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bc85767e5f
drgn/libdrgn/stack_trace.c
Omar Sandoval bc85767e5f libdrgn: support looking up parameters and variables in stack traces 
After all of the preparatory work, the last two missing pieces are a way
to find a variable by name in the list of scopes that we saved while
unwinding, and a way to find the containing scopes of an inlined
function. With that, we can finally look up parameters and variables in
stack traces.

Signed-off-by: Omar Sandoval <osandov@osandov.com>
2021-06-05 16:18:51 -07:00

1083 lines
30 KiB
C
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// Copyright (c) Facebook, Inc. and its affiliates.
// SPDX-License-Identifier: GPL-3.0-or-later
#include <assert.h>
#include <byteswap.h>
#include <dwarf.h>
#include <elfutils/libdw.h>
#include <elfutils/libdwfl.h>
#include <inttypes.h>
#include <stdlib.h>
#include <string.h>
#include "cfi.h"
#include "debug_info.h"
#include "drgn.h"
#include "error.h"
#include "hash_table.h"
#include "helpers.h"
#include "minmax.h"
#include "platform.h"
#include "program.h"
#include "register_state.h"
#include "serialize.h"
#include "stack_trace.h"
#include "string_builder.h"
#include "symbol.h"
#include "type.h"
#include "util.h"
static struct drgn_error *
drgn_stack_trace_append_frame(struct drgn_stack_trace **trace, size_t *capacity,
struct drgn_register_state *regs,
Dwarf_Die *scopes, size_t num_scopes,
size_t function_scope)
{
if ((*trace)->num_frames == *capacity) {
static const size_t max_capacity =
(SIZE_MAX - sizeof(struct drgn_stack_trace)) /
sizeof(struct drgn_stack_frame);
if (*capacity == max_capacity)
return &drgn_enomem;
size_t new_capacity;
if (*capacity > max_capacity / 2)
new_capacity = max_capacity;
else
new_capacity = 2 * (*capacity);
struct drgn_stack_trace *new_trace =
realloc((*trace),
offsetof(struct drgn_stack_trace,
frames[new_capacity]));
if (!new_trace)
return &drgn_enomem;
*trace = new_trace;
*capacity = new_capacity;
}
struct drgn_stack_frame *frame =
&(*trace)->frames[(*trace)->num_frames++];
frame->regs = regs;
frame->scopes = scopes;
frame->num_scopes = num_scopes;
frame->function_scope = function_scope;
return NULL;
}
static void drgn_stack_trace_shrink_to_fit(struct drgn_stack_trace **trace,
size_t capacity)
{
size_t num_frames = (*trace)->num_frames;
if (capacity > num_frames) {
struct drgn_stack_trace *new_trace =
realloc((*trace),
offsetof(struct drgn_stack_trace,
frames[num_frames]));
if (new_trace)
*trace = new_trace;
}
}
LIBDRGN_PUBLIC void drgn_stack_trace_destroy(struct drgn_stack_trace *trace)
{
struct drgn_register_state *regs = NULL;
for (size_t i = 0; i < trace->num_frames; i++) {
if (trace->frames[i].regs != regs) {
drgn_register_state_destroy(regs);
regs = trace->frames[i].regs;
}
free(trace->frames[i].scopes);
}
drgn_register_state_destroy(regs);
free(trace);
}
LIBDRGN_PUBLIC size_t
drgn_stack_trace_num_frames(struct drgn_stack_trace *trace)
{
return trace->num_frames;
}
LIBDRGN_PUBLIC struct drgn_error *
drgn_format_stack_trace(struct drgn_stack_trace *trace, char **ret)
{
struct string_builder str = {};
for (size_t frame = 0; frame < trace->num_frames; frame++) {
if (!string_builder_appendf(&str, "#%-2zu ", frame))
goto enomem;
struct drgn_register_state *regs = trace->frames[frame].regs;
struct optional_uint64 pc;
const char *name = drgn_stack_frame_name(trace, frame);
if (name) {
if (!string_builder_append(&str, name))
goto enomem;
} else if ((pc = drgn_register_state_get_pc(regs)).has_value) {
Dwfl_Module *dwfl_module =
regs->module ? regs->module->dwfl_module : NULL;
struct drgn_symbol sym;
if (dwfl_module &&
drgn_program_find_symbol_by_address_internal(trace->prog,
pc.value - !regs->interrupted,
dwfl_module,
&sym)) {
if (!string_builder_appendf(&str,
"%s+0x%" PRIx64 "/0x%" PRIx64,
sym.name,
pc.value - sym.address,
sym.size))
goto enomem;
} else {
if (!string_builder_appendf(&str, "0x%" PRIx64,
pc.value))
goto enomem;
}
} else {
if (!string_builder_append(&str, "???"))
