From adf77bac052bb5bf0722b2ce2af9fefc5b2d2a71 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Mon, 22 Dec 2008 17:56:05 -0800 Subject: [PATCH] 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: H. Peter Anvin --- arch/x86/kernel/traps.c | 34 +++++++++++++++------------------- 1 file changed, 15 insertions(+), 19 deletions(-) diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 04d242ab0161..c320c29255c2 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -664,7 +664,7 @@ void math_error(void __user *ip) { struct task_struct *task; siginfo_t info; - unsigned short cwd, swd; + unsigned short cwd, swd, err; /* * 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; info.si_signo = SIGFPE; info.si_errno = 0; - info.si_code = __SI_FAULT; info.si_addr = ip; /* * (~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); swd = get_fpu_swd(task); - switch (swd & ~cwd & 0x3f) { - case 0x000: /* No unmasked exception */ -#ifdef CONFIG_X86_32 + + err = swd & ~cwd & 0x3f; + +#if CONFIG_X86_32 + if (!err) return; #endif - default: /* Multiple exceptions */ - break; - case 0x001: /* Invalid Op */ + + if (err & 0x001) { /* Invalid op */ /* * 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 */ - case 0x010: /* Underflow */ - info.si_code = FPE_FLTUND; - break; - case 0x004: /* Zero Divide */ + } else if (err & 0x004) { /* Divide by Zero */ info.si_code = FPE_FLTDIV; - break; - case 0x008: /* Overflow */ + } else if (err & 0x008) { /* Overflow */ info.si_code = FPE_FLTOVF; - break; - case 0x020: /* Precision */ + } else if (err & 0x012) { /* Denormal, Underflow */ + info.si_code = FPE_FLTUND; + } else if (err & 0x020) { /* Precision */ info.si_code = FPE_FLTRES; - break; + } else { + info.si_code = __SI_FAULT|SI_KERNEL; /* WTF? */ } force_sig_info(SIGFPE, &info, task); }