The file-wide OBJECT_FILES_NON_STANDARD annotation is used with
CONFIG_FRAME_POINTER to tell objtool to skip the entire file when frame
pointers are enabled. However that annotation is now deprecated because
it doesn't work with IBT, where objtool runs on vmlinux.o instead of
individual translation units.
Instead, use more fine-grained function-specific annotations:
- The 'save_mcount_regs' macro does funny things with the frame pointer.
Use STACK_FRAME_NON_STANDARD_FP to tell objtool to ignore the
functions using it.
- The return_to_handler() "function" isn't actually a callable function.
Instead of being called, it's returned to. The real return address
isn't on the stack, so unwinding is already doomed no matter which
unwinder is used. So just remove the STT_FUNC annotation, telling
objtool to ignore it. That also removes the implicit
ANNOTATE_NOENDBR, which now needs to be made explicit.
Fixes the following warning:
vmlinux.o: warning: objtool: __fentry__+0x16: return with modified stack frame
Fixes: ed53a0d97192 ("x86/alternative: Use .ibt_endbr_seal to seal indirect calls")
Reported-by: kernel test robot <[email protected]>
Signed-off-by: Josh Poimboeuf <[email protected]>
---
v2:
- fix return_to_handler()
arch/x86/kernel/Makefile | 4 ----
arch/x86/kernel/ftrace_64.S | 11 ++++++++---
include/linux/objtool.h | 6 ++++++
tools/include/linux/objtool.h | 6 ++++++
4 files changed, 20 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 03364dc40d8d..4c8b6ae802ac 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -36,10 +36,6 @@ KCSAN_SANITIZE := n
OBJECT_FILES_NON_STANDARD_test_nx.o := y
-ifdef CONFIG_FRAME_POINTER
-OBJECT_FILES_NON_STANDARD_ftrace_$(BITS).o := y
-endif
-
# If instrumentation of this dir is enabled, boot hangs during first second.
# Probably could be more selective here, but note that files related to irqs,
# boot, dumpstack/stacktrace, etc are either non-interesting or can lead to
diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S
index 4ec13608d3c6..dfeb227de561 100644
--- a/arch/x86/kernel/ftrace_64.S
+++ b/arch/x86/kernel/ftrace_64.S
@@ -175,6 +175,7 @@ SYM_INNER_LABEL(ftrace_caller_end, SYM_L_GLOBAL)
jmp ftrace_epilogue
SYM_FUNC_END(ftrace_caller);
+STACK_FRAME_NON_STANDARD_FP(ftrace_caller)
SYM_FUNC_START(ftrace_epilogue)
/*
@@ -282,6 +283,7 @@ SYM_INNER_LABEL(ftrace_regs_caller_end, SYM_L_GLOBAL)
jmp ftrace_epilogue
SYM_FUNC_END(ftrace_regs_caller)
+STACK_FRAME_NON_STANDARD_FP(ftrace_regs_caller)
#else /* ! CONFIG_DYNAMIC_FTRACE */
@@ -311,10 +313,14 @@ trace:
jmp ftrace_stub
SYM_FUNC_END(__fentry__)
EXPORT_SYMBOL(__fentry__)
+STACK_FRAME_NON_STANDARD_FP(__fentry__)
+
#endif /* CONFIG_DYNAMIC_FTRACE */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
-SYM_FUNC_START(return_to_handler)
+SYM_CODE_START(return_to_handler)
+ UNWIND_HINT_EMPTY
+ ANNOTATE_NOENDBR
subq $16, %rsp
/* Save the return values */
@@ -339,7 +345,6 @@ SYM_FUNC_START(return_to_handler)
int3
.Ldo_rop:
mov %rdi, (%rsp)
- UNWIND_HINT_FUNC
RET
