From b1412a88bb616f449401be285d43b028962992b9 Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Mon, 1 Jul 2019 11:37:40 -0300 Subject: [PATCH 1/1] fprintf: Fixup handling classes with no members Will Cohen reported this NULL pointer dereference while processing some object linking with cuda: #0 0x00007ffff7f91453 in __class__fprintf (class=0x522560, cu=0x40ff80, conf=0x7fffffffa930, fp=0x7ffff7ece780 <_IO_2_1_stdout_>) at /home/acme/git/pahole/dwarves_fprintf.c:1624 #1 0x00007ffff7f92195 in tag__fprintf (tag=0x522560, cu=0x40ff80, conf=0x7fffffffa930, fp=0x7ffff7ece780 <_IO_2_1_stdout_>) at /home/acme/git/pahole/dwarves_fprintf.c:1835 #2 0x00007ffff7f90b57 in __class__fprintf (class=0x5224c0, cu=0x40ff80, conf=0x7fffffffaaa0, fp=0x7ffff7ece780 <_IO_2_1_stdout_>) at /home/acme/git/pahole/dwarves_fprintf.c:1406 #3 0x00007ffff7f92195 in tag__fprintf (tag=0x5224c0, cu=0x40ff80, conf=0x40a200 , fp=0x7ffff7ece780 <_IO_2_1_stdout_>) at /home/acme/git/pahole/dwarves_fprintf.c:1835 #4 0x0000000000402d03 in class_formatter (class=0x5224c0, cu=0x40ff80, id=1257) at /home/acme/git/pahole/pahole.c:224 #5 0x0000000000403074 in print_classes (cu=0x40ff80) at /home/acme/git/pahole/pahole.c:319 #6 0x0000000000404bb2 in pahole_stealer (cu=0x40ff80, conf_load=0x40a240 ) at /home/acme/git/pahole/pahole.c:1174 #7 0x00007ffff7f9ff73 in finalize_cu (cus=0x40b2b0, cu=0x40ff80, dcu=0x7fffffffacf0, conf=0x40a240 ) at /home/acme/git/pahole/dwarf_loader.c:2227 #8 0x00007ffff7f9ffac in finalize_cu_immediately (cus=0x40b2b0, cu=0x40ff80, dcu=0x7fffffffacf0, conf=0x40a240 ) at /home/acme/git/pahole/dwarf_loader.c:2236 #9 0x00007ffff7fa064c in cus__load_module (cus=0x40b2b0, conf=0x40a240 , mod=0x40d760, dw=0x40e980, elf=0x40b360, filename=0x7fffffffd5e3 "examples/wcohen/02_Exercise.cuda") at /home/acme/git/pahole/dwarf_loader.c:2389 #10 0x00007ffff7fa0760 in cus__process_dwflmod (dwflmod=0x40d760, userdata=0x40d770, name=0x40d910 "examples/wcohen/02_Exercise.cuda", base=4194304, arg=0x7fffffffcf10) at /home/acme/git/pahole/dwarf_loader.c:2434 #11 0x00007ffff7f32be1 in dwfl_getmodules () from /lib64/libdw.so.1 #12 0x00007ffff7fa0820 in cus__process_file (cus=0x40b2b0, conf=0x40a240 , fd=3, filename=0x7fffffffd5e3 "examples/wcohen/02_Exercise.cuda") at /home/acme/git/pahole/dwarf_loader.c:2487 #13 0x00007ffff7fa089c in dwarf__load_file (cus=0x40b2b0, conf=0x40a240 , filename=0x7fffffffd5e3 "examples/wcohen/02_Exercise.cuda") at /home/acme/git/pahole/dwarf_loader.c:2504 #14 0x00007ffff7f8b0dd in cus__load_file (cus=0x40b2b0, conf=0x40a240 , filename=0x7fffffffd5e3 "examples/wcohen/02_Exercise.cuda") at /home/acme/git/pahole/dwarves.c:1745 #15 0x00007ffff7f8bc2a in cus__load_files (cus=0x40b2b0, conf=0x40a240 , filenames=0x7fffffffd150) at /home/acme/git/pahole/dwarves.c:2109 #16 0x0000000000404ff0 in main (argc=2, argv=0x7fffffffd148) at /home/acme/git/pahole/pahole.c:1294 (gdb) (gdb) p class__name(class, cu) $6 = 0x5cbb85 "__nv_hdl_helper_trait<__nv_dl_tag, void (main(int, char**)::__lambda0::*)(int, double&)const>" (gdb) p class->type.nr_members $7 = 0 (gdb) p last $8 = (struct class_member *) 0x0 (gdb) So, before checking for bitfield details, first check if there were members. Now, if we show all structs/classes in that object file and look for the above data structure, we find it inside another: $ pahole examples/wcohen/02_Exercise.cuda struct __nv_hdl_helper_trait_outer, Kokkos::View, Kokkos::View > { struct __nv_hdl_helper_trait<__nv_dl_tag, void (main(int, char**)::__lambda0::*)(int, double&)const> { class __nv_hdl_wrapper_t, void(int, double&), int, Kokkos::View(class __lambda0, int, class View, class View, class View); /* size: 1, cachelines: 0, members: 0 */ /* padding: 1 */ /* last cacheline: 1 bytes */ }; /* size: 1, cachelines: 0, members: 0 */ /* padding: 1 */ /* last cacheline: 1 bytes */ }; $ Reported-by: William Cohen Fixes: 13e5b9fc00ee ("fprintf: Add unnamed bitfield padding at the end to rebuild original type") Signed-off-by: Arnaldo Carvalho de Melo --- dwarves_fprintf.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/dwarves_fprintf.c b/dwarves_fprintf.c index 8ad1ced7840c..706f1b5033f5 100644 --- a/dwarves_fprintf.c +++ b/dwarves_fprintf.c @@ -1620,7 +1620,7 @@ static size_t __class__fprintf(struct class *class, const struct cu *cu, * to avoid adding the forced bitfield paddings and have btfdiff happy. */ if (class->padding != 0 && type->alignment == 0 && cconf.has_alignment_info && - !cconf.suppress_force_paddings) { + !cconf.suppress_force_paddings && last != NULL) { tag_pos = cu__type(cu, last->tag.type); size = tag__size(tag_pos, cu); -- 2.20.1