2007-02-01 13:52:27

by Al Viro

Subject: [PATCH] __crc_... is intended to be absolute

i386 boot/compressed/relocs checks for absolute symbols and warns about
unexpected ones. If you build with modversions, you get ~2500 warnings
about __crc_<symbol>. These suckers are really absolute symbols - we
do _not_ want to modify them on relocation.

They are generated by genksyms - EXPORT_... generates a weak alias, then
genksyms produces an ld script with __crc_<symbol> = <checksum> and it's
fed to ld to produce the final object file. Their only use is to match
kernel and module at modprobe time; they _must_ be absolute.

boot/compressed/relocs has a whitelist of known absolute symbols, but
it doesn't know about __crc_... stuff. As the result, we get shitloads
of false positives on any ld(1) version.

Signed-off-by: Al Viro <[email protected]>
---
arch/i386/boot/compressed/relocs.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/arch/i386/boot/compressed/relocs.c b/arch/i386/boot/compressed/relocs.c
index 468da89..881951c 100644
--- a/arch/i386/boot/compressed/relocs.c
+++ b/arch/i386/boot/compressed/relocs.c
@@ -43,6 +43,8 @@ static int is_safe_abs_reloc(const char* sym_name)
/* Match found */
return 1;
}
+ if (strncmp(sym_name, "__crc_", 6) == 0)
+ return 1;
return 0;
}

--
1.5.0-rc2.GIT

2007-02-02 08:30:38

by Vivek Goyal

Subject: Re: [PATCH] __crc_... is intended to be absolute

On Thu, Feb 01, 2007 at 01:52:23PM +0000, Al Viro wrote:
>
> i386 boot/compressed/relocs checks for absolute symbols and warns about
> unexpected ones. If you build with modversions, you get ~2500 warnings
> about __crc_<symbol>. These suckers are really absolute symbols - we
> do _not_ want to modify them on relocation.
>
> They are generated by genksyms - EXPORT_... generates a weak alias, then
> genksyms produces an ld script with __crc_<symbol> = <checksum> and it's
> fed to ld to produce the final object file. Their only use is to match
> kernel and module at modprobe time; they _must_ be absolute.
>
> boot/compressed/relocs has a whitelist of known absolute symbols, but
> it doesn't know about __crc_... stuff. As the result, we get shitloads
> of false positives on any ld(1) version.
>
> Signed-off-by: Al Viro <[email protected]>
> ---
> arch/i386/boot/compressed/relocs.c | 2 ++
> 1 files changed, 2 insertions(+), 0 deletions(-)
>
> diff --git a/arch/i386/boot/compressed/relocs.c b/arch/i386/boot/compressed/relocs.c
> index 468da89..881951c 100644
> --- a/arch/i386/boot/compressed/relocs.c
> +++ b/arch/i386/boot/compressed/relocs.c
> @@ -43,6 +43,8 @@ static int is_safe_abs_reloc(const char* sym_name)
> /* Match found */
> return 1;
> }
> + if (strncmp(sym_name, "__crc_", 6) == 0)
> + return 1;
> return 0;
> }

Thanks Viro. Sorry, I missed this case.

Thanks
Vivek