This is the same patch that went into i386 just before 2.6.13
came out. I still can't build 64-bit user apps, so I tested
with program (see below) in 32-bit mode on 64-bit kernel:
Before:
$ fpsig
handler: nr = 8, si = 0x0804bc90, vuc = 0x0804bd10
handler: altstack is at 0x0804b000, ebp = 0x0804bc7c
handler: si_signo = 8, si_errno = 0, si_code = 0 [unknown]
handler: fpu cwd = 0xb40, fpu swd = 0xbaa0
handler: i387 unmasked precision exception, rounded up
After:
$ fpsig
handler: nr = 8, si = 0x0804bc90, vuc = 0x0804bd10
handler: altstack is at 0x0804b000, ebp = 0x0804bc7c
handler: si_signo = 8, si_errno = 0, si_code = 6 [inexact result]
handler: fpu cwd = 0xb40, fpu swd = 0xbaa0
handler: i387 unmasked precision exception, rounded up
Signed-off-by: Chuck Ebbert <[EMAIL PROTECTED]>
arch/x86_64/kernel/traps.c | 9 ++++++---
1 files changed, 6 insertions(+), 3 deletions(-)
--- 2.6.13-64.orig/arch/x86_64/kernel/traps.c
+++ 2.6.13-64/arch/x86_64/kernel/traps.c
@@ -786,13 +786,16 @@ asmlinkage void do_coprocessor_error(str
*/
cwd = get_fpu_cwd(task);
swd = get_fpu_swd(task);
- switch (((~cwd) & swd & 0x3f) | (swd & 0x240)) {
+ switch (swd & ~cwd & 0x3f) {
case 0x000:
default:
break;
case 0x001: /* Invalid Op */
- case 0x041: /* Stack Fault */
- case 0x241: /* Stack Fault | Direction */
+ /*
+ * swd & 0x240 == 0x040: Stack Underflow
+ * swd & 0x240 == 0x240: Stack Overflow
+ * User must clear the SF bit (0x40) if set
+ */
info.si_code = FPE_FLTINV;
break;
case 0x002: /* Denormalize */
================================================================================
/* i387 fp signal test */
#define _GNU_SOURCE
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <signal.h>
#include <errno.h>
/* define this to nozero to hexdump the altstack */
#define DUMP_STACK 0
#define STACKSIZE 4096
__attribute__ ((aligned(STACKSIZE))) unsigned char altstack[STACKSIZE];
stack_t ss = {
.ss_sp = altstack,
.ss_size = sizeof(altstack),
};
unsigned short cw = 0x0b40; /* unmask all exceptions, round up */
struct sigaction sa;
static void handler(int nr, siginfo_t *si, void *vuc)
{
char *decode;
unsigned int ebp;
int code = si->si_code;
struct ucontext *uc = (struct ucontext *)vuc;
struct sigcontext *sc = (struct sigcontext *)&uc->uc_mcontext;
unsigned short cwd = (unsigned short)sc->fpstate->cw;
unsigned short swd = (unsigned short)sc->fpstate->sw;
switch (code) {
case FPE_INTDIV:
decode = "divide by zero";
break;
case FPE_FLTRES:
decode = "inexact result";
break;
case FPE_FLTINV:
decode = "invalid operand";
break;
default:
decode = "unknown";
break;
}
asm volatile ("mov %%ebp, %0" : "=m" (ebp));
printf("handler: nr = %d, si = 0x%08x, vuc = 0x%08x\n",
nr, (unsigned int)si, (unsigned int)vuc);
printf("handler: altstack is at 0x%08x, ebp = 0x%08x\n",
(unsigned int)altstack, ebp);
printf("handler: si_signo = %d, si_errno = %d, si_code = %d [%s]\n",
si->si_signo, si->si_errno, code, decode);
#if DUMP_STACK
#define ROWSIZE 16
{
int empty, i, j;
for (i = 0; i < sizeof(altstack); i += ROWSIZE) {
empty = 1;
for (j = 0; j < ROWSIZE; j++)
if (altstack[i + j])
empty = 0;
if (!empty) {
printf("%04x: ", i);
for (j = 0; j < ROWSIZE; j++)
printf("%02hhx ", altstack[i + j]);
printf("\n");
}
}
}
#endif /* DUMP_STACK */
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 (
"mov $0xaaaaaaaa,%%eax ; mov $0xbbbbbbbb,%%ebx ; "
"mov $0xcccccccc,%%ecx ; mov $0xdddddddd,%%edx ; "
"fdivp ; fwait" : : : "eax", "ebx", "ecx", "edx");
return 0;
}
__
Chuck
-
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