goto enomem;
}
int line, column;
const char *filename = drgn_stack_frame_source(trace, frame,
&line, &column);
if (filename && column) {
if (!string_builder_appendf(&str, " (%s:%d:%d)",
filename, line, column))
goto enomem;
} else if (filename) {
if (!string_builder_appendf(&str, " (%s:%d)", filename,
line))
goto enomem;
}
if (frame != trace->num_frames - 1 &&
!string_builder_appendc(&str, '\n'))
goto enomem;
}
if (!string_builder_finalize(&str, ret))
goto enomem;
return NULL;
enomem:
free(str.str);
return &drgn_enomem;
}
LIBDRGN_PUBLIC struct drgn_error *
drgn_format_stack_frame(struct drgn_stack_trace *trace, size_t frame, char **ret)
{
struct string_builder str = {};
struct drgn_register_state *regs = trace->frames[frame].regs;
if (!string_builder_appendf(&str, "#%zu at ", frame))
goto enomem;
struct optional_uint64 pc = drgn_register_state_get_pc(regs);
if (pc.has_value) {
if (!string_builder_appendf(&str, "%#" PRIx64, pc.value))
goto enomem;
Dwfl_Module *dwfl_module =
regs->module ? regs->module->dwfl_module : NULL;
struct drgn_symbol sym;
if (dwfl_module &&
drgn_program_find_symbol_by_address_internal(trace->prog,
pc.value - !regs->interrupted,
dwfl_module,
&sym) &&
!string_builder_appendf(&str, " (%s+0x%" PRIx64 "/0x%" PRIx64 ")",
sym.name, pc.value - sym.address,
sym.size))
goto enomem;
} else {
if (!string_builder_append(&str, "???"))
goto enomem;
}
const char *name = drgn_stack_frame_name(trace, frame);
if (name && !string_builder_appendf(&str, " in %s", name))
goto enomem;
int line, column;
const char *filename = drgn_stack_frame_source(trace, frame, &line,
&column);
if (filename && column) {
if (!string_builder_appendf(&str, " at %s:%d:%d", filename,
line, column))
goto enomem;
} else if (filename) {
if (!string_builder_appendf(&str, " at %s:%d", filename, line))
goto enomem;
}
if (drgn_stack_frame_is_inline(trace, frame) &&
!string_builder_append(&str, " (inlined)"))
goto enomem;
if (!string_builder_finalize(&str, ret))
goto enomem;
return NULL;
enomem:
free(str.str);
return &drgn_enomem;
}
LIBDRGN_PUBLIC const char *drgn_stack_frame_name(struct drgn_stack_trace *trace,
size_t frame)
{
Dwarf_Die *scopes = trace->frames[frame].scopes;
size_t num_scopes = trace->frames[frame].num_scopes;
size_t function_scope = trace->frames[frame].function_scope;
if (function_scope >= num_scopes)
return NULL;
return dwarf_diename(&scopes[function_scope]);
}
LIBDRGN_PUBLIC bool drgn_stack_frame_is_inline(struct drgn_stack_trace *trace,
size_t frame)
{
Dwarf_Die *scopes = trace->frames[frame].scopes;
size_t num_scopes = trace->frames[frame].num_scopes;
size_t function_scope = trace->frames[frame].function_scope;
return (function_scope < num_scopes &&
dwarf_tag(&scopes[function_scope]) ==
DW_TAG_inlined_subroutine);
}
LIBDRGN_PUBLIC const char *
drgn_stack_frame_source(struct drgn_stack_trace *trace, size_t frame,
int *line_ret, int *column_ret)
{
if (frame > 0 &&
trace->frames[frame].regs == trace->frames[frame - 1].regs) {
/*
* This frame is the caller of an inline frame. Get the call
* location from the inlined_subroutine of the callee.
