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libdrgn: program: improve checks for userspace programs
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We have a bunch of places that check prog->flags to determine whether
the target is the Linux kernel, a userspace process, or a userspace core
dump. But they do so inconsistently, and the flag checks are often hard
to follow. Add a couple of helper functions,
drgn_program_is_userspace_process() and
drgn_program_is_userspace_core(), to unify these checks and make them
more clear. I left the checks in libdrgn/debug_info.c alone because
they're going to be replaced by the module API soon.

Signed-off-by: Omar Sandoval <[email protected]>
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@osandov
osandov committed Nov 8, 2024
1 parent dc7ca11 commit b7d8877
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Showing 3 changed files with 72 additions and 32 deletions.
75 changes: 45 additions & 30 deletions libdrgn/program.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -120,10 +120,10 @@ void drgn_program_deinit(struct drgn_program *prog)
* prog->thread_set and thus freed by the above call to
* drgn_thread_set_deinit().
*/
if (prog->flags & DRGN_PROGRAM_IS_LINUX_KERNEL)
if (!drgn_program_is_userspace_core(prog)) {
drgn_thread_destroy(prog->crashed_thread);
else if (prog->flags & DRGN_PROGRAM_IS_LIVE)
drgn_thread_destroy(prog->main_thread);
}
if (prog->pgtable_it)
prog->platform.arch->linux_kernel_pgtable_iterator_destroy(prog->pgtable_it);

Expand Down Expand Up @@ -917,8 +917,7 @@ struct drgn_error *drgn_thread_dup_internal(const struct drgn_thread *thread,
LIBDRGN_PUBLIC struct drgn_error *
drgn_thread_dup(const struct drgn_thread *thread, struct drgn_thread **ret)
{
if (!(thread->prog->flags &
(DRGN_PROGRAM_IS_LINUX_KERNEL | DRGN_PROGRAM_IS_LIVE))) {
if (drgn_program_is_userspace_core(thread->prog)) {
/*
* For userspace core dumps, all threads are cached and
* immutable, so we can return the same handle.
Expand All @@ -945,8 +944,7 @@ LIBDRGN_PUBLIC void drgn_thread_destroy(struct drgn_thread *thread)
{
if (thread) {
drgn_thread_deinit(thread);
if (thread->prog->flags &
(DRGN_PROGRAM_IS_LINUX_KERNEL | DRGN_PROGRAM_IS_LIVE))
if (!drgn_program_is_userspace_core(thread->prog))
free(thread);
}
}
Expand Down Expand Up @@ -1113,7 +1111,7 @@ drgn_thread_iterator_init_linux_kernel(struct drgn_thread_iterator *it)
}

static struct drgn_error *
drgn_thread_iterator_init_userspace_live(struct drgn_thread_iterator *it)
drgn_thread_iterator_init_userspace_process(struct drgn_thread_iterator *it)
{
#define FORMAT "/proc/%ld/task"
char path[sizeof(FORMAT)
Expand Down Expand Up @@ -1152,10 +1150,12 @@ drgn_thread_iterator_create(struct drgn_program *prog,
(*ret)->prog = prog;
if (prog->flags & DRGN_PROGRAM_IS_LINUX_KERNEL)
err = drgn_thread_iterator_init_linux_kernel(*ret);
else if (prog->flags & DRGN_PROGRAM_IS_LIVE)
err = drgn_thread_iterator_init_userspace_live(*ret);
else
else if (drgn_program_is_userspace_process(prog))
err = drgn_thread_iterator_init_userspace_process(*ret);
else if (drgn_program_is_userspace_core(prog))
err = drgn_thread_iterator_init_userspace_core(*ret);
else
err = NULL;
if (err)
free(*ret);
return err;
Expand All @@ -1168,7 +1168,7 @@ drgn_thread_iterator_destroy(struct drgn_thread_iterator *it)
if (it->prog->flags & DRGN_PROGRAM_IS_LINUX_KERNEL) {
drgn_object_deinit(&it->entry.object);
linux_helper_task_iterator_deinit(&it->task_iter);
} else if (it->prog->flags & DRGN_PROGRAM_IS_LIVE) {
} else if (drgn_program_is_userspace_process(it->prog)) {
closedir(it->tasks_dir);
}
free(it);
Expand Down Expand Up @@ -1202,8 +1202,8 @@ drgn_thread_iterator_next_linux_kernel(struct drgn_thread_iterator *it,
}

