| /* |
| * Copyright (C) 2009 Matt Fleming <matt@console-pimps.org> |
| * |
| * This file is subject to the terms and conditions of the GNU General Public |
| * License. See the file "COPYING" in the main directory of this archive |
| * for more details. |
| * |
| * This is an implementation of a DWARF unwinder. Its main purpose is |
| * for generating stacktrace information. Based on the DWARF 3 |
| * specification from http://www.dwarfstd.org. |
| * |
| * TODO: |
| * - DWARF64 doesn't work. |
| * - Registers with DWARF_VAL_OFFSET rules aren't handled properly. |
| */ |
| |
| /* #define DEBUG */ |
| #include <linux/kernel.h> |
| #include <linux/io.h> |
| #include <linux/list.h> |
| #include <linux/mempool.h> |
| #include <linux/mm.h> |
| #include <linux/elf.h> |
| #include <linux/ftrace.h> |
| #include <asm/dwarf.h> |
| #include <asm/unwinder.h> |
| #include <asm/sections.h> |
| #include <asm/unaligned.h> |
| #include <asm/stacktrace.h> |
| |
| /* Reserve enough memory for two stack frames */ |
| #define DWARF_FRAME_MIN_REQ 2 |
| /* ... with 4 registers per frame. */ |
| #define DWARF_REG_MIN_REQ (DWARF_FRAME_MIN_REQ * 4) |
| |
| static struct kmem_cache *dwarf_frame_cachep; |
| static mempool_t *dwarf_frame_pool; |
| |
| static struct kmem_cache *dwarf_reg_cachep; |
| static mempool_t *dwarf_reg_pool; |
| |
| static LIST_HEAD(dwarf_cie_list); |
| static DEFINE_SPINLOCK(dwarf_cie_lock); |
| |
| static LIST_HEAD(dwarf_fde_list); |
| static DEFINE_SPINLOCK(dwarf_fde_lock); |
| |
| static struct dwarf_cie *cached_cie; |
| |
| /** |
| * dwarf_frame_alloc_reg - allocate memory for a DWARF register |
| * @frame: the DWARF frame whose list of registers we insert on |
| * @reg_num: the register number |
| * |
| * Allocate space for, and initialise, a dwarf reg from |
| * dwarf_reg_pool and insert it onto the (unsorted) linked-list of |
| * dwarf registers for @frame. |
| * |
| * Return the initialised DWARF reg. |
| */ |
| static struct dwarf_reg *dwarf_frame_alloc_reg(struct dwarf_frame *frame, |
| unsigned int reg_num) |
| { |
| struct dwarf_reg *reg; |
| |
| reg = mempool_alloc(dwarf_reg_pool, GFP_ATOMIC); |
| if (!reg) { |
| printk(KERN_WARNING "Unable to allocate a DWARF register\n"); |
| /* |
| * Let's just bomb hard here, we have no way to |
| * gracefully recover. |
| */ |
| UNWINDER_BUG(); |
| } |
| |
| reg->number = reg_num; |
| reg->addr = 0; |
| reg->flags = 0; |
| |
| list_add(®->link, &frame->reg_list); |
| |
| return reg; |
| } |
| |
| static void dwarf_frame_free_regs(struct dwarf_frame *frame) |
| { |
| struct dwarf_reg *reg, *n; |
| |
| list_for_each_entry_safe(reg, n, &frame->reg_list, link) { |
| list_del(®->link); |
| mempool_free(reg, dwarf_reg_pool); |
| } |
| } |
| |
| /** |
| * dwarf_frame_reg - return a DWARF register |
| * @frame: the DWARF frame to search in for @reg_num |
| * @reg_num: the register number to search for |
| * |
| * Lookup and return the dwarf reg @reg_num for this frame. Return |
| * NULL if @reg_num is an register invalid number. |
| */ |
| static struct dwarf_reg *dwarf_frame_reg(struct dwarf_frame *frame, |
| unsigned int reg_num) |
| { |
| struct dwarf_reg *reg; |
| |
| list_for_each_entry(reg, &frame->reg_list, link) { |
| if (reg->number == reg_num) |
| return reg; |
| } |
| |
| return NULL; |
| } |
| |
| /** |
| * dwarf_read_addr - read dwarf data |
| * @src: source address of data |
| * @dst: destination address to store the data to |
| * |
| * Read 'n' bytes from @src, where 'n' is the size of an address on |
| * the native machine. We return the number of bytes read, which |
| * should always be 'n'. We also have to be careful when reading |
| * from @src and writing to @dst, because they can be arbitrarily |
| * aligned. Return 'n' - the number of bytes read. |
| */ |
