Re: [Crash-utility] [PATCH v2] Add support for kASLR for offline vmcore files

Andy, You must have missed my second question about the return value of relocate() -- see below: ----- Original Message ----- > > This patch adds a --kaslr command line parameter for loading x86_64 > crash dumps with kaslr enabled. This reuses the code from 32-bit > x86 relocations with some small changes. The ASLR offset is postive > instead of negative. Also had to move the code to traverse the > kernel section before the symbol storing code to figure out which > symbols were outside any sections and therefore were not relocated. > > Also made a very small change in search_for_switch_to it was > searching through gdb command output which can be different under > different settings. > > Tested: Tested by loading kdump files from kernels with aslr enabled > and not enabled. Ran bt, files, and struct file 0xXXXXXX. > > Signed-off-by: Andy Honig <ahonig(a)google.com&gt; > --- > defs.h | 2 ++ > main.c | 8 ++++++-- > symbols.c | 66 > +++++++++++++++++++++++++++++++++++++++++++++------------------ > x86_64.c | 20 +++++++++++++------ > 4 files changed, 69 insertions(+), 27 deletions(-) > > diff --git a/defs.h b/defs.h > index 83a4402..8de1fa4 100755 > --- a/defs.h > +++ b/defs.h > @@ -2394,6 +2394,8 @@ struct symbol_table_data { > ulong __per_cpu_end; > off_t dwarf_debug_frame_file_offset; > ulong dwarf_debug_frame_size; > + ulong first_section_start; > + ulong last_section_end; > }; > > /* flags for st */ > diff --git a/main.c b/main.c > index 3b469e3..5a41c1a 100755 > --- a/main.c > +++ b/main.c > @@ -57,6 +57,7 @@ static struct option long_options[] = { > {"CRASHPAGER", 0, 0, 0}, > {"no_scroll", 0, 0, 0}, > {"reloc", required_argument, 0, 0}, > + {"kaslr", required_argument, 0, 0}, > {"active", 0, 0, 0}, > {"minimal", 0, 0, 0}, > {"mod", required_argument, 0, 0}, > @@ -216,12 +217,15 @@ main(int argc, char **argv) > else if (STREQ(long_options[option_index].name, "mod")) > kt->module_tree = optarg; > > - else if (STREQ(long_options[option_index].name, "reloc")) { > + else if (STREQ(long_options[option_index].name, "reloc") || > + STREQ(long_options[option_index].name, "kaslr")) { > if (!calculate(optarg, &kt->relocate, NULL, 0)) { > error(INFO, "invalid --reloc argument: %s\n", > optarg); > program_usage(SHORT_FORM); > - } > + } else if (STREQ(long_options[option_index].name, "kaslr")) { > + kt->relocate *= -1; > + } > kt->flags |= RELOC_SET; > } > > diff --git a/symbols.c b/symbols.c > index 93d9c8c..345c0de 100755 > --- a/symbols.c > +++ b/symbols.c > @@ -192,22 +192,6 @@ symtab_init(void) > if (!check_gnu_debuglink(st->bfd)) > no_debugging_data(FATAL); > } > - > - symcount = bfd_read_minisymbols(st->bfd, FALSE, &minisyms, &size); > - > - if (symcount <= 0) > - no_debugging_data(FATAL); > - > - sort_x = bfd_make_empty_symbol(st->bfd); > - sort_y = bfd_make_empty_symbol(st->bfd); > - if (sort_x == NULL || sort_y == NULL) > - error(FATAL, "bfd_make_empty_symbol() failed\n"); > - > - gnu_qsort(st->bfd, minisyms, symcount, size, sort_x, sort_y); > - > - store_symbols(st->bfd, FALSE, minisyms, symcount, size); > - > - free(minisyms); > > /* > * Gather references to the kernel sections. > @@ -217,6 +201,7 @@ symtab_init(void) > error(FATAL, "symbol table section array malloc: %s\n", > strerror(errno)); > BZERO(st->sections, st->bfd->section_count * sizeof(struct sec *)); > + st->first_section_start = st->last_section_end = 0; > > bfd_map_over_sections(st->bfd, section_header_info, KERNEL_SECTIONS); > if ((st->flags & (NO_SEC_LOAD|NO_SEC_CONTENTS)) == > @@ -227,6 +212,23 @@ symtab_init(void) > error(FATAL, DEBUGINFO_ERROR_MESSAGE2); > } > } > + > + symcount = bfd_read_minisymbols(st->bfd, FALSE, &minisyms, &size); > + > + if (symcount <= 0) > + no_debugging_data(FATAL); > + > + sort_x = bfd_make_empty_symbol(st->bfd); > + sort_y = bfd_make_empty_symbol(st->bfd); > + if (sort_x == NULL || sort_y == NULL) > + error(FATAL, "bfd_make_empty_symbol() failed\n"); > + > + gnu_qsort(st->bfd, minisyms, symcount, size, sort_x, sort_y); > + > + store_symbols(st->bfd, FALSE, minisyms, symcount, size); > + > + free(minisyms); > + > > symname_hash_init(); > symval_hash_init(); > @@ -585,7 +587,7 @@ store_symbols(bfd *abfd, int dynamic, void *minisyms, > long symcount, > st->symcnt = 0; > sp = st->symtable; > > - if (machine_type("X86")) { > + if (machine_type("X86") || machine_type("X86_64")) { > if (!(kt->flags & RELOC_SET)) > kt->flags |= RELOC_FORCE; > } else > @@ -658,7 +660,7 @@ store_sysmap_symbols(void) > error(FATAL, "symbol table namespace malloc: %s\n", > strerror(errno)); > > - if (!machine_type("X86")) > + if (!machine_type("X86") && !machine_type("X86_64")) > kt->flags &= ~RELOC_SET; > > first = 0; > @@ -730,7 +732,17 @@ relocate(ulong symval, char *symname, int first_symbol) > break; > } > > - return (symval - kt->relocate); > + /* > + * There are some symbols which are outside of any section > + * either because they are offsets or because they are absolute > + * addresses. These should not be relocated. > + */ > + if (symval >= st->first_section_start && > + symval <= st->last_section_end) { > + return (symval - kt->relocate); > + } else { > + return symval; > + } > } The change above modifies the behavior for relocated 32-bit x86 relocated kernels (i.e., not -kalsr x86 kernels). I've never had any reports of problems with the old return value, so I'm a little nervous about changing it for both arches. Should the change above be restricted to --kalsr kernels? Dave -- Crash-utility mailing list Crash-utility(a)redhat.com https://www.redhat.com/mailman/listinfo/crash-utility