linux-kernel - [RFC][PATCH v5 49/51] objtool: mcount: Remove relocation size check

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Date:   Thu, 18 Jun 2020 13:38:35 -0700
From:   Matt Helsley <mhelsley@...are.com>
To:     <linux-kernel@...r.kernel.org>
CC:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Julien Thierry <jthierry@...hat.com>,
        Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
        Matt Helsley <mhelsley@...are.com>
Subject: [RFC][PATCH v5 49/51] objtool: mcount: Remove relocation size check

Rather than use the size of the relocations check the section
header type directly to see if the mcount relocations should
be rel or rela relocations.

Signed-off-by: Matt Helsley <mhelsley@...are.com>
---
 tools/objtool/elf.c    |  4 ++--
 tools/objtool/elf.h    |  2 +-
 tools/objtool/mcount.c | 15 +++++----------
 3 files changed, 8 insertions(+), 13 deletions(-)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 733e10d4a574..4948df31bba0 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -642,8 +642,8 @@ static int read_relocs(struct elf *elf)
 
 		sec->base->reloc = sec;
 		sec->mcountable = relocs_mcountable(sec);
-		if (sec->mcountable && !elf->mcount_rel_entsize)
-			elf->mcount_rel_entsize = sec->sh.sh_entsize;
+		if (sec->mcountable)
+			elf->mcount_r_addends = (sec->sh.sh_type == SHT_RELA);
 
 		nr_reloc = 0;
 		for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) {
diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h
index 8ece1ca79cca..f298e327af01 100644
--- a/tools/objtool/elf.h
+++ b/tools/objtool/elf.h
@@ -87,8 +87,8 @@ struct elf {
 	Elf *elf;
 	GElf_Ehdr ehdr;
 	int fd;
-	size_t mcount_rel_entsize;
 	bool changed;
+	bool mcount_r_addends;
 	char *name;
 	struct list_head sections;
 	DECLARE_HASHTABLE(symbol_hash, ELF_HASH_BITS);
diff --git a/tools/objtool/mcount.c b/tools/objtool/mcount.c
index 9527924af56b..084bbc02de0c 100644
--- a/tools/objtool/mcount.c
+++ b/tools/objtool/mcount.c
@@ -368,22 +368,17 @@ static void fill_mcount_locs(GElf_Sxword r_offset, GElf_Addr **rbuf,
 }
 
 /* Overall supervision for Elf32 ET_REL file. */
-static int do_mcount(unsigned const reltype, size_t rela_size)
+static int do_mcount(unsigned const reltype)
 {
-	GElf_Sxword r_offset = 0;
-
 	struct section *sec, *mlocs, *mrels;
 	const char * const mc_name =  "__mcount_loc";
-
-	const unsigned int rel_entsize = lf->mcount_rel_entsize;
+	GElf_Sxword r_offset = 0;
 	int result = -1;
-	bool is_rela;
+	const bool is_rela = lf->mcount_r_addends;
 
 	if (find_section_by_name(lf, "__mcount_loc") != NULL)
 		return 0;
 
-	is_rela = (rela_size == rel_entsize);
-
 	/* add section: __mcount_loc */
 	mlocs = elf_create_section(lf, mc_name, sizeof(GElf_Addr), 0);
 	if (!mlocs)
@@ -562,7 +557,7 @@ static int do_file(char const *const fname)
 			is_fake_mcount = MIPS_is_fake_mcount;
 		}
 		loc_size = 4;
-		rc = do_mcount(reltype, sizeof(Elf32_Rela));
+		rc = do_mcount(reltype);
 		break;
 	case ELFCLASS64: {
 		if (lf->ehdr.e_ehsize != sizeof(Elf64_Ehdr)
@@ -580,7 +575,7 @@ static int do_file(char const *const fname)
 			is_fake_mcount = MIPS_is_fake_mcount;
 		}
 		loc_size = 8;
-		rc = do_mcount(reltype, sizeof(Elf64_Rela));
+		rc = do_mcount(reltype);
 		break;
 	}
 	}  /* end switch */
-- 
2.20.1