linux-kernel - Re: arch/powerpc/kernel/head_85xx.o: warning: objtool: .head.text+0x1a6c: unannotated intra-function call

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Message-ID: <b2273730-f885-7658-7ec4-12fb5bfc515b@linux.ibm.com>
Date:   Thu, 19 Jan 2023 18:42:22 +0530
From:   Sathvika Vasireddy <sv@...ux.ibm.com>
To:     kernel test robot <lkp@...el.com>
Cc:     oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Michael Ellerman <mpe@...erman.id.au>,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Sathvika Vasireddy <sv@...ux.ibm.com>
Subject: Re: arch/powerpc/kernel/head_85xx.o: warning: objtool:
 .head.text+0x1a6c: unannotated intra-function call

Hi all,

On 16/01/23 17:25, kernel test robot wrote:
> Hi Sathvika,
>
> First bad commit (maybe != root cause):
>
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   5dc4c995db9eb45f6373a956eb1f69460e69e6d4
> commit: c984aef8c8326035570ff6e01d0ff9e79a5dfa76 objtool/powerpc: Add --mcount specific implementation
> date:   8 weeks ago
> config: powerpc-randconfig-c042-20230116
> compiler: powerpc-linux-gcc (GCC) 12.1.0
> reproduce (this is a W=1 build):
>          wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>          chmod +x ~/bin/make.cross
>          # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c984aef8c8326035570ff6e01d0ff9e79a5dfa76
>          git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>          git fetch --no-tags linus master
>          git checkout c984aef8c8326035570ff6e01d0ff9e79a5dfa76
>          # save the config file
>          mkdir build_dir && cp config build_dir/.config
>          COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=powerpc olddefconfig
>          COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=powerpc SHELL=/bin/bash arch/powerpc/
>
> If you fix the issue, kindly add following tag where applicable
> | Reported-by: kernel test robot <lkp@...el.com>
>
> All warnings (new ones prefixed by >>):
>
>>> arch/powerpc/kernel/head_85xx.o: warning: objtool: .head.text+0x1a6c: unannotated intra-function call

After annotating symbols with SYM_FUNC_START_LOCAL and SYM_FUNC_END 
macros, I don't see this warning anymore.

Below diff works for me:

diff --git a/arch/powerpc/kernel/head_85xx.S 
b/arch/powerpc/kernel/head_85xx.S
index d438ca74e96c..fdbee1093e2b 100644
--- a/arch/powerpc/kernel/head_85xx.S
+++ b/arch/powerpc/kernel/head_85xx.S
@@ -864,7 +864,7 @@ _GLOBAL(load_up_spe)
   * SPE unavailable trap from kernel - print a message, but let
   * the task use SPE in the kernel until it returns to user mode.
   */
-KernelSPE:
+SYM_FUNC_START_LOCAL(KernelSPE)
         lwz     r3,_MSR(r1)
         oris    r3,r3,MSR_SPE@h
         stw     r3,_MSR(r1)     /* enable use of SPE after return */
@@ -881,6 +881,7 @@ KernelSPE:
  #endif
         .align  4,0

+SYM_FUNC_END(KernelSPE)
  #endif /* CONFIG_SPE */

  /*

>>> arch/powerpc/kvm/booke.o: warning: objtool: kvmppc_fill_pt_regs+0x30: unannotated intra-function call

As an attempt to fix it, I tried expanding ANNOTATE_INTRA_FUNCTION_CALL 
macro to indicate that the branch target is valid. It then threw another 
warning (arch/powerpc/kvm/booke.o: warning: objtool: 
kvmppc_fill_pt_regs+0x38: intra_function_call not a direct call). The 
below diff just removes the warnings for me, but I'm not very sure if 
this is the best way to fix the objtool warnings seen with this 
particular file. Please let me know if there are any better ways to fix it.

diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index 0dce93ccaadf..b6a413824b98 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -917,7 +917,9 @@ static void kvmppc_fill_pt_regs(struct pt_regs *regs)
         asm("mr %0, 1" : "=r"(r1));
         asm("mflr %0" : "=r"(lr));
         asm("mfmsr %0" : "=r"(msr));
+       asm(".pushsection .discard.intra_function_calls; .long 999f; 
.popsection; 999:");
         asm("bl 1f; 1: mflr %0" : "=r"(ip));
+       asm("nop");

         memset(regs, 0, sizeof(*regs));
         regs->gpr[1] = r1;



Thanks,
Sathvika