| Message ID | 1469728748-3493-1-git-send-email-andrew.burgess@embecosm.com |
|---|---|
| State | New |
| Headers | show |
Hi Andrew, Andrew Burgess wrote, > I ran into this issue while trying to debug a _different_ issue witin > the uClinc(-ng) arc dynamic linker. I turned on debugging support > within the dynamic linker, and the linker would no longer complete its > bootstrap phase due to a lack of support for the R_ARC_JMP_SLOT > relocation type. > > To reproduce this issue it should be enough to configure uClibc(-ng) > for ARC with 'DODEBUG=y', then try to run anything that requires > dynamic linking. > > The R_ARC_JMP_SLOT relocation type is used within the .plt, so I > believe it makes sense for these relocations to be generated. > > I updated the associated comment above the boostrap patching code so > that it makes more sense (to me at least) with the extra relocation > support. > > I wonder if you would consider merging this patch? Yes, I merged it and pushed, Thanks Waldemar
On 07/28/2016 10:59 AM, Andrew Burgess wrote: > I ran into this issue while trying to debug a _different_ issue witin > the uClinc(-ng) arc dynamic linker. I turned on debugging support > within the dynamic linker, and the linker would no longer complete its > bootstrap phase due to a lack of support for the R_ARC_JMP_SLOT > relocation type. > > To reproduce this issue it should be enough to configure uClibc(-ng) > for ARC with 'DODEBUG=y', then try to run anything that requires > dynamic linking. > > The R_ARC_JMP_SLOT relocation type is used within the .plt, so I > believe it makes sense for these relocations to be generated. > > I updated the associated comment above the boostrap patching code so > that it makes more sense (to me at least) with the extra relocation > support. > > I wonder if you would consider merging this patch? > > Thanks, > Andrew > > > --- > > This commit adds support for R_ARC_JMP_SLOT relocations during the > bootstrap phase of the dynamic linker. These relocations will be > generated if uClibc is configured with 'DODEBUG=y'. > --- > ldso/ldso/arc/dl-startup.h | 11 +++++++---- > 1 file changed, 7 insertions(+), 4 deletions(-) > > diff --git a/ldso/ldso/arc/dl-startup.h b/ldso/ldso/arc/dl-startup.h > index ef89b53..fadc433 100644 > --- a/ldso/ldso/arc/dl-startup.h > +++ b/ldso/ldso/arc/dl-startup.h > @@ -64,10 +64,11 @@ __asm__( > > /* > * Dynamic loader bootstrapping: > - * Since we don't modify text at runtime, these can only be data relos > - * (so safe to assume that they are word aligned). > - * And also they HAVE to be RELATIVE relos only > - * @RELP is the relo entry being processed > + * The only relocations that should be found are either R_ARC_RELATIVE for > + * data relocations (.got, etc) or R_ARC_JMP_SLOT for code relocations > + * (.plt). It is safe to assume that all of these relocations are word > + * aligned. > + * @RELP is the reloc entry being processed > * @REL is the pointer to the address we are relocating. > * @SYMBOL is the symbol involved in the relocation > * @LOAD is the load address. > @@ -78,6 +79,8 @@ do { \ > int type = ELF32_R_TYPE((RELP)->r_info); \ > if (likely(type == R_ARC_RELATIVE)) \ > *REL += (unsigned long) LOAD; \ > + else if (type == R_ARC_JMP_SLOT) \ > + *REL = SYMBOL; \ > else \ > _dl_exit(1); \ > }while(0) So I know this has been merged and all - but I'm wondering if this is PIE safe. Cuper has been painfully fixing PIE related issues - including uClibc issues and since we are on the topic I'm wondering if this needs some additional fixup ? -Vineet
diff --git a/ldso/ldso/arc/dl-startup.h b/ldso/ldso/arc/dl-startup.h index ef89b53..fadc433 100644 --- a/ldso/ldso/arc/dl-startup.h +++ b/ldso/ldso/arc/dl-startup.h @@ -64,10 +64,11 @@ __asm__( /* * Dynamic loader bootstrapping: - * Since we don't modify text at runtime, these can only be data relos - * (so safe to assume that they are word aligned). - * And also they HAVE to be RELATIVE relos only - * @RELP is the relo entry being processed + * The only relocations that should be found are either R_ARC_RELATIVE for + * data relocations (.got, etc) or R_ARC_JMP_SLOT for code relocations + * (.plt). It is safe to assume that all of these relocations are word + * aligned. + * @RELP is the reloc entry being processed * @REL is the pointer to the address we are relocating. * @SYMBOL is the symbol involved in the relocation * @LOAD is the load address. @@ -78,6 +79,8 @@ do { \ int type = ELF32_R_TYPE((RELP)->r_info); \ if (likely(type == R_ARC_RELATIVE)) \ *REL += (unsigned long) LOAD; \ + else if (type == R_ARC_JMP_SLOT) \ + *REL = SYMBOL; \ else \ _dl_exit(1); \ }while(0)