diff options
Diffstat (limited to 'arch/sh/kernel/dwarf.c')
| -rw-r--r-- | arch/sh/kernel/dwarf.c | 876 |
1 files changed, 876 insertions, 0 deletions
diff --git a/arch/sh/kernel/dwarf.c b/arch/sh/kernel/dwarf.c new file mode 100644 index 00000000000..09c6fd7fd05 --- /dev/null +++ b/arch/sh/kernel/dwarf.c @@ -0,0 +1,876 @@ +/* + * 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. + */ + +/* #define DEBUG */ +#include <linux/kernel.h> +#include <linux/io.h> +#include <linux/list.h> +#include <linux/mm.h> +#include <asm/dwarf.h> +#include <asm/unwinder.h> +#include <asm/sections.h> +#include <asm-generic/unaligned.h> +#include <asm/dwarf.h> +#include <asm/stacktrace.h> + +static LIST_HEAD(dwarf_cie_list); +DEFINE_SPINLOCK(dwarf_cie_lock); + +static LIST_HEAD(dwarf_fde_list); +DEFINE_SPINLOCK(dwarf_fde_lock); + +static struct dwarf_cie *cached_cie; + +/* + * Figure out whether we need to allocate some dwarf registers. If dwarf + * registers have already been allocated then we may need to realloc + * them. "reg" is a register number that we need to be able to access + * after this call. + * + * Register numbers start at zero, therefore we need to allocate space + * for "reg" + 1 registers. + */ +static void dwarf_frame_alloc_regs(struct dwarf_frame *frame, + unsigned int reg) +{ + struct dwarf_reg *regs; + unsigned int num_regs = reg + 1; + size_t new_size; + size_t old_size; + + new_size = num_regs * sizeof(*regs); + old_size = frame->num_regs * sizeof(*regs); + + /* Fast path: don't allocate any regs if we've already got enough. */ + if (frame->num_regs >= num_regs) + return; + + regs = kzalloc(new_size, GFP_KERNEL); + if (!regs) { + printk(KERN_WARNING "Unable to allocate DWARF registers\n"); + /* + * Let's just bomb hard here, we have no way to + * gracefully recover. + */ + BUG(); + } + + if (frame->regs) { + memcpy(regs, frame->regs, old_size); + kfree(frame->regs); + } + + frame->regs = regs; + frame->num_regs = num_regs; +} + +/** + * 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(void *src, void *dst) +{ + u32 val = __get_unaligned_cpu32(src); + __put_unaligned_cpu32(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)); + 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_cpu32(addr); + __raw_writel(decoded_addr, val); + break; + default: + pr_debug("encoding=0x%x\n", encoding); + 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_cpu32(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_cpu64(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, *n; + 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_safe(cie, n, &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) +{ + unsigned long flags; + struct dwarf_fde *fde, *n; + + spin_lock_irqsave(&dwarf_fde_lock, flags); + list_for_each_entry_safe(fde, n, &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; + + 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; + dwarf_frame_alloc_regs(frame, reg); + frame->regs[reg].addr = offset; + frame->regs[reg].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_cpu16(current_insn); + current_insn += 2; + frame->pc += delta * cie->code_alignment_factor; + break; + case DW_CFA_advance_loc4: + delta = __get_unaligned_cpu32(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; + 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; + dwarf_frame_alloc_regs(frame, reg); + frame->regs[reg].flags |= DWARF_REG_OFFSET; + frame->regs[reg].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; + frame->regs[reg].flags |= DWARF_REG_OFFSET; + frame->regs[reg].addr = offset; + break; + default: + pr_debug("unhandled DWARF instruction 0x%x\n", insn); + break; + } + } + + return 0; +} + +/** + * dwarf_unwind_stack - recursively 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; + unsigned long addr; + int i, offset; + + /* + * If this is the first invocation of this recursive function we + * need get the contents of a physical register to get the CFA + * in order to begin the virtual unwinding of the stack. + * + * The constant DWARF_ARCH_UNWIND_OFFSET is added to the address