linux-kernel - Re: Build Warnings at arch/powerpc/

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Message-ID: <a8336412-7b66-447e-9a90-1a376960cd4c@csgroup.eu>
Date: Tue, 4 Mar 2025 14:13:09 +0100
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Venkat Rao Bagalkote <venkat88@...ux.ibm.com>,
 Madhavan Srinivasan <maddy@...ux.ibm.com>, linuxppc-dev@...ts.ozlabs.org,
 linux-kernel@...r.kernel.org, Stephen Rothwell <sfr@...b.auug.org.au>,
 Michael Ellerman <mpe@...erman.id.au>
Subject: Re: Build Warnings at arch/powerpc/



Le 04/03/2025 à 14:03, Venkat Rao Bagalkote a écrit :
> [Vous ne recevez pas souvent de courriers de venkat88@...ux.ibm.com. 
> Découvrez pourquoi ceci est important à https://aka.ms/ 
> LearnAboutSenderIdentification ]
> 
> On 04/03/25 6:08 pm, Madhavan Srinivasan wrote:
>>
>> On 3/4/25 4:58 PM, Madhavan Srinivasan wrote:
>>>
>>> On 3/4/25 2:26 PM, Christophe Leroy wrote:
>>>>
>>>> Le 04/03/2025 à 07:13, Madhavan Srinivasan a écrit :
>>>>>
>>>>> On 3/4/25 10:42 AM, Venkat Rao Bagalkote wrote:
>>>>>> Greetings!!
>>>>>>
>>>>>>
>>>>>> Observing build warnings with linux-next and powerpc repo's. Issue 
>>>>>> is currently not seen on mainline yet.
>>>>>>
>>>>>> PPC Repo: https://eur01.safelinks.protection.outlook.com/? 
>>>>>> url=https%3A%2F%2Fgit.kernel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Fpowerpc%2Flinux.git&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C6e17cc771a204b2998b508dd5b1cf2cf%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C638766902127463526%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=f0ubC0BiY%2Fw2XLfXcX955JKhJ%2BRkUmTUVO4fV%2F%2F4v2Y%3D&reserved=0 merge branch
>>>>>>
>>>>>> PPC Kernel Version: 6.14.0-rc4-g1304f486dbf1
>>>>>> next Repo: https://eur01.safelinks.protection.outlook.com/? 
>>>>>> url=https%3A%2F%2Fgit.kernel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Fnext%2Flinux-next.git&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C6e17cc771a204b2998b508dd5b1cf2cf%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C638766902127477000%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=GSDtRBQ35owCeEpjMMCNiJw3iizdrUPQcHznop2BLeQ%3D&reserved=0 master branch
>>>>>>
>>>>>> next Kernel Version: 6.14.0-rc5-next-20250303
>>>>>>
>>>>>>
>>>>>> On linux-next kernel issue got introduced b/w next-20250227 and 
>>>>>> next-20250303
>>>>>>
>>>>>>
>>>>>> Build Warnings:
>>>>>>
>>>>>> arch/powerpc/kvm/book3s_hv_rmhandlers.o: warning: 
>>>>>> objtool: .text+0xe84: intra_function_call not a direct call
>>>>>> arch/powerpc/crypto/ghashp8-ppc.o: warning: objtool: .text+0x22c: 
>>>>>> unannotated intra-function call
>>>>>> arch/powerpc/kernel/switch.o: warning: objtool: .text+0x4: 
>>>>>> intra_function_call not a direct call
>>>>>>
>>>>>>
>>>>> Can you please specific the compiler and compiler version you found 
>>>>> this issue with
>>>>>
>>>> Can you also tell which defconfig you are using or provide your .config
>>>>
>>>> It might also be helpfull if you can provide a disassembly of the 
>>>> three file.o around the warned address.
>>> I could recreate the issue with gcc 11.4.1 20231218 with today's 
>>> linux-next (but could not recreate with gcc 14 or gcc 11.3.0)
>>>
>>> (20d5c66e1810 (HEAD -> master, tag: next-20250304, origin/master, 
>>> origin/HEAD) Add linux-next specific files for 20250304)
>>>
>>> warning for one of the switch.S file :
>>>
>>>    CC      arch/powerpc/kernel/syscalls.o
>>>    AS      arch/powerpc/kernel/switch.o
>>> arch/powerpc/kernel/switch.o: warning: objtool: .text+0x4: 
>>> intra_function_call not a direct call
>> I guess this is becos, for bl .+4, we recently added in the 
>> arch_decode_instruction (decode.c) to set the type as INSN_OTHER
>>
>>          case 18: /* b[l][a] */
>>                  if (ins == 0x48000005)  /* bl .+4 */
>>                          typ = INSN_OTHER;
>>
>> Which I think is the issue here, changing it to INSN_CALL from 
>> INSN_OTHER fixes the warning
>>
>> diff --git a/tools/objtool/arch/powerpc/decode.c b/tools/objtool/arch/ 
>> powerpc/decode.c
>> index 26d5050424a9..ffd63a61a585 100644
>> --- a/tools/objtool/arch/powerpc/decode.c
>> +++ b/tools/objtool/arch/powerpc/decode.c
>> @@ -56,7 +56,7 @@ int arch_decode_instruction(struct objtool_file 
>> *file, const struct section *sec
>>          switch (opcode) {
>>          case 18: /* b[l][a] */
>>                  if (ins == 0x48000005)  /* bl .+4 */
>> -                       typ = INSN_OTHER;
>> +                       typ = INSN_CALL;
>>                  else if (ins & 1)       /* bl[a] */
>>                          typ = INSN_CALL;
>>                  else            /* b[a] */
>>
>>
>> Maddy
>>
> Maddy,
> 
> I changed the code manually and gave it a try. The Proposed fix,
> partially fixes the issue. It gets rid of two of the warnings, but below
> warning still persists.

