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Message-Id: <1644860537.hyunv1mld0.naveen@linux.ibm.com>
Date: Mon, 14 Feb 2022 23:21:56 +0530
From: "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To: Christophe Leroy <christophe.leroy@...roup.eu>,
Jiri Kosina <jikos@...nel.org>,
Joe Lawrence <joe.lawrence@...hat.com>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Miroslav Benes <mbenes@...e.cz>,
Ingo Molnar <mingo@...hat.com>, Petr Mladek <pmladek@...e.com>,
Steven Rostedt <rostedt@...dmis.org>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
"live-patching@...r.kernel.org" <live-patching@...r.kernel.org>
Subject: Re: [PATCH v2 12/13] powerpc/ftrace: Prepare ftrace_64_mprofile.S for
reuse by PPC32
Christophe Leroy wrote:
> PPC64 mprofile versions and PPC32 are very similar.
>
> Modify PPC64 version so that if can be reused for PPC32.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
> ---
> .../powerpc/kernel/trace/ftrace_64_mprofile.S | 73 +++++++++++++------
> 1 file changed, 51 insertions(+), 22 deletions(-)
While I agree that ppc32 and -mprofile-kernel ftrace code are very
similar, I think this patch adds way too many #ifdefs. IMHO, this
makes the resultant code quite difficult to follow.
- Naveen
>
> diff --git a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S b/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
> index 6071e0122797..56da60e98327 100644
> --- a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
> +++ b/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
> @@ -34,13 +34,16 @@
> */
> _GLOBAL(ftrace_regs_caller)
> /* Save the original return address in A's stack frame */
> - std r0,LRSAVE(r1)
> +#ifdef CONFIG_MPROFILE_KERNEL
> + PPC_STL r0,LRSAVE(r1)
> +#endif
>
> /* Create our stack frame + pt_regs */
> - stdu r1,-SWITCH_FRAME_SIZE(r1)
> + PPC_STLU r1,-SWITCH_FRAME_SIZE(r1)
>
> /* Save all gprs to pt_regs */
> SAVE_GPR(0, r1)
> +#ifdef CONFIG_PPC64
> SAVE_GPRS(2, 11, r1)
>
> /* Ok to continue? */
> @@ -49,10 +52,13 @@ _GLOBAL(ftrace_regs_caller)
> beq ftrace_no_trace
>
> SAVE_GPRS(12, 31, r1)
> +#else
> + stmw r2, GPR2(r1)
> +#endif
>
> /* Save previous stack pointer (r1) */
> addi r8, r1, SWITCH_FRAME_SIZE
> - std r8, GPR1(r1)
> + PPC_STL r8, GPR1(r1)
>
> /* Load special regs for save below */
> mfmsr r8
> @@ -63,10 +69,11 @@ _GLOBAL(ftrace_regs_caller)
> /* Get the _mcount() call site out of LR */
> mflr r7
> /* Save it as pt_regs->nip */
> - std r7, _NIP(r1)
> + PPC_STL r7, _NIP(r1)
> /* Save the read LR in pt_regs->link */
> - std r0, _LINK(r1)
> + PPC_STL r0, _LINK(r1)
>
> +#ifdef CONFIG_PPC64
> /* Save callee's TOC in the ABI compliant location */
> std r2, 24(r1)
> ld r2,PACATOC(r13) /* get kernel TOC in r2 */
> @@ -74,8 +81,12 @@ _GLOBAL(ftrace_regs_caller)
> addis r3,r2,function_trace_op@toc@ha
> addi r3,r3,function_trace_op@toc@l
> ld r5,0(r3)
> +#else
> + lis r3,function_trace_op@ha
> + lwz r5,function_trace_op@l(r3)
> +#endif
>
> -#ifdef CONFIG_LIVEPATCH
> +#ifdef CONFIG_LIVEPATCH_64
> mr r14,r7 /* remember old NIP */
> #endif
> /* Calculate ip from nip-4 into r3 for call below */
> @@ -85,10 +96,10 @@ _GLOBAL(ftrace_regs_caller)
> mr r4, r0
>
> /* Save special regs */
> - std r8, _MSR(r1)
> - std r9, _CTR(r1)
> - std r10, _XER(r1)
> - std r11, _CCR(r1)
