FIFO coredump files are useful for a remote system with contrained
resources that likely still contains some fatal bugs.
It allows a daemon to listen on the FIFO and mail the crashes
to the maintainer. The restriction that core_patten point to a
regular file is arbitrary anyway.
To get this to work, I had modify the wrappers to
file->f_op->{write,llseek} in binfmt_elf.c to act more like those
for a regular file. Instead I could have modified pipe_write and
no_llseek, which would be cleaner, but this was the change is localized.
I'm looking for comments, testing and inclusion in the next release.
I have tested it in UML and one i686 build. The coredump files
produced were valid.
Thanks, Devin Bayer.
diff -aur fs.orig/binfmt_elf.c linux/fs/binfmt_elf.c
--- fs.orig/binfmt_elf.c 2005-10-27 17:02:08.000000000 -0700
+++ linux/fs/binfmt_elf.c 2005-11-18 10:29:30.000000000 -0800
@@ -38,6 +38,7 @@
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/random.h>
+#include <linux/poll.h>
#include <asm/uaccess.h>
#include <asm/param.h>
@@ -1121,14 +1122,43 @@
* These are the only things you should do on a core-file: use only these
* functions to write out all the necessary info.
*/
+#define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR)
static int dump_write(struct file *file, const void *addr, int nr)
{
+ if(file->f_op->llseek == no_llseek) {
+ long timeout = msecs_to_jiffies(5000);
+ unsigned long mask;
+ struct poll_wqueues table;
+ poll_initwait(&table);
+
+ while(timeout > 0) {
+ mask = (*file->f_op->poll)(file, &table.pt);
+ if (mask & POLLOUT_SET)
+ break;
+
+ cond_resched();
+ set_current_state(TASK_INTERRUPTIBLE);
+ timeout = schedule_timeout(timeout);
+ }
+
+ poll_freewait(&table);
+ file->f_pos += nr;
+ }
+
return file->f_op->write(file, addr, nr, &file->f_pos) == nr;
}
static int dump_seek(struct file *file, loff_t off)
{
- if (file->f_op->llseek) {
+ if (off == file->f_pos)
+ return 1;
+ if (file->f_op->llseek == no_llseek && off > file->f_pos) {
+ int nr = off - file->f_pos;
+ char zeros[nr];
+
+ memset(zeros,0,nr);
+ return dump_write(file, zeros, nr);
+ } else if (file->f_op->llseek) {
if (file->f_op->llseek(file, off, 0) != off)
return 0;
} else
diff -aur fs.orig/exec.c linux/fs/exec.c
--- fs.orig/exec.c 2005-10-27 17:02:08.000000000 -0700
+++ linux/fs/exec.c 2005-11-18 10:29:38.000000000 -0800
@@ -65,6 +65,7 @@
static struct linux_binfmt *formats;
static DEFINE_RWLOCK(binfmt_lock);
+static DEFINE_SPINLOCK(fifo_core_lock);
int register_binfmt(struct linux_binfmt * fmt)
{
@@ -1492,7 +1493,7 @@
lock_kernel();
format_corename(corename, core_pattern, signr);
unlock_kernel();
- file = filp_open(corename, O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag, 0600);
+ file = filp_open(corename, O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | O_NONBLOCK | flag, 0600);
if (IS_ERR(file))
goto fail_unlock;
inode = file->f_dentry->d_inode;
@@ -1500,18 +1501,27 @@
goto close_fail; /* multiple links - don't dump */
if (d_unhashed(file->f_dentry))
goto close_fail;
-
- if (!S_ISREG(inode->i_mode))
- goto close_fail;
+
if (!file->f_op)
goto close_fail;
if (!file->f_op->write)
goto close_fail;
- if (do_truncate(file->f_dentry, 0) != 0)
- goto close_fail;
+ if (S_ISFIFO(inode->i_mode)) {
+ flush_signals(current);
+ recalc_sigpending();
+ spin_lock(&fifo_core_lock);
+ } else {
+ if (!S_ISREG(inode->i_mode))
+ goto close_fail;
+ if (do_truncate(file->f_dentry, 0) != 0)
+ goto close_fail;
+ }
retval = binfmt->core_dump(signr, regs, file);
+ if(S_ISFIFO(inode->i_mode))
+ spin_unlock(&fifo_core_lock);
+
if (retval)
current->signal->group_exit_code |= 0x80;
close_fail:
-
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