| /* 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) |
| { |
| struct gdbarch *arch = get_frame_arch (frame); |
| 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); |
| if (ctx->num_pieces > 0) |
| { |
| /* We haven't implemented splicing together pieces from |
| arbitrary sources yet. */ |
| error ("The value of variable '%s' is distributed across several\n" |
| "locations, and GDB cannot access its value.\n", |
| SYMBOL_NATURAL_NAME (var)); |
| } |
| else if (ctx->in_reg) |
| { |
| CORE_ADDR dwarf_regnum = dwarf_expr_fetch (ctx, 0); |
| int gdb_regnum = DWARF2_REG_TO_REGNUM (dwarf_regnum); |
| retval = value_from_register (SYMBOL_TYPE (var), gdb_regnum, frame); |
| } |
| else |
| { |
| CORE_ADDR address = dwarf_expr_fetch (ctx, 0); |
| |
| 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) = address; |
| } |
| |
| 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; |
| |
| if (ctx->num_pieces > 0) |
| { |
| int i; |
| |
| /* If the location has several pieces, and any of them are in |
| registers, then we will need a frame to fetch them from. */ |
| for (i = 0; i < ctx->num_pieces; i++) |
| if (ctx->pieces[i].in_reg) |
| in_reg = 1; |
| } |
| |
| 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 |
| }; |