*/
Dwarf_Die *inlined_scopes = trace->frames[frame - 1].scopes;
size_t inlined_num_scopes = trace->frames[frame - 1].num_scopes;
size_t inlined_function_scope =
trace->frames[frame - 1].function_scope;
if (inlined_function_scope >= inlined_num_scopes)
return NULL;
Dwarf_Die *inlined = &inlined_scopes[inlined_function_scope];
Dwarf_Die inlined_cu;
Dwarf_Files *files;
if (!dwarf_diecu(inlined, &inlined_cu, NULL, NULL) ||
dwarf_getsrcfiles(&inlined_cu, &files, NULL))
return NULL;
Dwarf_Attribute attr;
Dwarf_Word value;
if (dwarf_formudata(dwarf_attr(inlined, DW_AT_call_file, &attr),
&value))
return NULL;
const char *filename = dwarf_filesrc(files, value, NULL, NULL);
if (!filename)
return NULL;
if (line_ret) {
if (dwarf_formudata(dwarf_attr(inlined, DW_AT_call_line,
&attr), &value))
*line_ret = 0;
else
*line_ret = value;
}
if (column_ret) {
if (dwarf_formudata(dwarf_attr(inlined,
DW_AT_call_column,
&attr), &value))
*column_ret = 0;
else
*column_ret = value;
}
return filename;
} else {
struct drgn_register_state *regs = trace->frames[frame].regs;
Dwfl_Module *dwfl_module =
regs->module ? regs->module->dwfl_module : NULL;
if (!dwfl_module)
return NULL;
struct optional_uint64 pc = drgn_register_state_get_pc(regs);
if (!pc.has_value)
return NULL;
pc.value -= !regs->interrupted;
Dwfl_Line *line = dwfl_module_getsrc(dwfl_module, pc.value);
if (!line)
return NULL;
return dwfl_lineinfo(line, NULL, line_ret, column_ret, NULL,
NULL);
}
}
LIBDRGN_PUBLIC bool drgn_stack_frame_interrupted(struct drgn_stack_trace *trace,
size_t frame)
{
return trace->frames[frame].regs->interrupted;
}
LIBDRGN_PUBLIC bool drgn_stack_frame_pc(struct drgn_stack_trace *trace,
size_t frame, uint64_t *ret)
{
struct optional_uint64 pc =
drgn_register_state_get_pc(trace->frames[frame].regs);
if (pc.has_value)
*ret = pc.value;
return pc.has_value;
}
LIBDRGN_PUBLIC struct drgn_error *
drgn_stack_frame_symbol(struct drgn_stack_trace *trace, size_t frame,
struct drgn_symbol **ret)
{
struct drgn_register_state *regs = trace->frames[frame].regs;
struct optional_uint64 pc = drgn_register_state_get_pc(regs);
if (!pc.has_value) {
return drgn_error_create(DRGN_ERROR_LOOKUP,
"program counter is not known at stack frame");
}
pc.value -= !regs->interrupted;
Dwfl_Module *dwfl_module =
regs->module ? regs->module->dwfl_module : NULL;
if (!dwfl_module)
return drgn_error_symbol_not_found(pc.value);
struct drgn_symbol *sym = malloc(sizeof(*sym));
if (!sym)
return &drgn_enomem;
if (!drgn_program_find_symbol_by_address_internal(trace->prog, pc.value,
dwfl_module, sym)) {
free(sym);
return drgn_error_symbol_not_found(pc.value);
}
*ret = sym;
return NULL;
}
LIBDRGN_PUBLIC struct drgn_error *
drgn_stack_frame_find_object(struct drgn_stack_trace *trace, size_t frame_i,
const char *name, struct drgn_object *ret)
{
struct drgn_error *err;
struct drgn_stack_frame *frame = &trace->frames[frame_i];
if (frame->num_scopes == 0)
goto not_found;
Dwarf_Die die, type_die;
err = drgn_find_in_dwarf_scopes(frame->scopes, frame->num_scopes, name,
&die, &type_die);
if (err)
return err;
if (!die.addr && frame->function_scope == 0) {
/*
* Scope 0 must be a DW_TAG_inlined_subroutine, and we didn't
* find the name in the concrete inlined instance tree. We need
* to find the scopes that contain the the abstract instance
* root (i.e, the DW_TAG_subprogram definition). (We could do
* this ahead of time when unwinding the stack, but for
* efficiency we do it lazily.)
