[Bug libc/11357] New: SIGBUS in getenv().

["pluto at agmk dot net" <sourceware-bugzilla at sourceware dot org>]

hi,

during development a cross platform appliaction on x86 workstation
i've enabled an alignemnt checking in cpu by setting bit 18 in eflags.
(see "AC" at http://en.wikipedia.org/wiki/FLAGS_register_(computing))
for detecting on x86 unaligned accesses prohibited by sparc and arm.

right after i've stuck with SIGBUS in glibc getenv() function.
here's a reduced testcase:

$ cat p.c
#include <stdlib.h>
int main()
{
#if defined( __GNUC__ )
#if defined( __i386__ )
        /* enable alignment checking on x86 */
        asm( "pushf\n\torl $0x40000,(%esp)\n\tpopf" );
#elif defined( __x86_64__ )
        /* enable alignment checking on x86_64 */
        asm( "pushf\n\torl $0x40000,(%rsp)\n\tpopf");
#endif
#endif
        char const* p = getenv( "PATH" );
        return ( p != NULL );
}

$ gcc -Wall p.c -g2 -o p

$ gdb ./p

Program received signal SIGBUS, Bus error.
getenv (name=0x40060e "TH") at getenv.c:84
84                uint16_t ep_start = *(uint16_t *) *ep;
(gdb) l
79            name += 2;
80
81            for (ep = __environ; *ep != NULL; ++ep)
82              {
83      #if _STRING_ARCH_unaligned
84                uint16_t ep_start = *(uint16_t *) *ep;
85      #else
86                uint16_t ep_start = (((unsigned char *) *ep)[0]
87                                     | (((unsigned char *) *ep)[1] << 8));
88      #endif

(gdb) p/x *ep
$5 = 0x7fffffffe5bb

it dies on unaligned u16 access.

-- 
           Summary: SIGBUS in getenv().
           Product: glibc
           Version: 2.11
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: drepper at redhat dot com
        ReportedBy: pluto at agmk dot net
                CC: glibc-bugs at sources dot redhat dot com
 GCC build triplet: x86_64-gnu-linux
  GCC host triplet: x86_64-gnu-linux
GCC target triplet: x86_64-gnu-linux


http://sourceware.org/bugzilla/show_bug.cgi?id=11357

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