On Tue, 23 Aug 2005 02:20:07 +0200, Andi Kleen wrote:
> every reviewer has to look up all the bits in the manual?
I fixed the test program too:
Before patch:
$ ./fpsig
handler: signum = 8, errno = 0, code = 0 [unknown]
handler: fpu cwd = 0xb40, fpu swd = 0xbaa0
handler: i387 unmasked precision exception, rounded up
After:
$ ./fpsig
handler: signum = 8, errno = 0, code = 6 [inexact result]
handler: fpu cwd = 0xb40, fpu swd = 0xbaa0
handler: i387 unmasked precision exception, rounded up
/* i387 fp signal test */
#define _GNU_SOURCE
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <signal.h>
#include <errno.h>
__attribute__ ((aligned(4096))) unsigned char altstack[4096];
unsigned short cw = 0x0b40; /* unmask all exceptions, round up */
struct sigaction sa;
stack_t ss = {
.ss_sp = &altstack[2047],
.ss_size = sizeof(altstack)/2,
};
static void handler(int nr, siginfo_t *si, void *uc)
{
char *decode;
int code = si->si_code;
unsigned short cwd = *(unsigned short *)&altstack[0xd84];
unsigned short swd = *(unsigned short *)&altstack[0xd88];
switch (code) {
case FPE_INTDIV:
decode = "divide by zero";
break;
case FPE_FLTRES:
decode = "inexact result";
break;
case FPE_FLTINV:
decode = "invalid operation";
break;
default:
decode = "unknown";
break;
}
printf("handler: signum = %d, errno = %d, code = %d [%s]\n",
si->si_signo, si->si_errno, code, decode);
printf("handler: fpu cwd = 0x%hx, fpu swd = 0x%hx\n", cwd, swd);
if (swd & 0x20 & ~cwd)
printf("handler: i387 unmasked precision exception, rounded
%s\n",
swd & 0x200 ? "up" : "down");
exit(1);
}
int main(int argc, char * const argv[])
{
sa.sa_sigaction = handler;
sa.sa_flags = SA_ONSTACK | SA_SIGINFO;
if (sigaltstack(&ss, 0))
perror("sigaltstack");
if (sigaction(SIGFPE, &sa, NULL))
perror("sigaction");
asm volatile ("fnclex ; fldcw %0" : : "m" (cw));
asm volatile ( /* st(1) = 3.0, st = 1.0 */
"fld1 ; fld1 ; faddp ; fld1 ; faddp ; fld1");
asm volatile (
"fdivp ; fwait"); /* 1.0 / 3.0 */
return 0;
}
__
Chuck
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