Short version: likely looks like a bug in the *.c code, should use memcpy() instead of type-punning when the alignment is unknown.
Long version: The 'ldd' instruction is *l*oa*d* *d*ouble word, i.e. load 64-bit value. 0xf7d182fc is 4-byte aligned, but not 8-byte aligned, so 'ldd' faults and raises SIGBUS. The part where the value is stored in "*dst" isn't even reached (it is the 'std' after it), so whether "dst" is aligned or not is not in question here. It's suspicious to cast from some type to `GElf_auxv_t*` (64-bit type) and then dereference it: *dst = ((GElf_auxv_t *) data_scn->d.d_buf)[ndx]; If d.d_buf[] is not 8-byte aligned (which it may not be unless is an address returned from malloc() or a points to a naturally 8-byte aligned type allocated on stack -- i.e. char[] is NOT sufficient), then this should be done with memcpy() instead. On Sat, Aug 24, 2013 at 5:44 PM, Kurt Roeckx <k...@roeckx.be> wrote: > Hi, > > I'm seeing a SIGBUS in elfutils, and I'm not sure why I'm getting > this. > LD_LIBRARY_PATH=libdw:libelf:backends/ gdb ./src/readelf > [...] > (gdb) set args -n tests/testfile67 > (gdb) run > Starting program: /home/kroeckx/elfutils-0.156/src/readelf -n > tests/testfile67 > > Note segment of 1044 bytes at offset 0xe8: > Owner Data size Type > CORE 336 PRSTATUS > info.si_signo: 4, info.si_code: 0, info.si_errno: 0, cursig: 4 > sigpend: <> > sighold: <> > pid: 805, ppid: 804, pgrp: 804, sid: 699 > utime: 0.000042, stime: 0.000103, cutime: 0.000000, cstime: 0.000000 > orig_r2: 2571552016, fpvalid: 1 > pswm: 0x0705c00180000000 pswa: 0x00000000800000d6 > r0: 4393751543808 r1: 4398002544388 > r2: 11 r3: 2571578208 > r4: 2571702016 r5: 4398003235624 > r6: 2571580768 r7: 2571702016 > r8: 2571578208 r9: 2571552016 > r10: 2571552016 r11: 0 > r12: 4398003499008 r13: 2148274656 > r14: 0 r15: 4398040761216 > a0: 0x000003ff a1: 0xfd54a6f0 a2: 0x00000000 a3: 0x00000000 > a4: 0x00000000 a5: 0x00000000 a6: 0x00000000 a7: 0x00000000 > a8: 0x00000000 a9: 0x00000000 a10: 0x00000000 a11: 0x00000000 > a12: 0x00000000 a13: 0x00000000 a14: 0x00000000 a15: 0x00000000 > CORE 136 PRPSINFO > state: 0, sname: R, zomb: 0, nice: 0, flag: 0x0000000000400400 > uid: 0, gid: 0, pid: 805, ppid: 804, pgrp: 804, sid: 699 > fname: 1, psargs: ./1 > CORE 304 AUXV > > Program received signal SIGBUS, Bus error. > 0xf7f673f4 in gelf_getauxv (data=data@entry=0x4c8f8, ndx=ndx@entry=0, > dst=dst@entry=0xffffd070) at gelf_getauxv.c:100 > 100 *dst = ((GElf_auxv_t *) data_scn->d.d_buf)[ndx]; > (gdb) p ((GElf_auxv_t *) data_scn->d.d_buf) > $1 = (GElf_auxv_t *) 0xf7d182fc > (gdb) disass > Dump of assembler code for function gelf_getauxv: > 0xf7f673a0 <+0>: save %sp, -96, %sp > 0xf7f673a4 <+4>: mov %i0, %g1 > 0xf7f673a8 <+8>: cmp %g1, 0 > 0xf7f673ac <+12>: be,pn %icc, 0xf7f6744c <gelf_getauxv+172> > 0xf7f673b0 <+16>: clr %i0 > 0xf7f673b4 <+20>: ld [ %g1 + 4 ], %g2 > 0xf7f673b8 <+24>: cmp %g2, 0x18 > 0xf7f673bc <+28>: bne,pn %icc, 0xf7f67444 <gelf_getauxv+164> > 0xf7f673c0 <+32>: inc %i1 > 0xf7f673c4 <+36>: ld [ %g1 + 0x20 ], %g2 > 0xf7f673c8 <+40>: ld [ %g2 + 0x6c ], %g2 > 0xf7f673cc <+44>: ld [ %g2 + 0x14 ], %g2 > 0xf7f673d0 <+48>: cmp %g2, 1 > 0xf7f673d4 <+52>: be,pn %icc, 0xf7f6740c <gelf_getauxv+108> > 0xf7f673d8 <+56>: ld [ %g1 + 0xc ], %g2 > 0xf7f673dc <+60>: sll %i1, 4, %i1 > 0xf7f673e0 <+64>: cmp %i1, %g2 > 0xf7f673e4 <+68>: bgu,pn %icc, 0xf7f67458 <gelf_getauxv+184> > 0xf7f673e8 <+72>: mov 0x15, %o0 > 0xf7f673ec <+76>: ld [ %g1 ], %g1 > 0xf7f673f0 <+80>: add %g1, %i1, %i1 > => 0xf7f673f4 <+84>: ldd [ %i1 + -16 ], %g2 > 