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Diffstat (limited to 'contrib/gdb/gdb/dwarf2loc.c')
| -rw-r--r-- | contrib/gdb/gdb/dwarf2loc.c | 548 |
1 files changed, 548 insertions, 0 deletions
diff --git a/contrib/gdb/gdb/dwarf2loc.c b/contrib/gdb/gdb/dwarf2loc.c new file mode 100644 index 0000000..cdbeb10 --- /dev/null +++ b/contrib/gdb/gdb/dwarf2loc.c @@ -0,0 +1,548 @@ +/* DWARF 2 location expression support for GDB. + Copyright 2003 Free Software Foundation, Inc. + Contributed by Daniel Jacobowitz, MontaVista Software, Inc. + + 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 "ui-out.h" +#include "value.h" +#include "frame.h" +#include "gdbcore.h" +#include "target.h" +#include "inferior.h" +#include "ax.h" +#include "ax-gdb.h" +#include "regcache.h" +#include "objfiles.h" + +#include "elf/dwarf2.h" +#include "dwarf2expr.h" +#include "dwarf2loc.h" + +#include "gdb_string.h" + +#ifndef DWARF2_REG_TO_REGNUM +#define DWARF2_REG_TO_REGNUM(REG) (REG) +#endif + +/* A helper function for dealing with location lists. Given a + symbol baton (BATON) and a pc value (PC), find the appropriate + location expression, set *LOCEXPR_LENGTH, and return a pointer + to the beginning of the expression. Returns NULL on failure. + + For now, only return the first matching location expression; there + can be more than one in the list. */ + +static char * +find_location_expression (struct dwarf2_loclist_baton *baton, + size_t *locexpr_length, CORE_ADDR pc) +{ + CORE_ADDR low, high; + char *loc_ptr, *buf_end; + unsigned int addr_size = TARGET_ADDR_BIT / TARGET_CHAR_BIT, length; + CORE_ADDR base_mask = ~(~(CORE_ADDR)1 << (addr_size * 8 - 1)); + /* Adjust base_address for relocatable objects. */ + CORE_ADDR base_offset = ANOFFSET (baton->objfile->section_offsets, + SECT_OFF_TEXT (baton->objfile)); + CORE_ADDR base_address = baton->base_address + base_offset; + + loc_ptr = baton->data; + buf_end = baton->data + baton->size; + + while (1) + { + low = dwarf2_read_address (loc_ptr, buf_end, &length); + loc_ptr += length; + high = dwarf2_read_address (loc_ptr, buf_end, &length); + loc_ptr += length; + + /* An end-of-list entry. */ + if (low == 0 && high == 0) + return NULL; + + /* A base-address-selection entry. */ + if ((low & base_mask) == base_mask) + { + base_address = high; + continue; + } + + /* Otherwise, a location expression entry. */ + low += base_address; + high += base_address; + + length = extract_unsigned_integer (loc_ptr, 2); + loc_ptr += 2; + + if (pc >= low && pc < high) + { + *locexpr_length = length; + return loc_ptr; + } + + loc_ptr += length; + } +} + +/* This is the baton used when performing dwarf2 expression + evaluation. */ +struct dwarf_expr_baton +{ + struct frame_info *frame; + struct objfile *objfile; +}; + +/* Helper functions for dwarf2_evaluate_loc_desc. */ + +/* Using the frame specified in BATON, read register REGNUM. The lval + type will be returned in LVALP, and for lval_memory the register + save address will be returned in ADDRP. */ +static CORE_ADDR +dwarf_expr_read_reg (void *baton, int dwarf_regnum) +{ + struct dwarf_expr_baton *debaton = (struct dwarf_expr_baton *) baton; + CORE_ADDR result, save_addr; + enum lval_type lval_type; + char *buf; + int optimized, regnum, realnum, regsize; + + regnum = DWARF2_REG_TO_REGNUM (dwarf_regnum); + regsize = register_size (current_gdbarch, regnum); + buf = (char *) alloca (regsize); + + frame_register (debaton->frame, regnum, &optimized, &lval_type, &save_addr, + &realnum, buf); + /* NOTE: cagney/2003-05-22: This extract is assuming that a DWARF 2 + address is always unsigned. That may or may not be true. */ + result = extract_unsigned_integer (buf, regsize); + + return result; +} + +/* Read memory at ADDR (length LEN) into BUF. */ + +static void +dwarf_expr_read_mem (void *baton, char *buf, CORE_ADDR addr, size_t len) +{ + read_memory (addr, buf, len); +} + +/* Using