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authorKarol Swietlicki <magotari@gmail.com>2008-02-04 22:30:38 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-05 09:44:25 -0800
commit235a6f06eb5571db600a743cda7c73fd4f74127f (patch)
tree218c05cfe030a2debdfe8dc66485ad2bec4c1bc3 /arch/um/sys-i386
parent0ba9d3f91d213f6d07c84230a0b3e2b16a0bb176 (diff)
uml: improve detection of host cmov
This patch introduces a new way of checking for the cmov instruction. I use signal handling instead of reading /proc/cpuinfo. [ jdike - Fiddled the asm to make it obvious that it didn't mess with any in-use registers and made test_for_host_cmov void ] [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Karol Swietlicki <magotari@gmail.com> Signed-off-by: Jeff Dike <jdike@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/um/sys-i386')
-rw-r--r--arch/um/sys-i386/bugs.c40
1 files changed, 31 insertions, 9 deletions
diff --git a/arch/um/sys-i386/bugs.c b/arch/um/sys-i386/bugs.c
index 5ee4c366074e..797945cd3df2 100644
--- a/arch/um/sys-i386/bugs.c
+++ b/arch/um/sys-i386/bugs.c
@@ -10,11 +10,41 @@
#include "os.h"
#include "task.h"
#include "user.h"
+#include "sysdep/archsetjmp.h"
#define MAXTOKEN 64
/* Set during early boot */
int host_has_cmov = 1;
+static jmp_buf cmov_test_return;
+
+static void cmov_sigill_test_handler(int sig)
+{
+ host_has_cmov = 0;
+ longjmp(cmov_test_return, 1);
+}
+
+static void test_for_host_cmov(void)
+{
+ struct sigaction old, new;
+
+ printk(UM_KERN_INFO "Checking for host processor cmov support...");
+ new.sa_handler = cmov_sigill_test_handler;
+
+ /* Make sure that SIGILL is enabled after the handler longjmps back */
+ new.sa_flags = SA_NODEFER;
+ sigemptyset(&new.sa_mask);
+ sigaction(SIGILL, &new, &old);
+
+ if (setjmp(cmov_test_return) == 0) {
+ unsigned long foo = 0;
+ __asm__ __volatile__("cmovz %0, %1" : "=r" (foo) : "0" (foo));
+ printk(UM_KERN_CONT "Yes\n");
+ } else
+ printk(UM_KERN_CONT "No\n");
+
+ sigaction(SIGILL, &old, &new);
+}
static char token(int fd, char *buf, int len, char stop)
{
@@ -153,15 +183,7 @@ void arch_init_thread(void)
void arch_check_bugs(void)
{
- int have_it;
-
- if (os_access("/proc/cpuinfo", OS_ACC_R_OK) < 0) {
- printk(UM_KERN_ERR "/proc/cpuinfo not available - skipping CPU "
- "capability checks\n");
- return;
- }
- if (check_cpu_flag("cmov", &have_it))
- host_has_cmov = have_it;
+ test_for_host_cmov();
}
int arch_handle_signal(int sig, struct uml_pt_regs *regs)