It needs to be
+				 * non-preemptible so that .SUNW_dof relocations
+				 * may be resolved at static link time. Aliases
+				 * of weak symbols are given a non-unique name
+				 * so that they may be merged by the linker.
+				 */
 				dsym = fsym;
 				dsym.st_name = istr;
-				dsym.st_info = GELF_ST_INFO(bind == STB_LOCAL ?
-				    STB_GLOBAL : bind, STT_FUNC);
+				dsym.st_info = GELF_ST_INFO(bind, STT_FUNC);
 				dsym.st_other = GELF_ST_VISIBILITY(STV_HIDDEN);
 				(void) gelf_update_sym(data_sym, isym, &dsym);
 				r = (char *) data_str->d_buf + istr;
-				istr += 1 + sprintf(r, dt_symfmt, dt_symprefix, objkey,
-				    s);
+				s = (char *) data_str->d_buf + fsym.st_name;
+				if (bind == STB_WEAK)
+					istr += sprintf(r, dt_weaksymfmt,
+					    dt_symprefix, s);
+				else
+					istr += sprintf(r, dt_symfmt,
+					    dt_symprefix, objkey, s);
+				istr++;
 				isym++;
 				assert(isym <= nsym);
-			} else {
-				r = s;
-				s = strchr(s, '.');
-				assert(s != NULL);
-				s++;
-			}
+			} else
+				goto err;
 
 			if ((pvp = dt_provider_lookup(dtp, pname)) == NULL) {
 				return (dt_link_error(dtp, elf, fd, bufs,