diff options
Diffstat (limited to 'libdw/cfi.c')
| -rw-r--r-- | libdw/cfi.c | 504 |
1 files changed, 504 insertions, 0 deletions
diff --git a/libdw/cfi.c b/libdw/cfi.c new file mode 100644 index 00000000..632e91d3 --- /dev/null +++ b/libdw/cfi.c @@ -0,0 +1,504 @@ +/* CFI program execution. + Copyright (C) 2009-2010, 2014 Red Hat, Inc. + This file is part of elfutils. + + This file is free software; you can redistribute it and/or modify + it under the terms of either + + * the GNU Lesser General Public License as published by the Free + Software Foundation; either version 3 of the License, or (at + your option) any later version + + or + + * the GNU General Public License as published by the Free + Software Foundation; either version 2 of the License, or (at + your option) any later version + + or both in parallel, as here. + + elfutils is distributed in the hope that it will be useful, but + WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + General Public License for more details. + + You should have received copies of the GNU General Public License and + the GNU Lesser General Public License along with this program. If + not, see <http://www.gnu.org/licenses/>. */ + +#ifdef HAVE_CONFIG_H +# include <config.h> +#endif + +#include <dwarf.h> +#include "../libebl/libebl.h" +#include "cfi.h" +#include "memory-access.h" +#include "encoded-value.h" +#include "system.h" +#include <assert.h> +#include <stdlib.h> +#include <string.h> + +#define CFI_PRIMARY_MAX 0x3f + +static Dwarf_Frame * +duplicate_frame_state (const Dwarf_Frame *original, + Dwarf_Frame *prev) +{ + size_t size = offsetof (Dwarf_Frame, regs[original->nregs]); + Dwarf_Frame *copy = malloc (size); + if (likely (copy != NULL)) + { + memcpy (copy, original, size); + copy->prev = prev; + } + return copy; +} + +/* Returns a DWARF_E_* error code, usually NOERROR or INVALID_CFI. + Frees *STATE on failure. */ +static int +execute_cfi (Dwarf_CFI *cache, + const struct dwarf_cie *cie, + Dwarf_Frame **state, + const uint8_t *program, const uint8_t *const end, bool abi_cfi, + Dwarf_Addr loc, Dwarf_Addr find_pc) +{ + /* The caller should not give us anything out of range. */ + assert (loc <= find_pc); + + int result = DWARF_E_NOERROR; + +#define cfi_assert(ok) do { \ + if (likely (ok)) break; \ + result = DWARF_E_INVALID_CFI; \ + goto out; \ + } while (0) + + Dwarf_Frame *fs = *state; + inline bool enough_registers (Dwarf_Word reg) + { + if (fs->nregs <= reg) + { + size_t size = offsetof (Dwarf_Frame, regs[reg + 1]); + Dwarf_Frame *bigger = realloc (fs, size); + if (unlikely (bigger == NULL)) + { + result = DWARF_E_NOMEM; + return false; + } + else + { + eu_static_assert (reg_unspecified == 0); + memset (bigger->regs + bigger->nregs, 0, + (reg + 1 - bigger->nregs) * sizeof bigger->regs[0]); + bigger->nregs = reg + 1; + fs = bigger; + } + } + return true; + } + + inline void require_cfa_offset (void) + { + if (unlikely (fs->cfa_rule != cfa_offset)) + fs->cfa_rule = cfa_invalid; + } + +#define register_rule(regno, r_rule, r_value) do { \ + if (unlikely (! enough_registers (regno))) \ + goto out; \ + fs->regs[regno].rule = reg_##r_rule; \ + fs->regs[regno].value = (r_value); \ + } while (0) + + while (program < end) + { + uint8_t opcode = *program++; + Dwarf_Word regno; + Dwarf_Word offset; + Dwarf_Word sf_offset; + Dwarf_Word operand = opcode & CFI_PRIMARY_MAX; + switch (opcode) + { + /* These cases move LOC, i.e. "create a new table row". */ + + case DW_CFA_advance_loc1: + operand = *program++; + case DW_CFA_advance_loc + 0 ... DW_CFA_advance_loc + CFI_PRIMARY_MAX: + advance_loc: + loc += operand * cie->code_alignment_factor; + break; + + case DW_CFA_advance_loc2: + cfi_assert (program + 2 <= end); + operand = read_2ubyte_unaligned_inc (cache, program); + goto advance_loc; + case DW_CFA_advance_loc4: + cfi_assert (program + 4 <= end); + operand = read_4ubyte_unaligned_inc (cache, program); + goto advance_loc; + case DW_CFA_MIPS_advance_loc8: + cfi_assert (program + 8 <= end); + operand = read_8ubyte_unaligned_inc (cache, program); + goto advance_loc; + + case DW_CFA_set_loc: + if (likely (!read_encoded_value (cache, cie->fde_encoding, + &program, &loc))) + break; + result = INTUSE(dwarf_errno) (); + goto out; + + /* Now all following cases affect this row, but do not touch LOC. + These cases end with 'continue'. We only get out of the + switch block for the row-copying (LOC-moving) cases above. */ + + case DW_CFA_def_cfa: + get_uleb128 (operand, program, end); + cfi_assert (program < end); + get_uleb128 (offset, program, end); + def_cfa: + fs->cfa_rule = cfa_offset; + fs->cfa_val_reg = operand; + fs->cfa_val_offset = offset; + /* Prime the rest of the Dwarf_Op so dwarf_frame_cfa can use it. */ + fs->cfa_data.offset.atom = DW_OP_bregx; + fs->cfa_data.offset.offset = 0; + continue; + + case DW_CFA_def_cfa_register: + get_uleb128 (regno, program, end); + require_cfa_offset (); + fs->cfa_val_reg = regno; + continue; + + case DW_CFA_def_cfa_sf: + get_uleb128 (operand, program, end); + cfi_assert (program < end); + get_sleb128 (sf_offset, program, end); + offset = sf_offset * cie->data_alignment_factor; + goto def_cfa; + + case DW_CFA_def_cfa_offset: + get_uleb128 (offset, program, end); + def_cfa_offset: + require_cfa_offset (); + fs->cfa_val_offset = offset; + continue; + + case DW_CFA_def_cfa_offset_sf: + get_sleb128 (sf_offset, program, end); + offset = sf_offset * cie->data_alignment_factor; + goto def_cfa_offset; + + case DW_CFA_def_cfa_expression: + /* DW_FORM_block is a ULEB128 length followed by that many bytes. */ + get_uleb128 (operand, program, end); + cfi_assert (operand <= (Dwarf_Word) (end - program)); + fs->cfa_rule = cfa_expr; + fs->cfa_data.expr.data = (unsigned char *) program; + fs->cfa_data.expr.length = operand; + program += operand; + continue; + + case DW_CFA_undefined: + get_uleb128 (regno, program, end); + register_rule (regno, undefined, 0); + continue; + + case DW_CFA_same_value: + get_uleb128 (regno, program, end); + register_rule (regno, same_value, 0); + continue; + + case DW_CFA_offset_extended: + get_uleb128 (operand, program, end); + cfi_assert (program < end); + case DW_CFA_offset + 0 ... DW_CFA_offset + CFI_PRIMARY_MAX: + get_uleb128 (offset, program, end); + offset *= cie->data_alignment_factor; + offset_extended: + register_rule (operand, offset, offset); + continue; + + case DW_CFA_offset_extended_sf: + get_uleb128 (operand, program, end); + get_sleb128 (sf_offset, program, end); + offset_extended_sf: + offset = sf_offset * cie->data_alignment_factor; + goto offset_extended; + + case DW_CFA_GNU_negative_offset_extended: + /* GNU extension obsoleted by DW_CFA_offset_extended_sf. */ + get_uleb128 (operand, program, end); + cfi_assert (program < end); + get_uleb128 (offset, program, end); + sf_offset = -offset; + goto offset_extended_sf; + + case DW_CFA_val_offset: + get_uleb128 (operand, program, end); + cfi_assert (program < end); + get_uleb128 (offset, program, end); + offset *= cie->data_alignment_factor; + val_offset: + register_rule (operand, val_offset, offset); + continue; + + case DW_CFA_val_offset_sf: + get_uleb128 (operand, program, end); + cfi_assert (program < end); + get_sleb128 (sf_offset, program, end); + offset = sf_offset * cie->data_alignment_factor; + goto val_offset; + + case DW_CFA_register: + get_uleb128 (regno, program, end); + cfi_assert (program < end); + get_uleb128 (operand, program, end); + register_rule (regno, register, operand); + continue; + + case DW_CFA_expression: + /* Expression rule relies on section data, abi_cfi cannot use it. */ + assert (! abi_cfi); + get_uleb128 (regno, program, end); + offset = program - (const uint8_t *) cache->data->d.d_buf; + /* DW_FORM_block is a ULEB128 length followed by that many bytes. */ + cfi_assert (program < end); + get_uleb128 (operand, program, end); + cfi_assert (operand <= (Dwarf_Word) (end - program)); + program += operand; + register_rule (regno, expression, offset); + continue; + + case DW_CFA_val_expression: + /* Expression rule relies on section data, abi_cfi cannot use it. */ + assert (! abi_cfi); + get_uleb128 (regno, program, end); + /* DW_FORM_block is a ULEB128 length followed by that many bytes. */ + offset = program - (const uint8_t *) cache->data->d.d_buf; + get_uleb128 (operand, program, end); + cfi_assert (operand <= (Dwarf_Word) (end - program)); + program += operand; + register_rule (regno, val_expression, offset); + continue; + + case DW_CFA_restore_extended: + get_uleb128 (operand, program, end); + case DW_CFA_restore + 0 ... DW_CFA_restore + CFI_PRIMARY_MAX: + + if (unlikely (abi_cfi) && likely (opcode == DW_CFA_restore)) + { + /* Special case hack to give backend abi_cfi a shorthand. */ + cache->default_same_value = true; + continue; + } + + /* This can't be used in the CIE's own initial instructions. */ + cfi_assert (cie->initial_state != NULL); + + /* Restore the CIE's initial rule for this register. */ + if (unlikely (! enough_registers (operand))) + goto out; + if (cie->initial_state->nregs > operand) + fs->regs[operand] = cie->initial_state->regs[operand]; + else + fs->regs[operand].rule = reg_unspecified; + continue; + + case DW_CFA_remember_state: + { + /* Duplicate the state and chain the copy on. */ + Dwarf_Frame *copy = duplicate_frame_state (fs, fs); + if (unlikely (copy == NULL)) + { + result = DWARF_E_NOMEM; + goto out; + } + fs = copy; + continue; + } + + case DW_CFA_restore_state: + { + /* Pop the current state off and use the old one instead. */ + Dwarf_Frame *prev = fs->prev; + cfi_assert (prev != NULL); + free (fs); + fs = prev; + continue; + } + + case DW_CFA_nop: + continue; + + case DW_CFA_GNU_window_save: + /* This is magic shorthand used only by SPARC. It's equivalent + to a bunch of DW_CFA_register and DW_CFA_offset operations. */ + if (unlikely (! enough_registers (31))) + goto out; + for (regno = 8; regno < 16; ++regno) + { + /* Find each %oN in %iN. */ + fs->regs[regno].rule = reg_register; + fs->regs[regno].value = regno + 16; + } + unsigned int address_size = (cache->e_ident[EI_CLASS] == ELFCLASS32 + ? 4 : 8); + for (; regno < 32; ++regno) + { + /* Find %l0..%l7 and %i0..%i7 in a block at the CFA. */ + fs->regs[regno].rule = reg_offset; + fs->regs[regno].value = (regno - 16) * address_size; + } + continue; + + case DW_CFA_GNU_args_size: + /* XXX is this useful for anything? */ + get_uleb128 (operand, program, end); + continue; + + default: + cfi_assert (false); + continue; + } + + /* We get here only for the cases that have just moved LOC. */ + cfi_assert (cie->initial_state != NULL); + if (find_pc >= loc) + /* This advance has not yet reached FIND_PC. */ + fs->start = loc; + else + { + /* We have just advanced past the address we're looking for. + The state