the frame specified in BATON, find the location expression + describing the frame base. Return a pointer to it in START and + its length in LENGTH. */ +static void +dwarf_expr_frame_base (void *baton, unsigned char **start, size_t * length) +{ + /* FIXME: cagney/2003-03-26: This code should be using + get_frame_base_address(), and then implement a dwarf2 specific + this_base method. */ + struct symbol *framefunc; + struct dwarf_expr_baton *debaton = (struct dwarf_expr_baton *) baton; + + framefunc = get_frame_function (debaton->frame); + + if (SYMBOL_OPS (framefunc) == &dwarf2_loclist_funcs) + { + struct dwarf2_loclist_baton *symbaton; + symbaton = SYMBOL_LOCATION_BATON (framefunc); + *start = find_location_expression (symbaton, length, + get_frame_pc (debaton->frame)); + } + else + { + struct dwarf2_locexpr_baton *symbaton; + symbaton = SYMBOL_LOCATION_BATON (framefunc); + *length = symbaton->size; + *start = symbaton->data; + } + + if (*start == NULL) + error ("Could not find the frame base for \"%s\".", + SYMBOL_NATURAL_NAME (framefunc)); +} + +/* Using the objfile specified in BATON, find the address for the + current thread's thread-local storage with offset OFFSET. */ +static CORE_ADDR +dwarf_expr_tls_address (void *baton, CORE_ADDR offset) +{ + struct dwarf_expr_baton *debaton = (struct dwarf_expr_baton *) baton; + CORE_ADDR addr; + + if (target_get_thread_local_address_p ()) + addr = target_get_thread_local_address (inferior_ptid, + debaton->objfile, + offset); + /* It wouldn't be wrong here to try a gdbarch method, too; finding + TLS is an ABI-specific thing. But we don't do that yet. */ + else + error ("Cannot find thread-local variables on this target"); + + return addr; +} + +/* Evaluate a location description, starting at DATA and with length + SIZE, to find the current location of variable VAR in the context + of FRAME. */ +static struct value * +dwarf2_evaluate_loc_desc (struct symbol *var, struct frame_info *frame, + unsigned char *data, unsigned short size, + struct objfile *objfile) +{ + CORE_ADDR result; + struct value *retval; + struct dwarf_expr_baton baton; + struct dwarf_expr_context *ctx; + + if (size == 0) + { + retval = allocate_value (SYMBOL_TYPE (var)); + VALUE_LVAL (retval) = not_lval; + VALUE_OPTIMIZED_OUT (retval) = 1; + } + + baton.frame = frame; + baton.objfile = objfile; + + ctx = new_dwarf_expr_context (); + ctx->baton = &baton; + ctx->read_reg = dwarf_expr_read_reg; + ctx->read_mem = dwarf_expr_read_mem; + ctx->get_frame_base = dwarf_expr_frame_base; + ctx->get_tls_address = dwarf_expr_tls_address; + + dwarf_expr_eval (ctx, data, size); + result = dwarf_expr_fetch (ctx, 0); + + if (ctx->in_reg) + { + int regnum = DWARF2_REG_TO_REGNUM (result); + retval = value_from_register (SYMBOL_TYPE (var), regnum, frame); + } + else + { + retval = allocate_value (SYMBOL_TYPE (var)); + VALUE_BFD_SECTION (retval) = SYMBOL_BFD_SECTION (var); + + VALUE_LVAL (retval) = lval_memory; + VALUE_LAZY (retval) = 1; + VALUE_ADDRESS (retval) = result; + } + + free_dwarf_expr_context (ctx); + + return retval; +} + + + + + +/* Helper functions and baton for dwarf2_loc_desc_needs_frame. */ + +struct needs_frame_baton +{ + int needs_frame; +}; + +/* Reads from registers do require a frame. */ +static CORE_ADDR +needs_frame_read_reg (void *baton, int regnum) +{ + struct needs_frame_baton *nf_baton = baton; + nf_baton->needs_frame = 1; + return 1; +} + +/* Reads from memory do not require a frame. */ +static void +needs_frame_read_mem (void *baton, char *buf, CORE_ADDR addr, size_t len) +{ + memset (buf, 0, len); +} + +/* Frame-relative accesses do require a frame. */ +static void +needs_frame_frame_base (void *baton, unsigned char **start, size_t * length) +{ + static char lit0 = DW_OP_lit0; + struct needs_frame_baton *nf_baton = baton; + + *start = &lit0; + *length = 1; + + nf_baton->needs_frame = 