| static inline int dwarf_read_addr(unsigned long *src, unsigned long *dst) |
| { |
| u32 val = get_unaligned(src); |
| put_unaligned(val, dst); |
| return sizeof(unsigned long *); |
| } |
| |
| /** |
| * dwarf_read_uleb128 - read unsigned LEB128 data |
| * @addr: the address where the ULEB128 data is stored |
| * @ret: address to store the result |
| * |
| * Decode an unsigned LEB128 encoded datum. The algorithm is taken |
| * from Appendix C of the DWARF 3 spec. For information on the |
| * encodings refer to section "7.6 - Variable Length Data". Return |
| * the number of bytes read. |
| */ |
| static inline unsigned long dwarf_read_uleb128(char *addr, unsigned int *ret) |
| { |
| unsigned int result; |
| unsigned char byte; |
| int shift, count; |
| |
| result = 0; |
| shift = 0; |
| count = 0; |
| |
| while (1) { |
| byte = __raw_readb(addr); |
| addr++; |
| count++; |
| |
| result |= (byte & 0x7f) << shift; |
| shift += 7; |
| |
| if (!(byte & 0x80)) |
| break; |
| } |
| |
| *ret = result; |
| |
| return count; |
| } |
| |
| /** |
| * dwarf_read_leb128 - read signed LEB128 data |
| * @addr: the address of the LEB128 encoded data |
| * @ret: address to store the result |
| * |
| * Decode signed LEB128 data. The algorithm is taken from Appendix |
| * C of the DWARF 3 spec. Return the number of bytes read. |
| */ |
| static inline unsigned long dwarf_read_leb128(char *addr, int *ret) |
| { |
| unsigned char byte; |
| int result, shift; |
| int num_bits; |
| int count; |
| |
| result = 0; |
| shift = 0; |
| count = 0; |
| |
| while (1) { |
| byte = __raw_readb(addr); |
| addr++; |
| result |= (byte & 0x7f) << shift; |
| shift += 7; |
| count++; |
| |
| if (!(byte & 0x80)) |
| break; |
| } |
| |
| /* The number of bits in a signed integer. */ |
| num_bits = 8 * sizeof(result); |
| |
| if ((shift < num_bits) && (byte & 0x40)) |
| result |= (-1 << shift); |
| |
| *ret = result; |
| |
| return count; |
| } |
| |
| /** |
| * dwarf_read_encoded_value - return the decoded value at @addr |
| * @addr: the address of the encoded value |
| * @val: where to write the decoded value |
| * @encoding: the encoding with which we can decode @addr |
| * |
| * GCC emits encoded address in the .eh_frame FDE entries. Decode |
| * the value at @addr using @encoding. The decoded value is written |
| * to @val and the number of bytes read is returned. |
| */ |
| static int dwarf_read_encoded_value(char *addr, unsigned long *val, |
| char encoding) |
| { |
| unsigned long decoded_addr = 0; |
| int count = 0; |
| |
| switch (encoding & 0x70) { |
| case DW_EH_PE_absptr: |
| break; |
| case DW_EH_PE_pcrel: |
| decoded_addr = (unsigned long)addr; |
| break; |
| default: |
| pr_debug("encoding=0x%x\n", (encoding & 0x70)); |
| UNWINDER_BUG(); |
| } |
| |
| if ((encoding & 0x07) == 0x00) |
| encoding |= DW_EH_PE_udata4; |
| |
| switch (encoding & 0x0f) { |
| case DW_EH_PE_sdata4: |
| case DW_EH_PE_udata4: |
| count += 4; |
| decoded_addr += get_unaligned((u32 *)addr); |
| __raw_writel(decoded_addr, val); |
| break; |
| default: |
| pr_debug("encoding=0x%x\n", encoding); |
| UNWINDER_BUG(); |
| } |
| |
| return count; |
| } |
| |
| /** |
| * dwarf_entry_len - return the length of an FDE or CIE |
| * @addr: the address of the entry |
| * @len: the length of the entry |
| * |
| * Read the initial_length field of the entry and store the size of |
| * the entry in @len. We return the number of bytes read. Return a |
| * count of 0 on error. |
| */ |
| static inline int dwarf_entry_len(char *addr, unsigned long *len) |
| { |
| u32 initial_len; |
| int count; |
| |
| initial_len = get_unaligned((u32 *)addr); |
| count = 4; |
| |
| /* |
| * An initial length field value in the range DW_LEN_EXT_LO - |
| * DW_LEN_EXT_HI indicates an extension, and should not be |
| * interpreted as a length. The only extension that we currently |
