From: dave.martin@linaro•org (Dave Martin)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCHv2] ARM: ftrace: clear zero bit in reported IPs for Thumb-2
Date: Tue, 24 Jan 2012 12:05:20 +0000 [thread overview]
Message-ID: <20120124120520.GA2199@linaro.org> (raw)
In-Reply-To: <1327039102-17754-1-git-send-email-rabin@rab.in>
On Fri, Jan 20, 2012 at 11:28:22AM +0530, Rabin Vincent wrote:
> The dynamic ftrace ops startup test currently fails on Thumb-2 kernels:
>
> Testing tracer function: PASSED
> Testing dynamic ftrace: PASSED
> Testing dynamic ftrace ops #1: (0 0 0 0 0) FAILED!
>
> This is because while the addresses in the mcount records do not have
> the zero bit set, the IP reported by the mcount call does have it set
> (because it is copied from the LR). This mismatch causes the ops
> filtering in ftrace_ops_list_func() to not call the relevant tracers.
>
> Fix this by clearing the zero bit before adjusting the LR for the mcount
> instruction size. Also, combine the mov+sub into a single sub
> instruction.
>
> Signed-off-by: Rabin Vincent <rabin@rab•in>
I'm probably not going to have a lot of time to test this; in the
meantime, I'm satisfied that you addressed my concerns, so
Acked-By: Dave Martin <dave.martin@linaro•org>
Cheers
---Dave
> ---
> v2: use bic
>
> arch/arm/kernel/entry-common.S | 15 +++++++++------
> 1 files changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
> index b2a27b6..683195c 100644
> --- a/arch/arm/kernel/entry-common.S
> +++ b/arch/arm/kernel/entry-common.S
> @@ -149,6 +149,11 @@ ENDPROC(ret_from_fork)
> #endif
> #endif
>
> +.macro mcount_adjust_addr rd, rn
> + bic \rd, \rn, #1 @ clear the Thumb bit if present
> + sub \rd, \rd, #MCOUNT_INSN_SIZE
> +.endm
> +
> .macro __mcount suffix
> mcount_enter
> ldr r0, =ftrace_trace_function
> @@ -173,8 +178,7 @@ ENDPROC(ret_from_fork)
> mcount_exit
>
> 1: mcount_get_lr r1 @ lr of instrumented func
> - mov r0, lr @ instrumented function
> - sub r0, r0, #MCOUNT_INSN_SIZE
> + mcount_adjust_addr r0, lr @ instrumented function
> adr lr, BSYM(2f)
> mov pc, r2
> 2: mcount_exit
> @@ -184,8 +188,7 @@ ENDPROC(ret_from_fork)
> mcount_enter
>
> mcount_get_lr r1 @ lr of instrumented func
> - mov r0, lr @ instrumented function
> - sub r0, r0, #MCOUNT_INSN_SIZE
> + mcount_adjust_addr r0, lr @ instrumented function
>
> .globl ftrace_call\suffix
> ftrace_call\suffix:
> @@ -205,11 +208,11 @@ ftrace_graph_call\suffix:
> #ifdef CONFIG_DYNAMIC_FTRACE
> @ called from __ftrace_caller, saved in mcount_enter
> ldr r1, [sp, #16] @ instrumented routine (func)
> + mcount_adjust_addr r1, r1
> #else
> @ called from __mcount, untouched in lr
> - mov r1, lr @ instrumented routine (func)
> + mcount_adjust_addr r1, lr @ instrumented routine (func)
> #endif
> - sub r1, r1, #MCOUNT_INSN_SIZE
> mov r2, fp @ frame pointer
> bl prepare_ftrace_return
> mcount_exit
> --
> 1.7.7.3
>
prev parent reply other threads:[~2012-01-24 12:05 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-01 18:06 [PATCH] ARM: ftrace: clear zero bit in reported IPs for Thumb-2 Rabin Vincent
2011-12-02 12:44 ` Dave Martin
2012-01-20 5:58 ` [PATCHv2] " Rabin Vincent
2012-01-24 12:05 ` Dave Martin [this message]
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