# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1260971760 0
# Node ID cd04ba5b2f0c8b86efce74a032daf0771b348fea
# Parent b5e22d959c66c3c653257084a97ee6a5d143975e
xen-detect: Avoid dumping core
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>
Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
xen-unstable changeset: 20645:1e9441f4dcbd
xen-unstable date: Mon Dec 14 11:58:45 2009 +0000
---
tools/misc/xen-detect.c | 58 ++++++++++++++++--------------------------------
1 files changed, 20 insertions(+), 38 deletions(-)
diff -r b5e22d959c66 -r cd04ba5b2f0c tools/misc/xen-detect.c
--- a/tools/misc/xen-detect.c Mon Dec 14 09:43:26 2009 +0000
+++ b/tools/misc/xen-detect.c Wed Dec 16 13:56:00 2009 +0000
@@ -26,19 +26,16 @@
#include <stdint.h>
#include <stdio.h>
-#include <stdlib.h>
#include <string.h>
-#include <sys/types.h>
-#include <sys/wait.h>
-#include <unistd.h>
-
-static int pv_context;
+#include <setjmp.h>
+#include <signal.h>
static void cpuid(uint32_t idx,
uint32_t *eax,
uint32_t *ebx,
uint32_t *ecx,
- uint32_t *edx)
+ uint32_t *edx,
+ int pv_context)
{
asm volatile (
"test %1,%1 ; jz 1f ; ud2a ; .ascii \"xen\" ; 1: cpuid"
@@ -46,7 +43,7 @@ static void cpuid(uint32_t idx,
: "0" (idx), "1" (pv_context) );
}
-static int check_for_xen(void)
+static int check_for_xen(int pv_context)
{
uint32_t eax, ebx, ecx, edx;
char signature[13];
@@ -54,7 +51,7 @@ static int check_for_xen(void)
for ( base = 0x40000000; base < 0x40010000; base += 0x100 )
{
- cpuid(base, &eax, &ebx, &ecx, &edx);
+ cpuid(base, &eax, &ebx, &ecx, &edx, pv_context);
*(uint32_t *)(signature + 0) = ebx;
*(uint32_t *)(signature + 4) = ecx;
@@ -68,47 +65,32 @@ static int check_for_xen(void)
return 0;
found:
- cpuid(base + 1, &eax, &ebx, &ecx, &edx);
+ cpuid(base + 1, &eax, &ebx, &ecx, &edx, pv_context);
printf("Running in %s context on Xen v%d.%d.\n",
pv_context ? "PV" : "HVM", (uint16_t)(eax >> 16), (uint16_t)eax);
return 1;
}
+static jmp_buf sigill_jmp;
+void sigill_handler(int sig)
+{
+ longjmp(sigill_jmp, 1);
+}
+
int main(void)
{
- pid_t pid;
- int status;
- uint32_t dummy;
-
/* Check for execution in HVM context. */
- if ( check_for_xen() )
+ if ( check_for_xen(0) )
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.
+ * Set up a signal handler to test the paravirtualised CPUID instruction.
+ * If executed outside Xen PV context, the extended opcode will fault, we
+ * will longjmp via the signal handler, and 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;
- }
-
- /*
- * 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() )
+ if ( !setjmp(sigill_jmp)
+ && (signal(SIGILL, sigill_handler) != SIG_ERR)
+ && check_for_xen(1) )
return 0;
printf("Not running on Xen.\n");
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