| * understand is the use of DWARF64 addresses. |
| */ |
| if (initial_len >= DW_EXT_LO && initial_len <= DW_EXT_HI) { |
| /* |
| * The 64-bit length field immediately follows the |
| * compulsory 32-bit length field. |
| */ |
| if (initial_len == DW_EXT_DWARF64) { |
| *len = get_unaligned((u64 *)addr + 4); |
| count = 12; |
| } else { |
| printk(KERN_WARNING "Unknown DWARF extension\n"); |
| count = 0; |
| } |
| } else |
| *len = initial_len; |
| |
| return count; |
| } |
| |
| /** |
| * dwarf_lookup_cie - locate the cie |
| * @cie_ptr: pointer to help with lookup |
| */ |
| static struct dwarf_cie *dwarf_lookup_cie(unsigned long cie_ptr) |
| { |
| struct dwarf_cie *cie; |
| unsigned long flags; |
| |
| spin_lock_irqsave(&dwarf_cie_lock, flags); |
| |
| /* |
| * We've cached the last CIE we looked up because chances are |
| * that the FDE wants this CIE. |
| */ |
| if (cached_cie && cached_cie->cie_pointer == cie_ptr) { |
| cie = cached_cie; |
| goto out; |
| } |
| |
| list_for_each_entry(cie, &dwarf_cie_list, link) { |
| if (cie->cie_pointer == cie_ptr) { |
| cached_cie = cie; |
| break; |
| } |
| } |
| |
| /* Couldn't find the entry in the list. */ |
| if (&cie->link == &dwarf_cie_list) |
| cie = NULL; |
| out: |
| spin_unlock_irqrestore(&dwarf_cie_lock, flags); |
| return cie; |
| } |
| |
| /** |
| * dwarf_lookup_fde - locate the FDE that covers pc |
| * @pc: the program counter |
| */ |
| struct dwarf_fde *dwarf_lookup_fde(unsigned long pc) |
| { |
| struct dwarf_fde *fde; |
| unsigned long flags; |
| |
| spin_lock_irqsave(&dwarf_fde_lock, flags); |
| |
| list_for_each_entry(fde, &dwarf_fde_list, link) { |
| unsigned long start, end; |
| |
| start = fde->initial_location; |
| end = fde->initial_location + fde->address_range; |
| |
| if (pc >= start && pc < end) |
| break; |
| } |
| |
| /* Couldn't find the entry in the list. */ |
| if (&fde->link == &dwarf_fde_list) |
| fde = NULL; |
| |
| spin_unlock_irqrestore(&dwarf_fde_lock, flags); |
| |
| return fde; |
| } |
| |
| /** |
| * dwarf_cfa_execute_insns - execute instructions to calculate a CFA |
| * @insn_start: address of the first instruction |
| * @insn_end: address of the last instruction |
| * @cie: the CIE for this function |
| * @fde: the FDE for this function |
| * @frame: the instructions calculate the CFA for this frame |
| * @pc: the program counter of the address we're interested in |
| * |
| * Execute the Call Frame instruction sequence starting at |
| * @insn_start and ending at @insn_end. The instructions describe |
| * how to calculate the Canonical Frame Address of a stackframe. |
| * Store the results in @frame. |
| */ |
| static int dwarf_cfa_execute_insns(unsigned char *insn_start, |
| unsigned char *insn_end, |
| struct dwarf_cie *cie, |
| struct dwarf_fde *fde, |
| struct dwarf_frame *frame, |
| unsigned long pc) |
| { |
| unsigned char insn; |
| unsigned char *current_insn; |
| unsigned int count, delta, reg, expr_len, offset; |
| struct dwarf_reg *regp; |
| |
| current_insn = insn_start; |
| |
| while (current_insn < insn_end && frame->pc <= pc) { |
| insn = __raw_readb(current_insn++); |
| |
| /* |
| * Firstly, handle the opcodes that embed their operands |
| * in the instructions. |
| */ |
| switch (DW_CFA_opcode(insn)) { |
| case DW_CFA_advance_loc: |
| delta = DW_CFA_operand(insn); |
| delta *= cie->code_alignment_factor; |
| frame->pc += delta; |
| continue; |
| /* NOTREACHED */ |
| case DW_CFA_offset: |
| reg = DW_CFA_operand(insn); |
| count = dwarf_read_uleb128(current_insn, &offset); |
| current_insn += count; |
| offset *= cie->data_alignment_factor; |
| regp = dwarf_frame_alloc_reg(frame, reg); |
| regp->addr = offset; |
| regp->flags |= DWARF_REG_OFFSET; |
| continue; |
| /* NOTREACHED */ |
| case DW_CFA_restore: |
| reg = DW_CFA_operand(insn); |
| continue; |
