linux-kernel - [PATCH 2/5] objtool: Support Clang non-section symbols in ORC dump

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Message-Id: <b811b5eb1a42602c3b523576dc5efab9ad1c174d.1585761021.git.jpoimboe@redhat.com>
Date:   Wed,  1 Apr 2020 13:23:26 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Julien Thierry <jthierry@...hat.com>
Subject: [PATCH 2/5] objtool: Support Clang non-section symbols in ORC dump

Historically, the relocation symbols for ORC entries have only been
section symbols:

  .text+0: sp:sp+8 bp:(und) type:call end:0

However, the Clang assembler is aggressive about stripping section
symbols.  In that case we will need to use function symbols:

  freezing_slow_path+0: sp:sp+8 bp:(und) type:call end:0

In preparation for the generation of such entries in "objtool orc
generate", add support for reading them in "objtool orc dump".

Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 tools/objtool/orc_dump.c | 44 ++++++++++++++++++++++++----------------
 1 file changed, 27 insertions(+), 17 deletions(-)

diff --git a/tools/objtool/orc_dump.c b/tools/objtool/orc_dump.c
index 13ccf775a83a..ba4cbb1cdd63 100644
--- a/tools/objtool/orc_dump.c
+++ b/tools/objtool/orc_dump.c
@@ -66,7 +66,7 @@ int orc_dump(const char *_objname)
 	char *name;
 	size_t nr_sections;
 	Elf64_Addr orc_ip_addr = 0;
-	size_t shstrtab_idx;
+	size_t shstrtab_idx, strtab_idx = 0;
 	Elf *elf;
 	Elf_Scn *scn;
 	GElf_Shdr sh;
@@ -127,6 +127,8 @@ int orc_dump(const char *_objname)
 
 		if (!strcmp(name, ".symtab")) {
 			symtab = data;
+		} else if (!strcmp(name, ".strtab")) {
+			strtab_idx = i;
 		} else if (!strcmp(name, ".orc_unwind")) {
 			orc = data->d_buf;
 			orc_size = sh.sh_size;
@@ -138,7 +140,7 @@ int orc_dump(const char *_objname)
 		}
 	}
 
-	if (!symtab || !orc || !orc_ip)
+	if (!symtab || !strtab_idx || !orc || !orc_ip)
 		return 0;
 
 	if (orc_size % sizeof(*orc) != 0) {
@@ -159,21 +161,29 @@ int orc_dump(const char *_objname)
 				return -1;
 			}
 
-			scn = elf_getscn(elf, sym.st_shndx);
-			if (!scn) {
-				WARN_ELF("elf_getscn");
-				return -1;
-			}
-
-			if (!gelf_getshdr(scn, &sh)) {
-				WARN_ELF("gelf_getshdr");
-				return -1;
-			}
-
-			name = elf_strptr(elf, shstrtab_idx, sh.sh_name);
-			if (!name || !*name) {
-				WARN_ELF("elf_strptr");
-				return -1;
+			if (GELF_ST_TYPE(sym.st_info) == STT_SECTION) {
+				scn = elf_getscn(elf, sym.st_shndx);
+				if (!scn) {
+					WARN_ELF("elf_getscn");
+					return -1;
+				}
+
+				if (!gelf_getshdr(scn, &sh)) {
+					WARN_ELF("gelf_getshdr");
+					return -1;
+				}
+
+				name = elf_strptr(elf, shstrtab_idx, sh.sh_name);
+				if (!name) {
+					WARN_ELF("elf_strptr");
+					return -1;
+				}
+			} else {
+				name = elf_strptr(elf, strtab_idx, sym.st_name);
+				if (!name) {
+					WARN_ELF("elf_strptr");
+					return -1;
+				}
 			}
 
 			printf("%s+%llx:", name, (unsigned long long)rela.r_addend);
-- 
2.21.1