* [tip: objtool/core] objtool: Support stack-swizzle
@ 2021-02-10 20:01 tip-bot2 for Peter Zijlstra
2021-02-18 16:21 ` [PATCH] objtool: Fix stack-swizzle for FRAME_POINTER=y Peter Zijlstra
0 siblings, 1 reply; 5+ messages in thread
From: tip-bot2 for Peter Zijlstra @ 2021-02-10 20:01 UTC (permalink / raw)
To: linux-tip-commits
Cc: Peter Zijlstra (Intel),
Miroslav Benes, Josh Poimboeuf, x86, linux-kernel
The following commit has been merged into the objtool/core branch of tip:
Commit-ID: aafeb14e9da29e323b0605f8f1bae0d45d5f3acf
Gitweb: https://git.kernel.org/tip/aafeb14e9da29e323b0605f8f1bae0d45d5f3acf
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Wed, 03 Feb 2021 12:02:17 +01:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Wed, 10 Feb 2021 20:53:52 +01:00
objtool: Support stack-swizzle
Natively support the stack swizzle pattern:
mov %rsp, (%[tos])
mov %[tos], %rsp
...
pop %rsp
It uses the vals[] array to link the first two stack-ops, and detect
the SP to SP_INDIRECT swizzle.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
tools/objtool/check.c | 45 ++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 45 insertions(+)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 5f056dd..62cd211 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1945,6 +1945,38 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi,
cfa->offset = -cfi->vals[op->src.reg].offset;
cfi->stack_size = cfa->offset;
+ } else if (cfa->base == CFI_SP &&
+ cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
+ cfi->vals[op->src.reg].offset == cfa->offset) {
+
+ /*
+ * Stack swizzle:
+ *
+ * 1: mov %rsp, (%[tos])
+ * 2: mov %[tos], %rsp
+ * ...
+ * 3: pop %rsp
+ *
+ * Where:
+ *
+ * 1 - places a pointer to the previous
+ * stack at the Top-of-Stack of the
+ * new stack.
+ *
+ * 2 - switches to the new stack.
+ *
+ * 3 - pops the Top-of-Stack to restore
+ * the original stack.
+ *
+ * Note: we set base to SP_INDIRECT
+ * here and preserve offset. Therefore
+ * when the unwinder reaches ToS it
+ * will dereference SP and then add the
+ * offset to find the next frame, IOW:
+ * (%rsp) + offset.
+ */
+ cfa->base = CFI_SP_INDIRECT;
+
} else {
cfa->base = CFI_UNDEFINED;
cfa->offset = 0;
@@ -2047,6 +2079,13 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi,
case OP_SRC_POP:
case OP_SRC_POPF:
+ if (op->dest.reg == CFI_SP && cfa->base == CFI_SP_INDIRECT) {
+
+ /* pop %rsp; # restore from a stack swizzle */
+ cfa->base = CFI_SP;
+ break;
+ }
+
if (!cfi->drap && op->dest.reg == cfa->base) {
/* pop %rbp */
@@ -2193,6 +2232,12 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi,
/* mov reg, disp(%rsp) */
save_reg(cfi, op->src.reg, CFI_CFA,
op->dest.offset - cfi->stack_size);
+
+ } else if (op->src.reg == CFI_SP && op->dest.offset == 0) {
+
+ /* mov %rsp, (%reg); # setup a stack swizzle. */
+ cfi->vals[op->dest.reg].base = CFI_SP_INDIRECT;
+ cfi->vals[op->dest.reg].offset = cfa->offset;
}
break;
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH] objtool: Fix stack-swizzle for FRAME_POINTER=y
2021-02-10 20:01 [tip: objtool/core] objtool: Support stack-swizzle tip-bot2 for Peter Zijlstra
@ 2021-02-18 16:21 ` Peter Zijlstra
2021-02-18 17:53 ` Josh Poimboeuf
` (2 more replies)
0 siblings, 3 replies; 5+ messages in thread
From: Peter Zijlstra @ 2021-02-18 16:21 UTC (permalink / raw)
To: linux-kernel; +Cc: linux-tip-commits, Miroslav Benes, Josh Poimboeuf, x86
On Wed, Feb 10, 2021 at 08:01:23PM -0000, tip-bot2 for Peter Zijlstra wrote:
> objtool: Support stack-swizzle
---
Subject: objtool: Fix stack-swizzle for FRAME_POINTER=y
From: Peter Zijlstra <peterz@infradead.org>
Date: Thu Feb 18 17:14:10 CET 2021
When objtool encounters the stack-swizzle:
mov %rsp, (%[tos])
mov %[tos], %rsp
...
pop %rsp
Inside a FRAME_POINTER=y build, things go a little screwy because
clearly we're not adjusting the cfa->base. This then results in the
pop %rsp not being detected as a restore of cfa->base so it will turn
into a regular POP and offset the stack, resulting in:
kernel/softirq.o: warning: objtool: do_softirq()+0xdb: return with modified stack frame
Therefore, have "mov %[tos], %rsp" act like a PUSH (it sorta is
anyway) to balance the things out. We're not too concerned with the
actual stack_size for frame-pointer builds, since we don't generate
ORC data for them anyway.
