linux-kernel - [RFC][PATCH 1/3] objtool: Clean up elf

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Date:   Fri, 12 Jun 2020 16:30:35 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org, dvyukov@...gle.com,
        elver@...gle.com, andreyknvl@...gle.com, mark.rutland@....com,
        mhelsley@...are.com, rostedt@...dmis.org, jthierry@...hat.com,
        mbenes@...e.cz, peterz@...radead.org
Subject: [RFC][PATCH 1/3] objtool: Clean up elf_write() condition

With there being multiple ways to change the ELF data, let's more
concisely track modification.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 tools/objtool/check.c |    2 ++
 tools/objtool/elf.c   |    8 +++++++-
 tools/objtool/elf.h   |    3 ++-
 3 files changed, 11 insertions(+), 2 deletions(-)

--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2779,7 +2779,9 @@ int check(const char *_objname, bool orc
 		ret = create_orc_sections(&file);
 		if (ret < 0)
 			goto out;
+	}
 
+	if (file.elf->changed) {
 		ret = elf_write(file.elf);
 		if (ret < 0)
 			goto out;
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -746,6 +746,8 @@ struct section *elf_create_section(struc
 	elf_hash_add(elf->section_hash, &sec->hash, sec->idx);
 	elf_hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name));
 
+	elf->changed = true;
+
 	return sec;
 }
 
@@ -862,7 +864,7 @@ int elf_rebuild_reloc_section(struct sec
 	return elf_rebuild_rela_section(sec, nr);
 }
 
-int elf_write(const struct elf *elf)
+int elf_write(struct elf *elf)
 {
 	struct section *sec;
 	Elf_Scn *s;
@@ -879,6 +881,8 @@ int elf_write(const struct elf *elf)
 				WARN_ELF("gelf_update_shdr");
 				return -1;
 			}
+
+			sec->changed = false;
 		}
 	}
 
@@ -891,6 +895,8 @@ int elf_write(const struct elf *elf)
 		return -1;
 	}
 
+	elf->changed = false;
+
 	return 0;
 }
 
--- a/tools/objtool/elf.h
+++ b/tools/objtool/elf.h
@@ -79,6 +79,7 @@ struct elf {
 	Elf *elf;
 	GElf_Ehdr ehdr;
 	int fd;
+	bool changed;
 	char *name;
 	struct list_head sections;
 	DECLARE_HASHTABLE(symbol_hash, ELF_HASH_BITS);
@@ -121,7 +122,7 @@ struct elf *elf_open_read(const char *na
 struct section *elf_create_section(struct elf *elf, const char *name, size_t entsize, int nr);
 struct section *elf_create_reloc_section(struct elf *elf, struct section *base, int reltype);
 void elf_add_reloc(struct elf *elf, struct reloc *reloc);
-int elf_write(const struct elf *elf);
+int elf_write(struct elf *elf);
 void elf_close(struct elf *elf);
 
 struct section *find_section_by_name(const struct elf *elf, const char *name);