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

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Message-ID: <fe937273-d81a-4f6c-9eba-b96b711b4644@linux.ibm.com>
Date: Tue, 4 Mar 2025 18:08:45 +0530
From: Madhavan Srinivasan <maddy@...ux.ibm.com>
To: Christophe Leroy <christophe.leroy@...roup.eu>,
        Venkat Rao Bagalkote <venkat88@...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/



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.leroy2%40cs-soprasteria.com%7C8e0f8501f09c48dbb43608dd5ae3c9bf%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C638766656585342184%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=e5BrJzcrtlITkLF31KltGExQ5Qe8fDVTMV6VfR4w9o8%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.leroy2%40cs-soprasteria.com%7C8e0f8501f09c48dbb43608dd5ae3c9bf%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C638766656585355246%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=meQyZfB75HhJFCL6AX93slsyVwnogGPYFabDXl%2FLzDA%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

>   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
> 
>