[POWERPC] Fixup error handling when emulating a floating point instruction

When we do full FP emulation its possible that we need to post a SIGFPE based
on the results of the emulation.  The previous code ignored this case completely.

Additionally, the Soft_emulate_8xx case had two issues.  One, we should never
generate a SIGFPE since the code only does data movement.  Second, we were
interpreting the return codes incorrectly, it returns 0 on success, 1 on
illop and -EFAULT on a data access error.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

1 files changed, 60 insertions, 22 deletions

diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index f038caa3c2b9..dcc6f159fd94 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -535,34 +535,40 @@ static void emulate_single_step(struct pt_regs *regs)
         }
 }
 
-static void parse_fpe(struct pt_regs *regs)
+static inline int __parse_fpscr(unsigned long fpscr)
 {
-        int code = 0;
-        unsigned long fpscr;
-
-        flush_fp_to_thread(current);
-
-        fpscr = current->thread.fpscr.val;
+        int ret = 0;
 
         /* Invalid operation */
         if ((fpscr & FPSCR_VE) && (fpscr & FPSCR_VX))
-                code = FPE_FLTINV;
+                ret = FPE_FLTINV;
 
         /* Overflow */
         else if ((fpscr & FPSCR_OE) && (fpscr & FPSCR_OX))
-                code = FPE_FLTOVF;
+                ret = FPE_FLTOVF;
 
         /* Underflow */
         else if ((fpscr & FPSCR_UE) && (fpscr & FPSCR_UX))
-                code = FPE_FLTUND;
+                ret = FPE_FLTUND;
 
         /* Divide by zero */
         else if ((fpscr & FPSCR_ZE) && (fpscr & FPSCR_ZX))
-                code = FPE_FLTDIV;
+                ret = FPE_FLTDIV;
 
         /* Inexact result */
         else if ((fpscr & FPSCR_XE) && (fpscr & FPSCR_XX))
-                code = FPE_FLTRES;
+                ret = FPE_FLTRES;
+
+        return ret;
+}
+
+static void parse_fpe(struct pt_regs *regs)
+{
+        int code = 0;
+
+        flush_fp_to_thread(current);
+
+        code = __parse_fpscr(current->thread.fpscr.val);
 
         _exception(SIGFPE, regs, code, regs->nip);
 }
@@ -773,10 +779,21 @@ void __kprobes program_check_exception(struct pt_regs *regs)
          * hardware people - not sure if it can happen on any illegal
          * instruction or only on FP instructions, whether there is a
          * pattern to occurences etc. -dgibson 31/Mar/2003 */
-        if (do_mathemu(regs) == 0) {
+        switch (do_mathemu(regs)) {
+        case 0:
                 emulate_single_step(regs);
                 return;
+        case 1: {
+                        int code = 0;
+                        code = __parse_fpscr(current->thread.fpscr.val);
+                        _exception(SIGFPE, regs, code, regs->nip);
+                        return;
+                }
+        case -EFAULT:
+                _exception(SIGSEGV, regs, SEGV_MAPERR, regs->nip);
+                return;
         }
+        /* fall through on any other errors */
 #endif /* CONFIG_MATH_EMULATION */
 
         /* Try to emulate it if we should. */
@@ -892,18 +909,39 @@ void SoftwareEmulation(struct pt_regs *regs)
 
 #ifdef CONFIG_MATH_EMULATION
         errcode = do_mathemu(regs);
+
+        switch (errcode) {
+        case 0:
+                emulate_single_step(regs);
+                return;
+        case 1: {
+                        int code = 0;
+                        code = __parse_fpscr(current->thread.fpscr.val);
+                        _exception(SIGFPE, regs, code, regs->nip);
+                        return;
+                }
+        case -EFAULT:
+                _exception(SIGSEGV, regs, SEGV_MAPERR, regs->nip);
+                return;
+        default:
+                _exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
+                return;
+        }
+
 #else
         errcode = Soft_emulate_8xx(regs);
-#endif
-        if (errcode) {
-                if (errcode > 0)
-                        _exception(SIGFPE, regs, 0, 0);
-                else if (errcode == -EFAULT)
-                        _exception(SIGSEGV, regs, 0, 0);
-                else
-                        _exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
-        } else
+        switch (errcode) {
+        case 0:
                 emulate_single_step(regs);
+                return;
+        case 1:
+                _exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
+                return;
+        case -EFAULT:
+                _exception(SIGSEGV, regs, SEGV_MAPERR, regs->nip);
+                return;
+        }
+#endif
 }
 #endif /* CONFIG_8xx */