From: Peter Zijlstra <peterz@infradead.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Nathan Chancellor <natechancellor@gmail.com>,
clang-built-linux <clang-built-linux@googlegroups.com>,
x86@kernel.org, Arnd Bergmann <arnd@arndb.de>,
Sedat Dilek <sedat.dilek@gmail.com>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: [PATCH] objtool: Improve UACCESS coverage
Date: Wed, 24 Jul 2019 18:48:21 +0200 [thread overview]
Message-ID: <20190724164821.GB31425@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190724141040.GA31425@hirez.programming.kicks-ass.net>
On Wed, Jul 24, 2019 at 04:10:40PM +0200, Peter Zijlstra wrote:
> And that most certainly should trigger...
>
> Let me gdb that objtool thing.
---
Subject: objtool: Improve UACCESS coverage
A clang build reported an (obvious) double CLAC while a GCC build did
not; it turns out we only re-visit instructions if the first visit was
with AC=0. If OTOH the first visit was with AC=1, we completely ignore
any subsequent visit, even when it has AC=0.
Fix this by using a visited mask, instead of boolean and (explicitly)
mark the AC state.
$ ./objtool check -b --no-fp --retpoline --uaccess ../../defconfig-build/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o
../../defconfig-build/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: .altinstr_replacement+0x22: redundant UACCESS disable
../../defconfig-build/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: eb_copy_relocations.isra.34()+0xea: (alt)
../../defconfig-build/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: .altinstr_replacement+0xffffffffffffffff: (branch)
../../defconfig-build/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: eb_copy_relocations.isra.34()+0xd9: (alt)
../../defconfig-build/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: eb_copy_relocations.isra.34()+0xb2: (branch)
../../defconfig-build/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: eb_copy_relocations.isra.34()+0x39: (branch)
../../defconfig-build/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: eb_copy_relocations.isra.34()+0x0: <=== (func)
Reported-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reported-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
tools/objtool/check.c | 7 ++++---
tools/objtool/check.h | 3 ++-
2 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 5f26620f13f5..176f2f084060 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1946,6 +1946,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
struct alternative *alt;
struct instruction *insn, *next_insn;
struct section *sec;
+ u8 visited;
int ret;
insn = first;
@@ -1972,12 +1973,12 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
return 1;
}
+ visited = 1 << state.uaccess;
if (insn->visited) {
if (!insn->hint && !insn_state_match(insn, &state))
return 1;
- /* If we were here with AC=0, but now have AC=1, go again */
- if (insn->state.uaccess || !state.uaccess)
+ if (insn->visited & visited)
return 0;
}
@@ -2024,7 +2025,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
} else
insn->state = state;
- insn->visited = true;
+ insn->visited |= visited;
if (!insn->ignore_alts) {
bool skip_orig = false;
diff --git a/tools/objtool/check.h b/tools/objtool/check.h
index b881fafcf55d..6d875ca6fce0 100644
--- a/tools/objtool/check.h
+++ b/tools/objtool/check.h
@@ -33,8 +33,9 @@ struct instruction {
unsigned int len;
enum insn_type type;
unsigned long immediate;
- bool alt_group, visited, dead_end, ignore, hint, save, restore, ignore_alts;
+ bool alt_group, dead_end, ignore, hint, save, restore, ignore_alts;
bool retpoline_safe;
+ u8 visited;
struct symbol *call_dest;
struct instruction *jump_dest;
struct instruction *first_jump_src;
next prev parent reply other threads:[~2019-07-24 16:48 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-18 20:40 x86 - clang / objtool status Thomas Gleixner
2019-07-18 20:58 ` Nathan Chancellor
2019-07-19 6:39 ` Thomas Gleixner
2019-07-19 7:00 ` Arnd Bergmann
2019-07-19 7:03 ` Nathan Chancellor
2019-07-24 16:57 ` Nick Desaulniers
2019-07-18 22:42 ` Nick Desaulniers
2019-07-19 6:44 ` Thomas Gleixner
2019-07-19 11:37 ` Sedat Dilek
2019-07-19 13:48 ` Sedat Dilek
2019-07-22 15:40 ` Sedat Dilek
2019-07-25 6:17 ` Sedat Dilek
2019-07-24 2:43 ` Josh Poimboeuf
2019-07-24 7:47 ` Peter Zijlstra
2019-07-24 12:37 ` Josh Poimboeuf
2019-07-24 12:55 ` Josh Poimboeuf
2019-07-24 13:35 ` Peter Zijlstra
2019-07-24 14:05 ` Josh Poimboeuf
2019-07-24 14:10 ` Peter Zijlstra
2019-07-24 16:48 ` Peter Zijlstra [this message]
2019-07-24 16:54 ` [PATCH] objtool: Improve UACCESS coverage Nathan Chancellor
2019-07-24 16:55 ` Nick Desaulniers
2019-07-24 18:30 ` Sedat Dilek
2019-07-24 18:32 ` Sedat Dilek
2019-07-24 16:52 ` x86 - clang / objtool status Peter Zijlstra
2019-07-24 17:22 ` Nick Desaulniers
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190724164821.GB31425@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=arnd@arndb.de \
--cc=clang-built-linux@googlegroups.com \
--cc=jpoimboe@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=natechancellor@gmail.com \
--cc=ndesaulniers@google.com \
--cc=sedat.dilek@gmail.com \
--cc=tglx@linutronix.de \
--cc=torvalds@linux-foundation.org \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).