linux-kernel - [RFC][PATCH 3/6] objtool: Rework rebuild

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Date:   Fri, 19 Feb 2021 21:43:03 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     jpoimboe@...hat.com, x86@...nel.org, pjt@...gle.com,
        mbenes@...e.cz, jgross@...e.com
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org
Subject: [RFC][PATCH 3/6] objtool: Rework rebuild_reloc logic

Instead of manually calling elf_rebuild_reloc_section() on sections
we've called elf_add_reloc() on, have elf_write() DTRT.

This makes it easier to add random relocations in places without
carefully tracking when we're done and need to flush what section.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 tools/objtool/check.c               |    3 ---
 tools/objtool/elf.c                 |   13 ++++++++++++-
 tools/objtool/include/objtool/elf.h |    2 +-
 tools/objtool/orc_gen.c             |    3 ---
 4 files changed, 13 insertions(+), 8 deletions(-)

--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -542,9 +542,6 @@ static int create_static_call_sections(s
 		idx++;
 	}
 
-	if (elf_rebuild_reloc_section(file->elf, reloc_sec))
-		return -1;
-
 	return 0;
 }
 
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -479,6 +479,8 @@ void elf_add_reloc(struct elf *elf, stru
 
 	list_add_tail(&reloc->list, &sec->reloc_list);
 	elf_hash_add(elf->reloc_hash, &reloc->hash, reloc_hash(reloc));
+
+	sec->rereloc = true;
 }
 
 static int read_rel_reloc(struct section *sec, int i, struct reloc *reloc, unsigned int *symndx)
@@ -558,7 +560,9 @@ static int read_relocs(struct elf *elf)
 				return -1;
 			}
 
-			elf_add_reloc(elf, reloc);
+			list_add_tail(&reloc->list, &sec->reloc_list);
+			elf_hash_add(elf->reloc_hash, &reloc->hash, reloc_hash(reloc));
+
 			nr_reloc++;
 		}
 		max_reloc = max(max_reloc, nr_reloc);
@@ -890,6 +894,8 @@ int elf_rebuild_reloc_section(struct elf
 	case SHT_RELA: return elf_rebuild_rela_reloc_section(sec, nr);
 	default:       return -1;
 	}
+
+	sec->rereloc = false;
 }
 
 int elf_write_insn(struct elf *elf, struct section *sec,
@@ -944,6 +950,11 @@ int elf_write(struct elf *elf)
 	struct section *sec;
 	Elf_Scn *s;
 
+	list_for_each_entry(sec, &elf->sections, list) {
+		if (sec->reloc && sec->reloc->rereloc)
+			elf_rebuild_reloc_section(elf, sec->reloc);
+	}
+
 	/* Update section headers for changed sections: */
 	list_for_each_entry(sec, &elf->sections, list) {
 		if (sec->changed) {
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -39,7 +39,7 @@ struct section {
 	char *name;
 	int idx;
 	unsigned int len;
-	bool changed, text, rodata, noinstr;
+	bool changed, text, rodata, noinstr, rereloc;
 };
 
 struct symbol {
--- a/tools/objtool/orc_gen.c
+++ b/tools/objtool/orc_gen.c
@@ -254,8 +254,5 @@ int orc_create(struct objtool_file *file
 			return -1;
 	}
 
-	if (elf_rebuild_reloc_section(file->elf, ip_rsec))
-		return -1;
-
 	return 0;
 }