*/
Dwarf_Attribute attr_mem, *attr;
if (!(attr = dwarf_attr(frame->scopes, DW_AT_abstract_origin,
&attr_mem)))
goto not_found;
Dwarf_Die abstract_origin;
if (!dwarf_formref_die(attr, &abstract_origin))
return drgn_error_libdw();
Dwarf_Die *ancestors;
size_t num_ancestors;
err = drgn_find_die_ancestors(&abstract_origin, &ancestors,
&num_ancestors);
if (err)
return err;
size_t new_num_scopes = num_ancestors + frame->num_scopes;
Dwarf_Die *new_scopes = realloc(ancestors,
new_num_scopes *
sizeof(*new_scopes));
if (!new_scopes) {
free(ancestors);
return &drgn_enomem;
}
memcpy(&new_scopes[num_ancestors], frame->scopes,
frame->num_scopes * sizeof(*new_scopes));
free(frame->scopes);
frame->scopes = new_scopes;
frame->num_scopes = new_num_scopes;
frame->function_scope = num_ancestors;
/* Look for the name in the new scopes. */
err = drgn_find_in_dwarf_scopes(frame->scopes, num_ancestors,
name, &die, &type_die);
if (err)
return err;
}
if (!die.addr) {
not_found:;
const char *frame_name = drgn_stack_frame_name(trace, frame_i);
if (frame_name) {
return drgn_error_format(DRGN_ERROR_LOOKUP,
"could not find '%s' in '%s'",
name, frame_name);
} else {
return drgn_error_format(DRGN_ERROR_LOOKUP,
"could not find '%s'", name);
}
}
Dwarf_Die function_die = frame->scopes[frame->function_scope];
return drgn_object_from_dwarf(trace->prog->_dbinfo, frame->regs->module,
&die,
dwarf_tag(&die) == DW_TAG_enumerator ?
&type_die : NULL,
&function_die, frame->regs, ret);
}
LIBDRGN_PUBLIC bool drgn_stack_frame_register(struct drgn_stack_trace *trace,
size_t frame,
const struct drgn_register *reg,
uint64_t *ret)
{
struct drgn_program *prog = trace->prog;
struct drgn_register_state *regs = trace->frames[frame].regs;
if (!drgn_register_state_has_register(regs, reg->regno))
return false;
const struct drgn_register_layout *layout =
&prog->platform.arch->register_layout[reg->regno];
if (layout->size > sizeof(*ret))
return false;
*ret = 0;
copy_lsbytes(ret, sizeof(*ret), HOST_LITTLE_ENDIAN,
&regs->buf[layout->offset], layout->size,
drgn_platform_is_little_endian(&prog->platform));
if (drgn_platform_bswap(&prog->platform))
*ret = bswap_64(*ret);
return true;
}
static struct drgn_error *
drgn_get_stack_trace_obj(struct drgn_object *res,
const struct drgn_object *thread_obj,
bool *is_pt_regs_ret)
{
struct drgn_program *prog = drgn_object_program(res);
struct drgn_type *type = drgn_underlying_type(thread_obj->type);
if (drgn_type_kind(type) == DRGN_TYPE_STRUCT &&
strcmp(drgn_type_tag(type), "pt_regs") == 0) {
*is_pt_regs_ret = true;
return drgn_object_read(res, thread_obj);
}
if (drgn_type_kind(type) != DRGN_TYPE_POINTER)
goto type_error;
type = drgn_underlying_type(drgn_type_type(type).type);
if (drgn_type_kind(type) != DRGN_TYPE_STRUCT)
goto type_error;
if ((prog->flags & DRGN_PROGRAM_IS_LINUX_KERNEL) &&
strcmp(drgn_type_tag(type), "task_struct") == 0) {
*is_pt_regs_ret = false;
return drgn_object_read(res, thread_obj);
} else if (strcmp(drgn_type_tag(type), "pt_regs") == 0) {
*is_pt_regs_ret = true;
/*
* If the drgn_object_read() call fails, we're breaking
* the rule of not modifying the result on error, but we
* don't care in this context.
*/
struct drgn_error *err = drgn_object_dereference(res,
thread_obj);
if (err)
return err;
return drgn_object_read(res, res);
}
type_error:
return drgn_error_format(DRGN_ERROR_TYPE,
"expected struct pt_regs, struct pt_regs *%s, or int",
(prog->flags & DRGN_PROGRAM_IS_LINUX_KERNEL) ?
