Date: Wed, 10 Sep 2008 15:31:54 -0400 From: John Baldwin <jhb@FreeBSD.org> To: arch@FreeBSD.org Subject: PASSERT() - asserting for panics Message-ID: <200809101531.54646.jhb@FreeBSD.org>
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So one of the things I like to do is use kernel modules that do regression
tests. One of the things I want to test is that certain invalid operations
will cause a specific panic. In the past I've done nefarious things
like '#define panic printf' at the top of kern_rwlock.c and such. :)
However, this is not suitable for more widespread use. The other approach of
having the tests panic and verifying the panics that way is tedious. So what
I came up with is a way to assert that a given panic will be triggered by a
chunk of code, and if that panic happens, the kernel doesn't actually panic.
The way I implemented this was by having the actual test do a setjmp() and if
the "expected" panic triggers, then panic() does a longjmp() before setting
panicstr, etc. A simple example of using it would be:
PASSERT("foo", panic("foo"));
The patch is at http://www.FreeBSD.org/~jhb/patches/passert.patch and below:
--- //depot/projects/smpng/sys/kern/kern_shutdown.c 2008/03/18 12:54:14
+++ //depot/user/jhb/lock/kern/kern_shutdown.c 2008/09/10 17:40:44
@@ -531,6 +531,17 @@
if (panicstr)
bootopt |= RB_NOSYNC;
else {
+#ifdef INVARIANT_SUPPORT
+ if (td->td_expected_panic != NULL &&
+ strcmp(td->td_expected_panic, fmt) == 0) {
+ va_start(ap, fmt);
+ printf("expected panic: ");
+ vprintf(fmt, ap);
+ printf("\n");
+ va_end(ap);
+ longjmp(td->td_panic_buf, 1);
+ }
+#endif
panicstr = fmt;
newpanic = 1;
}
--- //depot/projects/smpng/sys/kern/kern_thread.c 2008/08/25 16:33:41
+++ //depot/user/jhb/lock/kern/kern_thread.c 2008/09/09 18:31:16
@@ -35,6 +35,7 @@
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/lock.h>
+#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
@@ -48,6 +49,7 @@
#include <sys/umtx.h>
#include <sys/cpuset.h>
+#include <machine/setjmp.h>
#include <security/audit/audit.h>
#include <vm/vm.h>
@@ -161,6 +163,9 @@
td->td_sched = (struct td_sched *)&td[1];
umtx_thread_init(td);
td->td_kstack = 0;
+#ifdef INVARIANT_SUPPORT
+ td->td_panic_buf = malloc(sizeof(struct _jmp_buf), M_SUBPROC, M_WAITOK);
+#endif
return (0);
}
@@ -178,6 +183,9 @@
sleepq_free(td->td_sleepqueue);
umtx_thread_fini(td);
seltdfini(td);
+#ifdef INVARIANT_SUPPORT
+ free(td->td_panic_buf, M_SUBPROC);
+#endif
}
/*
--- //depot/projects/smpng/sys/sys/proc.h 2008/08/25 16:33:41
+++ //depot/user/jhb/lock/sys/proc.h 2008/09/09 18:31:16
@@ -166,6 +166,7 @@
struct kdtrace_proc;
struct kdtrace_thread;
struct cpuset;
+struct _jmp_buf;
/*
* Kernel runnable context (thread).
@@ -273,6 +274,8 @@
struct lpohead td_lprof[2]; /* (a) lock profiling objects. */
struct kdtrace_thread *td_dtrace; /* (*) DTrace-specific data. */
int td_errno; /* Error returned by last syscall. */
+ struct _jmp_buf *td_panic_buf; /* (k) Jump buffer for PASSERT(). */
+ const char *td_expected_panic; /* (k) Expected panic. */
};
struct mtx *thread_lock_block(struct thread *);
--- //depot/projects/smpng/sys/sys/systm.h 2008/07/25 18:20:23
+++ //depot/user/jhb/lock/sys/systm.h 2008/09/09 18:31:16
@@ -71,9 +71,25 @@
if (__predict_false(!(exp))) \
panic msg; \
} while (0)
+
+#define PASSERT(panicstr, code) do { \
+ switch (setjmp(curthread->td_panic_buf)) { \
+ case 0: \
+ curthread->td_expected_panic = (panicstr); \
+ code; \
+ panic("Expected panic '%s' did not trigger", \
+ (panicstr)); \
+ case 1: \
+ curthread->td_expected_panic = NULL; \
+ break; \
+ default: \
+ panic("Unexpected return value from setjmp()"); \
+ } \
+} while (0)
+
#define VNASSERT(exp, vp, msg) do { \
if (__predict_false(!(exp))) { \
vn_printf(vp, "VNASSERT failed\n"); \
panic msg; \
} \
} while (0)
@@ -81,6 +97,9 @@
#define KASSERT(exp,msg) do { \
} while (0)
+#define PASSERT(panicstr, code) do { \
+} while (0)
+
#define VNASSERT(exp, vp, msg) do { \
} while (0)
#endif
Is this too evil for the tree?
--
John Baldwin
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