| /* NOTREACHED */ |
| } |
| |
| /* |
| * Secondly, handle the opcodes that don't embed their |
| * operands in the instruction. |
| */ |
| switch (insn) { |
| case DW_CFA_nop: |
| continue; |
| case DW_CFA_advance_loc1: |
| delta = *current_insn++; |
| frame->pc += delta * cie->code_alignment_factor; |
| break; |
| case DW_CFA_advance_loc2: |
| delta = get_unaligned((u16 *)current_insn); |
| current_insn += 2; |
| frame->pc += delta * cie->code_alignment_factor; |
| break; |
| case DW_CFA_advance_loc4: |
| delta = get_unaligned((u32 *)current_insn); |
| current_insn += 4; |
| frame->pc += delta * cie->code_alignment_factor; |
| break; |
| case DW_CFA_offset_extended: |
| count = dwarf_read_uleb128(current_insn, ®); |
| current_insn += count; |
| count = dwarf_read_uleb128(current_insn, &offset); |
| current_insn += count; |
| offset *= cie->data_alignment_factor; |
| break; |
| case DW_CFA_restore_extended: |
| count = dwarf_read_uleb128(current_insn, ®); |
| current_insn += count; |
| break; |
| case DW_CFA_undefined: |
| count = dwarf_read_uleb128(current_insn, ®); |
| current_insn += count; |
| regp = dwarf_frame_alloc_reg(frame, reg); |
| regp->flags |= DWARF_UNDEFINED; |
| break; |
| case DW_CFA_def_cfa: |
| count = dwarf_read_uleb128(current_insn, |
| &frame->cfa_register); |
| current_insn += count; |
| count = dwarf_read_uleb128(current_insn, |
| &frame->cfa_offset); |
| current_insn += count; |
| |
| frame->flags |= DWARF_FRAME_CFA_REG_OFFSET; |
| break; |
| case DW_CFA_def_cfa_register: |
| count = dwarf_read_uleb128(current_insn, |
| &frame->cfa_register); |
| current_insn += count; |
| frame->flags |= DWARF_FRAME_CFA_REG_OFFSET; |
| break; |
| case DW_CFA_def_cfa_offset: |
| count = dwarf_read_uleb128(current_insn, &offset); |
| current_insn += count; |
| frame->cfa_offset = offset; |
| break; |
| case DW_CFA_def_cfa_expression: |
| count = dwarf_read_uleb128(current_insn, &expr_len); |
| current_insn += count; |
| |
| frame->cfa_expr = current_insn; |
| frame->cfa_expr_len = expr_len; |
| current_insn += expr_len; |
| |
| frame->flags |= DWARF_FRAME_CFA_REG_EXP; |
| break; |
| case DW_CFA_offset_extended_sf: |
| count = dwarf_read_uleb128(current_insn, ®); |
| current_insn += count; |
| count = dwarf_read_leb128(current_insn, &offset); |
| current_insn += count; |
| offset *= cie->data_alignment_factor; |
| regp = dwarf_frame_alloc_reg(frame, reg); |
| regp->flags |= DWARF_REG_OFFSET; |
| regp->addr = offset; |
| break; |
| case DW_CFA_val_offset: |
| count = dwarf_read_uleb128(current_insn, ®); |
| current_insn += count; |
| count = dwarf_read_leb128(current_insn, &offset); |
| offset *= cie->data_alignment_factor; |
| regp = dwarf_frame_alloc_reg(frame, reg); |
| regp->flags |= DWARF_VAL_OFFSET; |
| regp->addr = offset; |
| break; |
| case DW_CFA_GNU_args_size: |
| count = dwarf_read_uleb128(current_insn, &offset); |
| current_insn += count; |
| break; |
| case DW_CFA_GNU_negative_offset_extended: |
| count = dwarf_read_uleb128(current_insn, ®); |
| current_insn += count; |
| count = dwarf_read_uleb128(current_insn, &offset); |
| offset *= cie->data_alignment_factor; |
| |
| regp = dwarf_frame_alloc_reg(frame, reg); |
| regp->flags |= DWARF_REG_OFFSET; |
| regp->addr = -offset; |
| break; |
| default: |
| pr_debug("unhandled DWARF instruction 0x%x\n", insn); |
| UNWINDER_BUG(); |
| break; |
| } |
| } |
| |
| return 0; |
| } |
| |
| /** |
| * dwarf_free_frame - free the memory allocated for @frame |
| * @frame: the frame to free |
| */ |
| void dwarf_free_frame(struct dwarf_frame *frame) |
| { |
| dwarf_frame_free_regs(frame); |
| mempool_free(frame, dwarf_frame_pool); |
| } |
| |
| extern void ret_from_irq(void); |
| |
| /** |
| * dwarf_unwind_stack - unwind the stack |
| * |
| * @pc: address of the function to unwind |