> + PPC_STL r8, _MSR(r1)
> + PPC_STL r9, _CTR(r1)
> + PPC_STL r10, _XER(r1)
> + PPC_STL r11, _CCR(r1)
>
> /* Load &pt_regs in r6 for call below */
> addi r6, r1 ,STACK_FRAME_OVERHEAD
> @@ -100,27 +111,32 @@ ftrace_regs_call:
> nop
>
> /* Load ctr with the possibly modified NIP */
> - ld r3, _NIP(r1)
> + PPC_LL r3, _NIP(r1)
> mtctr r3
> -#ifdef CONFIG_LIVEPATCH
> +#ifdef CONFIG_LIVEPATCH_64
> cmpd r14, r3 /* has NIP been altered? */
> #endif
>
> /* Restore gprs */
> - REST_GPR(0, r1)
> +#ifdef CONFIG_PPC64
> REST_GPRS(2, 31, r1)
> +#else
> + lmw r2, GPR2(r1)
> +#endif
>
> /* Restore possibly modified LR */
> - ld r0, _LINK(r1)
> + PPC_LL r0, _LINK(r1)
> mtlr r0
>
> +#ifdef CONFIG_PPC64
> /* Restore callee's TOC */
> ld r2, 24(r1)
> +#endif
>
> /* Pop our stack frame */
> addi r1, r1, SWITCH_FRAME_SIZE
>
> -#ifdef CONFIG_LIVEPATCH
> +#ifdef CONFIG_LIVEPATCH_64
> /* Based on the cmpd above, if the NIP was altered handle livepatch */
> bne- livepatch_handler
> #endif
> @@ -129,6 +145,7 @@ ftrace_regs_call:
> _GLOBAL(ftrace_stub)
> blr
>
> +#ifdef CONFIG_PPC64
> ftrace_no_trace:
> mflr r3
> mtctr r3
> @@ -136,25 +153,31 @@ ftrace_no_trace:
> addi r1, r1, SWITCH_FRAME_SIZE
> mtlr r0
> bctr
> +#endif
>
> _GLOBAL(ftrace_caller)
> /* Save the original return address in A's stack frame */
> - std r0, LRSAVE(r1)
> +#ifdef CONFIG_MPROFILE_KERNEL
> + PPC_STL r0, LRSAVE(r1)
> +#endif
>
> /* Create our stack frame + pt_regs */
> - stdu r1, -SWITCH_FRAME_SIZE(r1)
> + PPC_STLU r1, -SWITCH_FRAME_SIZE(r1)
>
> /* Save all gprs to pt_regs */
> SAVE_GPRS(3, 10, r1)
>
> +#ifdef CONFIG_PPC64
> lbz r3, PACA_FTRACE_ENABLED(r13)
> cmpdi r3, 0
> beq ftrace_no_trace
> +#endif
>
> /* Get the _mcount() call site out of LR */
> mflr r7
> - std r7, _NIP(r1)
> + PPC_STL r7, _NIP(r1)
>
> +#ifdef CONFIG_PPC64
> /* Save callee's TOC in the ABI compliant location */
> std r2, 24(r1)
> ld r2, PACATOC(r13) /* get kernel TOC in r2 */
> @@ -162,6 +185,10 @@ _GLOBAL(ftrace_caller)
> addis r3, r2, function_trace_op@toc@ha
> addi r3, r3, function_trace_op@toc@l
> ld r5, 0(r3)
> +#else
> + lis r3,function_trace_op@ha
> + lwz r5,function_trace_op@l(r3)
> +#endif
>
> #ifdef CONFIG_LIVEPATCH_64
> SAVE_GPR(14, r1)
> @@ -171,7 +198,7 @@ _GLOBAL(ftrace_caller)
> subi r3, r7, MCOUNT_INSN_SIZE
>
> /* Put the original return address in r4 as parent_ip */
> - std r0, _LINK(r1)
> + PPC_STL r0, _LINK(r1)
> mr r4, r0
>
> /* Load &pt_regs in r6 for call below */
> @@ -183,7 +210,7 @@ ftrace_call:
> bl ftrace_stub
> nop
>
> - ld r3, _NIP(r1)
> + PPC_LL r3, _NIP(r1)
> mtctr r3
> #ifdef CONFIG_LIVEPATCH_64
> cmpd r14, r3 /* has NIP been altered? */
> @@ -193,11 +220,13 @@ ftrace_call:
> /* Restore gprs */
> REST_GPRS(3, 10, r1)
>
> +#ifdef CONFIG_PPC64
> /* Restore callee's TOC */
> ld r2, 24(r1)
> +#endif
>
> /* Restore possibly modified LR */
> - ld r0, _LINK(r1)
> + PPC_LL r0, _LINK(r1)
> mtlr r0
>
> /* Pop our stack frame */
> @@ -209,7 +238,7 @@ ftrace_call:
> #endif
> bctr /* jump after _mcount site */
>
> -#ifdef CONFIG_LIVEPATCH
> +#ifdef CONFIG_LIVEPATCH_64
> /*
> * This function runs in the mcount context, between two functions. As
> * such it can only clobber registers which are volatile and used in
> --
> 2.33.1
>
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