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/* SPDX-License-Identifier: GPL-2.0 */
/*
* Convert sample address to data type using DWARF debug info.
*
* Written by Namhyung Kim <namhyung@kernel.org>
*/
#include <stdio.h>
#include <stdlib.h>
#include <inttypes.h>
#include "annotate-data.h"
#include "debuginfo.h"
#include "debug.h"
#include "dso.h"
#include "map.h"
#include "map_symbol.h"
#include "strbuf.h"
#include "symbol.h"
static bool find_cu_die(struct debuginfo *di, u64 pc, Dwarf_Die *cu_die)
{
Dwarf_Off off, next_off;
size_t header_size;
if (dwarf_addrdie(di->dbg, pc, cu_die) != NULL)
return cu_die;
/*
* There are some kernels don't have full aranges and contain only a few
* aranges entries. Fallback to iterate all CU entries in .debug_info
* in case it's missing.
*/
off = 0;
while (dwarf_nextcu(di->dbg, off, &next_off, &header_size,
NULL, NULL, NULL) == 0) {
if (dwarf_offdie(di->dbg, off + header_size, cu_die) &&
dwarf_haspc(cu_die, pc))
return true;
off = next_off;
}
return false;
}
/* The type info will be saved in @type_die */
static int check_variable(Dwarf_Die *var_die, Dwarf_Die *type_die, int offset)
{
Dwarf_Word size;
/* Get the type of the variable */
if (die_get_real_type(var_die, type_die) == NULL) {
pr_debug("variable has no type\n");
return -1;
}
/*
* It expects a pointer type for a memory access.
* Convert to a real type it points to.
*/
if (dwarf_tag(type_die) != DW_TAG_pointer_type ||
die_get_real_type(type_die, type_die) == NULL) {
pr_debug("no pointer or no type\n");
return -1;
}
/* Get the size of the actual type */
if (dwarf_aggregate_size(type_die, &size) < 0) {
pr_debug("type size is unknown\n");
return -1;
}
/* Minimal sanity check */
if ((unsigned)offset >= size) {
pr_debug("offset: %d is bigger than size: %" PRIu64 "\n", offset, size);
return -1;
}
return 0;
}
/* The result will be saved in @type_die */
static int find_data_type_die(struct debuginfo *di, u64 pc,
int reg, int offset, Dwarf_Die *type_die)
{
Dwarf_Die cu_die, var_die;
Dwarf_Die *scopes = NULL;
int ret = -1;
int i, nr_scopes;
/* Get a compile_unit for this address */
if (!find_cu_die(di, pc, &cu_die)) {
pr_debug("cannot find CU for address %" PRIx64 "\n", pc);
return -1;
}
/* Get a list of nested scopes - i.e. (inlined) functions and blocks. */
nr_scopes = die_get_scopes(&cu_die, pc, &scopes);
/* Search from the inner-most scope to the outer */
for (i = nr_scopes - 1; i >= 0; i--) {
/* Look up variables/parameters in this scope */
if (!die_find_variable_by_reg(&scopes[i], pc, reg, &var_die))
continue;
/* Found a variable, see if it's correct */
ret = check_variable(&var_die, type_die, offset);
break;
}
free(scopes);
return ret;
}
/**
* find_data_type - Return a data type at the location
* @ms: map and symbol at the location
* @ip: instruction address of the memory access
* @reg: register that holds the base address
* @offset: offset from the base address
*
* This functions searches the debug information of the binary to get the data
* type it accesses. The exact location is expressed by (ip, reg, offset).
* It return %NULL if not found.
*/
struct annotated_data_type *find_data_type(struct map_symbol *ms, u64 ip,
int reg, int offset)
{
struct annotated_data_type *result = NULL;
struct dso *dso = map__dso(ms->map);
struct debuginfo *di;
Dwarf_Die type_die;
struct strbuf sb;
u64 pc;
di = debuginfo__new(dso->long_name);
if (di == NULL) {
pr_debug("cannot get the debug info\n");
return NULL;
}
/*
* IP is a relative instruction address from the start of the map, as
* it can be randomized/relocated, it needs to translate to PC which is
* a file address for DWARF processing.
*/
pc = map__rip_2objdump(ms->map, ip);
if (find_data_type_die(di, pc, reg, offset, &type_die) < 0)
goto out;
result = zalloc(sizeof(*result));
if (result == NULL)
goto out;
strbuf_init(&sb, 32);
if (die_get_typename_from_type(&type_die, &sb) < 0)
strbuf_add(&sb, "(unknown type)", 14);
result->type_name = strbuf_detach(&sb, NULL);
out:
debuginfo__delete(di);
return result;
}
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