mirror of
https://github.com/varun-r-mallya/sysprof.git
synced 2026-02-12 16:10:54 +00:00
sysprofd: add support for unwinding without frame pointers
This provides a new sysprof-live-unwinder subprocess that runs as root to allow accessing all processes on the system via /proc/$pid/. It is spawned by sysprofd with various perf event FDs and a FD to write captures to. Ideally the capture_fd is something that will naturally error if the client application crashes (such as a socketpair() having the peer close). This is not enforced but encouraged. Additionally, an event_fd is used to allow the client application to signal the live-unwinder to exit. Unwinding is performed by looking at the modules loaded into the target pid and using libdwfl to access DWARF/CFI/etc state machinery. Stack data does not touch the disk as it exists in a mmap buffer from perf and is then translated into a callchain and sent to the Sysprof client. Unwinding occurs as normal post-mortem though is improved through the use of debuginfod to locate the appropriate symbols.
This commit is contained in:
Christian Hergert
427
src/sysprof-live-unwinder/sysprof-live-unwinder.c
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427
src/sysprof-live-unwinder/sysprof-live-unwinder.c
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@ -0,0 +1,427 @@
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/*
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* sysprof-live-unwinder.c
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*
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* Copyright 2024 Christian Hergert <chergert@redhat.com>
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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* SPDX-License-Identifier: GPL-3.0-or-later
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*/
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#include "config.h"
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#include <fcntl.h>
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#include <unistd.h>
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#include <linux/perf_event.h>
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#include <glib/gstdio.h>
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#include "sysprof-live-process.h"
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#include "sysprof-live-unwinder.h"
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#include "sysprof-maps-parser-private.h"
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struct _SysprofLiveUnwinder
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{
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GObject parent_instance;
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SysprofCaptureWriter *writer;
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GHashTable *live_pids_by_pid;
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};
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G_DEFINE_FINAL_TYPE (SysprofLiveUnwinder, sysprof_live_unwinder, G_TYPE_OBJECT)
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enum {
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CLOSED,
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N_SIGNALS
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};
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static guint signals[N_SIGNALS];
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static char *
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sysprof_live_unwinder_read_file (SysprofLiveUnwinder *self,
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const char *path,
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gboolean insert_into_capture)
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{
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gint64 when = SYSPROF_CAPTURE_CURRENT_TIME;
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char *contents = NULL;
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gsize len = 0;
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gsize offset = 0;
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g_assert (SYSPROF_IS_LIVE_UNWINDER (self));
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g_assert (self->writer != NULL);
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if (!g_file_get_contents (path, &contents, &len, NULL))
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return NULL;
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if (insert_into_capture)
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{
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while (len > 0)
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{
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gsize this_write = MIN (len, 4096*4);
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if (!sysprof_capture_writer_add_file (self->writer,
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when,
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-1,
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-1,
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path,
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this_write == len,
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(const guint8 *)&contents[offset], this_write))
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break;
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len -= this_write;
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offset += this_write;
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}
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}
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return contents;
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}
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static char *
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sysprof_live_unwinder_read_pid_file (SysprofLiveUnwinder *self,
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GPid pid,
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const char *path_part,
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gboolean insert_into_capture)
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{
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g_autofree char *path = NULL;
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g_assert (SYSPROF_IS_LIVE_UNWINDER (self));
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g_assert (self->writer != NULL);
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path = g_strdup_printf ("/proc/%d/%s", pid, path_part);
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return sysprof_live_unwinder_read_file (self, path, insert_into_capture);
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}
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static SysprofLiveProcess *
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sysprof_live_unwinder_find_pid (SysprofLiveUnwinder *self,
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GPid pid,
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gboolean send_comm)
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{
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SysprofLiveProcess *live_pid;
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g_assert (SYSPROF_IS_LIVE_UNWINDER (self));
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if (pid < 0)
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return NULL;
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if (!(live_pid = g_hash_table_lookup (self->live_pids_by_pid, GINT_TO_POINTER (pid))))
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{
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gint64 now = SYSPROF_CAPTURE_CURRENT_TIME;
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live_pid = sysprof_live_process_new (pid);
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g_hash_table_replace (self->live_pids_by_pid, GINT_TO_POINTER (pid), live_pid);
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if (send_comm)
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{
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g_autofree char *path = g_strdup_printf ("/proc/%d/comm", pid);
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g_autofree char *comm = NULL;
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gsize len;
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if (g_file_get_contents (path, &comm, &len, NULL))
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{
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g_autofree char *tmp = comm;
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comm = g_strstrip (g_utf8_make_valid (tmp, len));
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sysprof_capture_writer_add_process (self->writer, now, -1, pid, comm);
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}
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}
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if (sysprof_live_process_is_active (live_pid))
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{
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g_autofree char *mountinfo = sysprof_live_unwinder_read_pid_file (self, pid, "mountinfo", TRUE);
