Re: [musl] Tracking shared libraries in GDB not working?

[Rich Felker <dalias@libc.org>]

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On Mon, Dec 20, 2021 at 09:54:40AM +0100, d.dorau@avm.de wrote:
> Thanks for your thoughts. I used them to search for further information and found
> the missing piece:
> 
> https://lists.yoctoproject.org/g/yocto/message/48584
> 
> I applied that first patch
> https://lists.yoctoproject.org/g/yocto/attachment/48584/0/0007-Teach-dynlink.c-about-DT_MIPS_RLD_MAP_REL.patch
> 
> and apparently it seems to solve the issue. :-)
> 
> I did a search on this mailing list and couldn't find this patch mentioned here.
> Maybe you can include this patch in a future release if you think the solution is correct.

Thanks! This patch is not correct as-is, because the value of
DT_MIPS_RLD_MAP_REL is only meaningful on mips and could be reused on
other archs. But I've whipped up what I think is a correct version of
it here (attached), using the same approach as used for
DT_MIPS_RLD_MAP already. If you get a chance, please let me know if it
works.

Rich

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diff --git a/arch/mips/reloc.h b/arch/mips/reloc.h
index 88d23639..f4023b16 100644
--- a/arch/mips/reloc.h
+++ b/arch/mips/reloc.h
@@ -29,6 +29,7 @@
 
 #define NEED_MIPS_GOT_RELOCS 1
 #define DT_DEBUG_INDIRECT DT_MIPS_RLD_MAP
+#define DT_DEBUG_INDIRECT_REL DT_MIPS_RLD_MAP_REL
 #define ARCH_SYM_REJECT_UND(s) (!((s)->st_other & STO_MIPS_PLT))
 
 #define CRTJMP(pc,sp) __asm__ __volatile__( \
diff --git a/arch/mips64/reloc.h b/arch/mips64/reloc.h
index fdb5edc9..145d8b0b 100644
--- a/arch/mips64/reloc.h
+++ b/arch/mips64/reloc.h
@@ -38,6 +38,7 @@
 
 #define NEED_MIPS_GOT_RELOCS 1
 #define DT_DEBUG_INDIRECT DT_MIPS_RLD_MAP
+#define DT_DEBUG_INDIRECT_REL DT_MIPS_RLD_MAP_REL
 #define ARCH_SYM_REJECT_UND(s) (!((s)->st_other & STO_MIPS_PLT))
 
 #define CRTJMP(pc,sp) __asm__ __volatile__( \
diff --git a/arch/mipsn32/reloc.h b/arch/mipsn32/reloc.h
index 47c6e591..bf00bd6a 100644
--- a/arch/mipsn32/reloc.h
+++ b/arch/mipsn32/reloc.h
@@ -29,6 +29,7 @@
 
 #define NEED_MIPS_GOT_RELOCS 1
 #define DT_DEBUG_INDIRECT DT_MIPS_RLD_MAP
+#define DT_DEBUG_INDIRECT_REL DT_MIPS_RLD_MAP_REL
 #define ARCH_SYM_REJECT_UND(s) (!((s)->st_other & STO_MIPS_PLT))
 
 #define CRTJMP(pc,sp) __asm__ __volatile__( \
diff --git a/ldso/dynlink.c b/ldso/dynlink.c
index 5b9c8be4..93615cb6 100644
--- a/ldso/dynlink.c
+++ b/ldso/dynlink.c
@@ -1923,6 +1923,10 @@ void __dls3(size_t *sp, size_t *auxv)
 			size_t *ptr = (size_t *) app.dynv[i+1];
 			*ptr = (size_t)&debug;
 		}
+		if (app.dynv[i]==DT_DEBUG_INDIRECT_REL) {
+			size_t *ptr = (size_t *)((size_t)&app.dynv[i] + app.dynv[i+1]);
+			*ptr = (size_t)&debug;
+		}
 	}
 
 	/* This must be done before final relocations, since it calls
diff --git a/src/internal/dynlink.h b/src/internal/dynlink.h
index 51c0639f..d37ebbaa 100644
--- a/src/internal/dynlink.h
+++ b/src/internal/dynlink.h
@@ -92,6 +92,10 @@ struct fdpic_dummy_loadmap {
 #define DT_DEBUG_INDIRECT 0
 #endif
 
+#ifndef DT_DEBUG_INDIRECT_REL
+#define DT_DEBUG_INDIRECT_REL 0
+#endif
+
 #define AUX_CNT 32
 #define DYN_CNT 32