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main: Print backtrace on crash

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Since plymouth can crash before the root filesystem is mounted,
and since plymouth can prevent boot from proceeding, coredumpctl
isn't always a viable option for getting backtraces.

This commit changes the crash handler to output backtrace
information to assist when coredumpctl can't.
This commit is contained in:
Ray Strode 2023-12-27 16:30:15 -05:00 • committed by Ray Strode
parent 355197714f
commit f2bd492ac7
1 changed files with 88 additions and 12 deletions
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100
src/main.c
View file

@ -59,6 +59,8 @@
#define BOOT_DURATION_FILE PLYMOUTH_TIME_DIRECTORY "/boot-duration"
#define SHUTDOWN_DURATION_FILE PLYMOUTH_TIME_DIRECTORY "/shutdown-duration"
static int crash_fd = -1;
typedef struct
{
const char *keys;
@ -1970,10 +1972,13 @@ check_verbosity (state_t *state)
ply_trace ("streaming debug output to %s instead of screen", stream);
fd = open (stream, O_RDWR | O_NOCTTY | O_CREAT, 0600);
if (fd < 0)
if (fd < 0) {
ply_trace ("could not stream output to %s: %m", stream);
else
} else {
ply_logger_set_output_fd (ply_logger_get_error_default (), fd);
crash_fd = fd;
}
free (stream);
} else {
const char *device;
@ -2153,6 +2158,70 @@ dump_debug_buffer_to_file (void)
#include <termios.h>
#include <unistd.h>
#include <execinfo.h>
#define BACKTRACE_SIZE 1024
#define MAPS_SIZE 8192
#define BACKTRACE_FRAMES_TO_SKIP 2 /* write_backtrace and on_crash themselves */
static void
write_maps (int output_fd)
{
char maps_buffer[MAPS_SIZE];
ssize_t bytes_read;
ssize_t line_start = 0, buffer_end = 0;
int fd;
write (output_fd, "maps:\n", strlen ("maps:\n"));
fd = open ("/proc/self/maps", O_RDONLY);
if (fd < 0)
return;
while ((bytes_read = read (fd, maps_buffer + buffer_end, MAPS_SIZE - buffer_end)) > 0) {
bytes_read += buffer_end;
buffer_end = 0;
for (ssize_t i = line_start; i < bytes_read; ++i) {
if (maps_buffer[i] == '\n') {
write (output_fd, maps_buffer + line_start, i - line_start + 1);
line_start = i + 1;
}
}
if (line_start < bytes_read) {
memmove (maps_buffer, maps_buffer + line_start, bytes_read - line_start);
buffer_end = bytes_read - line_start;
line_start = 0;
} else {
line_start = 0;
}
}
if (buffer_end > 0) {
write (output_fd, maps_buffer, buffer_end);
}
close (fd);
}
static void
write_backtrace (int output_fd)
{
void *addresses[BACKTRACE_SIZE];
int number_of_addresses;
write (output_fd, "backtrace:\n", strlen ("backtrace:\n"));
number_of_addresses = backtrace (addresses, BACKTRACE_SIZE);
if (number_of_addresses <= BACKTRACE_FRAMES_TO_SKIP)
return;
backtrace_symbols_fd (addresses + BACKTRACE_FRAMES_TO_SKIP,
number_of_addresses - BACKTRACE_FRAMES_TO_SKIP,
output_fd);
}
static void
on_crash (int signum)
{
@ -2160,22 +2229,29 @@ on_crash (int signum)
int fd;
static const char *show_cursor_sequence = "\033[?25h";
fd = open ("/dev/tty1", O_RDWR | O_NOCTTY);
if (fd < 0) fd = open ("/dev/hvc0", O_RDWR | O_NOCTTY);
if (crash_fd != -1) {
fd = crash_fd;
} else {
fd = open ("/dev/tty1", O_RDWR | O_NOCTTY);
if (fd < 0) fd = open ("/dev/hvc0", O_RDWR | O_NOCTTY);
}
ioctl (fd, KDSETMODE, KD_TEXT);
if (fd >= 0) {
ioctl (fd, KDSETMODE, KD_TEXT);
write (fd, show_cursor_sequence, sizeof(show_cursor_sequence) - 1);
write (fd, show_cursor_sequence, sizeof(show_cursor_sequence) - 1);
tcgetattr (fd, &term_attributes);
tcgetattr (fd, &term_attributes);
term_attributes.c_iflag |= BRKINT | IGNPAR | ICRNL | IXON;
term_attributes.c_oflag |= OPOST;
term_attributes.c_lflag |= ECHO | ICANON | ISIG | IEXTEN;
term_attributes.c_iflag |= BRKINT | IGNPAR | ICRNL | IXON;
term_attributes.c_oflag |= OPOST;
term_attributes.c_lflag |= ECHO | ICANON | ISIG | IEXTEN;
tcsetattr (fd, TCSAFLUSH, &term_attributes);
tcsetattr (fd, TCSAFLUSH, &term_attributes);
close (fd);
write_maps (fd);
write_backtrace (fd);
}
if (debug_buffer != NULL) {
dump_debug_buffer_to_file ();