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g_autofree char *maps = sysprof_live_unwinder_read_pid_file (self, pid, "maps", FALSE);
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if (maps != NULL)
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{
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SysprofMapsParser maps_parser;
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guint64 begin, end, offset, inode;
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char *filename;
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sysprof_maps_parser_init (&maps_parser, maps, -1);
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while (sysprof_maps_parser_next (&maps_parser, &begin, &end, &offset, &inode, &filename))
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{
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sysprof_live_process_add_map (live_pid, begin, end, offset, inode, filename);
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sysprof_capture_writer_add_map (self->writer, now, -1, pid,
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begin, end, offset,
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inode, filename);
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g_free (filename);
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}
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}
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}
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}
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return live_pid;
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}
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static void
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sysprof_live_unwinder_mine_pids (SysprofLiveUnwinder *self)
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{
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g_autoptr(GDir) dir = NULL;
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const char *name;
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g_assert (SYSPROF_IS_LIVE_UNWINDER (self));
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g_assert (self->writer != NULL);
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if (!(dir = g_dir_open ("/proc", 0, NULL)))
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return;
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while ((name = g_dir_read_name (dir)))
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{
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GPid pid;
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if (!g_ascii_isdigit (*name))
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continue;
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if (!(pid = atoi (name)))
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continue;
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sysprof_live_unwinder_find_pid (self, pid, TRUE);
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}
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}
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static void
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sysprof_live_unwinder_finalize (GObject *object)
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{
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SysprofLiveUnwinder *self = (SysprofLiveUnwinder *)object;
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g_clear_pointer (&self->writer, sysprof_capture_writer_unref);
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g_clear_pointer (&self->live_pids_by_pid, g_hash_table_unref);
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G_OBJECT_CLASS (sysprof_live_unwinder_parent_class)->finalize (object);
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}
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static void
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sysprof_live_unwinder_class_init (SysprofLiveUnwinderClass *klass)
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{
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GObjectClass *object_class = G_OBJECT_CLASS (klass);
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object_class->finalize = sysprof_live_unwinder_finalize;
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signals[CLOSED] =
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g_signal_new ("closed",
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G_TYPE_FROM_CLASS (klass),
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G_SIGNAL_RUN_LAST,
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0,
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NULL, NULL,
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NULL,
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G_TYPE_NONE, 0);
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}
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static void
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sysprof_live_unwinder_init (SysprofLiveUnwinder *self)
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{
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self->live_pids_by_pid = g_hash_table_new_full (NULL,
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NULL,
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NULL,
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(GDestroyNotify)sysprof_live_process_unref);
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}
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SysprofLiveUnwinder *
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sysprof_live_unwinder_new (SysprofCaptureWriter *writer,
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int kallsyms_fd)
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{
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SysprofLiveUnwinder *self;
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g_autofree char *mounts = NULL;
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g_return_val_if_fail (writer != NULL, NULL);
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self = g_object_new (SYSPROF_TYPE_LIVE_UNWINDER, NULL);
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self->writer = sysprof_capture_writer_ref (writer);
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if (kallsyms_fd != -1)
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{
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sysprof_capture_writer_add_file_fd (writer,
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SYSPROF_CAPTURE_CURRENT_TIME,
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-1,
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-1,
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"/proc/kallsyms",
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kallsyms_fd);
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close (kallsyms_fd);
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}
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mounts = sysprof_live_unwinder_read_file (self, "/proc/mounts", TRUE);
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sysprof_live_unwinder_mine_pids (self);
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return self;
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}
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void
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sysprof_live_unwinder_seen_process (SysprofLiveUnwinder *self,
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gint64 time,
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int cpu,
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GPid pid,
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const char *comm)
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{
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G_GNUC_UNUSED SysprofLiveProcess *live_pid;
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g_assert (SYSPROF_IS_LIVE_UNWINDER (self));
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live_pid = sysprof_live_unwinder_find_pid (self, pid, FALSE);
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sysprof_capture_writer_add_process (self->writer, time, cpu, pid, comm);
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}
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void
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sysprof_live_unwinder_process_exited (SysprofLiveUnwinder *self,
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gint64 time,
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int cpu,
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GPid pid)
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{
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g_assert (SYSPROF_IS_LIVE_UNWINDER (self));
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sysprof_capture_writer_add_exit (self->writer, time, cpu, pid);
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}
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void
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sysprof_live_unwinder_process_forked (SysprofLiveUnwinder *self,
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gint64 time,
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int cpu,
