Bug#791537: Acknowledgement (nss: FTBFS on hppa: segmentation fault in PR_FindSymbol)

[John David Anglin]

On 2015-08-05, at 5:50 PM, John David Anglin wrote:

> If I was to guess, I would have to think the dladdr call in PR_GetLibraryFilePathname_stub fails because
> hppa uses function descriptors for indirect calls.  Did this work for ia64?  There seems to be some  trickiness
> there.

Not quite right but close.  PR_GetLibraryFilePathname() is actually in /usr/lib/hppa-linux-gnu/libnspr4.so.
This hunk is used:

#if defined(USE_DLFCN) && defined(HAVE_DLADDR)
    Dl_info dli;
    char *result;

    if (dladdr((void *)addr, &dli) == 0) {
        PR_SetError(PR_LIBRARY_NOT_LOADED_ERROR, _MD_ERRNO());
        DLLErrorInternal(_MD_ERRNO());
        return NULL;
    }
    result = PR_Malloc(strlen(dli.dli_fname)+1);
    if (result != NULL) {
        strcpy(result, dli.dli_fname);
    }
    return result;

PR_GetLibraryFilePathname is passed the following:

Breakpoint 1, 0xfc4e09d4 in PORT_LoadLibraryFromOrigin ()
   from debian/libnss3/usr/lib/hppa-linux-gnu/libnssutil3.so
(gdb) p/x $r25
$11 = 0x173f2
(gdb) p (char *)$r26
$12 = 0x15ff0 "libnssutil3.so"

$r5 contains a function pointer pointing to a function descriptor:
(gdb) x/2x 0x173f0
0x173f0:	0x0001756c	0x0000000c

0x0001756c is the address of a stub:
(gdb) disass 0x0001756c,0x0001756c+8
Dump of assembler code from 0x1756c to 0x17574:
   0x0001756c:	b,l 0x17560,r20
   0x00017570:	depwi 0,31,2,r20

On return from dladdr, dli contains:
Breakpoint 5, 0xfc6bd74c in PR_GetLibraryFilePathname ()
   from /usr/lib/hppa-linux-gnu/libnspr4.so
(gdb) p/x $sp-0x78
$8 = 0xfd703a08
(gdb) x/4x 0xfd703a08
0xfd703a08:	0xfd7016e1	0x00010000	0x00000000	0x00000000
(gdb) p (char *)0xfd7016e1
$9 = 0xfd7016e1 "/home/dave/debian/nss/nss-3.19.2/debian/libnss3-tools/usr/bin/shlibsign"

Thus, dladdr doesn't correctly handle function pointers on hppa.  On the other hand, it's
not clear how dladdr can tell the difference between a data pointer and a function pointer.

Dave
--
John David Anglin	dave.anglin at bell.net