static struct drgn_error *
drgn_thread_iterator_next_userspace_live(struct drgn_thread_iterator *it,
struct drgn_thread **ret)
drgn_thread_iterator_next_userspace_process(struct drgn_thread_iterator *it,
struct drgn_thread **ret)
{
struct dirent *task;
unsigned long tid;
Expand Down Expand Up @@ -1247,11 +1247,14 @@ drgn_thread_iterator_next(struct drgn_thread_iterator *it,
{
if (it->prog->flags & DRGN_PROGRAM_IS_LINUX_KERNEL) {
return drgn_thread_iterator_next_linux_kernel(it, ret);
} else if (it->prog->flags & DRGN_PROGRAM_IS_LIVE) {
return drgn_thread_iterator_next_userspace_live(it, ret);
} else {
} else if (drgn_program_is_userspace_process(it->prog)) {
return drgn_thread_iterator_next_userspace_process(it, ret);
} else if (drgn_program_is_userspace_core(it->prog)) {
drgn_thread_iterator_next_userspace_core(it, ret);
return NULL;
} else {
*ret = NULL;
return NULL;
}
}

Expand Down Expand Up @@ -1296,8 +1299,9 @@ drgn_program_find_thread_linux_kernel(struct drgn_program *prog, uint32_t tid,
}

static struct drgn_error *
drgn_program_find_thread_userspace_live(struct drgn_program *prog, uint32_t tid,
struct drgn_thread **ret)
drgn_program_find_thread_userspace_process(struct drgn_program *prog,
uint32_t tid,
struct drgn_thread **ret)
{
#define FORMAT "/proc/%ld/task/%" PRIu32
char path[sizeof(FORMAT)
Expand Down Expand Up @@ -1339,12 +1343,17 @@ LIBDRGN_PUBLIC struct drgn_error *
drgn_program_find_thread(struct drgn_program *prog, uint32_t tid,
struct drgn_thread **ret)
{
if (prog->flags & DRGN_PROGRAM_IS_LINUX_KERNEL)
if (prog->flags & DRGN_PROGRAM_IS_LINUX_KERNEL) {
return drgn_program_find_thread_linux_kernel(prog, tid, ret);
else if (prog->flags & DRGN_PROGRAM_IS_LIVE)
return drgn_program_find_thread_userspace_live(prog, tid, ret);
else
} else if (drgn_program_is_userspace_process(prog)) {
return drgn_program_find_thread_userspace_process(prog, tid,
ret);
} else if (drgn_program_is_userspace_core(prog)) {
return drgn_program_find_thread_userspace_core(prog, tid, ret);
} else {
*ret = NULL;
return NULL;
}
}

// Get the CPU that crashed in a Linux kernel core dump.
Expand Down Expand Up @@ -1470,7 +1479,7 @@ drgn_program_main_thread(struct drgn_program *prog, struct drgn_thread **ret)
return drgn_error_create(DRGN_ERROR_INVALID_ARGUMENT,
"main thread is not defined for the Linux kernel");
}
if (prog->flags & DRGN_PROGRAM_IS_LIVE) {
if (drgn_program_is_userspace_process(prog)) {
if (!prog->main_thread) {
err = drgn_program_find_thread(prog, prog->pid,
&prog->main_thread);
Expand All @@ -1479,7 +1488,7 @@ drgn_program_main_thread(struct drgn_program *prog, struct drgn_thread **ret)
return err;
}
}
} else {
} else if (drgn_program_is_userspace_core(prog)) {
err = drgn_program_cache_core_dump_threads(prog);
if (err)
return err;
Expand All @@ -1503,8 +1512,10 @@ drgn_program_crashed_thread(struct drgn_program *prog, struct drgn_thread **ret)
}
if (prog->flags & DRGN_PROGRAM_IS_LINUX_KERNEL)
err = drgn_program_kernel_core_dump_cache_crashed_thread(prog);
else
else if (drgn_program_is_userspace_core(prog))
err = drgn_program_cache_core_dump_threads(prog);
else
err = NULL;
if (err)
return err;
if (!prog->crashed_thread) {
Expand Down Expand Up @@ -1538,7 +1549,7 @@ drgn_thread_name_linux_kernel(struct drgn_thread *thread, char **ret)
}

