From b412e529e209fe31d919902d4866c33e177b81e7 Mon Sep 17 00:00:00 2001 From: Jason Molenda Date: Mon, 17 Nov 2014 11:43:37 +0000 Subject: [PATCH] Add a little sketch of a program that can extract unwind information from the compact unwind section used on darwin for exception handling, and dump that information.. The UNWIND_X86_64_MODE_RBP_FRAME and UNWIND_X86_64_MODE_DWARF entries look to be handled correctly. UNWIND_X86_64_MODE_STACK_IMMD and UNWIND_X86_64_MODE_STACK_IND are still a work in progress. Only x86_64 is supported right now. Given that this is an experiment in parsing the section contents, I don't expect to add other architectures; they are trivial variations on this arch. There exists a real dumper included in the Xcode tools, unwinddump. llvm-svn: 222127 --- lldb/tools/compact-unwind/compact-unwind-dumper.c | 664 ++++++++++++++++++++++ 1 file changed, 664 insertions(+) create mode 100644 lldb/tools/compact-unwind/compact-unwind-dumper.c diff --git a/lldb/tools/compact-unwind/compact-unwind-dumper.c b/lldb/tools/compact-unwind/compact-unwind-dumper.c new file mode 100644 index 0000000..cf819ac --- /dev/null +++ b/lldb/tools/compact-unwind/compact-unwind-dumper.c @@ -0,0 +1,664 @@ +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + + +// A quick sketch of a program which can parse the compact unwind info +// used on Darwin systems for exception handling. The output of +// unwinddump will be more authoritative/reliable but this program +// can dump at least the UNWIND_X86_64_MODE_RBP_FRAME format entries +// correctly. + +struct baton +{ + cpu_type_t cputype; + + uint8_t *mach_header_start; // pointer into this program's address space + uint8_t *compact_unwind_start; // pointer into this program's address space + + int addr_size; // 4 or 8 bytes, the size of addresses in this file + + uint64_t text_segment_vmaddr; + uint64_t eh_section_file_address; // the file address of the __TEXT,__eh_frame section + + uint8_t *lsda_array_start; // for the currently-being-processed first-level index + uint8_t *lsda_array_end; // the lsda_array_start for the NEXT first-level index + + struct unwind_info_section_header unwind_header; + struct unwind_info_section_header_index_entry first_level_index_entry; + struct unwind_info_compressed_second_level_page_header compressed_second_level_page_header; + struct unwind_info_regular_second_level_page_header regular_second_level_page_header; +}; + + +// step through the load commands in a thin mach-o binary, +// find the cputype and the start of the __TEXT,__unwind_info +// section, return a pointer to that section or NULL if not found. + +void +scan_macho_load_commands (struct baton *baton) +{ + baton->compact_unwind_start = 0; + + uint32_t *magic = (uint32_t *) baton->mach_header_start; + + if (*magic != MH_MAGIC && *magic != MH_MAGIC_64) + { + printf ("Unexpected magic number 0x%x in header, exiting.", *magic); + exit (1); + } + + bool is_64bit = false; + if (*magic == MH_MAGIC_64) + is_64bit = true; + + uint8_t *offset = baton->mach_header_start; + + struct mach_header mh; + memcpy (&mh, offset, sizeof (struct mach_header)); + if (is_64bit) + offset += sizeof (struct mach_header_64); + else + offset += sizeof (struct mach_header); + + if (is_64bit) + baton->addr_size = 8; + else + baton->addr_size = 4; + + baton->cputype = mh.cputype; + + uint32_t cur_cmd = 0; + while (cur_cmd < mh.ncmds && (offset - baton->mach_header_start) < mh.sizeofcmds) + { + struct load_command lc; + uint32_t *lc_cmd = (uint32_t *) offset; + uint32_t *lc_cmdsize = (uint32_t *) offset + 1; + uint8_t *start_of_this_load_cmd = offset; + + char segment_name[17]; + segment_name[0] = '\0'; + uint32_t nsects = 0; + uint64_t segment_offset = 0; + uint64_t segment_vmaddr = 0; + + if (*lc_cmd == LC_SEGMENT_64) + { + struct segment_command_64 seg; + memcpy (&seg, offset, sizeof (struct segment_command_64)); + memcpy (&segment_name, &seg.segname, 16); + segment_name[16] = '\0'; + nsects = seg.nsects; + segment_offset = seg.fileoff; + segment_vmaddr = seg.vmaddr; + offset += sizeof (struct segment_command_64); + } + + if (*lc_cmd == LC_SEGMENT) + { + struct segment_command seg; + memcpy (&seg, offset, sizeof (struct segment_command)); + memcpy (&segment_name, &seg.segname, 16); + segment_name[16] = '\0'; + nsects = seg.nsects; + segment_offset = seg.fileoff; + segment_vmaddr = seg.vmaddr; + offset += sizeof (struct segment_command); + } + + if (nsects != 0 && segment_name[0] != '\0' && strcmp (segment_name, "__TEXT") == 0) + { + baton->text_segment_vmaddr = segment_vmaddr; + + uint32_t current_sect = 0; + while (current_sect < nsects && (offset - start_of_this_load_cmd) < *lc_cmdsize) + { + char sect_name[17]; + memcpy (§_name, offset, 16); + sect_name[16] = '\0'; + if (strcmp (sect_name, "__unwind_info") == 0) + { + if (is_64bit) + { + struct section_64 sect; + memcpy (§, offset, sizeof (struct section_64)); + baton->compact_unwind_start = baton->mach_header_start + sect.offset; + } + else + { + struct section sect; + memcpy (§, offset, sizeof (struct section)); + baton->compact_unwind_start = baton->mach_header_start + sect.offset; + } + } + if (strcmp (sect_name, "__eh_frame") == 0) + { + if (is_64bit) + { + struct section_64 sect; + memcpy (§, offset, sizeof (struct section_64)); + baton->eh_section_file_address = sect.addr; + } + else + { + struct section sect; + memcpy (§, offset, sizeof (struct section)); + baton->eh_section_file_address = sect.addr; + } + } + + if (is_64bit) + { + offset += sizeof (struct section_64); + } + else + { + offset += sizeof (struct section); + } + } + + return; + } + + offset = start_of_this_load_cmd + *lc_cmdsize; + cur_cmd++; + } +} + +void +print_encoding_x86_64 (struct baton baton, uint32_t encoding) +{ + int mode = encoding & UNWIND_X86_64_MODE_MASK; + switch (mode) + { + case UNWIND_X86_64_MODE_RBP_FRAME: + { + printf (" - frame func: CFA is rbp+%d ", 16); + printf (" rip=[CFA-8] rbp=[CFA-16]"); + uint32_t saved_registers_offset = (encoding & UNWIND_X86_64_RBP_FRAME_OFFSET) >> (__builtin_ctz (UNWIND_X86_64_RBP_FRAME_OFFSET)); + + uint32_t saved_registers_locations = (encoding & UNWIND_X86_64_RBP_FRAME_REGISTERS) >> (__builtin_ctz (UNWIND_X86_64_RBP_FRAME_REGISTERS)); + + + saved_registers_offset += 2; + + for (int i = 0; i < 5; i++) + { + switch (saved_registers_locations & 0x7) + { + case UNWIND_X86_64_REG_NONE: + break; + case UNWIND_X86_64_REG_RBX: + printf (" rbx=[CFA-%d]", saved_registers_offset * 8); + break; + case UNWIND_X86_64_REG_R12: + printf (" r12=[CFA-%d]", saved_registers_offset * 8); + break; + case UNWIND_X86_64_REG_R13: + printf (" r13=[CFA-%d]", saved_registers_offset * 8); + break; + case UNWIND_X86_64_REG_R14: + printf (" r14=[CFA-%d]", saved_registers_offset * 8); + break; + case UNWIND_X86_64_REG_R15: + printf (" r15=[CFA-%d]", saved_registers_offset * 8); + break; + } + saved_registers_offset--; + saved_registers_locations >>= 3; + } + } + break; + + case UNWIND_X86_64_MODE_STACK_IND: + { + printf (" UNWIND_X86_64_MODE_STACK_IND not yet supported\n"); + break; + } + case UNWIND_X86_64_MODE_STACK_IMMD: + { + printf (" UNWIND_X86_64_MODE_STACK_IND not yet supported\n"); + break; + + // FIXME not