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[PATCH] i386: fix incorrect FP signal code

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i386 floating-point exception handling has a bug that can cause error
code 0 to be sent instead of the proper code during signal delivery.

This is caused by unconditionally checking the IS and c1 bits from the
FPU status word when they are not always relevant.  The IS bit tells
whether an exception is a stack fault and is only relevant when the
exception is IE (invalid operation.) The C1 bit determines whether a
stack fault is overflow or underflow and is only relevant when IS and IE
are set.

Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Chuck Ebbert 2005-08-23 21:36:40 -04:00 committed by Linus Torvalds
parent 11532cc6aa
commit b1daec3089
1 changed files with 6 additions and 4 deletions
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10
arch/i386/kernel/traps.c
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@ -803,15 +803,17 @@ void math_error(void __user *eip)
*/
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;
/* Should we clear the SF or let user space do it ???? */
break;
case 0x002: /* Denormalize */
case 0x010: /* Underflow */