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Message-ID: <tip-17bc33914bcc98ba3c6b426fd1c49587a25c0597@git.kernel.org>
Date: Tue, 30 Jan 2018 06:13:17 -0800
From: tip-bot for Josh Poimboeuf <tipbot@...or.com>
To: linux-tip-commits@...r.kernel.org
Cc: bp@...en8.de, gregkh@...uxfoundation.org, jpoimboe@...hat.com,
linux@...ck-us.net, linux-kernel@...r.kernel.org,
dwmw2@...radead.org, jgross@...e.com,
torvalds@...ux-foundation.org, luto@...nel.org, tglx@...utronix.de,
hpa@...or.com, mingo@...nel.org, dave.hansen@...ux.intel.com,
peterz@...radead.org
Subject: [tip:x86/pti] objtool: Add support for alternatives at the end of a
section
Commit-ID: 17bc33914bcc98ba3c6b426fd1c49587a25c0597
Gitweb: https://git.kernel.org/tip/17bc33914bcc98ba3c6b426fd1c49587a25c0597
Author: Josh Poimboeuf <jpoimboe@...hat.com>
AuthorDate: Mon, 29 Jan 2018 22:00:40 -0600
Committer: Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 30 Jan 2018 15:09:17 +0100
objtool: Add support for alternatives at the end of a section
Now that the previous patch gave objtool the ability to read retpoline
alternatives, it shows a new warning:
arch/x86/entry/entry_64.o: warning: objtool: .entry_trampoline: don't know how to handle alternatives at end of section
This is due to the JMP_NOSPEC in entry_SYSCALL_64_trampoline().
Previously, objtool ignored this situation because it wasn't needed, and
it would have required a bit of extra code. Now that this case exists,
add proper support for it.
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: David Woodhouse <dwmw2@...radead.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Guenter Roeck <linux@...ck-us.net>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Juergen Gross <jgross@...e.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/2a30a3c2158af47d891a76e69bb1ef347e0443fd.1517284349.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
tools/objtool/check.c | 53 ++++++++++++++++++++++++++++++---------------------
1 file changed, 31 insertions(+), 22 deletions(-)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index bc3490d..9cd028a 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -594,7 +594,7 @@ static int handle_group_alt(struct objtool_file *file,
struct instruction *orig_insn,
struct instruction **new_insn)
{
- struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump;
+ struct instruction *last_orig_insn, *last_new_insn, *insn, *fake_jump = NULL;
unsigned long dest_off;
last_orig_insn = NULL;
@@ -610,28 +610,30 @@ static int handle_group_alt(struct objtool_file *file,
last_orig_insn = insn;
}
- if (!next_insn_same_sec(file, last_orig_insn)) {
- WARN("%s: don't know how to handle alternatives at end of section",
- special_alt->orig_sec->name);
- return -1;
- }
-
- fake_jump = malloc(sizeof(*fake_jump));
- if (!fake_jump) {
- WARN("malloc failed");
- return -1;
+ if (next_insn_same_sec(file, last_orig_insn)) {
+ fake_jump = malloc(sizeof(*fake_jump));
+ if (!fake_jump) {
+ WARN("malloc failed");
+ return -1;
+ }
+ memset(fake_jump, 0, sizeof(*fake_jump));
+ INIT_LIST_HEAD(&fake_jump->alts);
+ clear_insn_state(&fake_jump->state);
+
+ fake_jump->sec = special_alt->new_sec;
+ fake_jump->offset = -1;
+ fake_jump->type = INSN_JUMP_UNCONDITIONAL;
+ fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
+ fake_jump->ignore = true;
}
- memset(fake_jump, 0, sizeof(*fake_jump));
- INIT_LIST_HEAD(&fake_jump->alts);
- clear_insn_state(&fake_jump->state);
-
- fake_jump->sec = special_alt->new_sec;
- fake_jump->offset = -1;
- fake_jump->type = INSN_JUMP_UNCONDITIONAL;
- fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
- fake_jump->ignore = true;
if (!special_alt->new_len) {
+ if (!fake_jump) {
+ WARN("%s: empty alternative at end of section",
+ special_alt->orig_sec->name);
+ return -1;
+ }
+
*new_insn = fake_jump;
return 0;
}
@@ -654,8 +656,14 @@ static int handle_group_alt(struct objtool_file *file,
continue;
dest_off = insn->offset + insn->len + insn->immediate;
- if (dest_off == special_alt->new_off + special_alt->new_len)
+ if (dest_off == special_alt->new_off + special_alt->new_len) {
+ if (!fake_jump) {
+ WARN("%s: alternative jump to end of section",
+ special_alt->orig_sec->name);
+ return -1;
+ }
insn->jump_dest = fake_jump;
+ }
if (!insn->jump_dest) {
WARN_FUNC("can't find alternative jump destination",
@@ -670,7 +678,8 @@ static int handle_group_alt(struct objtool_file *file,
return -1;
}
- list_add(&fake_jump->list, &last_new_insn->list);
+ if (fake_jump)
+ list_add(&fake_jump->list, &last_new_insn->list);
return 0;
}
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