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Diffstat (limited to 'gdb/dwarf2-frame.c')
| -rw-r--r-- | gdb/dwarf2-frame.c | 1259 |
1 files changed, 1259 insertions, 0 deletions
diff --git a/gdb/dwarf2-frame.c b/gdb/dwarf2-frame.c new file mode 100644 index 0000000..2b35dd7 --- /dev/null +++ b/gdb/dwarf2-frame.c @@ -0,0 +1,1259 @@ +/* Frame unwinder for frames with DWARF Call Frame Information. + + Copyright 2003 Free Software Foundation, Inc. + + Contributed by Mark Kettenis. + + This file is part of GDB. + + This program is free software; you can redistribute it and/or modify + it under the terms of 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. + + This program 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 a copy of the GNU General Public License + along with this program; if not, write to the Free Software + Foundation, Inc., 59 Temple Place - Suite 330, + Boston, MA 02111-1307, USA. */ + +#include "defs.h" +#include "dwarf2expr.h" +#include "elf/dwarf2.h" +#include "frame.h" +#include "frame-base.h" +#include "frame-unwind.h" +#include "gdbcore.h" +#include "gdbtypes.h" +#include "symtab.h" +#include "objfiles.h" +#include "regcache.h" + +#include "gdb_assert.h" +#include "gdb_string.h" + +#include "dwarf2-frame.h" + +/* Call Frame Information (CFI). */ + +/* Common Information Entry (CIE). */ + +struct dwarf2_cie +{ + /* Offset into the .debug_frame section where this CIE was found. + Used to identify this CIE. */ + ULONGEST cie_pointer; + + /* Constant that is factored out of all advance location + instructions. */ + ULONGEST code_alignment_factor; + + /* Constants that is factored out of all offset instructions. */ + LONGEST data_alignment_factor; + + /* Return address column. */ + ULONGEST return_address_register; + + /* Instruction sequence to initialize a register set. */ + unsigned char *initial_instructions; + unsigned char *end; + + /* Encoding of addresses. */ + unsigned char encoding; + + struct dwarf2_cie *next; +}; + +/* Frame Description Entry (FDE). */ + +struct dwarf2_fde +{ + /* CIE for this FDE. */ + struct dwarf2_cie *cie; + + /* First location associated with this FDE. */ + CORE_ADDR initial_location; + + /* Number of bytes of program instructions described by this FDE. */ + CORE_ADDR address_range; + + /* Instruction sequence. */ + unsigned char *instructions; + unsigned char *end; + + struct dwarf2_fde *next; +}; + +static struct dwarf2_fde *dwarf2_frame_find_fde (CORE_ADDR *pc); + + +/* Structure describing a frame state. */ + +struct dwarf2_frame_state +{ + /* Each register save state can be described in terms of a CFA slot, + another register, or a location expression. */ + struct dwarf2_frame_state_reg_info + { + struct dwarf2_frame_state_reg + { + union { + LONGEST offset; + ULONGEST reg; + unsigned char *exp; + } loc; + ULONGEST exp_len; + enum { + REG_UNSAVED, + REG_SAVED_OFFSET, + REG_SAVED_REG, + REG_SAVED_EXP, + REG_UNMODIFIED + } how; + } *reg; + int num_regs; + + /* Used to implement DW_CFA_remember_state. */ + struct dwarf2_frame_state_reg_info *prev; + } regs; + + LONGEST cfa_offset; + ULONGEST cfa_reg; + unsigned char *cfa_exp; + enum { + CFA_UNSET, + CFA_REG_OFFSET, + CFA_EXP + } cfa_how; + + /* The PC described by the current frame state. */ + CORE_ADDR pc; + + /* Initial register set from the CIE. + Used to implement DW_CFA_restore. */ + struct dwarf2_frame_state_reg_info initial; + + /* The information we care about from the CIE. */ + LONGEST data_align; + ULONGEST code_align; + ULONGEST retaddr_column; +}; + +/* Store the length the expression for the CFA in the `cfa_reg' field, + which is unused in that case. */ +#define cfa_exp_len cfa_reg + +/* Assert that the register set RS is large enough to store NUM_REGS + columns. If necessary, enlarge the register set. */ + +static void +dwarf2_frame_state_alloc_regs (struct dwarf2_frame_state_reg_info *rs, + int num_regs) +{ + size_t size = sizeof (struct dwarf2_frame_state_reg); + + if (num_regs <= rs->num_regs) + return; + + rs->reg = (struct dwarf2_frame_state_reg *) + xrealloc (rs->reg, num_regs * size); + + /* Initialize newly allocated registers. */ + memset (rs->reg + rs->num_regs * size, 0, (num_regs - rs->num_regs) * size); + rs->num_regs = num_regs; +} + +/* Copy the register columns in register set RS into newly allocated + memory and return a pointer to this newly created copy. */ + +static struct dwarf2_frame_state_reg * +dwarf2_frame_state_copy_regs (struct dwarf2_frame_state_reg_info *rs) +{ + size_t size = rs->num_regs * sizeof (struct dwarf2_frame_state_reg_info); + struct dwarf2_frame_state_reg *reg; + + reg = (struct dwarf2_frame_state_reg *) xmalloc (size); + memcpy (reg, rs->reg, size); + + return reg; +} + +/* Release the memory allocated to register set RS. */ + +static void +dwarf2_frame_state_free_regs (struct dwarf2_frame_state_reg_info *rs) +{ + if (rs) + { + dwarf2_frame_state_free_regs (rs->prev); + + xfree (rs->reg); + xfree (rs); + } +} + +/* Release the memory allocated to the frame state FS. */ + +static void +dwarf2_frame_state_free (void *p) +{ + struct dwarf2_frame_state *fs = p; + + dwarf2_frame_state_free_regs (fs->initial.prev); + dwarf2_frame_state_free_regs (fs->regs.prev); + xfree (fs->initial.reg); + xfree (fs->regs.reg); + xfree (fs); +} + + +/* Helper functions for execute_stack_op. */ + +static CORE_ADDR +read_reg (void *baton, int reg) +{ + struct frame_info *next_frame = (struct frame_info *) baton; + int regnum; + char *buf; + + regnum = DWARF2_REG_TO_REGNUM (reg); + + buf = (char *) alloca (register_size (current_gdbarch, regnum)); + frame_unwind_register (next_frame, regnum, buf); + return extract_typed_address (buf, builtin_type_void_data_ptr); +} + +static void +read_mem (void *baton, char *buf, CORE_ADDR addr, size_t len) +{ + read_memory (addr, buf, len); +} + +static void +no_get_frame_base (void *baton, unsigned char **start, size_t *length) +{ + internal_error (__FILE__, __LINE__, + "Support for DW_OP_fbreg is unimplemented"); +} + +static CORE_ADDR +no_get_tls_address (void *baton, CORE_ADDR offset) +{ + internal_error (__FILE__, __LINE__, + "Support for DW_OP_GNU_push_tls_address is unimplemented"); +} + +static CORE_ADDR +execute_stack_op (unsigned char *exp, ULONGEST len, + struct frame_info *next_frame, CORE_ADDR initial) +{ + struct dwarf_expr_context *ctx; + CORE_ADDR result; + + ctx = new_dwarf_expr_context (); + ctx->baton = next_frame; + ctx->read_reg = read_reg; + ctx->read_mem = read_mem; + ctx->get_frame_base = no_get_frame_base; + ctx->get_tls_address = no_get_tls_address; + + dwarf_expr_push (ctx, initial); + dwarf_expr_eval (ctx, exp, len); + result = dwarf_expr_fetch (ctx, 0); + + if (ctx->in_reg) + result = read_reg (next_frame, result); + + free_dwarf_expr_context (ctx); + + return result; +} + + +static void +execute_cfa_program (unsigned char *insn_ptr, unsigned char *insn_end, + struct frame_info *next_frame, + struct dwarf2_frame_state *fs) +{ + CORE_ADDR pc = frame_pc_unwind (next_frame); + int bytes_read; + + while (insn_ptr < insn_end && fs->pc <= pc) + { + unsigned char insn = *insn_ptr++; + ULONGEST utmp, reg; + LONGEST offset; + + if ((insn & 0xc0) == DW_CFA_advance_loc) + fs->pc += (insn & 0x3f) * fs->code_align; + else if ((insn & 0xc0) == DW_CFA_offset) + { + reg = insn & 0x3f; + insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp); + offset = utmp * fs->data_align; + dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1); + fs->regs.reg[reg].how = REG_SAVED_OFFSET; + fs->regs.reg[reg].loc.offset = offset; + } + else if ((insn & 0xc0) == DW_CFA_restore) + { + gdb_assert (fs->initial.reg); + reg = insn & 0x3f; + dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1); + fs->regs.reg[reg] = fs->initial.reg[reg]; + } + else + { + switch (insn) + { + case DW_CFA_set_loc: + fs->pc = dwarf2_read_address (insn_ptr, insn_end, &bytes_read); + insn_ptr += bytes_read; + break; + + case DW_CFA_advance_loc1: + utmp = extract_unsigned_integer (insn_ptr, 1); + fs->pc += utmp * fs->code_align; + insn_ptr++; + break; + case DW_CFA_advance_loc2: + utmp = extract_unsigned_integer (insn_ptr, 2); + fs->pc += utmp * fs->code_align; + insn_ptr += 2; + break; + case DW_CFA_advance_loc4: + utmp = extract_unsigned_integer (insn_ptr, 4); + fs->pc += utmp * fs->code_align; + insn_ptr += 4; + break; + + case DW_CFA_offset_extended: + insn_ptr = read_uleb128 (insn_ptr, insn_end, ®); + insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp); + offset = utmp * fs->data_align; + dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1); + fs->regs.reg[reg].how = REG_SAVED_OFFSET; + fs->regs.reg[reg].loc.offset = offset; + break; + + case DW_CFA_restore_extended: + gdb_assert (fs->initial.reg); + insn_ptr = read_uleb128 (insn_ptr, insn_end, ®); + dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1); + fs->regs.reg[reg] = fs->initial.reg[reg]; + break; + + case DW_CFA_undefined: + insn_ptr = read_uleb128 (insn_ptr, insn_end, ®); + dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1); + fs->regs.reg[reg].how = REG_UNSAVED; + break; + + case DW_CFA_same_value: + insn_ptr = read_uleb128 (insn_ptr, insn_end, ®); + dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1); + fs->regs.reg[reg].how = REG_UNMODIFIED; + break; + + case DW_CFA_register: + insn_ptr = read_uleb128 (insn_ptr, insn_end, ®); + insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp); + dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1); + fs->regs.reg[reg].loc.reg = utmp; + break; + + case DW_CFA_remember_state: + { + struct dwarf2_frame_state_reg_info *new_rs; + + new_rs = XMALLOC (struct dwarf2_frame_state_reg_info); + *new_rs = fs->regs; + fs->regs.reg = dwarf2_frame_state_copy_regs (&fs->regs); + fs->regs.prev = new_rs; + } + break; + + case DW_CFA_restore_state: + { + struct dwarf2_frame_state_reg_info *old_rs = fs->regs.prev; + + gdb_assert (old_rs); + + xfree (fs->regs.reg); + fs->regs = *old_rs; + xfree (old_rs); + } + break; + + case DW_CFA_def_cfa: + insn_ptr = read_uleb128 (insn_ptr, insn_end, &fs->cfa_reg); + insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp); + fs->cfa_offset = utmp; + fs->cfa_how = CFA_REG_OFFSET; + break; + + case DW_CFA_def_cfa_register: + insn_ptr = read_uleb128 (insn_ptr, insn_end, &fs->cfa_reg); + fs->cfa_how = CFA_REG_OFFSET; + break; + + case DW_CFA_def_cfa_offset: + insn_ptr = read_uleb128 (insn_ptr, insn_end, &fs->cfa_offset); + /* cfa_how deliberately not set. */ + break; + + case DW_CFA_def_cfa_expression: + insn_ptr = read_uleb128 (insn_ptr, insn_end, &fs->cfa_exp_len); + fs->cfa_exp = insn_ptr; + fs->cfa_how = CFA_EXP; + insn_ptr += fs->cfa_exp_len; + break; + + case DW_CFA_expression: + insn_ptr = read_uleb128 (insn_ptr, insn_end, ®); + dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1); + insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp); + fs->regs.reg[reg].loc.exp = insn_ptr; + fs->regs.reg[reg].exp_len = utmp; + fs->regs.reg[reg].how = REG_SAVED_EXP; + insn_ptr += utmp; + break; + + case DW_CFA_nop: + break; + + case DW_CFA_GNU_args_size: + /* Ignored. */ + insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp); + break; + + default: + internal_error (__FILE__, __LINE__, "Unknown CFI encountered."); + } + } + } + + /* Don't allow remember/restore between CIE and FDE programs. */ + dwarf2_frame_state_free_regs (fs->regs.prev); + fs->regs.prev = NULL; +} + +struct dwarf2_frame_cache +{ + /* DWARF Call Frame Address. */ + CORE_ADDR cfa; + + /* Saved registers, indexed by GDB register number, not by DWARF + register number. */ + struct dwarf2_frame_state_reg *reg; +}; + +struct dwarf2_frame_cache * +dwarf2_frame_cache (struct frame_info *next_frame, void **this_cache) +{ + struct cleanup *old_chain; + int num_regs = NUM_REGS + NUM_PSEUDO_REGS; + struct dwarf2_frame_cache *cache; + struct dwarf2_frame_state *fs; + struct dwarf2_fde *fde; + int reg; + + if (*this_cache) + return *this_cache; + + /* Allocate a new cache. */ + cache = FRAME_OBSTACK_ZALLOC (struct