", struct task_struct *" : "");
}
static struct drgn_error *
drgn_get_initial_registers(struct drgn_program *prog, uint32_t tid,
const struct drgn_object *thread_obj,
struct drgn_register_state **ret)
{
struct drgn_error *err;
struct drgn_object obj;
struct drgn_object tmp;
struct string prstatus;
drgn_object_init(&obj, prog);
drgn_object_init(&tmp, prog);
/* First, try pt_regs. */
if (thread_obj) {
bool is_pt_regs;
err = drgn_get_stack_trace_obj(&obj, thread_obj, &is_pt_regs);
if (err)
goto out;
if (is_pt_regs) {
assert(obj.encoding == DRGN_OBJECT_ENCODING_BUFFER);
assert(obj.kind == DRGN_OBJECT_VALUE);
if (!prog->platform.arch->pt_regs_get_initial_registers) {
err = drgn_error_format(DRGN_ERROR_INVALID_ARGUMENT,
"pt_regs stack unwinding is not supported for %s architecture",
prog->platform.arch->name);
goto out;
}
err = prog->platform.arch->pt_regs_get_initial_registers(&obj,
ret);
goto out;
}
} else if (prog->flags & DRGN_PROGRAM_IS_LINUX_KERNEL) {
err = drgn_program_find_object(prog, "init_pid_ns", NULL,
DRGN_FIND_OBJECT_ANY, &tmp);
if (err)
goto out;
err = drgn_object_address_of(&tmp, &tmp);
if (err)
goto out;
err = linux_helper_find_task(&obj, &tmp, tid);
if (err)
goto out;
bool found;
err = drgn_object_bool(&obj, &found);
if (err)
goto out;
if (!found) {
err = drgn_error_create(DRGN_ERROR_LOOKUP, "task not found");
goto out;
}
}
if (prog->flags & DRGN_PROGRAM_IS_LINUX_KERNEL) {
if (prog->flags & DRGN_PROGRAM_IS_LIVE) {
err = drgn_object_member_dereference(&tmp, &obj, "on_cpu");
if (!err) {
bool on_cpu;
err = drgn_object_bool(&tmp, &on_cpu);
if (err)
goto out;
if (on_cpu) {
err = drgn_error_create(DRGN_ERROR_INVALID_ARGUMENT,
"cannot unwind stack of running task");
goto out;
}
} else if (err->code == DRGN_ERROR_LOOKUP) {
/*
* The running kernel is !SMP. Assume that the
* task isn't running (which can only be wrong
* for this thread itself).
*/
drgn_error_destroy(err);
} else {
goto out;
}
} else {
/*
* For kernel core dumps, we look up the PRSTATUS note
* by CPU rather than by PID. This is because there is
* an idle task with PID 0 for each CPU, so we must find
* the idle task by CPU. Rather than making PID 0 a
* special case, we handle all tasks this way.
*/
union drgn_value value;
err = drgn_object_member_dereference(&tmp, &obj, "cpu");
if (!err) {
err = drgn_object_read_integer(&tmp, &value);
if (err)
goto out;
} else if (err->code == DRGN_ERROR_LOOKUP) {
/* !SMP. Must be CPU 0. */
drgn_error_destroy(err);
value.uvalue = 0;
} else {
goto out;
}
uint32_t prstatus_tid;
err = drgn_program_find_prstatus_by_cpu(prog,
value.uvalue,
&prstatus,
&prstatus_tid);
if (err)
goto out;
if (prstatus.str) {
/*
* The PRSTATUS note is for the CPU that the
* task is assigned to, but it is not
* necessarily for this task. Only use it if the
* PID matches.
*
* Note that this isn't perfect: the PID is
* populated by the kernel from "current" (the
* current task) via a non-maskable interrupt
* (NMI). During a context switch, the stack
* pointer and current are not updated
* atomically, so if the NMI arrives in the
* middle of a context switch, the stack pointer
* may not actually be that of current.
* Therefore, the stack pointer in PRSTATUS may
* not actually be for the PID in PRSTATUS.
* Unfortunately, we can't easily fix this.
