linux-kernel - Re: [linux-next:master 12681/13861] drivers/i2c/i2c-core-base.o: warning: objtool: __i2c_transfer+0x120: stack state mismatch: reg1[24]=-1+0 reg2[24]=-2-24

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Message-ID: <348cdb14-f8cf-1e7b-44b2-79dc4dda4e35@loongson.cn>
Date: Thu, 3 Apr 2025 17:35:51 +0800
From: Tiezhu Yang <yangtiezhu@...ngson.cn>
To: Josh Poimboeuf <jpoimboe@...nel.org>, Philip Li <philip.li@...el.com>
Cc: kernel test robot <lkp@...el.com>, Guenter Roeck <linux@...ck-us.net>,
 oe-kbuild-all@...ts.linux.dev, Andrew Morton <akpm@...ux-foundation.org>,
 Linux Memory Management List <linux-mm@...ck.org>,
 Alessandro Carminati <acarmina@...hat.com>,
 Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org,
 loongarch@...ts.linux.dev
Subject: Re: [linux-next:master 12681/13861] drivers/i2c/i2c-core-base.o:
 warning: objtool: __i2c_transfer+0x120: stack state mismatch: reg1[24]=-1+0
 reg2[24]=-2-24

On 04/02/2025 03:45 AM, Josh Poimboeuf wrote:
> On Tue, Apr 01, 2025 at 12:38:37PM +0800, Philip Li wrote:
>> On Tue, Apr 01, 2025 at 10:44:57AM +0800, kernel test robot wrote:
>>> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
>>> head:   405e2241def89c88f008dcb899eb5b6d4be8b43c
>>> commit: 9016dad4dca4bbe61c48ffd5a273cad980caa0d1 [12681/13861] loongarch: add support for suppressing warning backtraces
>>> config: loongarch-randconfig-001-20250401 (https://download.01.org/0day-ci/archive/20250401/202504011011.jyZ6NtXx-lkp@intel.com/config)
>>> compiler: loongarch64-linux-gcc (GCC) 14.2.0
>>> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250401/202504011011.jyZ6NtXx-lkp@intel.com/reproduce)
>>>
>>> If you fix the issue in a separate patch/commit (i.e. not just a new version of
>>> the same patch/commit), kindly add following tags
>>> | Reported-by: kernel test robot <lkp@...el.com>
>>> | Closes: https://lore.kernel.org/oe-kbuild-all/202504011011.jyZ6NtXx-lkp@intel.com/
>>>
>>> All warnings (new ones prefixed by >>):
>>>
>>>>> drivers/i2c/i2c-core-base.o: warning: objtool: __i2c_transfer+0x120: stack state mismatch: reg1[24]=-1+0 reg2[24]=-2-24
>
> Tiezhu, this looks like a loongarch GCC bug with asm goto, or am I
> confused?  See analysis below.

This is related with GCC optimization "-fshrink-wrap" which is default y
on LoongArch, use "-fno-shrink-wrap" can avoid such issues, like this:

---8<---

diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile
index 0304eabbe606..2d5529322357 100644
--- a/arch/loongarch/Makefile
+++ b/arch/loongarch/Makefile
@@ -106,6 +106,7 @@ KBUILD_CFLAGS                       += 
-mannotate-tablejump
  else
  KBUILD_CFLAGS                  += -fno-jump-tables # keep 
compatibility with older compilers
  endif
+KBUILD_CFLAGS                  += -fno-shrink-wrap
  endif

  KBUILD_RUSTFLAGS               += 
--target=loongarch64-unknown-none-softfloat -Ccode-model=small

If you are OK with this change, I will send a formal patch after the
merge window.

Thanks,
Tiezhu