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

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

[Al Viro]

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 <viro@zeniv.linux.org.uk>
---
 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

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

[Vivek Goyal]

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 <viro@zeniv.linux.org.uk>
> ---
>  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