linux-kernel - Re: [PATCH 5.15 00/59] 5.15.184-rc1 review

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Message-ID: <20250530052135.nz547z5ecbrb6muh@desk>
Date: Thu, 29 May 2025 22:21:35 -0700
From: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Richard Narron <richard@...zen.com>, Guenter Roeck <linux@...ck-us.net>,
	Linux stable <stable@...r.kernel.org>,
	Linux kernel <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [PATCH 5.15 00/59] 5.15.184-rc1 review

On Fri, May 30, 2025 at 07:11:58AM +0200, Greg Kroah-Hartman wrote:
> On Thu, May 29, 2025 at 10:40:17AM -0700, Pawan Gupta wrote:
> > On Wed, May 28, 2025 at 09:49:40PM -0700, Richard Narron wrote:
> > > On Tue, 27 May 2025, Pawan Gupta wrote:
> > > 
> > > > On Tue, May 27, 2025 at 12:31:47PM -0700, Richard Narron wrote:
> > > > > On Fri, 23 May 2025, Guenter Roeck wrote:
> > > > >
> > > > > > On 5/20/25 06:49, Greg Kroah-Hartman wrote:
> > > > > > > This is the start of the stable review cycle for the 5.15.184 release.
> > > > > > > There are 59 patches in this series, all will be posted as a response
> > > > > > > to this one.  If anyone has any issues with these being applied, please
> > > > > > > let me know.
> > > > > > >
> > > > > > > Responses should be made by Thu, 22 May 2025 12:57:37 +0000.
> > > > > > > Anything received after that time might be too late.
> > > > > > >
> > > > > >
> > > > > > Build reference: v5.15.184
> > > > > > Compiler version: x86_64-linux-gcc (GCC) 12.4.0
> > > > > > Assembler version: GNU assembler (GNU Binutils) 2.40
> > > > > >
> > > > > > Configuration file workarounds:
> > > > > >     "s/CONFIG_FRAME_WARN=.*/CONFIG_FRAME_WARN=0/"
> > > > > >
> > > > > > Building i386:defconfig ... passed
> > > > > > Building i386:allyesconfig ... failed
> > > > > > --------------
> > > > > > Error log:
> > > > > > x86_64-linux-ld: arch/x86/kernel/static_call.o: in function
> > > > > > `__static_call_transform':
> > > > > > static_call.c:(.ref.text+0x46): undefined reference to `cpu_wants_rethunk_at'
> > > > > > make[1]: [Makefile:1234: vmlinux] Error 1 (ignored)
> > > > > > --------------
> > > > > > Building i386:allmodconfig ... failed
> > > > > > --------------
> > > > > > Error log:
> > > > > > x86_64-linux-ld: arch/x86/kernel/static_call.o: in function
> > > > > > `__static_call_transform':
> > > > > > static_call.c:(.ref.text+0x46): undefined reference to `cpu_wants_rethunk_at'
> > > > > > make[1]: [Makefile:1234: vmlinux] Error 1 (ignored)
> > > > > > --------------
> > > > > >
> > > > > > In v5.15.y, cpu_wants_rethunk_at is only built if CONFIG_STACK_VALIDATION=y,
> > > > > > but that is not supported for i386 builds. The dummy function in
> > > > > > arch/x86/include/asm/alternative.h doesn't take that dependency into account.
> > > > > >
> > > > >
> > > > > I found this bug too using the Slackware 15.0 32-bit kernel
> > > > > configuration.
> > > > >
> > > > > Here is a simple work around patch, but there may be a better solution...
> > > > >
> > > > > --- arch/x86/kernel/static_call.c.orig	2025-05-22 05:08:28.000000000 -0700
> > > > > +++ arch/x86/kernel/static_call.c	2025-05-27 10:25:27.630496538 -0700
> > > > > @@ -81,9 +81,12 @@
> > > > >  		break;
> > > > >
> > > > >  	case RET:
> > > > > +
> > > > > +#ifdef CONFIG_64BIT
> > > > >  		if (cpu_wants_rethunk_at(insn))
> > > > >  			code = text_gen_insn(JMP32_INSN_OPCODE, insn, x86_return_thunk);
> > > > >  		else
> > > > > +#endif
> > > > >  			code = &retinsn;
> > > > >  		break;
> > > > >
> > > >
> > > > Another option is to define the empty function when CONFIG_STACK_VALIDATION=n as below:
> > > >
> > > > --- 8< ---
> > > > From: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
> > > > Subject: [PATCH] x86/its: Fix undefined reference to cpu_wants_rethunk_at()
> > > >
> > > > Below error was reported in 32-bit kernel build:
> > > >
> > > >   static_call.c:(.ref.text+0x46): undefined reference to `cpu_wants_rethunk_at'
> > > >   make[1]: [Makefile:1234: vmlinux] Error
> > > >
> > > > This is because the definition of cpu_wants_rethunk_at() depends on
> > > > CONFIG_STACK_VALIDATION which is only enabled in 64-bit mode.
> > > >
> > > > Define the empty function when CONFIG_STACK_VALIDATION=n, rethunk mitigation
> > > > is anyways not supported without it.
> > > >
> > > > Reported-by: Guenter Roeck <linux@...ck-us.net>
> > > > Link: https://lore.kernel.org/stable/0f597436-5da6-4319-b918-9f57bde5634a@roeck-us.net/
> > > > Signed-off-by: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
> > > > ---
> > > >  arch/x86/include/asm/alternative.h | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
> > > > index 1797f80c10de..a5f704dbb4a1 100644
> > > > --- a/arch/x86/include/asm/alternative.h
> > > > +++ b/arch/x86/include/asm/alternative.h
> > > > @@ -98,7 +98,7 @@ static inline u8 *its_static_thunk(int reg)
> > > >  }
> > > >  #endif
> > > >
> > > > -#ifdef CONFIG_RETHUNK
> > > > +#if defined(CONFIG_RETHUNK) && defined(CONFIG_STACK_VALIDATION)
> > > >  extern bool cpu_wants_rethunk(void);
> > > >  extern bool cpu_wants_rethunk_at(void *addr);
> > > >  #else
> > > > --
> > > > 2.34.1
> > > >
> > > 
> > > Thanks for looking at this Pawan.
> > > 
> > > Your new patch works fine on both Slackware 15.0 32-bit and 64-bit
> > > systems.
> > 
> > Thank you for verifying the patch.
> 
> Is someone going to submit this in a form we can apply it in?  (hint...)

Oops, sending it now.