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Commit 235a6f06 authored by Karol Swietlicki's avatar Karol Swietlicki Committed by Linus Torvalds
Browse files

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: default avatarKarol Swietlicki <magotari@gmail.com>
Signed-off-by: default avatarJeff Dike <jdike@linux.intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0ba9d3f9

arch/um/include/common-offsets.h

+1 −0
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ DEFINE_STR(UM_KERN_WARNING, KERN_WARNING); 
DEFINE_STR(UM_KERN_NOTICE, KERN_NOTICE);

DEFINE_STR(UM_KERN_INFO, KERN_INFO);

DEFINE_STR(UM_KERN_DEBUG, KERN_DEBUG);

DEFINE_STR(UM_KERN_CONT, KERN_CONT);



DEFINE(UM_ELF_CLASS, ELF_CLASS);

DEFINE(UM_ELFCLASS32, ELFCLASS32);

arch/um/sys-i386/bugs.c

+31 −9
Original line number Diff line number Diff line
@@ -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)