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

Ingo Molnar
2023-01-25T11:32:07Z

* David Rheinsberg <david@readahead.eu> wrote:

> 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@readahead.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

That hard-coded constant is a bit lame and will cause trouble the minute
*that* size is exceeded - don't we have some more natural figure, such as
KSYM_SYMBOL_LEN?

Thanks,

Ingo