-SYM_FUNC_END(return_to_handler)
+SYM_CODE_END(return_to_handler)
#endif
diff --git a/include/linux/objtool.h b/include/linux/objtool.h
index 6491fa8fba6d..15b940ec1eac 100644
--- a/include/linux/objtool.h
+++ b/include/linux/objtool.h
@@ -143,6 +143,12 @@ struct unwind_hint {
.popsection
.endm
+.macro STACK_FRAME_NON_STANDARD_FP func:req
+#ifdef CONFIG_FRAME_POINTER
+ STACK_FRAME_NON_STANDARD \func
+#endif
+.endm
+
.macro ANNOTATE_NOENDBR
.Lhere_\@:
.pushsection .discard.noendbr
diff --git a/tools/include/linux/objtool.h b/tools/include/linux/objtool.h
index 6491fa8fba6d..15b940ec1eac 100644
--- a/tools/include/linux/objtool.h
+++ b/tools/include/linux/objtool.h
@@ -143,6 +143,12 @@ struct unwind_hint {
.popsection
.endm
+.macro STACK_FRAME_NON_STANDARD_FP func:req
+#ifdef CONFIG_FRAME_POINTER
+ STACK_FRAME_NON_STANDARD \func
+#endif
+.endm
+
.macro ANNOTATE_NOENDBR
.Lhere_\@:
.pushsection .discard.noendbr
--
2.34.3
The following commit has been merged into the objtool/urgent branch of tip:
Commit-ID: 7b6c7a877cc616bc7dc9cd39646fe454acbed48b
Gitweb: https://git.kernel.org/tip/7b6c7a877cc616bc7dc9cd39646fe454acbed48b
Author: Josh Poimboeuf <[email protected]>
AuthorDate: Fri, 03 Jun 2022 08:04:44 -07:00
Committer: Josh Poimboeuf <[email protected]>
CommitterDate: Mon, 06 Jun 2022 11:50:22 -07:00
x86/ftrace: Remove OBJECT_FILES_NON_STANDARD usage
The file-wide OBJECT_FILES_NON_STANDARD annotation is used with
CONFIG_FRAME_POINTER to tell objtool to skip the entire file when frame
pointers are enabled. However that annotation is now deprecated because
it doesn't work with IBT, where objtool runs on vmlinux.o instead of
individual translation units.
Instead, use more fine-grained function-specific annotations:
- The 'save_mcount_regs' macro does funny things with the frame pointer.
Use STACK_FRAME_NON_STANDARD_FP to tell objtool to ignore the
functions using it.
- The return_to_handler() "function" isn't actually a callable function.
Instead of being called, it's returned to. The real return address
isn't on the stack, so unwinding is already doomed no matter which
unwinder is used. So just remove the STT_FUNC annotation, telling
objtool to ignore it. That also removes the implicit
ANNOTATE_NOENDBR, which now needs to be made explicit.
Fixes the following warning:
vmlinux.o: warning: objtool: __fentry__+0x16: return with modified stack frame
Fixes: ed53a0d97192 ("x86/alternative: Use .ibt_endbr_seal to seal indirect calls")
Reported-by: kernel test robot <[email protected]>
Signed-off-by: Josh Poimboeuf <[email protected]>
Link: https://lore.kernel.org/r/b7a7a42fe306aca37826043dac89e113a1acdbac.1654268610.git.jpoimboe@kernel.org
---
arch/x86/kernel/Makefile | 4 ----
arch/x86/kernel/ftrace_64.S | 11 ++++++++---
include/linux/objtool.h | 6 ++++++
tools/include/linux/objtool.h | 6 ++++++
4 files changed, 20 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 03364dc..4c8b6ae 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -36,10 +36,6 @@ KCSAN_SANITIZE := n
