On Fri, Oct 27, 2017 at 02:53:26PM +0200, Michal Meloun wrote:
> Sorry for top posting
> That's pity, we have clear problem in rtld code :(
> See:
> -----------------------------------------------------
> RESCUE WITHOUT JEMALLOC_ALIGNED(16);
> -----------------------------------------------------
> Program Headers:
> TLS 0xa732b0 0x00a832b0 0x00a832b0 0x00b40 0x011bc R 0x8
> Section Headers:
> 04 .tdata .tbss .init_array .fini_array .jcr .got
> Dump:
> 00a832b0 <__je_tsd_tls+0xa832b0>:
> a832b0: 00000005
>
> GDB
> (gdb) b tsd_fetch_impl
> Breakpoint 1 at 0x7c4c08: tsd_fetch_impl. (6 locations)
> (gdb) r
> Starting program: /usr/src/rescue.noalign sh
>
> Breakpoint 1, tsd_fetch_impl (init=true, minimal=false) at
> /usr/src/contrib/jemalloc/include/jemalloc/internal/tsd.h:261
> 261 tsd_t *tsd = tsd_get(init);
> (gdb) n
> 263 if (!init && tsd_get_allocates() && tsd == NULL) {
>
> (gdb) p tsd
> $1 = (tsd_t *) 0x20c83008
>
> (gdb) p *tsd
> $2 = {state = 5 '\005', ....
>
> (gdb) p *((tsd_t *)0x00a832b0)
> $3 = {state = 5 '\005', ...
>
>
>
> -----------------------------------------------------
> RESCUE WITH JEMALLOC_ALIGNED(16);
> -----------------------------------------------------
> Program Headers:
> TLS 0xa732b0 0x00a832b0 0x00a832b0 0x00b40 0x011bc R 0x10
> Section Headers:
> 04 .tdata .tbss .init_array .fini_array .jcr .got
> Dump:
> 00a832b0 <__je_tsd_tls+0xa832b0>:
> a832b0: 00000005
>
> GDB
> (gdb) b tsd_fetch_impl
> Breakpoint 1 at 0x7c4c08: tsd_fetch_impl. (6 locations)
> (gdb) r
> Starting program: /usr/obj/usr/src/rescue/rescue/rescue sh
> Breakpoint 1, tsd_fetch_impl (init=true, minimal=false) at
> /usr/src/contrib/jemalloc/include/jemalloc/internal/tsd.h:261
> 261 tsd_t *tsd = tsd_get(init);
> (gdb) n
> 263 if (!init && tsd_get_allocates() && tsd == NULL) {
>
> (gdb) p tsd
> $1 = (tsd_t *) 0x20c83010
>
> (gdb) p *tsd
> $2 = {state = 0 '\000', ...
>
> (gdb) p *((tsd_t *)0x00a832b0)
> $3 = {state = 5 '\005', ...
>
> !!!! BUT p *(tsd - 8 bytes) !!!!!!!!!!
> (gdb) p *((tsd_t *)0x20c83008)
> $4 = {state = 5 '\005', ...
>
> -----------------------------------------------------
> So it's clear that:
>
> - both binaries are valid, .tdata section have valid data.
> - requested alignment is propagated to binary.
> - .tdata section is properly loaded to memory because
> p *((tsd_t *)0x00a832b0) is {state = 5 '\005'
> in both cases
>
> - a per thread copy of .tdata respect requested alignment
> but the original data was copied to unaligned address.
> because for aligned binary
> p *tsd is {state = 0 '\000', ...
> p *(tsd - 8 bytes) is {state = 5 '\005'
>
> I'm right?
> Kib, please, can you help us?
Does it happen for rescue binary ?
Note that the binary is linked static, so the problem is in lib/libc/gen/tls.c
and not in rtld. There, I do not see any real use of the phdr' p_align
value.
BTW, is rescue linked to libthr ?
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