currently described is what we want to see. */ + fs->end = loc; + break; + } + } + + /* "The end of the instruction stream can be thought of as a + DW_CFA_set_loc (initial_location + address_range) instruction." + (DWARF 3.0 Section 6.4.3) + + When we fall off the end of the program without an advance_loc/set_loc + that put us past FIND_PC, the final state left by the FDE program + applies to this address (the caller ensured it was inside the FDE). + This address (FDE->end) is already in FS->end as set by the caller. */ + +#undef register_rule +#undef cfi_assert + + out: + + /* Pop any remembered states left on the stack. */ + while (fs->prev != NULL) + { + Dwarf_Frame *prev = fs->prev; + fs->prev = prev->prev; + free (prev); + } + + if (likely (result == DWARF_E_NOERROR)) + *state = fs; + else + free (fs); + + return result; +} + +static int +cie_cache_initial_state (Dwarf_CFI *cache, struct dwarf_cie *cie) +{ + int result = DWARF_E_NOERROR; + + if (likely (cie->initial_state != NULL)) + return result; + + /* This CIE has not been used before. Play out its initial + instructions and cache the initial state that results. + First we'll let the backend fill in the default initial + state for this machine's ABI. */ + + Dwarf_CIE abi_info = { DW_CIE_ID_64, NULL, NULL, 1, 1, -1, "", NULL, 0, 0 }; + + /* Make sure we have a backend handle cached. */ + if (unlikely (cache->ebl == NULL)) + { + cache->ebl = ebl_openbackend (cache->data->s->elf); + if (unlikely (cache->ebl == NULL)) + cache->ebl = (void *) -1l; + } + + /* Fetch the ABI's default CFI program. */ + if (likely (cache->ebl != (void *) -1l) + && unlikely (ebl_abi_cfi (cache->ebl, &abi_info) < 0)) + return DWARF_E_UNKNOWN_ERROR; + + Dwarf_Frame *cie_fs = calloc (1, sizeof (Dwarf_Frame)); + if (unlikely (cie_fs == NULL)) + return DWARF_E_NOMEM; + + /* If the default state of any register is not "undefined" + (i.e. call-clobbered), then the backend supplies instructions + for the standard initial state. */ + if (abi_info.initial_instructions_end > abi_info.initial_instructions) + { + /* Dummy CIE for backend's instructions. */ + struct dwarf_cie abi_cie = + { + .code_alignment_factor = abi_info.code_alignment_factor, + .data_alignment_factor = abi_info.data_alignment_factor, + }; + result = execute_cfi (cache, &abi_cie, &cie_fs, + abi_info.initial_instructions, + abi_info.initial_instructions_end, true, + 0, (Dwarf_Addr) -1l); + } + + /* Now run the CIE's initial instructions. */ + if (cie->initial_instructions_end > cie->initial_instructions + && likely (result == DWARF_E_NOERROR)) + result = execute_cfi (cache, cie, &cie_fs, + cie->initial_instructions, + cie->initial_instructions_end, false, + 0, (Dwarf_Addr) -1l); + + if (likely (result == DWARF_E_NOERROR)) + { + /* Now we have the initial state of things that all + FDEs using this CIE will start from. */ + cie_fs->cache = cache; + cie->initial_state = cie_fs; + } + + return result; +} + +int +internal_function +__libdw_frame_at_address (Dwarf_CFI *cache, struct dwarf_fde *fde, + Dwarf_Addr address, Dwarf_Frame **frame) +{ + int result = cie_cache_initial_state (cache, fde->cie); + if (likely (result == DWARF_E_NOERROR)) + { + Dwarf_Frame *fs = duplicate_frame_state (fde->cie->initial_state, NULL); + if (unlikely (fs == NULL)) + return DWARF_E_NOMEM; + + fs->fde = fde; + fs->start = fde->start; + fs->end = fde->end; + + result = execute_cfi (cache, fde->cie, &fs, + fde->instructions, fde->instructions_end, false, + fde->start, address); + if (likely (result == DWARF_E_NOERROR)) + *frame = fs; + } + return result; +} |