linux-kernel - [PATCH] x86/insn_decoder_test: allow longer symbol-names

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Message-Id: <320c4dba-9919-404b-8a26-a8af16be1845@app.fastmail.com>
Date:   Tue, 24 Jan 2023 12:04:59 +0100
From:   "David Rheinsberg" <david@...dahead.eu>
To:     linux-kernel@...r.kernel.org
Cc:     rust-for-linux@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
        x86@...nel.org, "Dave Hansen" <dave.hansen@...ux.intel.com>,
        "Borislav Petkov" <bp@...en8.de>, "Ingo Molnar" <mingo@...hat.com>,
        "Thomas Gleixner" <tglx@...utronix.de>
Subject: [PATCH] x86/insn_decoder_test: allow longer symbol-names

Increase the allowed line-length of the insn-decoder-test to 4k to allow
for symbol-names longer than 256 characters.

The insn-decoder-test takes objdump output as input, which may contain
symbol-names as instruction arguments. With rust-code entering the
kernel, those symbol-names will include mangled-symbols which might
exceed the current line-length-limit of the tool.

By bumping the line-length-limit of the tool to 4k, we get a reasonable
buffer for all objdump outputs I have seen so far. Unfortunately, ELF
symbol-names are not restricted in length, so technically this might
still end up failing if we encounter longer names in the future.

My compile-failure looks like this:

    arch/x86/tools/insn_decoder_test: error: malformed line 1152000:
    tBb_+0xf2>

..which overflowed by 10 characters reading this line:

    ffffffff81458193:   74 3d                   je     ffffffff814581d2 <_RNvXse_NtNtNtCshGpAVYOtgW1_4core4iter8adapters7flattenINtB5_13FlattenCompatINtNtB7_3map3MapNtNtNtBb_3str4iter5CharsNtB1v_17CharEscapeDefaultENtNtBb_4char13EscapeDefaultENtNtBb_3fmt5Debug3fmtBb_+0xf2>

Signed-off-by: David Rheinsberg <david@...dahead.eu>
---
 arch/x86/tools/insn_decoder_test.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/tools/insn_decoder_test.c b/arch/x86/tools/insn_decoder_test.c
index 472540aeabc2..366e07546344 100644
--- a/arch/x86/tools/insn_decoder_test.c
+++ b/arch/x86/tools/insn_decoder_test.c
@@ -106,7 +106,7 @@ static void parse_args(int argc, char **argv)
 	}
 }

-#define BUFSIZE 256
+#define BUFSIZE 4096

 int main(int argc, char **argv)
 {
-- 
2.39.1