*/
err = drgn_object_member_dereference(&tmp, &obj, "pid");
if (err)
goto out;
err = drgn_object_read_integer(&tmp, &value);
if (err)
goto out;
if (prstatus_tid == value.uvalue)
goto prstatus;
}
}
if (!prog->platform.arch->linux_kernel_get_initial_registers) {
err = drgn_error_format(DRGN_ERROR_INVALID_ARGUMENT,
"Linux kernel stack unwinding is not supported for %s architecture",
prog->platform.arch->name);
goto out;
}
err = prog->platform.arch->linux_kernel_get_initial_registers(&obj,
ret);
} else {
err = drgn_program_find_prstatus_by_tid(prog, tid, &prstatus);
if (err)
goto out;
if (!prstatus.str) {
err = drgn_error_create(DRGN_ERROR_LOOKUP, "thread not found");
goto out;
}
prstatus:
if (!prog->platform.arch->prstatus_get_initial_registers) {
err = drgn_error_format(DRGN_ERROR_INVALID_ARGUMENT,
"core dump stack unwinding is not supported for %s architecture",
prog->platform.arch->name);
goto out;
}
err = prog->platform.arch->prstatus_get_initial_registers(prog,
prstatus.str,
prstatus.len,
ret);
}
out:
drgn_object_deinit(&tmp);
drgn_object_deinit(&obj);
return err;
}
static void drgn_add_to_register(void *dst, size_t dst_size, const void *src,
size_t src_size, int64_t addend,
bool little_endian)
{
while (addend && dst_size && src_size) {
uint64_t uvalue;
copy_lsbytes(&uvalue, sizeof(uvalue), HOST_LITTLE_ENDIAN, src,
src_size, little_endian);
size_t n = min(sizeof(uvalue), src_size);
if (little_endian)
src = (char *)src + n;
src_size -= n;
bool carry = __builtin_add_overflow(uvalue, (uint64_t)addend,
&uvalue);
addend = (addend < 0 ? -1 : 0) + carry;
copy_lsbytes(dst, dst_size, little_endian, &uvalue,
sizeof(uvalue), HOST_LITTLE_ENDIAN);
n = min(sizeof(uvalue), dst_size);
if (little_endian)
dst = (char *)dst + n;
dst_size -= n;
}
if (dst != src) {
copy_lsbytes(dst, dst_size, little_endian, src, src_size,
little_endian);
}
}
static struct drgn_error *
drgn_stack_trace_add_frames(struct drgn_stack_trace **trace,
size_t *trace_capacity,
struct drgn_register_state *regs)
{
struct drgn_error *err;
if (!regs->module) {
err = drgn_stack_trace_append_frame(trace, trace_capacity, regs,
NULL, 0, 0);
goto out;
}
uint64_t pc = regs->_pc - !regs->interrupted;
uint64_t bias;
Dwarf_Die *scopes;
size_t num_scopes;
err = drgn_debug_info_module_find_dwarf_scopes(regs->module, pc, &bias,
&scopes, &num_scopes);
if (err)
goto out;
pc -= bias;
size_t orig_num_frames = (*trace)->num_frames;
/*
* Walk backwards through scopes, splitting into frames. Stop at index 1
* because 0 must be a unit DIE.
*/
size_t frame_end = num_scopes;
for (size_t i = num_scopes; i-- > 1;) {
bool has_pc;
if (i == num_scopes - 1) {
/*
* The last scope is guaranteed to contain PC, so avoid
* a call to dwarf_haspc().
*/
has_pc = true;
} else {
int r = dwarf_haspc(&scopes[i], pc);
if (r < 0) {
err = drgn_error_libdw();
goto out_scopes;
}
has_pc = r > 0;
}
if (has_pc) {
Dwarf_Die *frame_scopes;
switch (dwarf_tag(&scopes[i])) {
case DW_TAG_subprogram:
/*
* Reuse the original scopes array (shrinking it
* if necessary).
*/
if (frame_end == num_scopes ||
!(frame_scopes = realloc(scopes,
frame_end *
sizeof(scopes[i]))))
frame_scopes = scopes;
err = drgn_stack_trace_append_frame(trace,
trace_capacity,
regs,
frame_scopes,
frame_end,
i);
if (err) {
free(frame_scopes);
/*
* We stole scopes for frame_scopes, so
* not out_scopes.
*/
goto out;
}
/*
* Added the DW_TAG_subprogram frame. We're
* done.
*/
return NULL;
case DW_TAG_inlined_subroutine:
frame_scopes = memdup(&scopes[i],
(frame_end - i) *
sizeof(scopes[i]));
if (!frame_scopes) {
err = &drgn_enomem;
goto out_scopes;
}
err = drgn_stack_trace_append_frame(trace,
trace_capacity,
regs,
frame_scopes,
frame_end - i,
0);
if (err) {
free(frame_scopes);
goto out_scopes;
}
frame_end = i;
break;
default:
break;
}
} else {
/*
* This DIE doesn't contain PC. Ignore it and everything
* after it.
*/
frame_end = i;
}
}
/*
* We didn't find a matching DW_TAG_subprogram. Free any matching
* DW_TAG_inlined_subroutine frames we found and add a scopeless frame.