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GPid parent_tid,
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GPid tid)
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{
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g_assert (SYSPROF_IS_LIVE_UNWINDER (self));
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sysprof_capture_writer_add_fork (self->writer, time, cpu, parent_tid, tid);
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}
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void
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sysprof_live_unwinder_track_mmap (SysprofLiveUnwinder *self,
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gint64 time,
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int cpu,
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GPid pid,
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SysprofCaptureAddress begin,
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SysprofCaptureAddress end,
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SysprofCaptureAddress offset,
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guint64 inode,
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const char *filename,
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const char *build_id)
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{
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G_GNUC_UNUSED SysprofLiveProcess *live_pid;
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g_assert (SYSPROF_IS_LIVE_UNWINDER (self));
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live_pid = sysprof_live_unwinder_find_pid (self, pid, TRUE);
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if (build_id != NULL)
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sysprof_capture_writer_add_map_with_build_id (self->writer, time, cpu, pid,
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begin, end, offset,
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inode, filename,
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build_id);
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else
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sysprof_capture_writer_add_map (self->writer, time, cpu, pid,
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begin, end, offset,
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inode, filename);
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sysprof_live_process_add_map (live_pid, begin, end, offset, inode, filename);
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}
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void
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sysprof_live_unwinder_process_sampled (SysprofLiveUnwinder *self,
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gint64 time,
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int cpu,
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GPid pid,
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GPid tid,
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const SysprofCaptureAddress *addresses,
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guint n_addresses)
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{
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G_GNUC_UNUSED SysprofLiveProcess *live_pid;
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g_assert (SYSPROF_IS_LIVE_UNWINDER (self));
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live_pid = sysprof_live_unwinder_find_pid (self, pid, TRUE);
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sysprof_capture_writer_add_sample (self->writer, time, cpu, pid, tid,
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addresses, n_addresses);
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}
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void
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sysprof_live_unwinder_process_sampled_with_stack (SysprofLiveUnwinder *self,
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gint64 time,
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int cpu,
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GPid pid,
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GPid tid,
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const SysprofCaptureAddress *addresses,
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guint n_addresses,
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const guint8 *stack,
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guint64 stack_size,
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guint64 stack_dyn_size,
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guint64 abi,
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const guint64 *registers,
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guint n_registers)
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{
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SysprofLiveProcess *live_pid;
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SysprofCaptureAddress unwound[256];
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gboolean found_user = FALSE;
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guint pos;
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g_assert (SYSPROF_IS_LIVE_UNWINDER (self));
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g_assert (stack != NULL);
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g_assert (stack_dyn_size <= stack_size);
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if (stack_dyn_size == 0 || n_addresses >= G_N_ELEMENTS (unwound))
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{
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sysprof_live_unwinder_process_sampled (self, time, cpu, pid, tid, addresses, n_addresses);
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return;
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}
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live_pid = sysprof_live_unwinder_find_pid (self, pid, TRUE);
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/* Copy addresses over (which might be kernel, context-switch, etc until
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* we get to the PERF_CONTEXT_USER. We'll decode the stack right into the
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* location after that.
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*/
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for (pos = 0; pos < n_addresses; pos++)
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{
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unwound[pos] = addresses[pos];
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if (addresses[pos] == PERF_CONTEXT_USER)
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{
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found_user = TRUE;
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break;
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}
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}
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/* If we didn't find a user context (but we have a stack size) synthesize
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* the PERF_CONTEXT_USER now.
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*/
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if (!found_user && pos < G_N_ELEMENTS (unwound))
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unwound[pos++] = PERF_CONTEXT_USER;
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/* Now request the live process unwind the user-space stack */
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if (pos < G_N_ELEMENTS (unwound))
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{
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guint n_unwound;
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n_unwound = sysprof_live_process_unwind (live_pid,
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tid,
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abi,
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stack,
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stack_dyn_size,
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registers,
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n_registers,
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&unwound[pos],
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G_N_ELEMENTS (unwound) - pos);
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/* Only take DWARF unwind if it was better */
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if (pos + n_unwound > n_addresses)
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{
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addresses = unwound;
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n_addresses = pos + n_unwound;
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}
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}
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sysprof_capture_writer_add_sample (self->writer, time, cpu, pid, tid, addresses, n_addresses);
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}
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