From: pbonzini@xxxxxxxxxx
# HG changeset patch
# User Paolo Bonzini <pbonzini@xxxxxxxxxx>
# Date 1260787292 -3600
# Node ID 64b613c3664688602fa726f0910ba4bc620cc577
# Parent d44371e6e5d631f58d9a2ce829f12dafd1272f68
Avoid dumping core in xen-detect
F12 introduces a tool to automatically report bugs when there are core
dumps. Since xen-detect relies on fork+waitpid in order to trap a SIGILL
from a child, every time someone runs xen-detect on a bare metal kernel
a bug is reported into Red Hat's Bugzilla. :-)
However, even without this contingent need, leaving core dumps around is
not nice. So this patch just traps SIGILL using signal/sentjmp/longjmp,
without the need to fork.
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
diff --git a/tools/misc/xen-detect.c b/tools/misc/xen-detect.c
--- a/tools/misc/xen-detect.c
+++ b/tools/misc/xen-detect.c
@@ -29,9 +29,11 @@
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
-#include <sys/wait.h>
+#include <setjmp.h>
+#include <signal.h>
#include <unistd.h>
+jmp_buf j;
static int pv_context;
static void cpuid(uint32_t idx,
@@ -74,6 +76,11 @@
return 1;
}
+void sigill_handler (int sig)
+{
+ longjmp(j, 1);
+}
+
int main(void)
{
pid_t pid;
@@ -84,33 +91,18 @@
if ( check_for_xen() )
return 0;
- /* Now we check for execution in PV context. */
- pv_context = 1;
-
/*
- * Fork a child to test the paravirtualised CPUID instruction.
- * If executed outside Xen PV context, the extended opcode will fault.
+ * Setup a signal handler to test the paravirtualised CPUID instruction.
+ * If executed outside Xen PV context, the extended opcode will fault
+ * and we'll print "Not running on Xen".
*/
- pid = fork();
- switch ( pid )
- {
- case 0:
- /* Child: test paravirtualised CPUID opcode and then exit cleanly. */
- cpuid(0x40000000, &dummy, &dummy, &dummy, &dummy);
- exit(0);
- case -1:
- fprintf(stderr, "Fork failed.\n");
- return 0;
+ signal(SIGILL, sigill_handler);
+ if (setjmp(j) == 0) {
+ pv_context = 1;
+ if ( check_for_xen() )
+ return 0;
}
- /*
- * Parent waits for child to terminate and checks for clean exit.
- * Only if the exit is clean is it safe for us to try the extended CPUID.
- */
- waitpid(pid, &status, 0);
- if ( WIFEXITED(status) && check_for_xen() )
- return 0;
-
printf("Not running on Xen.\n");
return 0;
}
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