Much nicer, thanks!
-- Keir
On 14/12/2009 11:08, "Paolo Bonzini" <pbonzini@xxxxxxxxxx> wrote:
> 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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> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel
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