Fixes: aafeb14e9da2 ("objtool: Support stack-swizzle")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
tools/objtool/check.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1996,6 +1996,20 @@ static int update_cfi_state(struct instr
}
}
+ else if (op->dest.reg == CFI_SP &&
+ cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
+ cfi->vals[op->src.reg].offset == cfa->offset) {
+
+ /*
+ * The same stack swizzle case 2) as above. But
+ * because we can't change cfa->base, case 3)
+ * will become a regular POP. Pretend we're a
+ * PUSH so things don't go unbalanced.
+ */
+ cfi->stack_size += 8;
+ }
+
+
break;
case OP_SRC_ADD:
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] objtool: Fix stack-swizzle for FRAME_POINTER=y
2021-02-18 16:21 ` [PATCH] objtool: Fix stack-swizzle for FRAME_POINTER=y Peter Zijlstra
@ 2021-02-18 17:53 ` Josh Poimboeuf
2021-02-22 11:08 ` [tip: objtool/core] " tip-bot2 for Peter Zijlstra
2021-02-22 19:00 ` [tip: x86/entry] " tip-bot2 for Peter Zijlstra
2 siblings, 0 replies; 5+ messages in thread
From: Josh Poimboeuf @ 2021-02-18 17:53 UTC (permalink / raw)
To: Peter Zijlstra; +Cc: linux-kernel, linux-tip-commits, Miroslav Benes, x86
On Thu, Feb 18, 2021 at 05:21:31PM +0100, Peter Zijlstra wrote:
> On Wed, Feb 10, 2021 at 08:01:23PM -0000, tip-bot2 for Peter Zijlstra wrote:
> > objtool: Support stack-swizzle
>
> ---
> Subject: objtool: Fix stack-swizzle for FRAME_POINTER=y
> From: Peter Zijlstra <peterz@infradead.org>
> Date: Thu Feb 18 17:14:10 CET 2021
>
> When objtool encounters the stack-swizzle:
>
> mov %rsp, (%[tos])
> mov %[tos], %rsp
> ...
> pop %rsp
>
> Inside a FRAME_POINTER=y build, things go a little screwy because
> clearly we're not adjusting the cfa->base. This then results in the
> pop %rsp not being detected as a restore of cfa->base so it will turn
> into a regular POP and offset the stack, resulting in:
>
> kernel/softirq.o: warning: objtool: do_softirq()+0xdb: return with modified stack frame
>
> Therefore, have "mov %[tos], %rsp" act like a PUSH (it sorta is
> anyway) to balance the things out. We're not too concerned with the
> actual stack_size for frame-pointer builds, since we don't generate
> ORC data for them anyway.
>
> Fixes: aafeb14e9da2 ("objtool: Support stack-swizzle")
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
--
Josh
^ permalink raw reply [flat|nested] 5+ messages in thread* [tip: objtool/core] objtool: Fix stack-swizzle for FRAME_POINTER=y
2021-02-18 16:21 ` [PATCH] objtool: Fix stack-swizzle for FRAME_POINTER=y Peter Zijlstra
2021-02-18 17:53 ` Josh Poimboeuf
@ 2021-02-22 11:08 ` tip-bot2 for Peter Zijlstra
2021-02-22 19:00 ` [tip: x86/entry] " tip-bot2 for Peter Zijlstra
2 siblings, 0 replies; 5+ messages in thread
From: tip-bot2 for Peter Zijlstra @ 2021-02-22 11:08 UTC (permalink / raw)
To: linux-tip-commits
Cc: kernel test robot, Peter Zijlstra (Intel),
Josh Poimboeuf, x86, linux-kernel
The following commit has been merged into the objtool/core branch of tip:
Commit-ID: 23e34c5988088b8bb4c55905973ca76114cb33ee
Gitweb: https://git.kernel.org/tip/23e34c5988088b8bb4c55905973ca76114cb33ee
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Thu, 18 Feb 2021 17:14:10 +01:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 22 Feb 2021 12:05:18 +01:00
objtool: Fix stack-swizzle for FRAME_POINTER=y
When objtool encounters the stack-swizzle:
mov %rsp, (%[tos])
mov %[tos], %rsp
...
pop %rsp
Inside a FRAME_POINTER=y build, things go a little screwy because
clearly we're not adjusting the cfa->base. This then results in the
pop %rsp not being detected as a restore of cfa->base so it will turn
into a regular POP and offset the stack, resulting in:
kernel/softirq.o: warning: objtool: do_softirq()+0xdb: return with modified stack frame
Therefore, have "mov %[tos], %rsp" act like a PUSH (it sorta is
anyway) to balance the things out. We're not too concerned with the
actual stack_size for frame-pointer builds, since we don't generate
ORC data for them anyway.
