On Apr 14 13:28, Corinna Vinschen wrote:
> On Apr 14 13:09, Kai Tietz wrote:
> > No, IMHO it is a flaw to make const-data and text sections in
> > pe-coff-image by default writable without good need. v1 and v2
> > pseudo-relocation are capable to handle read-only sections.
>
> Sure. I'd say the same goes for Cygwin images. .text is R/O anyway, so
> that only leaves the .rdata content moved to .data when auto-image is
> enabled. Given that this seems to be old behaviour, based on an old
> assumption, it seems we could just get rid of the .xa ldscript to fix
> this issue in future.
>
> Does anybody volunteer to have a look into this and send a patch upstream
> to binutils?
For testing, I created a simple testcase:
$ cat <<EOF > x.c
#include <stdio.h>
extern int optind;
int main () { printf ("optind: %d,%p\n", optind, &optind);
EOF
On 32 bit:
$ gcc -o x x.c
$ objdump -h x
[...]
0 .text 00000748 00401000 00401000 00000400 2**4
CONTENTS, ALLOC, LOAD, READONLY, CODE, DATA
1 .data 00000098 00402000 00402000 00000c00 2**5
CONTENTS, ALLOC, LOAD, DATA
2 .rdata 00000024 00403000 00403000 00000e00 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
3 .eh_frame 00000004 00404000 00404000 00001000 2**2
CONTENTS, ALLOC, LOAD, DATA
4 .bss 00000110 00405000 00405000 00000000 2**5
ALLOC
5 .idata 000001e0 00406000 00406000 00001200 2**2
CONTENTS, ALLOC, LOAD, DATA
[...]
$ nm x | grep optind
0040117f T __fu0__optind
00401187 T __fu1__optind
004060a0 I __imp__optind
004060a0 I __imp__optind
00406140 I __nm__optind
So on 32 bit we have two symbols in .text and 3 symbols in .idata.
On 64 bit:
$ gcc -o x x.c
$ objdump -h x
[...]
0 .text 00000760 0000000100401000 0000000100401000 00000400 2**4
CONTENTS, ALLOC, LOAD, READONLY, CODE, DATA
1 .data 00000048 0000000100402000 0000000100402000 00000c00 2**5
CONTENTS, ALLOC, LOAD, DATA
2 .rdata 00000308 0000000100403000 0000000100403000 00000e00 2**4
CONTENTS, ALLOC, LOAD, READONLY, DATA
3 .pdata 000000e4 0000000100404000 0000000100404000 00001200 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
4 .xdata 00000088 0000000100405000 0000000100405000 00001400 2**2
CONTENTS, ALLOC, LOAD, READONLY, DATA
5 .bss 000001c0 0000000100406000 0000000100406000 00000000 2**5
ALLOC
6 .idata 0000025c 0000000100407000 0000000100407000 00001600 2**2
CONTENTS, ALLOC, LOAD, DATA
$ nm x | grep optind
0000000100403050 r .rdata$.refptr.optind
0000000100403050 R .refptr.optind
0000000100403050 R __fu0_optind
0000000100407104 I __imp_optind
0000000100407104 I __imp_optind
00000001004071bc I __nm_optind
So on 64 bit we have three symbols in .rdata and 3 in .idata.
On 32 bit, the .xa script is used, but has no influence, apparently.
On 64 bit, the .x script is used, even with --enable-auto-import.
Both versions work as expected:
$ ./x
optind: 1,0x611821e4
$ ./x
optind: 1,0x1801c37bc
To me this means, we should not use the .xa file on 32 bit either.
It moves all .rdata data to the .data section for no good reason,
thus adding unnecessary pressure to the pagefile.
Does that make sense or did I miss something?
Corinna
--
Corinna Vinschen Please, send mails regarding Cygwin to
Cygwin Maintainer cygwin AT cygwin DOT com
Red Hat