OBJECT_FILES_NON_STANDARD_test_nx.o := y
-ifdef CONFIG_FRAME_POINTER
-OBJECT_FILES_NON_STANDARD_ftrace_$(BITS).o := y
-endif
-
# If instrumentation of this dir is enabled, boot hangs during first second.
# Probably could be more selective here, but note that files related to irqs,
# boot, dumpstack/stacktrace, etc are either non-interesting or can lead to
diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S
index 4ec1360..dfeb227 100644
--- a/arch/x86/kernel/ftrace_64.S
+++ b/arch/x86/kernel/ftrace_64.S
@@ -175,6 +175,7 @@ SYM_INNER_LABEL(ftrace_caller_end, SYM_L_GLOBAL)
jmp ftrace_epilogue
SYM_FUNC_END(ftrace_caller);
+STACK_FRAME_NON_STANDARD_FP(ftrace_caller)
SYM_FUNC_START(ftrace_epilogue)
/*
@@ -282,6 +283,7 @@ SYM_INNER_LABEL(ftrace_regs_caller_end, SYM_L_GLOBAL)
jmp ftrace_epilogue
SYM_FUNC_END(ftrace_regs_caller)
+STACK_FRAME_NON_STANDARD_FP(ftrace_regs_caller)
#else /* ! CONFIG_DYNAMIC_FTRACE */
@@ -311,10 +313,14 @@ trace:
jmp ftrace_stub
SYM_FUNC_END(__fentry__)
EXPORT_SYMBOL(__fentry__)
+STACK_FRAME_NON_STANDARD_FP(__fentry__)
+
#endif /* CONFIG_DYNAMIC_FTRACE */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
-SYM_FUNC_START(return_to_handler)
+SYM_CODE_START(return_to_handler)
+ UNWIND_HINT_EMPTY
+ ANNOTATE_NOENDBR
subq $16, %rsp
/* Save the return values */
@@ -339,7 +345,6 @@ SYM_FUNC_START(return_to_handler)
int3
.Ldo_rop:
mov %rdi, (%rsp)
- UNWIND_HINT_FUNC
RET
-SYM_FUNC_END(return_to_handler)
+SYM_CODE_END(return_to_handler)
#endif
diff --git a/include/linux/objtool.h b/include/linux/objtool.h
index 6491fa8..15b940e 100644
--- a/include/linux/objtool.h
+++ b/include/linux/objtool.h
@@ -143,6 +143,12 @@ struct unwind_hint {
.popsection
.endm
+.macro STACK_FRAME_NON_STANDARD_FP func:req
+#ifdef CONFIG_FRAME_POINTER
+ STACK_FRAME_NON_STANDARD \func
+#endif
+.endm
+
.macro ANNOTATE_NOENDBR
.Lhere_\@:
.pushsection .discard.noendbr
diff --git a/tools/include/linux/objtool.h b/tools/include/linux/objtool.h
index 6491fa8..15b940e 100644
--- a/tools/include/linux/objtool.h
+++ b/tools/include/linux/objtool.h
@@ -143,6 +143,12 @@ struct unwind_hint {
.popsection
.endm
+.macro STACK_FRAME_NON_STANDARD_FP func:req
+#ifdef CONFIG_FRAME_POINTER
+ STACK_FRAME_NON_STANDARD \func
+#endif
+.endm
+
.macro ANNOTATE_NOENDBR
.Lhere_\@:
.pushsection .discard.noendbr
On Fri, 3 Jun 2022 08:04:44 -0700
Josh Poimboeuf <[email protected]> wrote:
> The file-wide OBJECT_FILES_NON_STANDARD annotation is used with
> CONFIG_FRAME_POINTER to tell objtool to skip the entire file when frame
> pointers are enabled. However that annotation is now deprecated because
> it doesn't work with IBT, where objtool runs on vmlinux.o instead of
> individual translation units.
>
> Instead, use more fine-grained function-specific annotations:
>
> - The 'save_mcount_regs' macro does funny things with the frame pointer.
> Use STACK_FRAME_NON_STANDARD_FP to tell objtool to ignore the
> functions using it.
>
> - The return_to_handler() "function" isn't actually a callable function.
> Instead of being called, it's returned to. The real return address
> isn't on the stack, so unwinding is already doomed no matter which
> unwinder is used. So just remove the STT_FUNC annotation, telling
> objtool to ignore it. That also removes the implicit
> ANNOTATE_NOENDBR, which now needs to be made explicit.
>
> Fixes the following warning:
>
> vmlinux.o: warning: objtool: __fentry__+0x16: return with modified stack frame
>
> Fixes: ed53a0d97192 ("x86/alternative: Use .ibt_endbr_seal to seal indirect calls")
> Reported-by: kernel test robot <[email protected]>
> Signed-off-by: Josh Poimboeuf <[email protected]>
> ---
> v2:
> - fix return_to_handler()
Acked-by: Steven Rostedt (Google) <[email protected]>
-- Steve