[tip: x86/core] objtool: Cache instruction relocs

[tip-bot2 for Peter Zijlstra]

The following commit has been merged into the x86/core branch of tip:

Commit-ID:     7bd2a600f3e9d27286bbf23c83d599e9cc7cf245
Gitweb:        https://git.kernel.org/tip/7bd2a600f3e9d27286bbf23c83d599e9cc7cf245
Author:        Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate:    Fri, 26 Mar 2021 16:12:13 +01:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Fri, 02 Apr 2021 12:46:15 +02:00

objtool: Cache instruction relocs

Track the reloc of instructions in the new instruction->reloc field
to avoid having to look them up again later.

( Technically x86 instructions can have two relocations, but not jumps
  and calls, for which we're using this. )

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Reviewed-by: Miroslav Benes <mbenes@xxxxxxx>
Link: https://lkml.kernel.org/r/20210326151300.195441549@xxxxxxxxxxxxx
---
 tools/objtool/check.c                 | 28 ++++++++++++++++++++------
 tools/objtool/include/objtool/check.h |  1 +-
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 77074db..1f4154f 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -797,6 +797,25 @@ __weak bool arch_is_retpoline(struct symbol *sym)
 	return false;
 }
 
+#define NEGATIVE_RELOC	((void *)-1L)
+
+static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
+{
+	if (insn->reloc == NEGATIVE_RELOC)
+		return NULL;
+
+	if (!insn->reloc) {
+		insn->reloc = find_reloc_by_dest_range(file->elf, insn->sec,
+						       insn->offset, insn->len);
+		if (!insn->reloc) {
+			insn->reloc = NEGATIVE_RELOC;
+			return NULL;
+		}
+	}
+
+	return insn->reloc;
+}
+
 /*
  * Find the destination instructions for all jumps.
  */
@@ -811,8 +830,7 @@ static int add_jump_destinations(struct objtool_file *file)
 		if (!is_static_jump(insn))
 			continue;
 
-		reloc = find_reloc_by_dest_range(file->elf, insn->sec,
-						 insn->offset, insn->len);
+		reloc = insn_reloc(file, insn);
 		if (!reloc) {
 			dest_sec = insn->sec;
 			dest_off = arch_jump_destination(insn);
@@ -944,8 +962,7 @@ static int add_call_destinations(struct objtool_file *file)
 		if (insn->type != INSN_CALL)
 			continue;
 
-		reloc = find_reloc_by_dest_range(file->elf, insn->sec,
-					       insn->offset, insn->len);
+		reloc = insn_reloc(file, insn);
 		if (!reloc) {
 			dest_off = arch_jump_destination(insn);
 			insn->call_dest = find_call_destination(insn->sec, dest_off);
@@ -1144,8 +1161,7 @@ static int handle_group_alt(struct objtool_file *file,
 		 * alternatives code can adjust the relative offsets
 		 * accordingly.
 		 */
-		alt_reloc = find_reloc_by_dest_range(file->elf, insn->sec,
-						   insn->offset, insn->len);
+		alt_reloc = insn_reloc(file, insn);
 		if (alt_reloc &&
 		    !arch_support_alt_relocation(special_alt, insn, alt_reloc)) {
 
diff --git a/tools/objtool/include/objtool/check.h b/tools/objtool/include/objtool/check.h
index e5528ce..56d50bc 100644
--- a/tools/objtool/include/objtool/check.h
+++ b/tools/objtool/include/objtool/check.h
@@ -56,6 +56,7 @@ struct instruction {
 	struct instruction *jump_dest;
 	struct instruction *first_jump_src;
 	struct reloc *jump_table;
+	struct reloc *reloc;
 	struct list_head alts;
 	struct symbol *func;
 	struct list_head stack_ops;