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Commit adf77bac authored by H. Peter Anvin's avatar H. Peter Anvin
Browse files

x86: prioritize the FPU traps for the error code 



In the case of multiple FPU errors, prioritize the error codes,
instead of returning __SI_FAULT, which ends up pushing a 0 as the
error code to userspace, a POSIX violation.

For i386, we will simply return if there are no errors at all; for
x86-64 this is probably a "can't happen" (and the code should be
unified), but for this patch, return __SI_FAULT|SI_KERNEL if this ever
happens.

Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
parent 55dac3a5

arch/x86/kernel/traps.c

+15 −19
Original line number Original line Diff line number Diff line
@@ -664,7 +664,7 @@ void math_error(void __user *ip) 
{

{

	struct task_struct *task;

	struct task_struct *task;

	siginfo_t info;

	siginfo_t info;

	unsigned short cwd, swd;

	unsigned short cwd, swd, err;





	/*

	/*

	 * Save the info for the exception handler and clear the error.

	 * Save the info for the exception handler and clear the error.
@@ -675,7 +675,6 @@ void math_error(void __user *ip) 
	task->thread.error_code = 0;

	task->thread.error_code = 0;

	info.si_signo = SIGFPE;

	info.si_signo = SIGFPE;

	info.si_errno = 0;

	info.si_errno = 0;

	info.si_code = __SI_FAULT;

	info.si_addr = ip;

	info.si_addr = ip;

	/*

	/*

	 * (~cwd & swd) will mask out exceptions that are not set to unmasked

	 * (~cwd & swd) will mask out exceptions that are not set to unmasked
@@ -689,34 +688,31 @@ void math_error(void __user *ip) 
	 */

	 */

	cwd = get_fpu_cwd(task);

	cwd = get_fpu_cwd(task);

	swd = get_fpu_swd(task);

	swd = get_fpu_swd(task);

	switch (swd & ~cwd & 0x3f) {



	case 0x000: /* No unmasked exception */

	err = swd & ~cwd & 0x3f;

#ifdef CONFIG_X86_32



#if CONFIG_X86_32

	if (!err)

		return;

		return;

#endif

#endif

	default: /* Multiple exceptions */



		break;

	if (err & 0x001) {	/* Invalid op */

	case 0x001: /* Invalid Op */

		/*

		/*

		 * swd & 0x240 == 0x040: Stack Underflow

		 * swd & 0x240 == 0x040: Stack Underflow

		 * swd & 0x240 == 0x240: Stack Overflow

		 * swd & 0x240 == 0x240: Stack Overflow

		 * User must clear the SF bit (0x40) if set

		 * User must clear the SF bit (0x40) if set

		 */

		 */

		info.si_code = FPE_FLTINV;

		info.si_code = FPE_FLTINV;

		break;

	} else if (err & 0x004) { /* Divide by Zero */

	case 0x002: /* Denormalize */

	case 0x010: /* Underflow */

		info.si_code = FPE_FLTUND;

		break;

	case 0x004: /* Zero Divide */

		info.si_code = FPE_FLTDIV;

		info.si_code = FPE_FLTDIV;

		break;

	} else if (err & 0x008) { /* Overflow */

	case 0x008: /* Overflow */

		info.si_code = FPE_FLTOVF;

		info.si_code = FPE_FLTOVF;

		break;

	} else if (err & 0x012) { /* Denormal, Underflow */

	case 0x020: /* Precision */

		info.si_code = FPE_FLTUND;

	} else if (err & 0x020) { /* Precision */

		info.si_code = FPE_FLTRES;

		info.si_code = FPE_FLTRES;

		break;

	} else {

		info.si_code = __SI_FAULT|SI_KERNEL; /* WTF? */

	}

	}

	force_sig_info(SIGFPE, &info, task);

	force_sig_info(SIGFPE, &info, task);

}

}