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Subject[PATCH v2.1 01-B/14] objtool: Uniquely identify alternative instruction groups
Subject: objtool: Uniquely identify alternative instruction groups
From: Alexandre Chartre <alexandre.chartre@oracle.com>
Date: Tue, 14 Apr 2020 12:36:11 +0200

From: Alexandre Chartre <alexandre.chartre@oracle.com>

Assign a unique identifier to every alternative instruction group in
order to be able to tell which instructions belong to what
alternative.

[peterz: extracted from a larger patch]
Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
tools/objtool/check.c | 26 ++++++++++++++++++++------
tools/objtool/check.h | 3 ++-
2 files changed, 22 insertions(+), 7 deletions(-)

--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -770,7 +770,9 @@ static int handle_group_alt(struct objto
struct instruction *orig_insn,
struct instruction **new_insn)
{
+ static unsigned int alt_group_next_index = 1;
struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL;
+ unsigned int alt_group = alt_group_next_index++;
unsigned long dest_off;

last_orig_insn = NULL;
@@ -779,7 +781,7 @@ static int handle_group_alt(struct objto
if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
break;

- insn->alt_group = true;
+ insn->alt_group = alt_group;
last_orig_insn = insn;
}

@@ -813,6 +815,7 @@ static int handle_group_alt(struct objto
}

last_new_insn = NULL;
+ alt_group = alt_group_next_index++;
insn = *new_insn;
sec_for_each_insn_from(file, insn) {
if (insn->offset >= special_alt->new_off + special_alt->new_len)
@@ -822,6 +825,7 @@ static int handle_group_alt(struct objto

insn->ignore = orig_insn->ignore_alts;
insn->func = orig_insn->func;
+ insn->alt_group = alt_group;

/*
* Since alternative replacement code is copy/pasted by the
--- a/tools/objtool/check.h
+++ b/tools/objtool/check.h
@@ -30,12 +30,13 @@ struct instruction {
unsigned int len;
enum insn_type type;
unsigned long immediate;
- bool alt_group, dead_end, ignore, ignore_alts;
+ bool dead_end, ignore, ignore_alts;
bool hint;
bool retpoline_safe;
s8 instr;
u8 visited;
u8 ret_offset;
+ int alt_group;
struct symbol *call_dest;
struct instruction *jump_dest;
struct instruction *first_jump_src;
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