| * @prev: struct dwarf_frame of the previous stackframe on the callstack |
| * |
| * Return a struct dwarf_frame representing the most recent frame |
| * on the callstack. Each of the lower (older) stack frames are |
| * linked via the "prev" member. |
| */ |
| struct dwarf_frame * dwarf_unwind_stack(unsigned long pc, |
| struct dwarf_frame *prev) |
| { |
| struct dwarf_frame *frame; |
| struct dwarf_cie *cie; |
| struct dwarf_fde *fde; |
| struct dwarf_reg *reg; |
| unsigned long addr; |
| |
| /* |
| * If we're starting at the top of the stack we need get the |
| * contents of a physical register to get the CFA in order to |
| * begin the virtual unwinding of the stack. |
| * |
| * NOTE: the return address is guaranteed to be setup by the |
| * time this function makes its first function call. |
| */ |
| if (!pc || !prev) |
| pc = (unsigned long)current_text_addr(); |
| |
| #ifdef CONFIG_FUNCTION_GRAPH_TRACER |
| /* |
| * If our stack has been patched by the function graph tracer |
| * then we might see the address of return_to_handler() where we |
| * expected to find the real return address. |
| */ |
| if (pc == (unsigned long)&return_to_handler) { |
| int index = current->curr_ret_stack; |
| |
| /* |
| * We currently have no way of tracking how many |
| * return_to_handler()'s we've seen. If there is more |
| * than one patched return address on our stack, |
| * complain loudly. |
| */ |
| WARN_ON(index > 0); |
| |
| pc = current->ret_stack[index].ret; |
| } |
| #endif |
| |
| frame = mempool_alloc(dwarf_frame_pool, GFP_ATOMIC); |
| if (!frame) { |
| printk(KERN_ERR "Unable to allocate a dwarf frame\n"); |
| UNWINDER_BUG(); |
| } |
| |
| INIT_LIST_HEAD(&frame->reg_list); |
| frame->flags = 0; |
| frame->prev = prev; |
| frame->return_addr = 0; |
| |
| fde = dwarf_lookup_fde(pc); |
| if (!fde) { |
| /* |
| * This is our normal exit path. There are two reasons |
| * why we might exit here, |
| * |
| * a) pc has no asscociated DWARF frame info and so |
| * we don't know how to unwind this frame. This is |
| * usually the case when we're trying to unwind a |
| * frame that was called from some assembly code |
| * that has no DWARF info, e.g. syscalls. |
| * |
| * b) the DEBUG info for pc is bogus. There's |
| * really no way to distinguish this case from the |
| * case above, which sucks because we could print a |
| * warning here. |
| */ |
| goto bail; |
| } |
| |
| cie = dwarf_lookup_cie(fde->cie_pointer); |
| |
| frame->pc = fde->initial_location; |
| |
| /* CIE initial instructions */ |
| dwarf_cfa_execute_insns(cie->initial_instructions, |
| cie->instructions_end, cie, fde, |
| frame, pc); |
| |
| /* FDE instructions */ |
| dwarf_cfa_execute_insns(fde->instructions, fde->end, cie, |
| fde, frame, pc); |
| |
| /* Calculate the CFA */ |
| switch (frame->flags) { |
| case DWARF_FRAME_CFA_REG_OFFSET: |
| if (prev) { |
| reg = dwarf_frame_reg(prev, frame->cfa_register); |
| UNWINDER_BUG_ON(!reg); |
| UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET); |
| |
| addr = prev->cfa + reg->addr; |
| frame->cfa = __raw_readl(addr); |
| |
| } else { |
| /* |
| * Again, we're starting from the top of the |
| * stack. We need to physically read |
| * the contents of a register in order to get |
| * the Canonical Frame Address for this |
| * function. |
| */ |
| frame->cfa = dwarf_read_arch_reg(frame->cfa_register); |
| } |
| |
| frame->cfa += frame->cfa_offset; |
| break; |
| default: |
| UNWINDER_BUG(); |
| } |
| |
| reg = dwarf_frame_reg(frame, DWARF_ARCH_RA_REG); |
| |
| /* |
| * If we haven't seen the return address register or the return |
| * address column is undefined then we must assume that this is |
| * the end of the callstack. |
| */ |
| if (!reg || reg->flags == DWARF_UNDEFINED) |
| goto bail; |
| |
| UNWINDER_BUG_ON(reg->flags != DWARF_REG_OFFSET); |