Fixes: aafeb14e9da2 ("objtool: Support stack-swizzle")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/YC6UC+rc9KKmQrkd@hirez.programming.kicks-ass.net
---
tools/objtool/check.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 62cd211..d7f1496 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1983,6 +1983,20 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi,
}
}
+ else if (op->dest.reg == CFI_SP &&
+ cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
+ cfi->vals[op->src.reg].offset == cfa->offset) {
+
+ /*
+ * The same stack swizzle case 2) as above. But
+ * because we can't change cfa->base, case 3)
+ * will become a regular POP. Pretend we're a
+ * PUSH so things don't go unbalanced.
+ */
+ cfi->stack_size += 8;
+ }
+
+
break;
case OP_SRC_ADD:
^ permalink raw reply related [flat|nested] 5+ messages in thread* [tip: x86/entry] objtool: Fix stack-swizzle for FRAME_POINTER=y
2021-02-18 16:21 ` [PATCH] objtool: Fix stack-swizzle for FRAME_POINTER=y Peter Zijlstra
2021-02-18 17:53 ` Josh Poimboeuf
2021-02-22 11:08 ` [tip: objtool/core] " tip-bot2 for Peter Zijlstra
@ 2021-02-22 19:00 ` tip-bot2 for Peter Zijlstra
2 siblings, 0 replies; 5+ messages in thread
From: tip-bot2 for Peter Zijlstra @ 2021-02-22 19:00 UTC (permalink / raw)
To: linux-tip-commits
Cc: kernel test robot, Peter Zijlstra (Intel),
Thomas Gleixner, Josh Poimboeuf, x86, linux-kernel
The following commit has been merged into the x86/entry branch of tip:
Commit-ID: 724c8a23d589d8a002d2e39633c2f9a5a429616f
Gitweb: https://git.kernel.org/tip/724c8a23d589d8a002d2e39633c2f9a5a429616f
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Thu, 18 Feb 2021 17:14:10 +01:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Mon, 22 Feb 2021 19:54:09 +01:00
objtool: Fix stack-swizzle for FRAME_POINTER=y
When objtool encounters the stack-swizzle:
mov %rsp, (%[tos])
mov %[tos], %rsp
...
pop %rsp
Inside a FRAME_POINTER=y build, things go a little screwy because
clearly we're not adjusting the cfa->base. This then results in the
pop %rsp not being detected as a restore of cfa->base so it will turn
into a regular POP and offset the stack, resulting in:
kernel/softirq.o: warning: objtool: do_softirq()+0xdb: return with modified stack frame
Therefore, have "mov %[tos], %rsp" act like a PUSH (it sorta is
anyway) to balance the things out. We're not too concerned with the
actual stack_size for frame-pointer builds, since we don't generate
ORC data for them anyway.
Fixes: aafeb14e9da2 ("objtool: Support stack-swizzle")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/YC6UC+rc9KKmQrkd@hirez.programming.kicks-ass.net
---
tools/objtool/check.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 8e74210..2087974 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1983,6 +1983,20 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi,
}
}
+ else if (op->dest.reg == CFI_SP &&
+ cfi->vals[op->src.reg].base == CFI_SP_INDIRECT &&
+ cfi->vals[op->src.reg].offset == cfa->offset) {
+
+ /*
+ * The same stack swizzle case 2) as above. But
+ * because we can't change cfa->base, case 3)
+ * will become a regular POP. Pretend we're a
+ * PUSH so things don't go unbalanced.
+ */
+ cfi->stack_size += 8;
+ }
+
+
break;
case OP_SRC_ADD:
^ permalink raw reply related [flat|nested] 5+ messages in thread
end of thread, other threads:[~2021-02-22 19:02 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-02-10 20:01 [tip: objtool/core] objtool: Support stack-swizzle tip-bot2 for Peter Zijlstra
2021-02-18 16:21 ` [PATCH] objtool: Fix stack-swizzle for FRAME_POINTER=y Peter Zijlstra
2021-02-18 17:53 ` Josh Poimboeuf
2021-02-22 11:08 ` [tip: objtool/core] " tip-bot2 for Peter Zijlstra
2021-02-22 19:00 ` [tip: x86/entry] " tip-bot2 for Peter Zijlstra
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