1; +} + +/* Thread-local accesses do require a frame. */ +static CORE_ADDR +needs_frame_tls_address (void *baton, CORE_ADDR offset) +{ + struct needs_frame_baton *nf_baton = baton; + nf_baton->needs_frame = 1; + return 1; +} + +/* Return non-zero iff the location expression at DATA (length SIZE) + requires a frame to evaluate. */ + +static int +dwarf2_loc_desc_needs_frame (unsigned char *data, unsigned short size) +{ + struct needs_frame_baton baton; + struct dwarf_expr_context *ctx; + int in_reg; + + baton.needs_frame = 0; + + ctx = new_dwarf_expr_context (); + ctx->baton = &baton; + ctx->read_reg = needs_frame_read_reg; + ctx->read_mem = needs_frame_read_mem; + ctx->get_frame_base = needs_frame_frame_base; + ctx->get_tls_address = needs_frame_tls_address; + + dwarf_expr_eval (ctx, data, size); + + in_reg = ctx->in_reg; + + free_dwarf_expr_context (ctx); + + return baton.needs_frame || in_reg; +} + +static void +dwarf2_tracepoint_var_ref (struct symbol * symbol, struct agent_expr * ax, + struct axs_value * value, unsigned char *data, + int size) +{ + if (size == 0) + error ("Symbol \"%s\" has been optimized out.", + SYMBOL_PRINT_NAME (symbol)); + + if (size == 1 + && data[0] >= DW_OP_reg0 + && data[0] <= DW_OP_reg31) + { + value->kind = axs_lvalue_register; + value->u.reg = data[0] - DW_OP_reg0; + } + else if (data[0] == DW_OP_regx) + { + ULONGEST reg; + read_uleb128 (data + 1, data + size, ®); + value->kind = axs_lvalue_register; + value->u.reg = reg; + } + else if (data[0] == DW_OP_fbreg) + { + /* And this is worse than just minimal; we should honor the frame base + as above. */ + int frame_reg; + LONGEST frame_offset; + unsigned char *buf_end; + + buf_end = read_sleb128 (data + 1, data + size, &frame_offset); + if (buf_end != data + size) + error ("Unexpected opcode after DW_OP_fbreg for symbol \"%s\".", + SYMBOL_PRINT_NAME (symbol)); + + TARGET_VIRTUAL_FRAME_POINTER (ax->scope, &frame_reg, &frame_offset); + ax_reg (ax, frame_reg); + ax_const_l (ax, frame_offset); + ax_simple (ax, aop_add); + + ax_const_l (ax, frame_offset); + ax_simple (ax, aop_add); + value->kind = axs_lvalue_memory; + } + else + error ("Unsupported DWARF opcode in the location of \"%s\".", + SYMBOL_PRINT_NAME (symbol)); +} + +/* Return the value of SYMBOL in FRAME using the DWARF-2 expression + evaluator to calculate the location. */ +static struct value * +locexpr_read_variable (struct symbol *symbol, struct frame_info *frame) +{ + struct dwarf2_locexpr_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); + struct value *val; + val = dwarf2_evaluate_loc_desc (symbol, frame, dlbaton->data, dlbaton->size, + dlbaton->objfile); + + return val; +} + +/* Return non-zero iff we need a frame to evaluate SYMBOL. */ +static int +locexpr_read_needs_frame (struct symbol *symbol) +{ + struct dwarf2_locexpr_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); + return dwarf2_loc_desc_needs_frame (dlbaton->data, dlbaton->size); +} + +/* Print a natural-language description of SYMBOL to STREAM. */ +static int +locexpr_describe_location (struct symbol *symbol, struct ui_file *stream) +{ + /* FIXME: be more extensive. */ + struct dwarf2_locexpr_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); + + if (dlbaton->size == 1 + && dlbaton->data[0] >= DW_OP_reg0 + && dlbaton->data[0] <= DW_OP_reg31) + { + int regno = DWARF2_REG_TO_REGNUM (dlbaton->data[0] - DW_OP_reg0); + fprintf_filtered (stream, + "a variable in register %s", REGISTER_NAME (regno)); + return 1; + } + + /* The location expression for a TLS variable looks like this (on a + 64-bit LE machine): + + DW_AT_location : 10 byte block: 3 4 0 0 0 0 0 0 0 e0 + (DW_OP_addr: 4; DW_OP_GNU_push_tls_address) + + 0x3 is the encoding for DW_OP_addr, which has an operand as long + as the size of an address on the target machine (here is 8 + bytes). 