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Diffstat (limited to '')
| -rw-r--r-- | arch/sh/kernel/dwarf.c | 1206 |
1 files changed, 1206 insertions, 0 deletions
diff --git a/arch/sh/kernel/dwarf.c b/arch/sh/kernel/dwarf.c new file mode 100644 index 000000000..bf8682e71 --- /dev/null +++ b/arch/sh/kernel/dwarf.c @@ -0,0 +1,1206 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2009 Matt Fleming <matt@console-pimps.org> + * + * 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 <linux/module.h> +#include <linux/slab.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 struct rb_root cie_root; +static DEFINE_SPINLOCK(dwarf_cie_lock); + +static struct rb_root fde_root; +static DEFINE_SPINLOCK(dwarf_fde_lock); + +static struct dwarf_cie *cached_cie; + +static unsigned int dwarf_unwinder_ready; + +/** + * 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 rb_node **rb_node = &cie_root.rb_node; + struct dwarf_cie *cie = NULL; + 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; + } + + while (*rb_node) { + struct dwarf_cie *cie_tmp; + + cie_tmp = rb_entry(*rb_node, struct dwarf_cie, node); + BUG_ON(!cie_tmp); + + if (cie_ptr == cie_tmp->cie_pointer) { + cie = cie_tmp; + cached_cie = cie_tmp; + goto out; + } else { + if (cie_ptr < cie_tmp->cie_pointer) + rb_node = &(*rb_node)->rb_left; + else + rb_node = &(*rb_node)->rb_right; + } + } + +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 rb_node **rb_node = &fde_root.rb_node; + struct dwarf_fde *fde = NULL; + unsigned long flags; + + spin_lock_irqsave(&dwarf_fde_lock, flags); + + while (*rb_node) { + struct dwarf_fde *fde_tmp; + unsigned long tmp_start, tmp_end; + + fde_tmp = rb_entry(*rb_node, struct dwarf_fde, node); + BUG_ON(!fde_tmp); + + tmp_start = fde_tmp->initial_location; + tmp_end = fde_tmp->initial_location + fde_tmp->address_range; + + if (pc < tmp_start) { + rb_node = &(*rb_node)->rb_left; + } else { + if (pc < tmp_end) { + fde = fde_tmp; + goto out; + } else + rb_node = &(*rb_node)->rb_right; + } + } + +out: + 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've been called in to before initialization has + * completed, bail out immediately. + */ + if (!dwarf_unwinder_ready) + return NULL; + + /* + * 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 = _THIS_IP_; + +#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) { + struct ftrace_ret_stack *ret_stack; + + ret_stack = ftrace_graph_get_ret_stack(current, 0); + if (ret_stack) + pc = ret_stack->ret; + /* + * 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(ftrace_graph_get_ret_stack(current, 1)); + } +#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 rb_node **rb_node = &cie_root.rb_node; + struct rb_node *parent = *rb_node; + 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; + + /* Add to list */ + spin_lock_irqsave(&dwarf_cie_lock, flags); + + while (*rb_node) { + struct dwarf_cie *cie_tmp; + + cie_tmp = rb_entry(*rb_node, struct dwarf_cie, node); + + parent = *rb_node; + + if (cie->cie_pointer < cie_tmp->cie_pointer) + rb_node = &parent->rb_left; + else if (cie->cie_pointer >= cie_tmp->cie_pointer) + rb_node = &parent->rb_right; + else + WARN_ON(1); + } + + rb_link_node(&cie->node, parent, rb_node); + rb_insert_color(&cie->node, &cie_root); + +#ifdef CONFIG_MODULES + if (mod != NULL) + list_add_tail(&cie->link, &mod->arch.cie_list); +#endif + + 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 rb_node **rb_node = &fde_root.rb_node; + struct rb_node *parent = *rb_node; + 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; + + /* Add to list. */ + spin_lock_irqsave(&dwarf_fde_lock, flags); + + while (*rb_node) { + struct dwarf_fde *fde_tmp; + unsigned long tmp_start, tmp_end; + unsigned long start, end; + + fde_tmp = rb_entry(*rb_node, struct dwarf_fde, node); + + start = fde->initial_location; + end = fde->initial_location + fde->address_range; + + tmp_start = fde_tmp->initial_location; + tmp_end = fde_tmp->initial_location + fde_tmp->address_range; + + parent = *rb_node; + + if (start < tmp_start) + rb_node = &parent->rb_left; + else if (start >= tmp_end) + rb_node = &parent->rb_right; + else + WARN_ON(1); + } + + rb_link_node(&fde->node, parent, rb_node); + rb_insert_color(&fde->node, &fde_root); + +#ifdef CONFIG_MODULES + if (mod != NULL) + list_add_tail(&fde->link, &mod->arch.fde_list); +#endif + + 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 __init dwarf_unwinder_cleanup(void) +{ + struct dwarf_fde *fde, *next_fde; + struct dwarf_cie *cie, *next_cie; + + /* + * 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. + */ + rbtree_postorder_for_each_entry_safe(fde, next_fde, &fde_root, node) + kfree(fde); + + rbtree_postorder_for_each_entry_safe(cie, next_cie, &cie_root, node) + kfree(cie); + + mempool_destroy(dwarf_reg_pool); + mempool_destroy(dwarf_frame_pool); + 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) { + INIT_LIST_HEAD(&me->arch.cie_list); + INIT_LIST_HEAD(&me->arch.fde_list); + 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, *ftmp; + struct dwarf_cie *cie, *ctmp; + unsigned long flags; + + spin_lock_irqsave(&dwarf_cie_lock, flags); + + list_for_each_entry_safe(cie, ctmp, &mod->arch.cie_list, link) { + list_del(&cie->link); + rb_erase(&cie->node, &cie_root); + kfree(cie); + } + + spin_unlock_irqrestore(&dwarf_cie_lock, flags); + + spin_lock_irqsave(&dwarf_fde_lock, flags); + + list_for_each_entry_safe(fde, ftmp, &mod->arch.fde_list, link) { + list_del(&fde->link); + rb_erase(&fde->node, &fde_root); + kfree(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 = -ENOMEM; + + dwarf_frame_cachep = kmem_cache_create("dwarf_frames", + sizeof(struct dwarf_frame), 0, + SLAB_PANIC | SLAB_HWCACHE_ALIGN, NULL); + + dwarf_reg_cachep = kmem_cache_create("dwarf_regs", + sizeof(struct dwarf_reg), 0, + SLAB_PANIC | SLAB_HWCACHE_ALIGN, NULL); + + dwarf_frame_pool = mempool_create_slab_pool(DWARF_FRAME_MIN_REQ, + dwarf_frame_cachep); + if (!dwarf_frame_pool) + goto out; + + dwarf_reg_pool = mempool_create_slab_pool(DWARF_REG_MIN_REQ, + dwarf_reg_cachep); + if (!dwarf_reg_pool) + goto out; + + err = dwarf_parse_section(__start_eh_frame, __stop_eh_frame, NULL); + if (err) + goto out; + + err = unwinder_register(&dwarf_unwinder); + if (err) + goto out; + + dwarf_unwinder_ready = 1; + + return 0; + +out: + printk(KERN_ERR "Failed to initialise DWARF unwinder: %d\n", err); + dwarf_unwinder_cleanup(); + return err; +} +early_initcall(dwarf_unwinder_init); |