linux-kernel - Re: [GIT PULL] objtool fixes and updates

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Message-ID: <ttv3iy3i57mvmkdp2mwh4cjwk3qx5eoyr7zmgjl5beohfxvwar@4na7dgto7r6m>
Date: Mon, 31 Mar 2025 15:19:23 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Borislav Petkov <bp@...en8.de>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>, 
	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org, 
	Peter Zijlstra <a.p.zijlstra@...llo.nl>, Thomas Gleixner <tglx@...utronix.de>, 
	Andrew Morton <akpm@...ux-foundation.org>, Tiezhu Yang <yangtiezhu@...ngson.cn>
Subject: Re: [GIT PULL] objtool fixes and updates

On Sun, Mar 30, 2025 at 06:39:51PM -0700, Josh Poimboeuf wrote:
> On Mon, Mar 31, 2025 at 01:13:55AM +0200, Borislav Petkov wrote:
> > On Sun, Mar 30, 2025 at 03:19:40PM -0700, Linus Torvalds wrote:
> > > On Sat, 29 Mar 2025 at 08:33, Borislav Petkov <bp@...en8.de> wrote:
> > > >
> > > > Btw, test bot complains:
> > > >
> > > > https://lore.kernel.org/r/202503292202.Sge7ZEUc-lkp@intel.com
> > > 
> > > That's not a very helpful error message
> > 
> > I found this:
> > 
> > https://lore.kernel.org/r/202503280703.OARM8SrY-lkp@intel.com
> > 
> > which looks like the original report.
> > 
> > Looks unsolved yet...
> 
> The "new" warning is just the "skipping duplicate warning", which was
> already merged with commit 0a7fb6f07e3a ("objtool: Increase per-function
> WARN_FUNC() rate limit").  So none of the warnings are specific to this
> pull request.
> 
> Tiezhu, can you please look at this warning?
>   
>    arch/loongarch/kernel/traps.o: warning: objtool: show_stack+0xe0: stack state mismatch: reg1[22]=-1+0 reg2[22]=-2-160
>    arch/loongarch/kernel/traps.o: warning: objtool: show_stack+0xe0: stack state mismatch: reg1[23]=-1+0 reg2[23]=-2-152

Here's a fix.  Will post a real fix soon, along with another pile of
fixes.

diff --git a/arch/loongarch/include/asm/stacktrace.h b/arch/loongarch/include/asm/stacktrace.h
index f23adb15f418..fc8b64773794 100644
--- a/arch/loongarch/include/asm/stacktrace.h
+++ b/arch/loongarch/include/asm/stacktrace.h
@@ -8,6 +8,7 @@
 #include <asm/asm.h>
 #include <asm/ptrace.h>
 #include <asm/loongarch.h>
+#include <asm/unwind_hints.h>
 #include <linux/stringify.h>
 
 enum stack_type {
@@ -43,6 +44,7 @@ int get_stack_info(unsigned long stack, struct task_struct *task, struct stack_i
 static __always_inline void prepare_frametrace(struct pt_regs *regs)
 {
 	__asm__ __volatile__(
+		UNWIND_HINT_SAVE
 		/* Save $ra */
 		STORE_ONE_REG(1)
 		/* Use $ra to save PC */
@@ -80,6 +82,7 @@ static __always_inline void prepare_frametrace(struct pt_regs *regs)
 		STORE_ONE_REG(29)
 		STORE_ONE_REG(30)
 		STORE_ONE_REG(31)
+		UNWIND_HINT_RESTORE
 		: "=m" (regs->csr_era)
 		: "r" (regs->regs)
 		: "memory");
diff --git a/arch/loongarch/include/asm/unwind_hints.h b/arch/loongarch/include/asm/unwind_hints.h
index a01086ad9dde..2c68bc72736c 100644
--- a/arch/loongarch/include/asm/unwind_hints.h
+++ b/arch/loongarch/include/asm/unwind_hints.h
@@ -23,6 +23,14 @@
 	UNWIND_HINT sp_reg=ORC_REG_SP type=UNWIND_HINT_TYPE_CALL
 .endm
 
-#endif /* __ASSEMBLY__ */
+#else /* !__ASSEMBLY__ */
+
+#define UNWIND_HINT_SAVE \
+	UNWIND_HINT(UNWIND_HINT_TYPE_SAVE, 0, 0, 0)
+
+#define UNWIND_HINT_RESTORE \
+	UNWIND_HINT(UNWIND_HINT_TYPE_RESTORE, 0, 0, 0)
+
+#endif /* !__ASSEMBLY__ */
 
 #endif /* _ASM_LOONGARCH_UNWIND_HINTS_H */