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Date: Sat, 30 Jan 2016 13:24:49 -0500
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: [PATCH] ldso: fix GDB dynamic linker info on MIPS
On Sat, Jan 30, 2016 at 07:20:19PM +0100, Felix Fietkau wrote:
> GDB is looking for a pointer to the ldso debug info in the data of the
> ..rld_map section.
>
> Signed-off-by: Felix Fietkau <nbd@...nwrt.org>
> ---
> arch/mips/reloc.h | 1 +
> src/ldso/dynlink.c | 9 ++++++++-
> 2 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/arch/mips/reloc.h b/arch/mips/reloc.h
> index 9b40e3d..e9cb209 100644
> --- a/arch/mips/reloc.h
> +++ b/arch/mips/reloc.h
> @@ -25,6 +25,7 @@
>
> #define NEED_MIPS_GOT_RELOCS 1
> #define DYNAMIC_IS_RO 1
> +#define DT_DEBUG_INDIRECT DT_MIPS_RLD_MAP
> #define ARCH_SYM_REJECT_UND(s) (!((s)->st_other & STO_MIPS_PLT))
>
> #define CRTJMP(pc,sp) __asm__ __volatile__( \
> diff --git a/src/ldso/dynlink.c b/src/ldso/dynlink.c
> index 93e7d67..dd85eea 100644
> --- a/src/ldso/dynlink.c
> +++ b/src/ldso/dynlink.c
> @@ -1584,11 +1584,18 @@ _Noreturn void __dls3(size_t *sp)
> load_deps(&app);
> make_global(&app);
>
> + for (i=0; app.dynv[i]; i+=2) {
> #ifndef DYNAMIC_IS_RO
> - for (i=0; app.dynv[i]; i+=2)
> if (app.dynv[i]==DT_DEBUG)
> app.dynv[i+1] = (size_t)&debug;
> #endif
> +#ifdef DT_DEBUG_INDIRECT
> + if (app.dynv[i]==DT_DEBUG_INDIRECT) {
> + size_t *ptr = (size_t *) app.dynv[i+1];
> + *ptr = (size_t)&debug;
> + }
> +#endif
> + }
>
> /* The main program must be relocated LAST since it may contin
> * copy relocations which depend on libraries' relocations. */
> --
> 2.2.2
This certainly works, but DYNAMIC_IS_RO and DT_DEBUG_INDIRECT are
probably redundant now; I can't imagine wanting one without the other.
I've also tried to replace #if/#ifdef in dynlink.c with if, in the
interest of catching warnings/errors no matter what arch we're
compiling for, so maybe we could do in internal/dynlink.h:
#ifndef DT_DEBUG_INDIRECT
#define DT_DEBUG_INDIRECT 0
#endif
then in dynlink.c:
if (!DT_DEBUG_INDIRECT && app.dynv[i]==DT_DEBUG)
...
if (DT_DEBUG_INDIRECT && app.dynv[i]==DT_DEBUG_INDIRECT)
What do you think?
Rich
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