>
> Hello,
>
> When starting Asterisk 1.8 on a mips (32 bits, BE) board, the linker
> crashes early during startup. I've traced the problem to the
> MIPS_RLD_MAP dynamic section being 0 (not sure if this is a size or
> address when reported by readelf). The asterisk binary is built with
> the --version-script option, which seems to be the reason why there is
> a MIPS_RLD_MAP entry, and AIUI, this option is intended to be used for
> shared objects. Question: can it be safely used by executables too ?
>
> The crash happens here :
>
> ldso/ldso/mips/dl-sysdep.h:102:
> #define ARCH_DYNAMIC_INFO(dpnt, dynamic, debug_addr) \
> do { \
> if (dpnt->d_tag == DT_MIPS_GOTSYM) \
> dynamic[DT_MIPS_GOTSYM_IDX] = dpnt->d_un.d_val; \
> else if (dpnt->d_tag == DT_MIPS_LOCAL_GOTNO) \
> dynamic[DT_MIPS_LOCAL_GOTNO_IDX] = dpnt->d_un.d_val; \
> else if (dpnt->d_tag == DT_MIPS_SYMTABNO) \
> dynamic[DT_MIPS_SYMTABNO_IDX] = dpnt->d_un.d_val; \
> else if (dpnt->d_tag == DT_MIPS_PLTGOT) \
> dynamic[DT_MIPS_PLTGOT_IDX] = dpnt->d_un.d_val; \
> else if ((dpnt->d_tag == DT_MIPS_RLD_MAP) && (dpnt->d_un.d_ptr)) \
> *(ElfW(Addr) *)(dpnt->d_un.d_ptr) = (ElfW(Addr)) debug_addr; \
> } while (0)
>
> The line
>
> *(ElfW(Addr) *)(dpnt->d_un.d_ptr) = (ElfW(Addr)) debug_addr;
>
> doesn't check that the destination address isn't null. It looks like the
> linker is inconsistent about how this entry type is handled, i.e. it
> doesn't allocate any memory for it, but still references it without
> checking. A similar problem was reported at Debian [1], which resulted
> in a patch checking that d_ptr isn't null before storing debug_addr.
> This effectively fixes the segfault I was getting. It looks like this
> code was inherited from glibc/eglibc, neither of which includes this
> fix (although the Debian patch applies on eglibc). Question: is this
> an appropriate fix or just a workaround, meaning the build process of
> the crashing executable should be fixed instead ?
DT_MIPS_RLD_MAP stuff looks like my work several years ago. There were
complaints
that debugging didn't work on MIPS and nobody knew why. I scanned glibc and
found
out how they did it and impl. the same in uClibc. Needless to say, I don't
know anything about MIPS though.
I do think your conclusion is a vague though. What do you mean with
d_ptr isn't checked? What is wrong with:
if ((dpnt->d_tag == DT_MIPS_RLD_MAP) && (dpnt->d_un.d_ptr))
You need to provide an example of what you want and possibly some MIPS
person can review it.
Jocke
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