| Message ID | 531B63DE.5090803@linux.vnet.ibm.com |
|---|---|
| State | Rejected |
| Delegated to: | Adhemerval Zanella Netto |
| Headers | show |
On 03/08/2014 01:39 PM, Adhemerval Zanella wrote: > While reviewing the strncat optimization for powerpc64 I noted in the > disassembled object that a call to strlen (bl strlen) generates a PLT > call to strlen (since now strlen is an IFUNC for powerpc64). Strangely > it was not being caught by check-localplt testcase. > > GNU_IFUNC are shown by readelf in 'Relocation section' value as (symbol) > instead of expected hexadecimal value. This causes the check-localplt > script to igore potential PLT stub begin generated by wrong IFUNC usage. > This patch changes the localplt script to emit such PLT cases. > > Checked on PPC64 and X86_64. > > -- > > 2014-03-03 Adhemerval Zanella <azanella@linux.vnet.ibm.com> > > * scripts/localplt.awk: Do not ignore IFUNC relocation while parsing > relocation sections. Can you show example output? On x86-64 I see: 0000003000bba030 0000034400000007 R_X86_64_JUMP_SLOT memset() memset + 0 0000003000bba048 000007ba00000007 R_X86_64_JUMP_SLOT memmove() memmove + 0 Not (memset) or (memmove). I'd like to see this fixed... and this is the first patch in patchtracker :-) > --- > > diff --git a/scripts/localplt.awk b/scripts/localplt.awk > index 2265b02..5e38073 100644 > --- a/scripts/localplt.awk > +++ b/scripts/localplt.awk > @@ -32,9 +32,15 @@ $1 == "Offset" && $2 == "Info" { in_relocs = 1; next } > NF == 0 { in_relocs = 0 } > > in_relocs && relocs_offset == jmprel_offset && NF >= 5 { > - symval = strtonum("0x" $4); > - if (symval != 0) > + # Relocations against GNU_IFUNC symbols are not shown as an hexadecimal > + # value, but rather as the resolver symbol name between (). > + if ($4 ~ /\(.*\)/) { > print whatfile, $5 > + } else { > + symval = strtonum("0x" $4); > + if (symval != 0) > + print whatfile, $5 > + } > } > > in_relocs { next } >
diff --git a/scripts/localplt.awk b/scripts/localplt.awk index 2265b02..5e38073 100644 --- a/scripts/localplt.awk +++ b/scripts/localplt.awk @@ -32,9 +32,15 @@ $1 == "Offset" && $2 == "Info" { in_relocs = 1; next } NF == 0 { in_relocs = 0 } in_relocs && relocs_offset == jmprel_offset && NF >= 5 { - symval = strtonum("0x" $4); - if (symval != 0) + # Relocations against GNU_IFUNC symbols are not shown as an hexadecimal + # value, but rather as the resolver symbol name between (). + if ($4 ~ /\(.*\)/) { print whatfile, $5 + } else { + symval = strtonum("0x" $4); + if (symval != 0) + print whatfile, $5 + } } in_relocs { next }
While reviewing the strncat optimization for powerpc64 I noted in the disassembled object that a call to strlen (bl strlen) generates a PLT call to strlen (since now strlen is an IFUNC for powerpc64). Strangely it was not being caught by check-localplt testcase. GNU_IFUNC are shown by readelf in 'Relocation section' value as (symbol) instead of expected hexadecimal value. This causes the check-localplt script to igore potential PLT stub begin generated by wrong IFUNC usage. This patch changes the localplt script to emit such PLT cases. Checked on PPC64 and X86_64. -- 2014-03-03 Adhemerval Zanella <azanella@linux.vnet.ibm.com> * scripts/localplt.awk: Do not ignore IFUNC relocation while parsing relocation sections. ---