Messages in this thread | | | Date | Mon, 18 Apr 2022 11:51:16 +0530 | From | "Naveen N. Rao" <> | Subject | Re: [PATCH v1 07/22] powerpc/ftrace: Use patch_instruction() return directly |
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Christophe Leroy wrote: > Instead of returning -EPERM when patch_instruction() fails, > just return what patch_instruction returns. > > That simplifies ftrace_modify_code(): > > 0: 94 21 ff c0 stwu r1,-64(r1) > 4: 93 e1 00 3c stw r31,60(r1) > 8: 7c 7f 1b 79 mr. r31,r3 > c: 40 80 00 30 bge 3c <ftrace_modify_code+0x3c> > 10: 93 c1 00 38 stw r30,56(r1) > 14: 7c 9e 23 78 mr r30,r4 > 18: 7c a4 2b 78 mr r4,r5 > 1c: 80 bf 00 00 lwz r5,0(r31) > 20: 7c 1e 28 40 cmplw r30,r5 > 24: 40 82 00 34 bne 58 <ftrace_modify_code+0x58> > 28: 83 c1 00 38 lwz r30,56(r1) > 2c: 7f e3 fb 78 mr r3,r31 > 30: 83 e1 00 3c lwz r31,60(r1) > 34: 38 21 00 40 addi r1,r1,64 > 38: 48 00 00 00 b 38 <ftrace_modify_code+0x38> > 38: R_PPC_REL24 patch_instruction > > Before: > > 0: 94 21 ff c0 stwu r1,-64(r1) > 4: 93 e1 00 3c stw r31,60(r1) > 8: 7c 7f 1b 79 mr. r31,r3 > c: 40 80 00 4c bge 58 <ftrace_modify_code+0x58> > 10: 93 c1 00 38 stw r30,56(r1) > 14: 7c 9e 23 78 mr r30,r4 > 18: 7c a4 2b 78 mr r4,r5 > 1c: 80 bf 00 00 lwz r5,0(r31) > 20: 7c 08 02 a6 mflr r0 > 24: 90 01 00 44 stw r0,68(r1) > 28: 7c 1e 28 40 cmplw r30,r5 > 2c: 40 82 00 48 bne 74 <ftrace_modify_code+0x74> > 30: 7f e3 fb 78 mr r3,r31 > 34: 48 00 00 01 bl 34 <ftrace_modify_code+0x34> > 34: R_PPC_REL24 patch_instruction > 38: 80 01 00 44 lwz r0,68(r1) > 3c: 20 63 00 00 subfic r3,r3,0 > 40: 83 c1 00 38 lwz r30,56(r1) > 44: 7c 63 19 10 subfe r3,r3,r3 > 48: 7c 08 03 a6 mtlr r0 > 4c: 83 e1 00 3c lwz r31,60(r1) > 50: 38 21 00 40 addi r1,r1,64 > 54: 4e 80 00 20 blr > > It improves ftrace activation/deactivation duration by about 3%. > > Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> > --- > arch/powerpc/kernel/trace/ftrace.c | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) > > diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c > index 98e82fa4980f..1b05d33f96c6 100644 > --- a/arch/powerpc/kernel/trace/ftrace.c > +++ b/arch/powerpc/kernel/trace/ftrace.c > @@ -78,10 +78,7 @@ ftrace_modify_code(unsigned long ip, ppc_inst_t old, ppc_inst_t new) > } > > /* replace the text with the new text */ > - if (patch_instruction((u32 *)ip, new)) > - return -EPERM; > - > - return 0; > + return patch_instruction((u32 *)ip, new);
I think the reason we were returning -EPERM is so that ftrace_bug() can throw the right error message. That will change due to this patch, though I'm not sure how much it matters. -EFAULT and -EPERM seem to print almost the same error message.
- Naveen
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