[Libguestfs] [PATCH 1/4] Add a core_pattern debug command

This adds a new debug command, core_pattern, which writes a new pattern for coredump files to the appliance kernel, and sets the daemon's hard and soft core limits to infinity. --- daemon/debug.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 46 insertions(+), 0 deletions(-) diff --git a/daemon/debug.c b/daemon/debug.c index 0867ccd..37d5237 100644 --- a/daemon/debug.c +++ b/daemon/debug.c @@ -26,6 +26,7 @@ #include <unistd.h> #include <fcntl.h> #include <dirent.h> +#include <sys/resource.h> #include "../src/guestfs_protocol.h" #include "daemon.h" @@ -52,6 +53,7 @@ static char *debug_ls (const char *subcmd, int argc, char *const *const argv); static char *debug_ll (const char *subcmd, int argc, char *const *const argv); static char *debug_segv (const char *subcmd, int argc, char *const *const argv); static char *debug_sh (const char *subcmd, int argc, char *const *const argv); +static char *debug_core_pattern (const char *subcmd, int argc, char *const *const argv); static struct cmd cmds[] = { { "help", debug_help }, @@ -61,6 +63,7 @@ static struct cmd cmds[] = { { "ll", debug_ll }, { "segv", debug_segv }, { "sh", debug_sh }, + { "core_pattern", debug_core_pattern }, { NULL, NULL } }; #endif @@ -338,6 +341,49 @@ debug_ll (const char *subcmd, int argc, char *const *const argv) return out; } +/* Enable core dumping to the given core pattern. + * Note that this pattern is relative to any chroot of the process which + * crashes. This means that if you want to write the core file to the guest's + * storage the pattern must start with /sysroot only if the command which + * crashes doesn't chroot. + */ +static char * +debug_core_pattern (const char *subcmd, int argc, char *const *const argv) +{ + if (argc < 1) { + reply_with_error ("core_pattern: expecting a core pattern"); + } + + const char *pattern = argv[0]; + const size_t pattern_len = strlen(pattern); + +#define CORE_PATTERN "/proc/sys/kernel/core_pattern" + int fd = open (CORE_PATTERN, O_WRONLY); + if (fd == -1) { + reply_with_error ("open: " CORE_PATTERN); + return NULL; + } + if (write (fd, pattern, pattern_len) < (ssize_t) pattern_len) { + reply_with_error ("write: " CORE_PATTERN); + return NULL; + } + if (close (fd) == -1) { + reply_with_error ("close: " CORE_PATTERN); + return NULL; + } + + struct rlimit limit = { + .rlim_cur = RLIM_INFINITY, + .rlim_max = RLIM_INFINITY + }; + if (setrlimit (RLIMIT_CORE, &limit) == -1) { + reply_with_error ("setrlimit (RLIMIT_CORE)"); + return NULL; + } + + return strdup("ok"); +} + #endif /* ENABLE_DEBUG_COMMAND */ #if ENABLE_DEBUG_COMMAND -- 1.7.2.2