Re: Build Warnings at arch/powerpc/

Madhavan Srinivasan
2025-03-04T12:39:11Z

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
>
>