of + * this function because the return address register + * (DWARF_ARCH_RA_REG) will probably not be initialised until a + * few instructions into the prologue. + */ + if (!pc && !prev) { + pc = (unsigned long)&dwarf_unwind_stack; + pc += DWARF_ARCH_UNWIND_OFFSET; + } + + frame = kzalloc(sizeof(*frame), GFP_KERNEL); + if (!frame) + return NULL; + + frame->prev = prev; + + fde = dwarf_lookup_fde(pc); + if (!fde) { + /* + * This is our normal exit path - the one that stops the + * recursion. There's 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. + */ + return NULL; + } + + 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) { + BUG_ON(!prev->regs[frame->cfa_register].flags); + + addr = prev->cfa; + addr += prev->regs[frame->cfa_register].addr; + frame->cfa = __raw_readl(addr); + + } else { + /* + * Again, this is the first invocation of this + * recurisve function. 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: + BUG(); + } + + /* If we haven't seen the return address reg, we're screwed. */ + BUG_ON(!frame->regs[DWARF_ARCH_RA_REG].flags); + + for (i = 0; i <= frame->num_regs; i++) { + struct dwarf_reg *reg = &frame->regs[i]; + + if (!reg->flags) + continue; + + offset = reg->addr; + offset += frame->cfa; + } + + addr = frame->cfa + frame->regs[DWARF_ARCH_RA_REG].addr; + frame->return_addr = __raw_readl(addr); + + frame->next = dwarf_unwind_stack(frame->return_addr, frame); + return frame; +} + +static int dwarf_parse_cie(void *entry, void *p, unsigned long len, + unsigned char *end) +{ + 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++; + 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; + + 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. + */ + BUG(); + } else if (*cie->augmentation == 'S') { + BUG(); + } else { + /* + * Unknown augmentation. Assume + * 'z' augmentation. + */ + p = cie->initial_instructions; + BUG_ON(!p); + break; + } + } + + cie->initial_instructions = p; + cie->instructions_end = end; + + /* 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) +{ + 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 = start + len; + + /* 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 = dwarf_unwind_stack(0, NULL); + + while (frame && frame->return_addr) { + ops->address(data, frame->return_addr, 1); + frame = frame->next; + } +} + +static struct unwinder dwarf_unwinder = { + .name = "dwarf-unwinder", + .dump = dwarf_unwinder_dump, + .rating = 150, +}; + +static void dwarf_unwinder_cleanup(void) +{ + struct dwarf_cie *cie, *m; + struct dwarf_fde *fde, *n; + unsigned long flags; + + /* + * 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. + */ + spin_lock_irqsave(&dwarf_cie_lock, flags); + list_for_each_entry_safe(cie, m, &dwarf_cie_list, link) + kfree(cie); + spin_unlock_irqrestore(&dwarf_cie_lock, flags); + + spin_lock_irqsave(&dwarf_fde_lock, flags); + list_for_each_entry_safe(fde, n, &dwarf_fde_list, link) + kfree(fde); + spin_unlock_irqrestore(&dwarf_fde_lock, flags); +} + +/** + * 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. + */ +void dwarf_unwinder_init(void) +{ + u32 entry_type; + void *p, *entry; + int count, err; + unsigned long len; + unsigned int c_entries, f_entries; + unsigned char *end; + INIT_LIST_HEAD(&dwarf_cie_list); + INIT_LIST_HEAD(&dwarf_fde_list); + + c_entries = 0; + f_entries = 0; + entry = &__start_eh_frame; + + while ((char *)entry < __stop_eh_frame) { + 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. + */ + goto out; + } else + p += count; + + /* initial length does not include itself */ + end = p + len; + + entry_type = __get_unaligned_cpu32(p); + p += 4; + + if (entry_type == DW_EH_FRAME_CIE) { + err = dwarf_parse_cie(entry, p, len, end); + if (err < 0) + goto out; + else + c_entries++; + } else { + err = dwarf_parse_fde(entry, entry_type, p, len); + 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); + + err = unwinder_register(&dwarf_unwinder); + if (err) + goto out; + + return; + +out: + printk(KERN_ERR "Failed to initialise DWARF unwinder: %d\n", err); + dwarf_unwinder_cleanup(); +} |