Re: [Valgrind-users] Unknown instructions on x86_64: 0F 1F 40 00 and 0F 1F 00 75

[Nicholas M. <nm...@gm...>]

On Fri, 28 Jul 2006 22:03:54 -0400, Pavel Roskin wrote:

> Hello!
> 
> Valgrind 3.2.0 reports an unknown instruction in git-http-fetch (path of
> git) compiled on Fedora Development for x86_64 (glibc-2.4.90, gcc-4.1.1,
> Linux 2.6.18-rc2):
> 
> vex amd64->IR: unhandled instruction bytes: 0xF 0x1F 0x40 0x0
> (help text skipped)
> ==20768== Process terminating with default action of signal 4 (SIGILL): dumping core
> ==20768==  Illegal opcode at address 0x3003E9D34C
> ==20768==    at 0x3003E9D34C: lh_new (in /lib64/libcrypto.so.0.9.8b)
> ==20768==    by 0x3003E58874: (within /lib64/libcrypto.so.0.9.8b)
> ==20768==    by 0x3003E58995: (within /lib64/libcrypto.so.0.9.8b)
> ==20768==    by 0x3003E58D3A: (within /lib64/libcrypto.so.0.9.8b)
> ==20768==    by 0x3003E9098B: ENGINE_new (in /lib64/libcrypto.so.0.9.8b)
> ==20768==    by 0x3003E93975: ENGINE_load_dynamic (in /lib64/libcrypto.so.0.9.8b)
> ==20768==    by 0x3003E927F8: ENGINE_load_builtin_engines (in /lib64/libcrypto.so.0.9.8b)
> ==20768==    by 0x302B020278: Curl_ossl_init (in /usr/lib64/libcurl.so.3.0.0)
> ==20768==    by 0x302B0282EF: curl_global_init (in /usr/lib64/libcurl.so.3.0.0)
> ==20768==    by 0x403BC3: http_init (http.c:207)
> ==20768==    by 0x4076E9: main (http-fetch.c:1255)
> 
> Current Valgrind from Subversion finds something different:
> 
> vex amd64->IR: unhandled instruction bytes: 0xF 0x1F 0x0 0x75
> (help text skipped)
> ==20826== Process terminating with default action of signal 4 (SIGILL): dumping core
> ==20826==  Illegal opcode at address 0x4A065AD
> ==20826==    at 0x4A065AD: index (mc_replace_strmem.c:165)
> ==20826==    by 0x347A60B6DD: _dl_map_object_deps (in /lib64/ld-2.4.90.so)
> ==20826==    by 0x347A603301: dl_main (in /lib64/ld-2.4.90.so)
> ==20826==    by 0x347A612E3A: _dl_sysdep_start (in /lib64/ld-2.4.90.so)
> ==20826==    by 0x347A601467: _dl_start (in /lib64/ld-2.4.90.so)
> ==20826==    by 0x347A600B57: (within /lib64/ld-2.4.90.so)
> ==20826==    by 0xFFF: ???
> ==20826==    by 0x0: ???
> 
> gdb 6.5 doesn't know those instructions.

0xOF 0x19 through 0x0F 0x1F are NOPs taking a ModRM byte. Recent binutils
generate them instead of one-byte NOPs with operand size override prefixes.