getting the rbp register saves out of the register permutation yet + + uint32_t stack_size = (encoding & UNWIND_X86_64_FRAMELESS_STACK_SIZE) >> (__builtin_ctz (UNWIND_X86_64_FRAMELESS_STACK_SIZE)); + uint32_t stack_adjust = (encoding & UNWIND_X86_FRAMELESS_STACK_ADJUST) >> (__builtin_ctz (UNWIND_X86_FRAMELESS_STACK_ADJUST)); + uint32_t register_count = (encoding & UNWIND_X86_64_FRAMELESS_STACK_REG_COUNT) >> (__builtin_ctz (UNWIND_X86_64_FRAMELESS_STACK_REG_COUNT)); + uint32_t permutation = (encoding & UNWIND_X86_FRAMELESS_STACK_REG_PERMUTATION) >> (__builtin_ctz (UNWIND_X86_FRAMELESS_STACK_REG_PERMUTATION)); + +// printf (" frameless function: stack size %d, stack adjust %d, register count %d ", stack_size * 8, stack_adjust * 8, register_count); + if ((encoding & UNWIND_X86_64_MODE_MASK) == UNWIND_X86_64_MODE_STACK_IND) + { + printf (" UNWIND_X86_64_MODE_STACK_IND not handled "); + // stack size is too large to store in UNWIND_X86_64_FRAMELESS_STACK_SIZE; instead + // stack_size is an offset into the function's instruction stream to the 32-bit literal + // value in a "sub $xxx, %rsp" instruction. + return; + } + + if (register_count == 0) + { + printf (" no registers saved"); + } + else + { + int permunreg[6]; + switch (register_count) + { + case 6: + permunreg[0] = permutation/120; + permutation -= (permunreg[0]*120); + permunreg[1] = permutation/24; + permutation -= (permunreg[1]*24); + permunreg[2] = permutation/6; + permutation -= (permunreg[2]*6); + permunreg[3] = permutation/2; + permutation -= (permunreg[3]*2); + permunreg[4] = permutation; + permunreg[5] = 0; + break; + case 5: + permunreg[0] = permutation/120; + permutation -= (permunreg[0]*120); + permunreg[1] = permutation/24; + permutation -= (permunreg[1]*24); + permunreg[2] = permutation/6; + permutation -= (permunreg[2]*6); + permunreg[3] = permutation/2; + permutation -= (permunreg[3]*2); + permunreg[4] = permutation; + break; + case 4: + permunreg[0] = permutation/60; + permutation -= (permunreg[0]*60); + permunreg[1] = permutation/12; + permutation -= (permunreg[1]*12); + permunreg[2] = permutation/3; + permutation -= (permunreg[2]*3); + permunreg[3] = permutation; + break; + case 3: + permunreg[0] = permutation/20; + permutation -= (permunreg[0]*20); + permunreg[1] = permutation/4; + permutation -= (permunreg[1]*4); + permunreg[2] = permutation; + break; + case 2: + permunreg[0] = permutation/5; + permutation -= (permunreg[0]*5); + permunreg[1] = permutation; + break; + case 1: + permunreg[0] = permutation; + break; + } + + int registers[6]; + bool used[7] = { false, false, false, false, false, false, false }; + for (int i = 0; i < register_count; i++) + { + int renum = 0; + for (int j = 0; j < 7; j++) + { + if (used[j] == false) + { + if (renum == permunreg[i]) + { + registers[i] = j; + used[j] = true; + break; + } + renum++; + } + } + } + + + printf ("CFA is rsp+%d ", stack_size * 8); + + uint32_t saved_registers_offset = 1; + printf (" rip=[CFA-%d]", saved_registers_offset * 8); + saved_registers_offset++; + + for (int i = (sizeof (registers) / sizeof (int)) - 1; i >= 0; i--) + { + switch (registers[i]) + { + case UNWIND_X86_64_REG_NONE: + break; + case UNWIND_X86_64_REG_RBX: + printf (" rbx=[CFA-%d]", saved_registers_offset * 8); + break; + case UNWIND_X86_64_REG_R12: + printf (" r12=[CFA-%d]", saved_registers_offset * 8); + break; + case UNWIND_X86_64_REG_R13: + printf (" r13=[CFA-%d]", saved_registers_offset * 8); + break; + case UNWIND_X86_64_REG_R14: + printf (" r14=[CFA-%d]", saved_registers_offset * 8); + break; + case UNWIND_X86_64_REG_R15: + printf (" r15=[CFA-%d]", saved_registers_offset * 8); + break; + case UNWIND_X86_64_REG_RBP: + printf (" rbp=[CFA-%d]", saved_registers_offset * 8); + break; + } + saved_registers_offset++; + } + + } + + } + break; + + case UNWIND_X86_64_MODE_DWARF: + { + uint32_t dwarf_offset = encoding & UNWIND_X86_DWARF_SECTION_OFFSET; + printf (" use DWARF unwind instructions: FDE at offset %d (file address 0x%" PRIx64 ")\n", + dwarf_offset, dwarf_offset + baton.eh_section_file_address); + } + break; + + } +} + +void print_encoding (struct baton baton, uint32_t encoding) +{ + + if (baton.cputype == CPU_TYPE_X86_64) + { + print_encoding_x86_64 (baton, encoding); + } + else + { + printf (" -- unsupported encoding arch -- "); + } +} + +void +print_function_encoding (struct baton baton, uint32_t idx, uint32_t encoding, uint32_t entry_encoding_index, uint32_t entry_func_offset) +{ + + char *entry_encoding_index_str = ""; + if (entry_encoding_index != (uint32_t) -1) + { + asprintf (&entry_encoding_index_str, ", encoding #%d", entry_encoding_index); + } + else + { + asprintf (&entry_encoding_index_str, ""); + } + printf (" func [%d] offset %d (file addr 0x%" PRIx64 ")%s - 0x%x", + idx, entry_func_offset, + entry_func_offset + baton.first_level_index_entry.functionOffset + baton.text_segment_vmaddr, + entry_encoding_index_str, + encoding); + + print_encoding (baton, encoding); + + bool has_lsda = encoding & UNWIND_HAS_LSDA; + + if (has_lsda) + { + uint32_t func_offset = entry_func_offset + baton.first_level_index_entry.functionOffset; + + uint32_t lsda_offset = 0; + + uint32_t low = 0; + uint32_t high = (baton.lsda_array_end - baton.lsda_array_start) / sizeof (struct unwind_info_section_header_lsda_index_entry); + + while (low < high) + { + uint32_t mid = (low + high) / 2; + + uint8_t *mid_lsda_entry_addr = (baton.lsda_array_start + (mid * sizeof (struct unwind_info_section_header_lsda_index_entry))); + struct unwind_info_section_header_lsda_index_entry mid_lsda_entry; + memcpy (&mid_lsda_entry, mid_lsda_entry_addr, sizeof (struct unwind_info_section_header_lsda_index_entry)); + if (mid_lsda_entry.functionOffset == func_offset) + { + lsda_offset = mid_lsda_entry.lsdaOffset; + break; + } + else if (mid_lsda_entry.functionOffset < func_offset) + { + low = mid + 1; + } + else + { + high = mid; + } + } + + printf (", LSDA offset %d", lsda_offset); + } + + uint32_t pers_idx = (encoding & UNWIND_PERSONALITY_MASK) >> (__builtin_ctz(UNWIND_PERSONALITY_MASK)); + if (pers_idx != 0) + { + pers_idx--; // Change 1-based to 0-based index + uint32_t pers_delta = *((uint32_t*) (baton.compact_unwind_start + baton.unwind_header.personalityArraySectionOffset + pers_idx * 4)); + + uint8_t **personality_addr = (uint8_t **) (baton.mach_header_start + pers_delta); + void *personality = *personality_addr; + printf (", personality func addr @ offset %d", pers_delta); +// printf (", personality %p", personality); + } + + printf ("\n"); +} + +void +print_second_level_index_regular (struct baton baton) +{ + uint8_t *page_entries = baton.compact_unwind_start + baton.first_level_index_entry.secondLevelPagesSectionOffset + baton.regular_second_level_page_header.entryPageOffset; + uint8_t entries_count = baton.regular_second_level_page_header.entryCount; + + uint8_t *offset = page_entries; + uint8_t idx = 0; + + for (uint32_t idx = 0; idx < entries_count; idx++, offset += 8) + { + uint32_t func_offset = *((uint32_t *) (offset)); + uint32_t encoding = *((uint32_t *) (offset + 4)); + print_function_encoding (baton, idx, encoding, (uint32_t) -1, func_offset); + } +} + +void +print_second_level_index_compressed (struct baton baton) +{ + uint8_t *this_index = baton.compact_unwind_start + baton.first_level_index_entry.secondLevelPagesSectionOffset; + uint8_t *start_of_entries = this_index + baton.compressed_second_level_page_header.entryPageOffset; + uint8_t *offset = start_of_entries; + for (uint16_t idx = 0; idx < baton.compressed_second_level_page_header.entryCount; idx++) + { + uint32_t entry = *((uint32_t*) offset); + offset += 4; + uint32_t encoding; + + uint32_t entry_encoding_index = UNWIND_INFO_COMPRESSED_ENTRY_ENCODING_INDEX (entry); + uint32_t entry_func_offset = UNWIND_INFO_COMPRESSED_ENTRY_FUNC_OFFSET (entry); + + if (entry_encoding_index < baton.unwind_header.commonEncodingsArrayCount) + { + // encoding is in common table in section header + encoding = *((uint32_t*) (baton.compact_unwind_start + baton.unwind_header.commonEncodingsArraySectionOffset + (entry_encoding_index * sizeof (uint32_t)))); + } + else + { + // encoding is in page specific table + uint32_t page_encoding_index = entry_encoding_index - baton.unwind_header.commonEncodingsArrayCount; + encoding = *((uint32_t*) (this_index + baton.compressed_second_level_page_header.encodingsPageOffset + (page_encoding_index * sizeof (uint32_t)))); + } + + + print_function_encoding (baton, idx, encoding, entry_encoding_index, entry_func_offset); + } +} + +void +print_second_level_index (struct baton baton) +{ + uint8_t *index_start = baton.compact_unwind_start + baton.first_level_index_entry.secondLevelPagesSectionOffset; + + if ((*(uint32_t*) index_start) == UNWIND_SECOND_LEVEL_REGULAR) + { + struct unwind_info_regular_second_level_page_header header; + memcpy (&header, index_start, sizeof (struct unwind_info_regular_second_level_page_header)); + printf (" UNWIND_SECOND_LEVEL_REGULAR entryPageOffset %d, entryCount %d\n", header.entryPageOffset, header.entryCount); + baton.regular_second_level_page_header = header; + print_second_level_index_regular (baton); + } + + if ((*(uint32_t*) index_start) == UNWIND_SECOND_LEVEL_COMPRESSED) + { + struct unwind_info_compressed_second_level_page_header header; + memcpy (&header, index_start, sizeof (struct unwind_info_compressed_second_level_page_header)); + printf (" UNWIND_SECOND_LEVEL_COMPRESSED entryPageOffset %d, entryCount %d, encodingsPageOffset %d, encodingsCount %d\n", header.entryPageOffset, header.entryCount, header.encodingsPageOffset, header.encodingsCount); + baton.compressed_second_level_page_header = header; + print_second_level_index_compressed (baton); + } +} + + +void +print_index_sections (struct baton baton) +{ + uint8_t *index_section_offset = baton.compact_unwind_start + baton.unwind_header.indexSectionOffset; + uint32_t index_count = baton.unwind_header.indexCount; + + uint32_t cur_idx = 0; + + uint8_t *offset = index_section_offset; + while (cur_idx < index_count) + { + struct unwind_info_section_header_index_entry index_entry; + memcpy (&index_entry, offset, sizeof (struct unwind_info_section_header_index_entry)); + printf ("index section #%d: functionOffset %d, secondLevelPagesSectionOffset %d, lsdaIndexArraySectionOffset %d\n", cur_idx, index_entry.functionOffset, index_entry.secondLevelPagesSectionOffset, index_entry.lsdaIndexArraySectionOffset); + + // secondLevelPagesSectionOffset == 0 means this is a sentinel entry + if (index_entry.secondLevelPagesSectionOffset != 0) + { + struct unwind_info_section_header_index_entry next_index_entry; + memcpy (&next_index_entry, offset + sizeof (struct unwind_info_section_header_index_entry), sizeof (struct unwind_info_section_header_index_entry)); + + baton.lsda_array_start = baton.compact_unwind_start + index_entry.lsdaIndexArraySectionOffset; + baton.lsda_array_end = baton.compact_unwind_start + next_index_entry.lsdaIndexArraySectionOffset; + + uint8_t *lsda_entry_offset = baton.lsda_array_start; + uint32_t lsda_count = 0; + while (lsda_entry_offset < baton.lsda_array_end) + { + struct unwind_info_section_header_lsda_index_entry lsda_entry; + memcpy (&lsda_entry, lsda_entry_offset, sizeof (struct unwind_info_section_header_lsda_index_entry)); + printf (" LSDA [%d] functionOffset %d (%d) (file address 0x%" PRIx64 "), lsdaOffset %d (file address 0x%" PRIx64 ")\n", + lsda_count, lsda_entry.functionOffset, + lsda_entry.functionOffset - index_entry.functionOffset, + lsda_entry.functionOffset + baton.text_segment_vmaddr, + lsda_entry.lsdaOffset, lsda_entry.lsdaOffset + baton.text_segment_vmaddr); + lsda_count++; + lsda_entry_offset += sizeof (struct unwind_info_section_header_lsda_index_entry); + } + + printf ("\n"); + + baton.first_level_index_entry = index_entry; + print_second_level_index (baton); + } + + printf ("\n"); + + cur_idx++; + offset += sizeof (struct unwind_info_section_header_index_entry); + } +} + +int main (int argc, char **argv) +{ + struct stat st; + char *file = argv[0]; + if (argc > 1) + file = argv[1]; + int fd = open (file, O_RDONLY); + if (fd == -1) + { + printf ("Failed to open '%s'\n", file); + exit (1); + } + fstat (fd, &st); + uint8_t *file_mem = (uint8_t*) mmap (0, st.st_size, PROT_READ, MAP_PRIVATE | MAP_FILE, fd, 0); + if (file_mem == MAP_FAILED) + { + printf ("Failed to mmap() '%s'\n", file); + } + + FILE *f = fopen ("a.out", "r"); + + struct baton baton; + baton.mach_header_start = file_mem; + scan_macho_load_commands (&baton); + + if (baton.compact_unwind_start == NULL) + { + printf ("could not find __TEXT,__unwind_info section\n"); + exit (1); + } + + + struct unwind_info_section_header header; + memcpy (&header, baton.compact_unwind_start, sizeof (struct unwind_info_section_header)); + printf ("Header:\n"); + printf (" version %u\n", header.version); + printf (" commonEncodingsArraySectionOffset is %d\n", header.commonEncodingsArraySectionOffset); + printf (" commonEncodingsArrayCount is %d\n", header.commonEncodingsArrayCount); + printf (" personalityArraySectionOffset is %d\n", header.personalityArraySectionOffset); + printf (" personalityArrayCount is %d\n", header.personalityArrayCount); + printf (" indexSectionOffset is %d\n", header.indexSectionOffset); + printf (" indexCount is %d\n", header.indexCount); + + uint8_t *common_encodings = baton.compact_unwind_start + header.commonEncodingsArraySectionOffset; + uint32_t encoding_idx = 0; + while (encoding_idx < header.commonEncodingsArrayCount) + { + uint32_t encoding = *((uint32_t*) common_encodings); + printf (" Common Encoding [%d]: 0x%x", encoding_idx, encoding); + print_encoding (baton, encoding); + printf ("\n"); + common_encodings += sizeof (uint32_t); + encoding_idx++; + } + + uint8_t *pers_arr = baton.compact_unwind_start + header.personalityArraySectionOffset; + uint32_t pers_idx = 0; + while (pers_idx < header.personalityArrayCount) + { + int32_t pers_delta = *((int32_t*) (baton.compact_unwind_start + header.personalityArraySectionOffset + (pers_idx * sizeof (uint32_t)))); + printf (" Personality [%d]: offset to personality function address ptr %d (file address 0x%" PRIx64 ")\n", pers_idx, pers_delta, baton.text_segment_vmaddr + pers_delta); + pers_idx++; + pers_arr += sizeof (uint32_t); + } + + printf ("\n"); + + baton.unwind_header = header; + + print_index_sections (baton); + + + return 0; +} -- 2.7.4