dwarf2_frame_cache); + cache->reg = FRAME_OBSTACK_CALLOC (num_regs, struct dwarf2_frame_state_reg); + + /* Allocate and initialize the frame state. */ + fs = XMALLOC (struct dwarf2_frame_state); + memset (fs, 0, sizeof (struct dwarf2_frame_state)); + old_chain = make_cleanup (dwarf2_frame_state_free, fs); + + /* Unwind the PC. + + Note that if NEXT_FRAME is never supposed to return (i.e. a call + to abort), the compiler might optimize away the instruction at + NEXT_FRAME's return address. As a result the return address will + point at some random instruction, and the CFI for that + instruction is probably wortless to us. GCC's unwinder solves + this problem by substracting 1 from the return address to get an + address in the middle of a presumed call instruction (or the + instruction in the associated delay slot). This should only be + done for "normal" frames and not for resume-type frames (signal + handlers, sentinel frames, dummy frames). + + We don't do what GCC's does here (yet). It's not clear how + reliable the method is. There's also a problem with finding the + right FDE; see the comment in dwarf_frame_p. If dwarf_frame_p + selected this frame unwinder because it found the FDE for the + next function, using the adjusted return address might not yield + a FDE at all. The problem isn't specific to DWARF CFI; other + unwinders loose in similar ways. Therefore it's probably + acceptable to leave things slightly broken for now. */ + fs->pc = frame_pc_unwind (next_frame); + + /* Find the correct FDE. */ + fde = dwarf2_frame_find_fde (&fs->pc); + gdb_assert (fde != NULL); + + /* Extract any interesting information from the CIE. */ + fs->data_align = fde->cie->data_alignment_factor; + fs->code_align = fde->cie->code_alignment_factor; + fs->retaddr_column = fde->cie->return_address_register; + + /* First decode all the insns in the CIE. */ + execute_cfa_program (fde->cie->initial_instructions, + fde->cie->end, next_frame, fs); + + /* Save the initialized register set. */ + fs->initial = fs->regs; + fs->initial.reg = dwarf2_frame_state_copy_regs (&fs->regs); + + /* Then decode the insns in the FDE up to our target PC. */ + execute_cfa_program (fde->instructions, fde->end, next_frame, fs); + + /* Caclulate the CFA. */ + switch (fs->cfa_how) + { + case CFA_REG_OFFSET: + cache->cfa = read_reg (next_frame, fs->cfa_reg); + cache->cfa += fs->cfa_offset; + break; + + case CFA_EXP: + cache->cfa = + execute_stack_op (fs->cfa_exp, fs->cfa_exp_len, next_frame, 0); + break; + + default: + internal_error (__FILE__, __LINE__, "Unknown CFA rule."); + } + + /* Save the register info in the cache. */ + for (reg = 0; reg < fs->regs.num_regs; reg++) + { + int regnum; + + /* Skip the return address column. */ + if (reg == fs->retaddr_column) + continue; + + /* Use the GDB register number as index. */ + regnum = DWARF2_REG_TO_REGNUM (reg); + + if (regnum >= 0 && regnum < num_regs) + cache->reg[regnum] = fs->regs.reg[reg]; + } + + /* Stored the location of the return addess. */ + if (fs->retaddr_column < fs->regs.num_regs) + cache->reg[PC_REGNUM] = fs->regs.reg[fs->retaddr_column]; + + do_cleanups (old_chain); + + *this_cache = cache; + return cache; +} + +static void +dwarf2_frame_this_id (struct frame_info *next_frame, void **this_cache, + struct frame_id *this_id) +{ + struct dwarf2_frame_cache *cache = + dwarf2_frame_cache (next_frame, this_cache); + + (*this_id) = frame_id_build (cache->cfa, frame_func_unwind (next_frame)); +} + +static void +dwarf2_frame_prev_register (struct frame_info *next_frame, void **this_cache, + int regnum, int *optimizedp, + enum lval_type *lvalp, CORE_ADDR *addrp, + int *realnump, void *valuep) +{ + struct dwarf2_frame_cache *cache = + dwarf2_frame_cache (next_frame, this_cache); + + switch (cache->reg[regnum].how) + { + case REG_UNSAVED: + *optimizedp = 1; + *lvalp = not_lval; + *addrp = 0; + *realnump = -1; + if (regnum == SP_REGNUM) + { + /* GCC defines the CFA as the value of the stack pointer + just before the call instruction is executed. Do