It fixes the issue for you but will reintroduce the issue with clang.

The real fix is to remove the ANNOTATE_INTRA_FUNCTION_CALL in:

arch/powerpc/kernel/switch.S:42:        ANNOTATE_INTRA_FUNCTION_CALL
arch/powerpc/kvm/book3s_hv_rmhandlers.S:1527:   ANNOTATE_INTRA_FUNCTION_CALL
arch/powerpc/kvm/book3s_hv_rmhandlers.S:1534:   ANNOTATE_INTRA_FUNCTION_CALL

Can you give it a try ?

For the last one, can you provide an assembly dump ? You get it with 
"objtool -dr arch/powerpc/crypto/ghashp8-ppc.o"

Also can you tell which defconfig you use or provide your .config if not 
standard one ?

Christophe


> 
> arch/powerpc/crypto/ghashp8-ppc.o: warning: objtool: .text+0x22c:
> unannotated intra-function call
> 
>>>    CC      arch/powerpc/kernel/irq.o
>>>    CC      arch/powerpc/kernel/align.o
>>>    CC      arch/powerpc/kernel/signal_64.o
>>>
>>> Objdump of switch.o:
>>> arch/powerpc/kernel/switch.o:     file format elf64-powerpcle
>>>
>>> Disassembly of section .text:
>>>
>>> 0000000000000000 <flush_branch_caches>:
>>>         0:   a6 02 28 7d     mflr    r9
>>>         4:   05 00 00 48     bl      8 <flush_branch_caches+0x8>
>>>         8:   05 00 00 48     bl      c <flush_branch_caches+0xc>
>>>         c:   05 00 00 48     bl      10 <flush_branch_caches+0x10>
>>>        10:   05 00 00 48     bl      14 <flush_branch_caches+0x14>
>>>        14:   05 00 00 48     bl      18 <flush_branch_caches+0x18>
>>>        18:   05 00 00 48     bl      1c <flush_branch_caches+0x1c>
>>>        1c:   05 00 00 48     bl      20 <flush_branch_caches+0x20>
>>>        20:   05 00 00 48     bl      24 <flush_branch_caches+0x24>
>>>        24:   05 00 00 48     bl      28 <flush_branch_caches+0x28>
>>>        28:   05 00 00 48     bl      2c <flush_branch_caches+0x2c>
>>>
>>>
>>> arch/powerpc/kernel/switch.S failing src section:
>>>
>>> .balign 32
>>> .global flush_branch_caches
>>> flush_branch_caches:
>>>          /* Save LR into r9 */
>>>          mflr    r9
>>>
>>>          // Flush the link stack
>>>          .rept 64
>>>          ANNOTATE_INTRA_FUNCTION_CALL
>>>          bl      .+4
>>>          .endr
>>>          b       1f
>>>          nops    6
>>>
>>> Maddy
>>>
>>>
>>>> Christophe
>>>
>>
> Regards,
> 
> Venkat.
>