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SubjectRe: [PATCH] scripts/kallsyms: skip ppc compiler stub *.long_branch.* / *.plt_branch.*
On Wed, Sep 23, 2020 at 02:48:56AM +0900, Masahiro Yamada wrote:
> PowerPC allmodconfig often fails to build as follows:
>
> LD .tmp_vmlinux.kallsyms1
> KSYM .tmp_vmlinux.kallsyms1.o
> LD .tmp_vmlinux.kallsyms2
> KSYM .tmp_vmlinux.kallsyms2.o
> LD .tmp_vmlinux.kallsyms3
> KSYM .tmp_vmlinux.kallsyms3.o
> LD vmlinux
> SORTTAB vmlinux
> SYSMAP System.map
> Inconsistent kallsyms data
> Try make KALLSYMS_EXTRA_PASS=1 as a workaround
> make[2]: *** [../Makefile:1162: vmlinux] Error 1
>
> Setting KALLSYMS_EXTRA_PASS=1 does not help.
>
> This is caused by the compiler inserting stubs such as *.long_branch.*
> and *.plt_branch.*
>
> $ powerpc-linux-nm -n .tmp_vmlinux.kallsyms2
> [ snip ]
> c00000000210c000 T __init_begin
> c00000000210c000 T _sinittext
> c00000000210c010 t 00000075.plt_branch.da9:19
> c00000000210c020 t 00000075.plt_branch.1677:5
> c00000000210c030 t 00000075.long_branch.memmove
> c00000000210c034 t 00000075.plt_branch.9e0:5
> c00000000210c044 t 00000075.plt_branch.free_initrd_mem
> ...
>
> Actually, the problem mentioned in scripts/link-vmlinux.sh comments;
> "In theory it's possible this results in even more stubs, but unlikely"
> is happening here, and ends up with another kallsyms step required.
>
> scripts/kallsyms.c already ignores various compiler stubs. Let's do
> similar to make kallsysms for PowerPC always succeed in 2 steps.
>
> Reported-by: Guenter Roeck <linux@roeck-us.net>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Tested-by: Guenter Roeck <linux@roeck-us.net>

Thanks,
Guenter

> ---
>
> scripts/kallsyms.c | 16 +++++++++++++++-
> 1 file changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
> index 0096cd965332..306b9b38150f 100644
> --- a/scripts/kallsyms.c
> +++ b/scripts/kallsyms.c
> @@ -120,17 +120,25 @@ static bool is_ignored_symbol(const char *name, char type)
> NULL
> };
>
> + static const char * const ignored_matches[] = {
> + ".long_branch.", /* ppc stub */
> + ".plt_branch.", /* ppc stub */
> + NULL
> + };
> +
> const char * const *p;
>
> - /* Exclude symbols which vary between passes. */
> + /* ignore symbol names that exactly match to a particular string. */
> for (p = ignored_symbols; *p; p++)
> if (!strcmp(name, *p))
> return true;
>
> + /* ignore symbol names that start with a particular string. */
> for (p = ignored_prefixes; *p; p++)
> if (!strncmp(name, *p, strlen(*p)))
> return true;
>
> + /* ignore symbol names that end with a particular string. */
> for (p = ignored_suffixes; *p; p++) {
> int l = strlen(name) - strlen(*p);
>
> @@ -138,6 +146,12 @@ static bool is_ignored_symbol(const char *name, char type)
> return true;
> }
>
> + /* ignore symbol names that contain a particular string. */
> + for (p = ignored_matches; *p; p++) {
> + if (strstr(name, *p))
> + return true;
> + }
> +
> if (type == 'U' || type == 'u')
> return true;
> /* exclude debugging symbols */
> --
> 2.25.1
>

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