0xf7f673f8 <+88>: std %g2, [ %i2 ] > 0xf7f673fc <+92>: ldd [ %i1 + -8 ], %g2 > 0xf7f67400 <+96>: std %g2, [ %i2 + 8 ] > 0xf7f67404 <+100>: rett %i7 + 8 > 0xf7f67408 <+104>: mov %o2, %o0 > 0xf7f6740c <+108>: sll %i1, 3, %i1 > 0xf7f67410 <+112>: cmp %i1, %g2 > 0xf7f67414 <+116>: bgu,pn %icc, 0xf7f67454 <gelf_getauxv+180> > 0xf7f67418 <+120>: add %i1, -8, %i1 > 0xf7f6741c <+124>: ld [ %g1 ], %g1 > 0xf7f67420 <+128>: ld [ %g1 + %i1 ], %g2 > 0xf7f67424 <+132>: add %g1, %i1, %i1 > 0xf7f67428 <+136>: clr [ %i2 ] > 0xf7f6742c <+140>: st %g2, [ %i2 + 4 ] > 0xf7f67430 <+144>: ld [ %i1 + 4 ], %g1 > 0xf7f67434 <+148>: clr [ %i2 + 8 ] > 0xf7f67438 <+152>: st %g1, [ %i2 + 0xc ] > 0xf7f6743c <+156>: rett %i7 + 8 > 0xf7f67440 <+160>: mov %o2, %o0 > 0xf7f67444 <+164>: call 0xf7f56940 <__libelf_seterrno> > 0xf7f67448 <+168>: mov 4, %o0 > 0xf7f6744c <+172>: rett %i7 + 8 > 0xf7f67450 <+176>: nop > 0xf7f67454 <+180>: mov 0x15, %o0 ! 0x15 > 0xf7f67458 <+184>: call 0xf7f56940 <__libelf_seterrno> > 0xf7f6745c <+188>: clr %i0 > 0xf7f67460 <+192>: rett %i7 + 8 > 0xf7f67464 <+196>: nop > End of assembler dump. > (gdb) info reg > g0 0x0 0 > g1 0xf7d182fc -137264388 > g2 0x130 304 > g3 0x3dfd9c 4062620 > g4 0xf871cd58 -126759592 > g5 0x8 8 > g6 0x5554494c 1431587148 > g7 0xf7ff26d0 -134273328 > o0 0x15 21 > o1 0x354 852 > o2 0x111f8 70136 > o3 0x0 0 > o4 0xf7ffbcc0 -134234944 > o5 0x4a644 304708 > sp 0xffffcf38 0xffffcf38 > o7 0xf7fe1e0c -134341108 > l0 0x0 0 > l1 0x2fc 764 > l2 0xffffcf28 -12504 > l3 0xf7f109f8 -135198216 > l4 0x0 0 > l5 0xf7ffbf40 -134234304 > l6 0x0 0 > l7 0xf7f7c000 -134758400 > i0 0x0 0 > i1 0xf7d1830c -137264372 > i2 0xffffd070 -12176 > i3 0x1 1 > i4 0x18 24 > i5 0x4c068 311400 > fp 0xffffcf98 0xffffcf98 > i7 0x28474 164980 > y 0x0 0 > psr 0xff990082 [ #1 S #16 #19 #20 #23 #24 #25 #26 #27 #28 > #29 #30 #31 ] > wim *value not available* > tbr *value not available* > pc 0xf7f673f4 0xf7f673f4 <gelf_getauxv+84> > npc 0xf7f673f8 0xf7f673f8 <gelf_getauxv+88> > fsr 0x0 [ ] > csr *value not available* > (gdb) bt > #0 0xf7f673f4 in gelf_getauxv (data=data@entry=0x4c8f8, ndx=ndx@entry=0, > dst=dst@entry=0xffffd070) at gelf_getauxv.c:100 > #1 0x0002847c in handle_auxv_note (desc_pos=<optimized out>, > descsz=<optimized out>, core=<optimized out>, ebl=0x4c298) at readelf.c:8613 > #2 handle_notes_data (ebl=ebl@entry=0x4c298, start=<optimized out>, > data=<optimized out>, ehdr=<optimized out>) at readelf.c:8743 > #3 0x000298ec in handle_notes (ehdr=0xffffd3b8, ebl=0x4c298) at > readelf.c:8812 > #4 process_elf_file (dwflmod=<optimized out>, fd=<optimized out>) at > readelf.c:884 > #5 0x0002b9a0 in process_dwflmod (dwflmod=<optimized out>, > userdata=0x4c158, name=0x4c268 "tests/testfile67", base=2147483648, > arg=0xffffd5b0) at readelf.c:690 > #6 0xf7fa075c in dwfl_getmodules (dwfl=dwfl@entry=0x4c018, > callback=callback@entry=0x2b940 <process_dwflmod>, arg=arg@entry=0xffffd5b0, > offset=offset@entry=0) at dwfl_getmodules.c:82 > #7 0x00017788 in process_file (fd=7, fname=0xffffd8a1 "tests/testfile67", > only_one=true) at readelf.c:775 > #8 0x00012818 in main (argc=3, argv=0xffffd764) at readelf.c:295 > > dst is a stack allocated GElf_auxv_t. I can't see anything obvious > wrong with the code, and it works on all other arches. > > Is there some requirement from alligned access? > > > Kurt > > > -- > To UNSUBSCRIBE, email to debian-sparc-requ...@lists.debian.org > with a subject of "unsubscribe". Trouble? Contact > listmas...@lists.debian.org > Archive: http://lists.debian.org/20130824224459.gb11...@roeckx.be > >