| |
| addr = frame->cfa + reg->addr; |
| frame->return_addr = __raw_readl(addr); |
| |
| /* |
| * Ah, the joys of unwinding through interrupts. |
| * |
| * Interrupts are tricky - the DWARF info needs to be _really_ |
| * accurate and unfortunately I'm seeing a lot of bogus DWARF |
| * info. For example, I've seen interrupts occur in epilogues |
| * just after the frame pointer (r14) had been restored. The |
| * problem was that the DWARF info claimed that the CFA could be |
| * reached by using the value of the frame pointer before it was |
| * restored. |
| * |
| * So until the compiler can be trusted to produce reliable |
| * DWARF info when it really matters, let's stop unwinding once |
| * we've calculated the function that was interrupted. |
| */ |
| if (prev && prev->pc == (unsigned long)ret_from_irq) |
| frame->return_addr = 0; |
| |
| return frame; |
| |
| bail: |
| dwarf_free_frame(frame); |
| return NULL; |
| } |
| |
| static int dwarf_parse_cie(void *entry, void *p, unsigned long len, |
| unsigned char *end, struct module *mod) |
| { |
| struct dwarf_cie *cie; |
| unsigned long flags; |
| int count; |
| |
| cie = kzalloc(sizeof(*cie), GFP_KERNEL); |
| if (!cie) |
| return -ENOMEM; |
| |
| cie->length = len; |
| |
| /* |
| * Record the offset into the .eh_frame section |
| * for this CIE. It allows this CIE to be |
| * quickly and easily looked up from the |
| * corresponding FDE. |
| */ |
| cie->cie_pointer = (unsigned long)entry; |
| |
| cie->version = *(char *)p++; |
| UNWINDER_BUG_ON(cie->version != 1); |
| |
| cie->augmentation = p; |
| p += strlen(cie->augmentation) + 1; |
| |
| count = dwarf_read_uleb128(p, &cie->code_alignment_factor); |
| p += count; |
| |
| count = dwarf_read_leb128(p, &cie->data_alignment_factor); |
| p += count; |
| |
| /* |
| * Which column in the rule table contains the |
| * return address? |
| */ |
| if (cie->version == 1) { |
| cie->return_address_reg = __raw_readb(p); |
| p++; |
| } else { |
| count = dwarf_read_uleb128(p, &cie->return_address_reg); |
| p += count; |
| } |
| |
| if (cie->augmentation[0] == 'z') { |
| unsigned int length, count; |
| cie->flags |= DWARF_CIE_Z_AUGMENTATION; |
| |
| count = dwarf_read_uleb128(p, &length); |
| p += count; |
| |
| UNWINDER_BUG_ON((unsigned char *)p > end); |
| |
| cie->initial_instructions = p + length; |
| cie->augmentation++; |
| } |
| |
| while (*cie->augmentation) { |
| /* |
| * "L" indicates a byte showing how the |
| * LSDA pointer is encoded. Skip it. |
| */ |
| if (*cie->augmentation == 'L') { |
| p++; |
| cie->augmentation++; |
| } else if (*cie->augmentation == 'R') { |
| /* |
| * "R" indicates a byte showing |
| * how FDE addresses are |
| * encoded. |
| */ |
| cie->encoding = *(char *)p++; |
| cie->augmentation++; |
| } else if (*cie->augmentation == 'P') { |
| /* |
| * "R" indicates a personality |
| * routine in the CIE |
| * augmentation. |
| */ |
| UNWINDER_BUG(); |
| } else if (*cie->augmentation == 'S') { |
| UNWINDER_BUG(); |
| } else { |
| /* |
| * Unknown augmentation. Assume |
| * 'z' augmentation. |
| */ |
| p = cie->initial_instructions; |
| UNWINDER_BUG_ON(!p); |
| break; |
| } |
| } |
| |
| cie->initial_instructions = p; |
| cie->instructions_end = end; |
| |
| cie->mod = mod; |
| |
| /* Add to list */ |
| spin_lock_irqsave(&dwarf_cie_lock, flags); |
| list_add_tail(&cie->link, &dwarf_cie_list); |
| spin_unlock_irqrestore(&dwarf_cie_lock, flags); |
| |
| return 0; |
| } |
| |
| static int dwarf_parse_fde(void *entry, u32 entry_type, |
| void *start, unsigned long len, |
| unsigned char *end, struct module *mod) |
| { |
| struct dwarf_fde *fde; |
| struct dwarf_cie *cie; |
| unsigned long flags; |
| int count; |
| void *p = start; |
| |
| fde = kzalloc(sizeof(*fde), GFP_KERNEL); |
| if (!fde) |
| return -ENOMEM; |
| |
| fde->length = len; |
