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Re: [PATCH] BZ #14831: Segfault in _dl_profile_fixup with IRELATIVEand LD_AUDIT
On Tue, Nov 13, 2012 at 4:50 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Tue, Nov 13, 2012 at 4:26 PM, Roland McGrath <roland@hack.frob.com> wrote:
>>> + if (l->l_reloc_result == NULL)
>>> + {
>>> + /* Skip audit if l_reloc_result is NULL which happens with
>>> + IRELATIVE relocations in other DSOs, like libm.so. */
>>> + *framesizep = -1;
>>
>> This needs a more extensive comment about how it arises that we get here
>> with l_reloc_result NULL and why it is OK to short-circuit this way.
>
> R_X86_IRELATIVE lazy relocation in libm.so leads to:
>
> 00042010 00000507 R_386_JUMP_SLOT 00000000 __get_cpu_features
>
> But __get_cpu_features isn't set up yet and requires a lazy relocation.
> That is why l_reloc_result is NULL. We don't want audit in R_X86_IRELATIVE
> relocations. What is what my patch does.
>
>>> + return _dl_fixup (l, reloc_arg);
>>
>> How can this be right when ELF_MACHINE_RUNTIME_FIXUP_ARGS is nonempty?
>>
>
> My post has
>
> ---
> Targets which define ELF_MACHINE_RUNTIME_FIXUP_ARGS must find a way
> to pass ELF_MACHINE_RUNTIME_FIXUP_ARGS from _dl_fixup/_dl_profile_fixup
> to _dl_runtime_fixup.
> ---
>
> Only
>
> ports/sysdeps/m68k/dl-machine.h:#define ELF_MACHINE_RUNTIME_FIXUP_ARGS
> long int save_a0, long int save_a1
> sysdeps/sh/dl-machine.h:#define ELF_MACHINE_RUNTIME_FIXUP_ARGS int plt_type
>
> I can work with sh and m68k maintainers on a solution. It shouldn't be
> too hard.
Here is the updated patch.
--
H.J.
---2012-11-13 H.J. Lu <hongjiu.lu@intel.com>
[BZ #14831]
* elf/Makefile (tests): Add tst-audit8.
($(objpfx)tst-audit8): Also depend on $(common-objpfx)math/libm.so.
($(objpfx)tst-audit8.out): New target.
(tst-audit8-ENV): New variable.
* elf/dl-runtime.c (_dl_profile_fixup): Call _dl_fixup to skip
audit if l_reloc_result is NULL.
(ELF_MACHINE_RUNTIME_FIXUP_PARAMS): Issue an error if it isn't
defined and ELF_MACHINE_RUNTIME_FIXUP_ARGS is defined.
* elf/tst-audit8.c: New file.
diff --git a/elf/Makefile b/elf/Makefile
index c2f0e20..7e5c9c8 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -142,7 +142,7 @@ tests += loadtest restest1 preloadtest loadfail
multiload origtest resolvfail \
tst-dlmodcount tst-dlopenrpath tst-deep1 \
tst-dlmopen1 tst-dlmopen2 tst-dlmopen3 \
unload3 unload4 unload5 unload6 unload7 unload8 tst-global1 order2 \
- tst-audit1 tst-audit2 \
+ tst-audit1 tst-audit2 tst-audit8 \
tst-stackguard1 tst-addr1 tst-thrlock \
tst-unique1 tst-unique2 tst-unique3 tst-unique4 \
tst-initorder tst-initorder2 tst-relsort1
@@ -1020,6 +1020,10 @@ $(objpfx)tst-audit7: $(objpfx)tst-auditmod7a.so
$(objpfx)tst-audit7.out: $(objpfx)tst-auditmod7b.so
tst-audit7-ENV = LD_AUDIT=$(objpfx)tst-auditmod7b.so
+$(objpfx)tst-audit8: $(common-objpfx)math/libm.so
+$(objpfx)tst-audit8.out: $(objpfx)tst-auditmod1.so
+tst-audit8-ENV = LD_AUDIT=$(objpfx)tst-auditmod1.so
+
$(objpfx)tst-global1: $(libdl)
$(objpfx)tst-global1.out: $(objpfx)testobj6.so $(objpfx)testobj2.so
diff --git a/elf/dl-runtime.c b/elf/dl-runtime.c
index 2e02a21..51356a6 100644
--- a/elf/dl-runtime.c
+++ b/elf/dl-runtime.c
@@ -164,6 +164,25 @@ _dl_profile_fixup (
{
void (*mcount_fct) (ElfW(Addr), ElfW(Addr)) = INTUSE(_dl_mcount);
+ if (l->l_reloc_result == NULL)
+ {
+ /* Resolve an IRELATIVE relocation in another DSO may reference a
+ function defined in libc.so, which leads to l_reloc_result == NULL.
+ For example, __get_cpu_features in libc.so is called to resolve
+ R_X86_64_IRELATIVE relocations in x86-64 libm.so. Skip audit and
+ resolve the function in this case. It is OK since we aren't
+ supposed to audit IRELATIVE relocations. */
+ *framesizep = -1;
+ return _dl_fixup (
+# ifdef ELF_MACHINE_RUNTIME_FIXUP_ARGS
+# ifndef ELF_MACHINE_RUNTIME_FIXUP_PARAMS
+# error Please define ELF_MACHINE_RUNTIME_FIXUP_PARAMS.
+# endif
+ ELF_MACHINE_RUNTIME_FIXUP_PARAMS,
+# endif
+ l, reloc_arg);
+ }
+
/* This is the address in the array where we store the result of previous
relocations. */
struct reloc_result *reloc_result = &l->l_reloc_result[reloc_index];
diff --git a/elf/tst-audit8.c b/elf/tst-audit8.c
new file mode 100644
index 0000000..63656b4
--- /dev/null
+++ b/elf/tst-audit8.c
@@ -0,0 +1 @@
+#include "../io/pwd.c"
--
1.7.11.7