From: Karol Swietlicki 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 ] Signed-off-by: Karol Swietlicki Signed-off-by: Jeff Dike Signed-off-by: Andrew Morton --- arch/um/sys-i386/bugs.c | 41 +++++++++++++++++++++++++++++--------- 1 file changed, 32 insertions(+), 9 deletions(-) diff -puN arch/um/sys-i386/bugs.c~uml-improve-detection-of-host-cmov arch/um/sys-i386/bugs.c --- a/arch/um/sys-i386/bugs.c~uml-improve-detection-of-host-cmov +++ a/arch/um/sys-i386/bugs.c @@ -10,11 +10,42 @@ #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("Yes\n"); + } + else + printk("No\n"); + + sigaction(SIGILL, &old, &new); +} static char token(int fd, char *buf, int len, char stop) { @@ -153,15 +184,7 @@ 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) _