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Re: PATCH: Update DF_1_XXX from Solaris
On Wed, Nov 21, 2012 at 1:38 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Wed, Nov 21, 2012 at 10:23 AM, Markus Trippelsdorf
> <markus@trippelsdorf.de> wrote:
>> On 2012.11.16 at 08:49 -0800, H.J. Lu wrote:
>>>
>>> Here is the new patch. However, I'd like to fix
>>>
>>> http://www.sourceware.org/bugzilla/show_bug.cgi?id=14853
>>>
>>> so that we can add DF_1_GLOBAL to supported bits. To test
>>> it, I need to add a "-z global" linker option to set DF_1_GLOBAL.
>>
>> This breaks valgrind on my system (Linux amd64):
>>
>> Inconsistency detected by ld.so: get-dynamic-info.h: 155: elf_get_dynamic_info: Assertion `(l->l_flags_1 & ~(0x00000001 | 0x00000008 | 0x00000020 | 0x00000040 | 0x00000080 | 0x00000800)) == 0' failed!
>> ==18162== Jump to the invalid address stated on the next line
>> ==18162== at 0x546: ???
>> ==18162== by 0x40155C8: __assert_fail (dl-minimal.c:206)
>> ==18162== by 0x4006E29: _dl_map_object_from_fd (get-dynamic-info.h:155)
>> ==18162== by 0x4007EDC: _dl_map_object (dl-load.c:2365)
>> ==18162== by 0x40013FD: map_doit (rtld.c:626)
>> ==18162== by 0x400E445: _dl_catch_error (dl-error.c:177)
>> ==18162== by 0x4000F4D: do_preload (rtld.c:815)
>> ==18162== by 0x4003294: dl_main (rtld.c:1629)
>> ==18162== by 0x4014D3D: _dl_sysdep_start (dl-sysdep.c:241)
>> ==18162== by 0x4004A35: _dl_start (rtld.c:331)
>> ==18162== by 0x4001217: ??? (in /lib64/ld-2.16.90.so)
>> ==18162== by 0xF: ???
>> ==18162== Address 0x546 is not stack'd, malloc'd or (recently) free'd
>> ==18162==
>> ==18162==
>> ==18162== Process terminating with default action of signal 11 (SIGSEGV)
>> ==18162== Bad permissions for mapped region at address 0x546
>> ==18162== at 0x546: ???
>> ==18162== by 0x40155C8: __assert_fail (dl-minimal.c:206)
>> ==18162== by 0x4006E29: _dl_map_object_from_fd (get-dynamic-info.h:155)
>> ==18162== by 0x4007EDC: _dl_map_object (dl-load.c:2365)
>> ==18162== by 0x40013FD: map_doit (rtld.c:626)
>> ==18162== by 0x400E445: _dl_catch_error (dl-error.c:177)
>> ==18162== by 0x4000F4D: do_preload (rtld.c:815)
>> ==18162== by 0x4003294: dl_main (rtld.c:1629)
>> ==18162== by 0x4014D3D: _dl_sysdep_start (dl-sysdep.c:241)
>> ==18162== by 0x4004A35: _dl_start (rtld.c:331)
>> ==18162== by 0x4001217: ??? (in /lib64/ld-2.16.90.so)
>> ==18162== by 0xF: ???
>>
>
> That is exactly the problem my patch tries to catch:
>
> [hjl@gnu-6 valgrind]$ readelf -d
> /usr/lib64/valgrind/vgpreload_memcheck-x86-linux.so | grep FLAGS_1
> 0x6ffffffb (FLAGS_1) Flags: INITFIRST INTERPOSE
> [hjl@gnu-6 valgrind]$
>
> We don't support INTERPOSE. We used to ignore it. What should we
> do when seeing an unsupported DF_1_XXX bit?
Let's try to understand what's going on here...
In Valgrind trunk Makefile.all.am has:
...
# Baseline link flags for making vgpreload shared objects.
#
PRELOAD_LDFLAGS_COMMON_LINUX = -nodefaultlibs -shared
-Wl,-z,interpose,-z,initfirst
...
Thus INTERPOSE is set *only* for Linux hosts.
We've never supported INTERPOSE for Linux hosts and glibc has always
ignored this DF_1_* flag.
Therefore this is a valgrind bug, whose fix is the one-liner:
Index: Makefile.all.am
===================================================================
--- Makefile.all.am (revision 13132)
+++ Makefile.all.am (working copy)
@@ -195,7 +195,7 @@
# Baseline link flags for making vgpreload shared objects.
#
-PRELOAD_LDFLAGS_COMMON_LINUX = -nodefaultlibs -shared
-Wl,-z,interpose,-z,initfirst
+PRELOAD_LDFLAGS_COMMON_LINUX = -nodefaultlibs -shared -Wl,-z,initfirst
PRELOAD_LDFLAGS_COMMON_DARWIN = -dynamic -dynamiclib -all_load
if VGCONF_PLATVARIANT_IS_ANDROID
---
However, given that binutils accepted the flag in the first place
without consideration for support from glibc it looks like asserting
risks breaking programs at runtime (as opposed to build time if ld had
rejected the unsupported flag).
H.J.,
What do you think about softening the assert to a _dl_debug_printf?
That way we can diagnose the ignored flag by using LD_DEBUG=all?
Cheers,
Carlos.