[PATCH] export.h: reduce __ksymtab_strings string duplication by using "MS" section flags
Jessica Yu
jeyu@kernel.org
Mon Nov 25 09:46:00 GMT 2019
+++ Rasmus Villemoes [25/11/19 10:29 +0100]:
>cc += binutils ML
>
>[on @progbits v %progbits in generic (data only) assembly code]
>
>On 22/11/2019 12.44, Masahiro Yamada wrote:
>> On Fri, Nov 22, 2019 at 1:09 AM Jessica Yu <jeyu@kernel.org> wrote:
>>>
>
>>> I think this would work, and it feels like the more correct solution
>>> especially if arm isn't the only one with the odd progbits char. It
>>> might be overkill if it's just arm that's affected though. I leave it
>>> to Masahiro to see what he prefers.
>>>
>>
>>
>> BTW, is there any reason why
>> not use %progbits all the time?
>>
>>
>> include/linux/init.h hard-codes %progbits
>>
>> #define __INITDATA .section ".init.data","aw",%progbits
>> #define __INITRODATA .section ".init.rodata","a",%progbits
>>
>>
>> So, my understanding is '%' works for all architectures,
>> but it is better to ask 0-day bot to test it.
>
>It seems that you're absolutely right. The binutils source has code like
>
>+ if (*input_line_pointer == '@' || *input_line_pointer == '%')
>+ {
>+ ++input_line_pointer;
>+ if (strncmp (input_line_pointer, "progbits",
>+ sizeof "progbits" - 1) == 0)
>+ {
>+ type = SHT_PROGBITS;
>+ input_line_pointer += sizeof "progbits" - 1;
>+ }
>+ else if (strncmp (input_line_pointer, "nobits",
>+ sizeof "nobits" - 1) == 0)
>+ {
>+ type = SHT_NOBITS;
>+ input_line_pointer += sizeof "nobits" - 1;
>+ }
Yeah, I saw this too while digging. I also came across this commit in
the binutils source:
commit ecc054c097e7ced281d02ef9632eb0261a410b96
Author: Thomas Preud'homme <thomas.preudhomme@arm.com>
Date: Fri Mar 2 11:51:34 2018 +0000
[GDB/testsuite] Use %progbits in watch-loc.c
While using @progbits in .pushsection work on some targets, it does not
work on arm target where this introduces a comment. This patch replaces
its use in gdb.dlang/watch-loc.c and gdb.mi/dw2-ref-missing-frame-func.c
by %progbits which should work on all targets since it is used in
target-independent elf/section7.s GAS test.
2018-03-02 Thomas Preud'homme <thomas.preudhomme@arm.com>
gdb/testsuite/
* gdb.dlang/watch-loc.c: Use %progbits instead of @progbits.
* gdb.mi/dw2-ref-missing-frame-func.c: Likewise.
So that seems to confirm this theory :-) I'm just surprised it isn't
documented anywhere it seems.
>The only reason I thought one needed to do it differently on ARM is this
>from the gas docs:
>
>===
> The optional TYPE argument may contain one of the following
>constants:
>
>'@progbits'
> section contains data
>...
> Note on targets where the '@' character is the start of a comment (eg
>ARM) then another character is used instead. For example the ARM port
>uses the '%' character.
>===
>
>That doesn't suggest the possibility that % or some other character
>might work on all architectures.
>
>Jessica, can you resend using just %progbits to let kbuild chew on that?
>Please include a comment about the misleading gas documentation.
Yup, sounds good. Thanks!
Jessica
More information about the Binutils
mailing list