From: Fangrui Song <maskray@google.com>
To: Nathan Chancellor <nathan@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Albert Ou <aou@eecs.berkeley.edu>,
linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
clang-built-linux@googlegroups.com, stable@vger.kernel.org
Subject: Re: [PATCH 1/3] scripts/recordmcount.pl: Fix RISC-V regex for clang
Date: Thu, 25 Mar 2021 16:36:40 -0700 [thread overview]
Message-ID: <20210325233640.jzi7uvaohvqwixiu@google.com> (raw)
In-Reply-To: <20210325223807.2423265-2-nathan@kernel.org>
On 2021-03-25, Nathan Chancellor wrote:
>Clang can generate R_RISCV_CALL_PLT relocations to _mcount:
>
>$ llvm-objdump -dr build/riscv/init/main.o | rg mcount
> 000000000000000e: R_RISCV_CALL_PLT _mcount
> 000000000000004e: R_RISCV_CALL_PLT _mcount
>
>After this, the __start_mcount_loc section is properly generated and
>function tracing still works.
>
R_RISCV_CALL_PLT can replace R_RISCV_CALL in all use cases.
R_RISCV_CALL can/may be deprecated:
https://github.com/ClangBuiltLinux/linux/issues/1331#issuecomment-802468296
Reviewed-by: Fangrui Song <maskray@google.com>
>Cc: stable@vger.kernel.org
>Link: https://github.com/ClangBuiltLinux/linux/issues/1331
>Signed-off-by: Nathan Chancellor <nathan@kernel.org>
>---
> scripts/recordmcount.pl | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl
>index 867860ea57da..a36df04cfa09 100755
>--- a/scripts/recordmcount.pl
>+++ b/scripts/recordmcount.pl
>@@ -392,7 +392,7 @@ if ($arch eq "x86_64") {
> $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
> } elsif ($arch eq "riscv") {
> $function_regex = "^([0-9a-fA-F]+)\\s+<([^.0-9][0-9a-zA-Z_\\.]+)>:";
>- $mcount_regex = "^\\s*([0-9a-fA-F]+):\\sR_RISCV_CALL\\s_mcount\$";
>+ $mcount_regex = "^\\s*([0-9a-fA-F]+):\\sR_RISCV_CALL(_PLT)?\\s_mcount\$";
> $type = ".quad";
> $alignment = 2;
> } elsif ($arch eq "nds32") {
>--
>2.31.0
>
>--
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next prev parent reply other threads:[~2021-03-25 23:37 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-25 22:38 [PATCH 0/3] Fix CONFIG_FUNCTION_TRACER with clang Nathan Chancellor
2021-03-25 22:38 ` [PATCH 1/3] scripts/recordmcount.pl: Fix RISC-V regex for clang Nathan Chancellor
2021-03-25 23:36 ` Fangrui Song [this message]
2021-03-25 22:38 ` [PATCH 2/3] riscv: Workaround mcount name prior to clang-13 Nathan Chancellor
2021-03-29 18:32 ` Nick Desaulniers
2021-03-25 22:38 ` [PATCH 3/3] riscv: Select HAVE_DYNAMIC_FTRACE when -fpatchable-function-entry is available Nathan Chancellor
2021-03-25 23:38 ` Fangrui Song
2021-03-26 8:37 ` [PATCH 0/3] Fix CONFIG_FUNCTION_TRACER with clang Sedat Dilek
2021-03-26 13:07 ` Nathan Chancellor
2021-03-27 12:16 ` Sedat Dilek
2021-04-11 21:27 ` Palmer Dabbelt
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