0xe0 is the encoding for DW_OP_GNU_push_tls_address. + The operand represents the offset at which the variable is within + the thread local storage. */ + + if (dlbaton->size > 1 + && dlbaton->data[dlbaton->size - 1] == DW_OP_GNU_push_tls_address) + if (dlbaton->data[0] == DW_OP_addr) + { + int bytes_read; + CORE_ADDR offset = dwarf2_read_address (&dlbaton->data[1], + &dlbaton->data[dlbaton->size - 1], + &bytes_read); + fprintf_filtered (stream, + "a thread-local variable at offset %s in the " + "thread-local storage for `%s'", + paddr_nz (offset), dlbaton->objfile->name); + return 1; + } + + + fprintf_filtered (stream, + "a variable with complex or multiple locations (DWARF2)"); + return 1; +} + + +/* Describe the location of SYMBOL as an agent value in VALUE, generating + any necessary bytecode in AX. + + NOTE drow/2003-02-26: This function is extremely minimal, because + doing it correctly is extremely complicated and there is no + publicly available stub with tracepoint support for me to test + against. When there is one this function should be revisited. */ + +static void +locexpr_tracepoint_var_ref (struct symbol * symbol, struct agent_expr * ax, + struct axs_value * value) +{ + struct dwarf2_locexpr_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); + + dwarf2_tracepoint_var_ref (symbol, ax, value, dlbaton->data, dlbaton->size); +} + +/* The set of location functions used with the DWARF-2 expression + evaluator. */ +const struct symbol_ops dwarf2_locexpr_funcs = { + locexpr_read_variable, + locexpr_read_needs_frame, + locexpr_describe_location, + locexpr_tracepoint_var_ref +}; + + +/* Wrapper functions for location lists. These generally find + the appropriate location expression and call something above. */ + +/* Return the value of SYMBOL in FRAME using the DWARF-2 expression + evaluator to calculate the location. */ +static struct value * +loclist_read_variable (struct symbol *symbol, struct frame_info *frame) +{ + struct dwarf2_loclist_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); + struct value *val; + unsigned char *data; + size_t size; + + data = find_location_expression (dlbaton, &size, + frame ? get_frame_pc (frame) : 0); + if (data == NULL) + error ("Variable \"%s\" is not available.", SYMBOL_NATURAL_NAME (symbol)); + + val = dwarf2_evaluate_loc_desc (symbol, frame, data, size, dlbaton->objfile); + + return val; +} + +/* Return non-zero iff we need a frame to evaluate SYMBOL. */ +static int +loclist_read_needs_frame (struct symbol *symbol) +{ + /* If there's a location list, then assume we need to have a frame + to choose the appropriate location expression. With tracking of + global variables this is not necessarily true, but such tracking + is disabled in GCC at the moment until we figure out how to + represent it. */ + + return 1; +} + +/* Print a natural-language description of SYMBOL to STREAM. */ +static int +loclist_describe_location (struct symbol *symbol, struct ui_file *stream) +{ + /* FIXME: Could print the entire list of locations. */ + fprintf_filtered (stream, "a variable with multiple locations"); + return 1; +} + +/* Describe the location of SYMBOL as an agent value in VALUE, generating + any necessary bytecode in AX. */ +static void +loclist_tracepoint_var_ref (struct symbol * symbol, struct agent_expr * ax, + struct axs_value * value) +{ + struct dwarf2_loclist_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); + unsigned char *data; + size_t size; + + data = find_location_expression (dlbaton, &size, ax->scope); + if (data == NULL) + error ("Variable \"%s\" is not available.", SYMBOL_NATURAL_NAME (symbol)); + + dwarf2_tracepoint_var_ref (symbol, ax, value, data, size); +} + +/* The set of location functions used with the DWARF-2 expression + evaluator and location lists. */ +const struct symbol_ops dwarf2_loclist_funcs = { + loclist_read_variable, + loclist_read_needs_frame, + loclist_describe_location, + loclist_tracepoint_var_ref +}; |