*/
for (size_t i = orig_num_frames; i < (*trace)->num_frames; i++)
free((*trace)->frames[i].scopes);
(*trace)->num_frames = orig_num_frames;
err = drgn_stack_trace_append_frame(trace, trace_capacity, regs, NULL,
0, 0);
out_scopes:
free(scopes);
out:
if (err)
drgn_register_state_destroy(regs);
return err;
}
static struct drgn_error *
drgn_unwind_one_register(struct drgn_program *prog,
const struct drgn_cfi_rule *rule,
const struct drgn_register_state *regs, void *buf,
size_t size)
{
struct drgn_error *err;
bool little_endian = drgn_platform_is_little_endian(&prog->platform);
SWITCH_ENUM(rule->kind,
case DRGN_CFI_RULE_UNDEFINED:
return &drgn_not_found;
case DRGN_CFI_RULE_AT_CFA_PLUS_OFFSET: {
struct optional_uint64 cfa = drgn_register_state_get_cfa(regs);
if (!cfa.has_value)
return &drgn_not_found;
err = drgn_program_read_memory(prog, buf,
cfa.value + rule->offset, size,
false);
break;
}
case DRGN_CFI_RULE_CFA_PLUS_OFFSET: {
struct optional_uint64 cfa = drgn_register_state_get_cfa(regs);
if (!cfa.has_value)
return &drgn_not_found;
cfa.value += rule->offset;
copy_lsbytes(buf, size, little_endian, &cfa.value,
sizeof(cfa.value), HOST_LITTLE_ENDIAN);
return NULL;
}
case DRGN_CFI_RULE_AT_REGISTER_PLUS_OFFSET:
case DRGN_CFI_RULE_AT_REGISTER_ADD_OFFSET: {
if (!drgn_register_state_has_register(regs, rule->regno))
return &drgn_not_found;
const struct drgn_register_layout *layout =
&prog->platform.arch->register_layout[rule->regno];
uint64_t address;
copy_lsbytes(&address, sizeof(address), HOST_LITTLE_ENDIAN,
&regs->buf[layout->offset], layout->size,
little_endian);
if (rule->kind == DRGN_CFI_RULE_AT_REGISTER_PLUS_OFFSET)
address += rule->offset;
address &= drgn_platform_address_mask(&prog->platform);
err = drgn_program_read_memory(prog, buf, address, size, false);
if (!err && rule->kind == DRGN_CFI_RULE_AT_REGISTER_ADD_OFFSET) {
drgn_add_to_register(buf, size, buf, size, rule->offset,
little_endian);
}
break;
}
case DRGN_CFI_RULE_REGISTER_PLUS_OFFSET: {
if (!drgn_register_state_has_register(regs, rule->regno))
return &drgn_not_found;
const struct drgn_register_layout *layout =
&prog->platform.arch->register_layout[rule->regno];
drgn_add_to_register(buf, size, &regs->buf[layout->offset],
layout->size, rule->offset, little_endian);
return NULL;
}
case DRGN_CFI_RULE_AT_DWARF_EXPRESSION:
case DRGN_CFI_RULE_DWARF_EXPRESSION:
err = drgn_eval_cfi_dwarf_expression(prog, rule, regs, buf,
size);
break;
)
/*
* If we couldn't read from memory, leave the register unknown instead
* of failing hard.
*/
if (err && err->code == DRGN_ERROR_FAULT) {
drgn_error_destroy(err);
err = &drgn_not_found;
}
return err;
}
static struct drgn_error *drgn_unwind_cfa(struct drgn_program *prog,
const struct drgn_cfi_row *row,
struct drgn_register_state *regs)
{
struct drgn_error *err;
struct drgn_cfi_rule rule;
drgn_cfi_row_get_cfa(row, &rule);
uint8_t address_size = drgn_platform_address_size(&prog->platform);
char buf[8];
err = drgn_unwind_one_register(prog, &rule, regs, buf, address_size);
if (!err) {
uint64_t cfa;
copy_lsbytes(&cfa, sizeof(cfa), HOST_LITTLE_ENDIAN, buf,
address_size,
drgn_platform_is_little_endian(&prog->platform));
drgn_register_state_set_cfa(prog, regs, cfa);
} else if (err == &drgn_not_found) {
err = NULL;
}
return err;
}
static struct drgn_error *
drgn_unwind_with_cfi(struct drgn_program *prog, struct drgn_cfi_row **row,
struct drgn_register_state *regs,
struct drgn_register_state **ret)
{
struct drgn_error *err;
if (!regs->module)
return &drgn_not_found;
bool interrupted;
drgn_register_number ret_addr_regno;
/* If we found the module, then we must have the PC. */
