[patch+7.5.1] Work around PR libc/13097 "linux-vdso.so.1" #3

[Luis Machado]

On 11/23/2012 10:39 AM, Jan Kratochvil wrote:
> On Fri, 23 Nov 2012 13:02:41 +0100, Pedro Alves wrote:
>> Won't real file based DSOs in the loader list _always_ be full paths,
>> never relative paths?  I'd think we could always ignore DSOs whose
>> path doesn't start with '/', everywhere.
>
> :|gcc -shared -fPIC -o x.so -x c -;echo 'main(){}'|gcc -o x ./x.so -x c -;gdb ./x -ex start -ex 'p *_r_debug.r_map' -ex 'p *_r_debug.r_map.l_next' -ex 'p *_r_debug.r_map.l_next.l_next' -ex 'p *_r_debug.r_map.l_next.l_next.l_next' -ex 'p *_r_debug.r_map.l_next.l_next.l_next.l_next' -ex 'p *_r_debug.r_map.l_next.l_next.l_next.l_next.l_next'
>
> $1 = {l_addr = 0, l_name = 0x37e3a1bd69 "", l_ld = 0x600778, l_next = 0x37e3c23818, l_prev = 0x0}
> $2 = {l_addr = 140737363566592, l_name = 0x37e3a1bd69 "", l_ld = 0x7ffff7ffe488, l_next = 0x7ffff7ffd648, l_prev = 0x37e3c23288}
> $3 = {l_addr = 140737352024064, l_name = 0x7ffff7ffd640 "./x.so", l_ld = 0x7ffff7ffc5e8, l_next = 0x7ffff7dd5000, l_prev = 0x37e3c23818}
>                                                          ^^^^^^^^
> $4 = {l_addr = 0, l_name = 0x7ffff7ffdb60 "/lib64/libc.so.6", l_ld = 0x37e45b0b40, l_next = 0x37e3c22998, l_prev = 0x7ffff7ffd648}
> $5 = {l_addr = 0, l_name = 0x400200 "/lib64/ld-linux-x86-64.so.2", l_ld = 0x37e3c21de8, l_next = 0x0, l_prev = 0x7ffff7dd5000}
>
> So file based solibs do not have to start with '/'.
>
> Besides that there is no standard for any such rule and I consider this patch
> only as a workaround of a WONTFIXed glibc PR.  In such case I believe the
> impact should be minimal.
>
> Maybe there is even a way how to make l_name really "x.so" above, not sure.
>
>
> Jan
>

Maybe something like lrealpath? That would canonicalize the library path.

Luis