linux-kernel - Re: [PATCH V4 6/7] riscv: ftrace: Add DYNAMIC_FTRACE_WITH_DIRECT

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Date:   Thu, 01 Dec 2022 12:06:39 -0800 (PST)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     Conor Dooley <conor@...nel.org>
CC:     guoren@...nel.org, anup@...infault.org,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Conor Dooley <conor.dooley@...rochip.com>, heiko@...ech.de,
        rostedt@...dmis.org, mhiramat@...nel.org, jolsa@...hat.com,
        bp@...e.de, jpoimboe@...nel.org, suagrfillet@...il.com,
        andy.chiu@...ive.com, mark.rutland@....com,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject:     Re: [PATCH V4 6/7] riscv: ftrace: Add DYNAMIC_FTRACE_WITH_DIRECT_CALLS support

On Thu, 01 Dec 2022 12:02:56 PST (-0800), Conor Dooley wrote:
> On Mon, Nov 28, 2022 at 10:32:29PM -0500, guoren@...nel.org wrote:
>> From: Song Shuai <suagrfillet@...il.com>
>>
>> This patch adds DYNAMIC_FTRACE_WITH_DIRECT_CALLS support for RISC-V.
>>
>> select the DYNAMIC_FTRACE_WITH_DIRECT_CALLS to provide the
>> register_ftrace_direct[_multi] interfaces allowing users to register
>> the customed trampoline (direct_caller) as the mcount for one or
>> more target functions. And modify_ftrace_direct[_multi] are also
>> provided for modifying direct_caller.
>>
>> To make the direct_caller and the other ftrace hooks (eg. function/fgraph
>> tracer, k[ret]probes) co-exist, a temporary register is nominated to
>> store the address of direct_caller in ftrace_regs_caller. After the
>> setting of the address direct_caller by direct_ops->func and the
>> RESTORE_REGS in ftrace_regs_caller, direct_caller will be jumped to
>> by the `jr` inst.
>>
>> Signed-off-by: Song Shuai <suagrfillet@...il.com>
>> Tested-by: Guo Ren <guoren@...nel.org>
>> Signed-off-by: Guo Ren <guoren@...nel.org>
>> ---
>>  arch/riscv/Kconfig              | 1 +
>>  arch/riscv/include/asm/ftrace.h | 6 ++++++
>>  arch/riscv/kernel/mcount-dyn.S  | 4 ++++
>>  3 files changed, 11 insertions(+)
>>
>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
>> index 1d0e5838b11b..2828537abfcd 100644
>> --- a/arch/riscv/Kconfig
>> +++ b/arch/riscv/Kconfig
>> @@ -278,6 +278,7 @@ config ARCH_RV64I
>>  	select ARCH_SUPPORTS_INT128 if CC_HAS_INT128
>>  	select HAVE_DYNAMIC_FTRACE if !XIP_KERNEL && MMU && $(cc-option,-fpatchable-function-entry=8)
>>  	select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE
>> +	select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
>>  	select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
>>  	select HAVE_FUNCTION_GRAPH_TRACER
>>  	select HAVE_FUNCTION_TRACER if !XIP_KERNEL && !PREEMPTION
>
> Please sort new entries here in alphabetical order, so move the new
> entry up by one line :)

IIRC whomever sorted these entrties orignially posted a script that does 
that.  Maybe that should be integrated into either checkpatch or one of 
the patchwork robots so we don't have to manually remember the alphabet?