err = drgn_debug_info_module_find_cfi(prog, regs->module,
regs->_pc - !regs->interrupted,
row, &interrupted,
&ret_addr_regno);
if (err)
return err;
err = drgn_unwind_cfa(prog, *row, regs);
if (err)
return err;
size_t num_regs = (*row)->num_regs;
if (num_regs == 0)
return &drgn_stop;
const struct drgn_register_layout *layout =
&prog->platform.arch->register_layout[num_regs - 1];
struct drgn_register_state *unwound =
drgn_register_state_create_impl(layout->offset + layout->size,
num_regs, interrupted);
if (!unwound)
return &drgn_enomem;
bool has_any_register = false;
for (drgn_register_number regno = 0; regno < num_regs; regno++) {
struct drgn_cfi_rule rule;
drgn_cfi_row_get_register(*row, regno, &rule);
layout = &prog->platform.arch->register_layout[regno];
err = drgn_unwind_one_register(prog, &rule, regs,
&unwound->buf[layout->offset],
layout->size);
if (!err) {
drgn_register_state_set_has_register(unwound, regno);
has_any_register = true;
} else if (err != &drgn_not_found) {
drgn_register_state_destroy(unwound);
return err;
}
}
if (!has_any_register) {
/* Couldn't unwind any registers. We're done. */
drgn_register_state_destroy(unwound);
return &drgn_stop;
}
if (drgn_register_state_has_register(unwound, ret_addr_regno)) {
layout = &prog->platform.arch->register_layout[ret_addr_regno];
drgn_register_state_set_pc_from_register_impl(prog, unwound,
ret_addr_regno,
layout->offset,
layout->size);
}
*ret = unwound;
return NULL;
}
static struct drgn_error *drgn_get_stack_trace(struct drgn_program *prog,
uint32_t tid,
const struct drgn_object *obj,
struct drgn_stack_trace **ret)
{
struct drgn_error *err;
if (!prog->has_platform) {
return drgn_error_create(DRGN_ERROR_INVALID_ARGUMENT,
"cannot unwind stack without platform");
}
if ((prog->flags & (DRGN_PROGRAM_IS_LINUX_KERNEL |
DRGN_PROGRAM_IS_LIVE)) == DRGN_PROGRAM_IS_LIVE) {
return drgn_error_create(DRGN_ERROR_INVALID_ARGUMENT,
"stack unwinding is not yet supported for live processes");
}
size_t trace_capacity = 1;
struct drgn_stack_trace *trace =
malloc(offsetof(struct drgn_stack_trace,
frames[trace_capacity]));
if (!trace)
return &drgn_enomem;
trace->prog = prog;
trace->num_frames = 0;
struct drgn_cfi_row *row = drgn_empty_cfi_row;
struct drgn_register_state *regs;
err = drgn_get_initial_registers(prog, tid, obj, &regs);
if (err)
goto out;
/* Limit iterations so we don't get caught in a loop. */
for (int i = 0; i < 1024; i++) {
err = drgn_stack_trace_add_frames(&trace, &trace_capacity,
regs);
if (err)
goto out;
err = drgn_unwind_with_cfi(prog, &row, regs, &regs);
if (err == &drgn_not_found) {
err = prog->platform.arch->fallback_unwind(prog, regs,
&regs);
}
if (err == &drgn_stop)
break;
else if (err)
goto out;
}
err = NULL;
out:
drgn_cfi_row_destroy(row);
if (err) {
drgn_stack_trace_destroy(trace);
} else {
drgn_stack_trace_shrink_to_fit(&trace, trace_capacity);
*ret = trace;
}
return err;
}
LIBDRGN_PUBLIC struct drgn_error *
drgn_program_stack_trace(struct drgn_program *prog, uint32_t tid,
struct drgn_stack_trace **ret)
{
return drgn_get_stack_trace(prog, tid, NULL, ret);
}
LIBDRGN_PUBLIC struct drgn_error *
drgn_object_stack_trace(const struct drgn_object *obj,
struct drgn_stack_trace **ret)
{
struct drgn_error *err;
if (drgn_type_kind(drgn_underlying_type(obj->type)) == DRGN_TYPE_INT) {
union drgn_value value;
err = drgn_object_read_integer(obj, &value);
if (err)
return err;
return drgn_get_stack_trace(drgn_object_program(obj),
value.uvalue, NULL, ret);
} else {
return drgn_get_stack_trace(drgn_object_program(obj), 0, obj,
ret);
}
}
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