other + compilers use the same definition? */ + *optimizedp = 0; + if (valuep) + { + /* Store the value. */ + store_typed_address (valuep, builtin_type_void_data_ptr, + cache->cfa); + } + } + else if (valuep) + { + /* In some cases, for example %eflags on the i386, we have + to provide a sane value, even though this register wasn't + saved. Assume we can get it from NEXT_FRAME. */ + frame_unwind_register (next_frame, regnum, valuep); + } + break; + + case REG_SAVED_OFFSET: + *optimizedp = 0; + *lvalp = lval_memory; + *addrp = cache->cfa + cache->reg[regnum].loc.offset; + *realnump = -1; + if (valuep) + { + /* Read the value in from memory. */ + read_memory (*addrp, valuep, + register_size (current_gdbarch, regnum)); + } + break; + + case REG_SAVED_REG: + regnum = DWARF2_REG_TO_REGNUM (cache->reg[regnum].loc.reg); + frame_register_unwind (next_frame, regnum, + optimizedp, lvalp, addrp, realnump, valuep); + break; + + case REG_SAVED_EXP: + *optimizedp = 0; + *lvalp = lval_memory; + *addrp = execute_stack_op (cache->reg[regnum].loc.exp, + cache->reg[regnum].exp_len, + next_frame, cache->cfa); + *realnump = -1; + if (valuep) + { + /* Read the value in from memory. */ + read_memory (*addrp, valuep, + register_size (current_gdbarch, regnum)); + } + break; + + case REG_UNMODIFIED: + frame_register_unwind (next_frame, regnum, + optimizedp, lvalp, addrp, realnump, valuep); + break; + + default: + internal_error (__FILE__, __LINE__, "Unknown register rule."); + } +} + +static const struct frame_unwind dwarf2_frame_unwind = +{ + NORMAL_FRAME, + dwarf2_frame_this_id, + dwarf2_frame_prev_register +}; + +const struct frame_unwind * +dwarf2_frame_p (CORE_ADDR pc) +{ + /* The way GDB works, this function can be called with PC just after + the last instruction of the function we're supposed to return the + unwind methods for. In that case we won't find the correct FDE; + instead we find the FDE for the next function, or we won't find + an FDE at all. There is a possible solution (see the comment in + dwarf2_frame_cache), GDB doesn't pass us enough information to + implement it. */ + if (dwarf2_frame_find_fde (&pc)) + return &dwarf2_frame_unwind; + + return NULL; +} + + +/* There is no explicitly defined relationship between the CFA and the + location of frame's local variables and arguments/parameters. + Therefore, frame base methods on this page should probably only be + used as a last resort, just to avoid printing total garbage as a + response to the "info frame" command. */ + +static CORE_ADDR +dwarf2_frame_base_address (struct frame_info *next_frame, void **this_cache) +{ + struct dwarf2_frame_cache *cache = + dwarf2_frame_cache (next_frame, this_cache); + + return cache->cfa; +} + +static const struct frame_base dwarf2_frame_base = +{ + &dwarf2_frame_unwind, + dwarf2_frame_base_address, + dwarf2_frame_base_address, + dwarf2_frame_base_address +}; + +const struct frame_base * +dwarf2_frame_base_p (CORE_ADDR pc) +{ + if (dwarf2_frame_find_fde (&pc)) + return &dwarf2_frame_base; + + return NULL; +} + +/* A minimal decoding of DWARF2 compilation units. We only decode + what's needed to get to the call frame information. */ + +struct comp_unit +{ + /* Keep the bfd convenient. */ + bfd *abfd; + + struct objfile *objfile; + + /* Linked list of CIEs for this object. */ + struct dwarf2_cie *cie; + + /* Address size for this unit - from unit header. */ + unsigned char addr_size; + + /* Pointer to the .debug_frame section loaded into memory. */ + char *dwarf_frame_buffer; + + /* Length of the loaded .debug_frame section. */ + unsigned long dwarf_frame_size; + + /* Pointer to the .debug_frame section. */ + asection *dwarf_frame_section; +}; + +static unsigned int +read_1_byte (bfd *bfd, char *buf) +{ + return bfd_get_8 (abfd, (bfd_byte *) buf); +} + +static unsigned int +read_4_bytes (bfd *abfd, char *buf) +{ + return bfd_get_32 (abfd, (bfd_byte *) buf); +} + +static ULONGEST +read_8_bytes (bfd *abfd, char *buf) +{ + return bfd_get_64 (abfd, (bfd_byte *) buf); +} + +static ULONGEST +read_unsigned_leb128 (bfd *abfd, char *buf, unsigned int *bytes_read_ptr) +{ + ULONGEST result; + unsigned int num_read; + int shift; + unsigned char byte; + + result = 0; + shift = 0; + num_read = 0; + + do + { + byte = bfd_get_8 (abfd, (bfd_byte *) buf); + buf++; + num_read++; + result |= ((byte & 0x7f) << shift); + shift += 7; + } + while (byte & 0x80); + + *bytes_read_ptr = num_read; + + return result; +} + +static LONGEST +read_signed_leb128 (bfd *abfd, char *buf, unsigned int *bytes_read_ptr) +{ + LONGEST result; + int shift; + unsigned int num_read; + unsigned char byte; + + result = 0; + shift = 0; + num_read = 0; + + do + { + byte = bfd_get_8 (abfd, (bfd_byte *) buf); + buf++; + num_read++; + result |= ((byte & 0x7f) << shift); + shift += 7; + } + while (byte & 0x80); + + if ((shift < 32) && (byte & 0x40)) + result |= -(1 << shift); + + *bytes_read_ptr = num_read; + + return result; +} + +static ULONGEST +read_initial_length (bfd *abfd, char *buf, unsigned int *bytes_read_ptr) +{ + LONGEST result; + + result = bfd_get_32 (abfd, (bfd_byte *) buf); + if (result == 0xffffffff) + { + result = bfd_get_64 (abfd, (bfd_byte *) buf + 4); + *bytes_read_ptr = 12; + } + else + *bytes_read_ptr = 4; + + return result; +} + + +/* Pointer encoding helper functions. */ + +/* GCC supports exception handling based on DWARF2 CFI. However, for + technical reasons, it encodes addresses in its FDE's in a different + way. Several "pointer encodings" are supported. The encoding + that's used for a particular FDE is determined by the 'R' + augmentation in the associated CIE. The argument of this + augmentation is a single byte. + + The address can be encoded as 2 bytes, 4 bytes, 8 bytes, or as a + LEB128. This is encoded in bits 0, 1 and 2. Bit 3 encodes whether + the address is signed or unsigned. Bits 4, 5 and 6 encode how the + address should be interpreted (absolute, relative to the current + position in the FDE, ...). Bit 7, indicates that the address + should be dereferenced. */ + +static unsigned char +encoding_for_size (unsigned int size) +{ + switch (size) + { + case 2: + return DW_EH_PE_udata2; + case 4: + return DW_EH_PE_udata4; + case 8: + return DW_EH_PE_udata8; + default: + internal_error (__FILE__, __LINE__, "Unsupported address size"); + } +} + +static unsigned int +size_of_encoded_value (unsigned char encoding) +{ + if (encoding == DW_EH_PE_omit) + return 0; + + switch (encoding & 0x07) + { + case DW_EH_PE_absptr: + return TYPE_LENGTH (builtin_type_void_data_ptr); + case DW_EH_PE_udata2: + return 2; + case DW_EH_PE_udata4: + return 4; + case DW_EH_PE_udata8: + return 8; + default: + internal_error (__FILE__, __LINE__, "Invalid or unsupported encoding"); + } +} + +static CORE_ADDR +read_encoded_value (struct comp_unit *unit, unsigned char encoding, + char *buf, unsigned int *bytes_read_ptr) +{ + CORE_ADDR base; + + /* GCC currently doesn't generate DW_EH_PE_indirect encodings for + FDE's. */ + if (encoding & DW_EH_PE_indirect) + internal_error (__FILE__, __LINE__, + "Unsupported encoding: DW_EH_PE_indirect"); + + switch (encoding & 0x70) + { + case DW_EH_PE_absptr: + base = 0; + break; + case DW_EH_PE_pcrel: + base = bfd_get_section_vma (unit->bfd, unit->dwarf_frame_section); + base += (buf - unit->dwarf_frame_buffer); + break; + default: + internal_error (__FILE__, __LINE__, "Invalid or unsupported encoding"); + } + + if ((encoding & 0x0f) == 0x00) + encoding |= encoding_for_size (TYPE_LENGTH(builtin_type_void_data_ptr)); + + switch (encoding & 0x0f) + { + case DW_EH_PE_udata2: + *bytes_read_ptr = 2; + return (base + bfd_get_16 (unit->abfd, (bfd_byte *) buf)); + case DW_EH_PE_udata4: + *bytes_read_ptr = 4; + return (base + bfd_get_32 (unit->abfd, (bfd_byte *) buf)); + case DW_EH_PE_udata8: + *bytes_read_ptr = 8; + return (base + bfd_get_64 (unit->abfd, (bfd_byte *) buf)); + case DW_EH_PE_sdata2: + *bytes_read_ptr = 2; + return (base + bfd_get_signed_16 (unit->abfd, (bfd_byte *) buf)); + case DW_EH_PE_sdata4: + *bytes_read_ptr = 4; + return (base + bfd_get_signed_32 (unit->abfd, (bfd_byte *) buf)); + case DW_EH_PE_sdata8: + *bytes_read_ptr = 8; + return (base + bfd_get_signed_64 (unit->abfd, (bfd_byte *) buf)); + default: + internal_error (__FILE__, __LINE__, "Invalid or unsupported encoding"); + } +} + + +/* GCC uses a single CIE for all FDEs in a .debug_frame section. + That's why we use a simple linked list here. */ + +static struct dwarf2_cie * +find_cie (struct comp_unit *unit, ULONGEST cie_pointer) +{ + struct dwarf2_cie *cie = unit->cie; + + while (cie) + { + if (cie->cie_pointer == cie_pointer) + return cie; + + cie = cie->next; + } + + return NULL; +} + +static void +add_cie (struct comp_unit *unit, struct dwarf2_cie *cie) +{ + cie->next = unit->cie; + unit->cie = cie; +} + +/* Find the FDE for *PC. Return a pointer to the FDE, and store the + inital location associated with it into *PC. */ + +static struct dwarf2_fde * +dwarf2_frame_find_fde (CORE_ADDR *pc) +{ + struct objfile *objfile; + + ALL_OBJFILES (objfile) + { + struct dwarf2_fde *fde; + CORE_ADDR offset; + + offset = ANOFFSET (objfile->section_offsets, SECT_OFF_TEXT (objfile)); + + fde = objfile->sym_private; + while (fde) + { + if (*pc >= fde->initial_location + offset + && *pc < fde->initial_location + offset + fde->address_range) + { + *pc = fde->initial_location + offset; + return fde; + } + + fde = fde->next; + } + } + + return NULL; +} + +static void +add_fde (struct comp_unit *unit, struct dwarf2_fde *fde) +{ + fde->next = unit->objfile->sym_private; + unit->objfile->sym_private = fde; +} + +#ifdef CC_HAS_LONG_LONG +#define DW64_CIE_ID 0xffffffffffffffffULL +#else +#define DW64_CIE_ID ~0 +#endif + +/* Read a CIE or FDE in BUF and decode it. */ + +static char * +decode_frame_entry (struct comp_unit *unit, char *buf, int eh_frame_p) +{ + LONGEST length; + unsigned int bytes_read; + int dwarf64_p = 0; + ULONGEST cie_id = DW_CIE_ID; + ULONGEST cie_pointer; + char *start = buf; + char *end; + + length = read_initial_length (unit->abfd, buf, &bytes_read); + buf += bytes_read; + end = buf + length; + + if (length == 0) + return end; + + if (bytes_read == 12) + dwarf64_p = 1; + + /* In a .eh_frame section, zero is used to distinguish CIEs from + FDEs. */ + if (eh_frame_p) + cie_id = 0; + else if (dwarf64_p) + cie_id = DW64_CIE_ID; + + if (dwarf64_p) + { + cie_pointer = read_8_bytes (unit->abfd, buf); + buf += 8; + } + else + { + cie_pointer = read_4_bytes (unit->abfd, buf); + buf += 4; + } + + if (cie_pointer == cie_id) + { + /* This is a CIE. */ + struct dwarf2_cie *cie; + char *augmentation; + + /* Record the offset into the .debug_frame section of this CIE. */ + cie_pointer = start - unit->dwarf_frame_buffer; + + /* Check whether we've already read it. */ + if (find_cie (unit, cie_pointer)) + return end; + + cie = (struct dwarf2_cie *) + obstack_alloc (&unit->objfile->psymbol_obstack, + sizeof (struct dwarf2_cie)); + cie->initial_instructions = NULL; + cie->cie_pointer = cie_pointer; + + /* The encoding for FDE's in a normal .debug_frame section + depends on the target address size as specified in the + Compilation Unit Header. */ + cie->encoding = encoding_for_size (unit->addr_size); + + /* Check version number. */ + gdb_assert (read_1_byte (unit->abfd, buf) == DW_CIE_VERSION); + buf += 1; + + /* Interpret the interesting bits of the augmentation. */ + augmentation = buf; + buf = augmentation + strlen (augmentation) + 1; + + /* The GCC 2.x "eh" augmentation has a pointer immediately + following the augmentation string, so it must be handled + first. */ + if (augmentation[0] == 'e' && augmentation[1] == 'h') + { + /* Skip. */ + buf += TYPE_LENGTH (builtin_type_void_data_ptr); + augmentation += 2; + } + + cie->code_alignment_factor = + read_unsigned_leb128 (unit->abfd, buf, &bytes_read); + buf += bytes_read; + + cie->data_alignment_factor = + read_signed_leb128 (unit->abfd, buf, &bytes_read); + buf += bytes_read; + + cie->return_address_register = read_1_byte (unit->abfd, buf); + buf += 1; + + if (*augmentation == 'z') + { + ULONGEST length; + + length = read_unsigned_leb128 (unit->abfd, buf, &bytes_read); + buf += bytes_read; + cie->initial_instructions = buf + length; + augmentation++; + } + + while (*augmentation) + { + /* "L" indicates a byte showing how the LSDA pointer is encoded. */ + if (*augmentation == 'L') + { + /* Skip. */ + buf++; + augmentation++; + } + + /* "R" indicates a byte indicating how FDE addresses are encoded. */ + else if (*augmentation == 'R') + { + cie->encoding = *buf++; + augmentation++; + } + + /* "P" indicates a personality routine in the CIE augmentation. */ + else if (*augmentation == 'P') + { + /* Skip. */ + buf += size_of_encoded_value (*buf++); + augmentation++; + } + + /* Otherwise we have an unknown augmentation. + Bail out unless we saw a 'z' prefix. */ + else + { + if (cie->initial_instructions == NULL) + return end; + + /* Skip unknown augmentations. */ + buf = cie->initial_instructions; + break; + } + } + + cie->initial_instructions = buf; + cie->end = end; + + add_cie (unit, cie); + } + else + { + /* This is a FDE. */ + struct dwarf2_fde *fde; + + if (eh_frame_p) + { + /* In an .eh_frame section, the CIE pointer is the delta + between the address within the FDE where the CIE pointer + is stored and the address of the CIE. Convert it to an + offset into the .eh_frame section. */ + cie_pointer = buf - unit->dwarf_frame_buffer - cie_pointer; + cie_pointer -= (dwarf64_p ? 8 : 4); + } + + fde = (struct dwarf2_fde *) + obstack_alloc (&unit->objfile->psymbol_obstack, + sizeof (struct dwarf2_fde)); + fde->cie = find_cie (unit, cie_pointer); + if (fde->cie == NULL) + { + decode_frame_entry (unit, unit->dwarf_frame_buffer + cie_pointer, + eh_frame_p); + fde->cie = find_cie (unit, cie_pointer); + } + + gdb_assert (fde->cie != NULL); + + fde->initial_location = + read_encoded_value (unit, fde->cie->encoding, buf, &bytes_read); + buf += bytes_read; + + fde->address_range = + read_encoded_value (unit, fde->cie->encoding & 0x0f, buf, &bytes_read); + buf += bytes_read; + + fde->instructions = buf; + fde->end = end; + + add_fde (unit, fde); + } + + return end; +} + + +/* FIXME: kettenis/20030504: This still needs to be integrated with + dwarf2read.c in a better way. */ + +/* Imported from dwarf2read.c. */ +extern file_ptr dwarf_frame_offset; +extern unsigned int dwarf_frame_size; +extern asection *dwarf_frame_section; +extern file_ptr dwarf_eh_frame_offset; +extern unsigned int dwarf_eh_frame_size; +extern asection *dwarf_eh_frame_section; + +/* Imported from dwarf2read.c. */ +extern char *dwarf2_read_section (struct objfile *objfile, file_ptr offset, + unsigned int size, asection *sectp); + +void +dwarf2_build_frame_info (struct objfile *objfile) +{ + struct comp_unit unit; + char *frame_ptr; + + /* Build a minimal decoding of the DWARF2 compilation unit. */ + unit.abfd = objfile->obfd; + unit.objfile = objfile; + unit.addr_size = objfile->obfd->arch_info->bits_per_address / 8; + + /* First add the information from the .eh_frame section. That way, + the FDEs from that section are searched last. */ + if (dwarf_eh_frame_offset) + { + unit.cie = NULL; + unit.dwarf_frame_buffer = dwarf2_read_section (objfile, + dwarf_eh_frame_offset, + dwarf_eh_frame_size, + dwarf_eh_frame_section); + + unit.dwarf_frame_size = dwarf_eh_frame_size; + unit.dwarf_frame_section = dwarf_eh_frame_section; + + frame_ptr = unit.dwarf_frame_buffer; + while (frame_ptr < unit.dwarf_frame_buffer + unit.dwarf_frame_size) + frame_ptr = decode_frame_entry (&unit, frame_ptr, 1); + } + + if (dwarf_frame_offset) + { + unit.cie = NULL; + unit.dwarf_frame_buffer = dwarf2_read_section (objfile, + dwarf_frame_offset, + dwarf_frame_size, + dwarf_frame_section); + unit.dwarf_frame_size = dwarf_frame_size; + unit.dwarf_frame_section = dwarf_frame_section; + + frame_ptr = unit.dwarf_frame_buffer; + while (frame_ptr < unit.dwarf_frame_buffer + unit.dwarf_frame_size) + frame_ptr = decode_frame_entry (&unit, frame_ptr, 0); + } +} |