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Use binary search on dynamic relocations

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Replace linear search with binary search on dynamic relocations.  After
finding a match, scan backward to the first matching relocation, then
scan forward for a matching relocation with non-absolute symbol.

On Fedora 27 x86-64, time for "objdump -d" on libxul.so from RHEL 7.4
x86-64 went from

134.46user 0.12system 2:15.03elapsed

to

8.49user 0.14system 0:08.64elapsed

	PR binutils/22911
	* objdump.c (is_significant_symbol_name): Return TRUE for all
	.plt* sections.
	(find_symbol_for_address): Replace linear search with binary
	search on dynamic relocations.
This commit is contained in:
H.J. Lu 2018-03-05 03:44:46 -08:00
parent 3dea1ef72c
commit 0e70b27ba9
2 changed files with 50 additions and 19 deletions
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8
binutils/ChangeLog
View file

@ -1,3 +1,11 @@
2018-03-05 H.J. Lu <hongjiu.lu@intel.com>
PR binutils/22911
* objdump.c (is_significant_symbol_name): Return TRUE for all
.plt* sections.
(find_symbol_for_address): Replace linear search with binary
search on dynamic relocations.
2018-03-01 Nick Clifton <nickc@redhat.com>
PR 22905

61
binutils/objdump.c
View file

@ -664,9 +664,7 @@ slurp_dynamic_symtab (bfd *abfd)
static bfd_boolean
is_significant_symbol_name (const char * name)
{
return strcmp (name, ".plt") == 0
|| strcmp (name, ".got") == 0
|| strcmp (name, ".plt.got") == 0;
return strncmp (name, ".plt", 4) == 0 || strcmp (name, ".got") == 0;
}
/* Filter out (in place) symbols that are useless for disassembly.
@ -937,6 +935,7 @@ find_symbol_for_address (bfd_vma vma,
asection *sec;
unsigned int opb;
bfd_boolean want_section;
long rel_count;
if (sorted_symcount < 1)
return NULL;
@ -1065,33 +1064,57 @@ find_symbol_for_address (bfd_vma vma,
and we have dynamic relocations available, then we can produce
a better result by matching a relocation to the address and
using the symbol associated with that relocation. */
rel_count = aux->dynrelcount;
if (!want_section
&& aux->dynrelbuf != NULL
&& sorted_syms[thisplace]->value != vma
&& rel_count > 0
&& aux->dynrelbuf != NULL
&& aux->dynrelbuf[0]->address <= vma
&& aux->dynrelbuf[rel_count - 1]->address >= vma
/* If we have matched a synthetic symbol, then stick with that. */
&& (sorted_syms[thisplace]->flags & BSF_SYNTHETIC) == 0)
{
long rel_count;
arelent ** rel_pp;
arelent ** rel_low;
arelent ** rel_high;
for (rel_count = aux->dynrelcount, rel_pp = aux->dynrelbuf;
rel_count--;)
rel_low = aux->dynrelbuf;
rel_high = rel_low + rel_count - 1;
while (rel_low <= rel_high)
{
arelent * rel = rel_pp[rel_count];
arelent **rel_mid = &rel_low[(rel_high - rel_low) / 2];
arelent * rel = *rel_mid;
if (rel->address == vma
&& rel->sym_ptr_ptr != NULL
/* Absolute relocations do not provide a more helpful symbolic address. */
&& ! bfd_is_abs_section ((* rel->sym_ptr_ptr)->section))
if (rel->address == vma)
{
if (place != NULL)
* place = thisplace;
return * rel->sym_ptr_ptr;
/* Absolute relocations do not provide a more helpful
symbolic address. Find a non-absolute relocation
with the same address. */
arelent **rel_vma = rel_mid;
for (rel_mid--;
rel_mid >= rel_low && rel_mid[0]->address == vma;
rel_mid--)
rel_vma = rel_mid;
for (; rel_vma <= rel_high && rel_vma[0]->address == vma;
rel_vma++)
{
rel = *rel_vma;
if (rel->sym_ptr_ptr != NULL
&& ! bfd_is_abs_section ((* rel->sym_ptr_ptr)->section))
{
if (place != NULL)
* place = thisplace;
return * rel->sym_ptr_ptr;
}
}
break;
}
/* We are scanning backwards, so if we go below the target address
we have failed. */
if (rel_pp[rel_count]->address < vma)
if (vma < rel->address)
rel_high = rel_mid;
else if (vma >= rel_mid[1]->address)
rel_low = rel_mid + 1;
else
break;
}
}