static struct drgn_error *
drgn_thread_name_userspace_live(struct drgn_thread *thread, char **ret)
drgn_thread_name_userspace_process(struct drgn_thread *thread, char **ret)
{
#define FORMAT "/proc/%" PRIu32 "/comm"
char path[sizeof(FORMAT)
Expand Down Expand Up @@ -1589,12 +1600,16 @@ drgn_thread_name_userspace_core(struct drgn_thread *thread, char **ret)
LIBDRGN_PUBLIC struct drgn_error *
drgn_thread_name(struct drgn_thread *thread, char **ret)
{
if (thread->prog->flags & DRGN_PROGRAM_IS_LINUX_KERNEL)
if (thread->prog->flags & DRGN_PROGRAM_IS_LINUX_KERNEL) {
return drgn_thread_name_linux_kernel(thread, ret);
else if (thread->prog->flags & DRGN_PROGRAM_IS_LIVE)
return drgn_thread_name_userspace_live(thread, ret);
else
} else if (drgn_program_is_userspace_process(thread->prog)) {
return drgn_thread_name_userspace_process(thread, ret);
} else if (drgn_program_is_userspace_core(thread->prog)) {
return drgn_thread_name_userspace_core(thread, ret);
} else {
*ret = NULL;
return NULL;
}
}

struct drgn_error *drgn_program_find_prstatus(struct drgn_program *prog,
Expand Down
22 changes: 22 additions & 0 deletions libdrgn/program.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -282,6 +282,28 @@ struct drgn_error *drgn_program_init_kernel(struct drgn_program *prog);
*/
struct drgn_error *drgn_program_init_pid(struct drgn_program *prog, pid_t pid);

/**
* Return whether a @ref drgn_program is a userspace process running on the
* local machine.
*/
static inline bool
drgn_program_is_userspace_process(struct drgn_program *prog)
{
return (prog->flags & (DRGN_PROGRAM_IS_LINUX_KERNEL
| DRGN_PROGRAM_IS_LIVE
| DRGN_PROGRAM_IS_LOCAL))
== (DRGN_PROGRAM_IS_LIVE | DRGN_PROGRAM_IS_LOCAL);
}

/** Return whether a @ref drgn_program is a core dump of a userspace process. */
static inline bool
drgn_program_is_userspace_core(struct drgn_program *prog)
{
return (prog->flags &
(DRGN_PROGRAM_IS_LINUX_KERNEL | DRGN_PROGRAM_IS_LIVE)) == 0
&& prog->core;
}

static inline struct drgn_error *
drgn_program_is_little_endian(struct drgn_program *prog, bool *ret)
{
Expand Down
7 changes: 5 additions & 2 deletions libdrgn/stack_trace.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1150,10 +1150,13 @@ static struct drgn_error *drgn_get_stack_trace(struct drgn_program *prog,
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) {
if (drgn_program_is_userspace_process(prog)) {
return drgn_error_create(DRGN_ERROR_NOT_IMPLEMENTED,
"stack unwinding is not yet supported for live processes");
} else if (!(prog->flags & DRGN_PROGRAM_IS_LINUX_KERNEL)
&& !drgn_program_is_userspace_core(prog)) {
return drgn_error_create(DRGN_ERROR_NOT_IMPLEMENTED,
"stack unwinding is not supported for this program");
}

size_t trace_capacity = 1;
Expand Down

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