| |
| /* |
| * In a .eh_frame section the CIE pointer is the |
| * delta between the address within the FDE |
| */ |
| fde->cie_pointer = (unsigned long)(p - entry_type - 4); |
| |
| cie = dwarf_lookup_cie(fde->cie_pointer); |
| fde->cie = cie; |
| |
| if (cie->encoding) |
| count = dwarf_read_encoded_value(p, &fde->initial_location, |
| cie->encoding); |
| else |
| count = dwarf_read_addr(p, &fde->initial_location); |
| |
| p += count; |
| |
| if (cie->encoding) |
| count = dwarf_read_encoded_value(p, &fde->address_range, |
| cie->encoding & 0x0f); |
| else |
| count = dwarf_read_addr(p, &fde->address_range); |
| |
| p += count; |
| |
| if (fde->cie->flags & DWARF_CIE_Z_AUGMENTATION) { |
| unsigned int length; |
| count = dwarf_read_uleb128(p, &length); |
| p += count + length; |
| } |
| |
| /* Call frame instructions. */ |
| fde->instructions = p; |
| fde->end = end; |
| |
| fde->mod = mod; |
| |
| /* Add to list. */ |
| spin_lock_irqsave(&dwarf_fde_lock, flags); |
| list_add_tail(&fde->link, &dwarf_fde_list); |
| spin_unlock_irqrestore(&dwarf_fde_lock, flags); |
| |
| return 0; |
| } |
| |
| static void dwarf_unwinder_dump(struct task_struct *task, |
| struct pt_regs *regs, |
| unsigned long *sp, |
| const struct stacktrace_ops *ops, |
| void *data) |
| { |
| struct dwarf_frame *frame, *_frame; |
| unsigned long return_addr; |
| |
| _frame = NULL; |
| return_addr = 0; |
| |
| while (1) { |
| frame = dwarf_unwind_stack(return_addr, _frame); |
| |
| if (_frame) |
| dwarf_free_frame(_frame); |
| |
| _frame = frame; |
| |
| if (!frame || !frame->return_addr) |
| break; |
| |
| return_addr = frame->return_addr; |
| ops->address(data, return_addr, 1); |
| } |
| |
| if (frame) |
| dwarf_free_frame(frame); |
| } |
| |
| static struct unwinder dwarf_unwinder = { |
| .name = "dwarf-unwinder", |
| .dump = dwarf_unwinder_dump, |
| .rating = 150, |
| }; |
| |
| static void dwarf_unwinder_cleanup(void) |
| { |
| struct dwarf_cie *cie, *cie_tmp; |
| struct dwarf_fde *fde, *fde_tmp; |
| |
| /* |
| * Deallocate all the memory allocated for the DWARF unwinder. |
| * Traverse all the FDE/CIE lists and remove and free all the |
| * memory associated with those data structures. |
| */ |
| list_for_each_entry_safe(cie, cie_tmp, &dwarf_cie_list, link) |
| kfree(cie); |
| |
| list_for_each_entry_safe(fde, fde_tmp, &dwarf_fde_list, link) |
| kfree(fde); |
| |
| kmem_cache_destroy(dwarf_reg_cachep); |
| kmem_cache_destroy(dwarf_frame_cachep); |
| } |
| |
| /** |
| * dwarf_parse_section - parse DWARF section |
| * @eh_frame_start: start address of the .eh_frame section |
| * @eh_frame_end: end address of the .eh_frame section |
| * @mod: the kernel module containing the .eh_frame section |
| * |
| * Parse the information in a .eh_frame section. |
| */ |
| static int dwarf_parse_section(char *eh_frame_start, char *eh_frame_end, |
| struct module *mod) |
| { |
| u32 entry_type; |
| void *p, *entry; |
| int count, err = 0; |
| unsigned long len = 0; |
| unsigned int c_entries, f_entries; |
| unsigned char *end; |
| |
| c_entries = 0; |
| f_entries = 0; |
| entry = eh_frame_start; |
| |
| while ((char *)entry < eh_frame_end) { |
| p = entry; |
| |
| count = dwarf_entry_len(p, &len); |
| if (count == 0) { |
| /* |
| * We read a bogus length field value. There is |
| * nothing we can do here apart from disabling |
| * the DWARF unwinder. We can't even skip this |
| * entry and move to the next one because 'len' |
| * tells us where our next entry is. |
| */ |
| err = -EINVAL; |
| goto out; |
| } else |
| p += count; |
| |
| /* initial length does not include itself */ |
| end = p + len; |
| |
| entry_type = get_unaligned((u32 *)p); |
| p += 4; |
| |
| if (entry_type == DW_EH_FRAME_CIE) { |
| err = dwarf_parse_cie(entry, p, len, end, mod); |
| if (err < 0) |
| goto out; |
| else |
