Fix a segfault that occurs when built with Clang.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'objtool-urgent-2020-12-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull objtool fix from Ingo Molnar:
 "Fix a segfault that occurs when built with Clang"

* tag 'objtool-urgent-2020-12-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  objtool: Fix seg fault with Clang non-section symbols

tools/objtool/check.c

@@ -467,13 +467,20 @@ static int create_static_call_sections(struct objtool_file *file)
 
 		/* populate reloc for 'addr' */
 		reloc = malloc(sizeof(*reloc));
+
 		if (!reloc) {
 			perror("malloc");
 			return -1;
 		}
 		memset(reloc, 0, sizeof(*reloc));
-		reloc->sym = insn->sec->sym;
-		reloc->addend = insn->offset;
+
+		insn_to_reloc_sym_addend(insn->sec, insn->offset, reloc);
+		if (!reloc->sym) {
+			WARN_FUNC("static call tramp: missing containing symbol",
+				  insn->sec, insn->offset);
+			return -1;
+		}
+
 		reloc->type = R_X86_64_PC32;
 		reloc->offset = idx * sizeof(struct static_call_site);
 		reloc->sec = reloc_sec;

tools/objtool/elf.c

@@ -262,6 +262,32 @@ struct reloc *find_reloc_by_dest(const struct elf *elf, struct section *sec, uns
 	return find_reloc_by_dest_range(elf, sec, offset, 1);
 }
 
+void insn_to_reloc_sym_addend(struct section *sec, unsigned long offset,
+			      struct reloc *reloc)
+{
+	if (sec->sym) {
+		reloc->sym = sec->sym;
+		reloc->addend = offset;
+		return;
+	}
+
+	/*
+	 * The Clang assembler strips section symbols, so we have to reference
+	 * the function symbol instead:
+	 */
+	reloc->sym = find_symbol_containing(sec, offset);
+	if (!reloc->sym) {
+		/*
+		 * Hack alert.  This happens when we need to reference the NOP
+		 * pad insn immediately after the function.
+		 */
+		reloc->sym = find_symbol_containing(sec, offset - 1);
+	}
+
+	if (reloc->sym)
+		reloc->addend = offset - reloc->sym->offset;
+}
+
 static int read_sections(struct elf *elf)
 {
 	Elf_Scn *s = NULL;

tools/objtool/elf.h

@@ -140,6 +140,8 @@ struct reloc *find_reloc_by_dest(const struct elf *elf, struct section *sec, uns
 struct reloc *find_reloc_by_dest_range(const struct elf *elf, struct section *sec,
 				     unsigned long offset, unsigned int len);
 struct symbol *find_func_containing(struct section *sec, unsigned long offset);
+void insn_to_reloc_sym_addend(struct section *sec, unsigned long offset,
+			      struct reloc *reloc);
 int elf_rebuild_reloc_section(struct elf *elf, struct section *sec);
 
 #define for_each_sec(file, sec)						\

tools/objtool/orc_gen.c

@@ -105,30 +105,11 @@ static int create_orc_entry(struct elf *elf, struct section *u_sec, struct secti
 	}
 	memset(reloc, 0, sizeof(*reloc));
 
-	if (insn_sec->sym) {
-		reloc->sym = insn_sec->sym;
-		reloc->addend = insn_off;
-	} else {
-		/*
-		 * The Clang assembler doesn't produce section symbols, so we
-		 * have to reference the function symbol instead:
-		 */
-		reloc->sym = find_symbol_containing(insn_sec, insn_off);
-		if (!reloc->sym) {
-			/*
-			 * Hack alert.  This happens when we need to reference
-			 * the NOP pad insn immediately after the function.
-			 */
-			reloc->sym = find_symbol_containing(insn_sec,
-							   insn_off - 1);
-		}
-		if (!reloc->sym) {
-			WARN("missing symbol for insn at offset 0x%lx\n",
-			     insn_off);
-			return -1;
-		}
-
-		reloc->addend = insn_off - reloc->sym->offset;
+	insn_to_reloc_sym_addend(insn_sec, insn_off, reloc);
+	if (!reloc->sym) {
+		WARN("missing symbol for insn at offset 0x%lx",
+		     insn_off);
+		return -1;
 	}
 
 	reloc->type = R_X86_64_PC32;