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authorKarol Swietlicki <magotari@gmail.com>2008-02-05 01:30:38 -0500
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-05 12:44:25 -0500
commit235a6f06eb5571db600a743cda7c73fd4f74127f (patch)
tree218c05cfe030a2debdfe8dc66485ad2bec4c1bc3 /arch/um/sys-i386/bugs.c
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/bugs.c')
-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 @@
10#include "os.h" 10#include "os.h"
11#include "task.h" 11#include "task.h"
12#include "user.h" 12#include "user.h"
13#include "sysdep/archsetjmp.h"
13 14
14#define MAXTOKEN 64 15#define MAXTOKEN 64
15 16
16/* Set during early boot */ 17/* Set during early boot */
17int host_has_cmov = 1; 18int host_has_cmov = 1;
19static jmp_buf cmov_test_return;
20
21static void cmov_sigill_test_handler(int sig)
22{
23 host_has_cmov = 0;
24 longjmp(cmov_test_return, 1);
25}
26
27static void test_for_host_cmov(void)
28{
29 struct sigaction old, new;
30
31 printk(UM_KERN_INFO "Checking for host processor cmov support...");
32 new.sa_handler = cmov_sigill_test_handler;
33
34 /* Make sure that SIGILL is enabled after the handler longjmps back */
35 new.sa_flags = SA_NODEFER;
36 sigemptyset(&new.sa_mask);
37 sigaction(SIGILL, &new, &old);
38
39 if (setjmp(cmov_test_return) == 0) {
40 unsigned long foo = 0;
41 __asm__ __volatile__("cmovz %0, %1" : "=r" (foo) : "0" (foo));
42 printk(UM_KERN_CONT "Yes\n");
43 } else
44 printk(UM_KERN_CONT "No\n");
45
46 sigaction(SIGILL, &old, &new);
47}
18 48
19static char token(int fd, char *buf, int len, char stop) 49static char token(int fd, char *buf, int len, char stop)
20{ 50{
@@ -153,15 +183,7 @@ void arch_init_thread(void)
153 183
154void arch_check_bugs(void) 184void arch_check_bugs(void)
155{ 185{
156 int have_it; 186 test_for_host_cmov();
157
158 if (os_access("/proc/cpuinfo", OS_ACC_R_OK) < 0) {
159 printk(UM_KERN_ERR "/proc/cpuinfo not available - skipping CPU "
160 "capability checks\n");
161 return;
162 }
163 if (check_cpu_flag("cmov", &have_it))
164 host_has_cmov = have_it;
165} 187}
166 188
167int arch_handle_signal(int sig, struct uml_pt_regs *regs) 189int arch_handle_signal(int sig, struct uml_pt_regs *regs)