| c_entries++; |
| } else { |
| err = dwarf_parse_fde(entry, entry_type, p, len, |
| end, mod); |
| if (err < 0) |
| goto out; |
| else |
| f_entries++; |
| } |
| |
| entry = (char *)entry + len + 4; |
| } |
| |
| printk(KERN_INFO "DWARF unwinder initialised: read %u CIEs, %u FDEs\n", |
| c_entries, f_entries); |
| |
| return 0; |
| |
| out: |
| return err; |
| } |
| |
| #ifdef CONFIG_MODULES |
| int module_dwarf_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, |
| struct module *me) |
| { |
| unsigned int i, err; |
| unsigned long start, end; |
| char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset; |
| |
| start = end = 0; |
| |
| for (i = 1; i < hdr->e_shnum; i++) { |
| /* Alloc bit cleared means "ignore it." */ |
| if ((sechdrs[i].sh_flags & SHF_ALLOC) |
| && !strcmp(secstrings+sechdrs[i].sh_name, ".eh_frame")) { |
| start = sechdrs[i].sh_addr; |
| end = start + sechdrs[i].sh_size; |
| break; |
| } |
| } |
| |
| /* Did we find the .eh_frame section? */ |
| if (i != hdr->e_shnum) { |
| err = dwarf_parse_section((char *)start, (char *)end, me); |
| if (err) { |
| printk(KERN_WARNING "%s: failed to parse DWARF info\n", |
| me->name); |
| return err; |
| } |
| } |
| |
| return 0; |
| } |
| |
| /** |
| * module_dwarf_cleanup - remove FDE/CIEs associated with @mod |
| * @mod: the module that is being unloaded |
| * |
| * Remove any FDEs and CIEs from the global lists that came from |
| * @mod's .eh_frame section because @mod is being unloaded. |
| */ |
| void module_dwarf_cleanup(struct module *mod) |
| { |
| struct dwarf_fde *fde; |
| struct dwarf_cie *cie; |
| unsigned long flags; |
| |
| spin_lock_irqsave(&dwarf_cie_lock, flags); |
| |
| again_cie: |
| list_for_each_entry(cie, &dwarf_cie_list, link) { |
| if (cie->mod == mod) |
| break; |
| } |
| |
| if (&cie->link != &dwarf_cie_list) { |
| list_del(&cie->link); |
| kfree(cie); |
| goto again_cie; |
| } |
| |
| spin_unlock_irqrestore(&dwarf_cie_lock, flags); |
| |
| spin_lock_irqsave(&dwarf_fde_lock, flags); |
| |
| again_fde: |
| list_for_each_entry(fde, &dwarf_fde_list, link) { |
| if (fde->mod == mod) |
| break; |
| } |
| |
| if (&fde->link != &dwarf_fde_list) { |
| list_del(&fde->link); |
| kfree(fde); |
| goto again_fde; |
| } |
| |
| spin_unlock_irqrestore(&dwarf_fde_lock, flags); |
| } |
| #endif /* CONFIG_MODULES */ |
| |
| /** |
| * dwarf_unwinder_init - initialise the dwarf unwinder |
| * |
| * Build the data structures describing the .dwarf_frame section to |
| * make it easier to lookup CIE and FDE entries. Because the |
| * .eh_frame section is packed as tightly as possible it is not |
| * easy to lookup the FDE for a given PC, so we build a list of FDE |
| * and CIE entries that make it easier. |
| */ |
| static int __init dwarf_unwinder_init(void) |
| { |
| int err; |
| INIT_LIST_HEAD(&dwarf_cie_list); |
| INIT_LIST_HEAD(&dwarf_fde_list); |
| |
| dwarf_frame_cachep = kmem_cache_create("dwarf_frames", |
| sizeof(struct dwarf_frame), 0, |
| SLAB_PANIC | SLAB_HWCACHE_ALIGN | SLAB_NOTRACK, NULL); |
| |
| dwarf_reg_cachep = kmem_cache_create("dwarf_regs", |
| sizeof(struct dwarf_reg), 0, |
| SLAB_PANIC | SLAB_HWCACHE_ALIGN | SLAB_NOTRACK, NULL); |
| |
| dwarf_frame_pool = mempool_create(DWARF_FRAME_MIN_REQ, |
| mempool_alloc_slab, |
| mempool_free_slab, |
| dwarf_frame_cachep); |
| |
| dwarf_reg_pool = mempool_create(DWARF_REG_MIN_REQ, |
| mempool_alloc_slab, |
| mempool_free_slab, |
| dwarf_reg_cachep); |
| |
| err = dwarf_parse_section(__start_eh_frame, __stop_eh_frame, NULL); |
| if (err) |
| goto out; |
| |
| err = unwinder_register(&dwarf_unwinder); |
| if (err) |
| goto out; |
| |
| return 0; |
| |
| out: |
| printk(KERN_ERR "Failed to initialise DWARF unwinder: %d\n", err); |
| dwarf_unwinder_cleanup(); |
| return -EINVAL; |
| } |
| early_initcall(dwarf_unwinder_init); |