Re: [PATCH] perf machine: Don't ignore _etext when not a text symbol

[Arnaldo Carvalho de Melo <acme@kernel.org>]

On Wed, Jan 08, 2025 at 10:15:24AM +0100, Christophe Leroy wrote:
> Depending on how vmlinux.lds is written, _etext might be the very
> first data symbol instead of the very last text symbol.
> 
> Don't require it to be a text symbol, accept any symbol type.

I'm adding a Link:

Link: https://lore.kernel.org/all/752a31b0-4370-4f52-b7cc-45f0078c1d6c@csgroup.eu

To give more context as where this has been observed, and also add a
snippet of your explanation there, this:

----
# grep -e _stext -e _etext -e _edata /proc/kallsyms
c0000000 T _stext
c08b8000 D _etext

So there is no _edata and _etext is not text

$ ppc-linux-objdump -x vmlinux | grep -e _stext -e _etext -e _edata
c0000000 g       .head.text	00000000 _stext
c08b8000 g       .rodata	00000000 _etext
c1378000 g       .sbss	00000000 _edata
----

Thanks,

- Arnaldo

> Fixes: ed9adb2035b5 ("perf machine: Read also the end of the kernel")
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  tools/perf/util/machine.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> index 27d5345d2b30..9be2f4479f52 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -1003,7 +1003,7 @@ static int machine__get_running_kernel_start(struct machine *machine,
>  
>  	err = kallsyms__get_symbol_start(filename, "_edata", &addr);
>  	if (err)
> -		err = kallsyms__get_function_start(filename, "_etext", &addr);
> +		err = kallsyms__get_symbol_start(filename, "_etext", &addr);
>  	if (!err)
>  		*end = addr;
>  
> -- 
> 2.47.0