x86/fpu/math-emu: Fix possible uninitialized variable use

When building the kernel with "make EXTRA_CFLAGS=...", this overrides
the "PARANOID" preprocessor macro defined in arch/x86/math-emu/Makefile,
and we run into a build warning:

  arch/x86/math-emu/reg_compare.c: In function ‘compare_i_st_st’:
  arch/x86/math-emu/reg_compare.c:254:6: error: ‘f’ may be used uninitialized in this function [-Werror=maybe-uninitialized]

This fixes the implementation to work correctly even without the PARANOID
flag, and also fixes the Makefile to not use the EXTRA_CFLAGS variable
but instead use the ccflags-y variable in the Makefile that is meant
for this purpose.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Bill Metzenthen <billm@melbpc.org.au>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170719125310.2487451-3-arnd@arndb.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/math-emu/Makefile b/arch/x86/math-emu/Makefile
index 9b0c63b..1b2dac1 100644 (file)
--- a/arch/x86/math-emu/Makefile
+++ b/arch/x86/math-emu/Makefile
@@ -5,8 +5,8 @@
 #DEBUG = -DDEBUGGING
 DEBUG  =
 PARANOID = -DPARANOID
-EXTRA_CFLAGS   := $(PARANOID) $(DEBUG) -fno-builtin $(MATH_EMULATION)
-EXTRA_AFLAGS   := $(PARANOID)
+ccflags-y += $(PARANOID) $(DEBUG) -fno-builtin $(MATH_EMULATION)
+asflags-y += $(PARANOID)
 
 # From 'C' language sources:
 C_OBJS =fpu_entry.o errors.o \

diff --git a/arch/x86/math-emu/reg_compare.c b/arch/x86/math-emu/reg_compare.c
index b77360f..19b33b5 100644 (file)
--- a/arch/x86/math-emu/reg_compare.c
+++ b/arch/x86/math-emu/reg_compare.c
@@ -168,7 +168,7 @@ static int compare(FPU_REG const *b, int tagb)
 /* This function requires that st(0) is not empty */
 int FPU_compare_st_data(FPU_REG const *loaded_data, u_char loaded_tag)
 {
-       int f = 0, c;
+       int f, c;
 
        c = compare(loaded_data, loaded_tag);
 
@@ -189,12 +189,12 @@ int FPU_compare_st_data(FPU_REG const *loaded_data, u_char loaded_tag)
                case COMP_No_Comp:
                        f = SW_C3 | SW_C2 | SW_C0;
                        break;
-#ifdef PARANOID
                default:
+#ifdef PARANOID
                        EXCEPTION(EX_INTERNAL | 0x121);
+#endif /* PARANOID */
                        f = SW_C3 | SW_C2 | SW_C0;
                        break;
-#endif /* PARANOID */
                }
        setcc(f);
        if (c & COMP_Denormal) {
@@ -205,7 +205,7 @@ int FPU_compare_st_data(FPU_REG const *loaded_data, u_char loaded_tag)
 
 static int compare_st_st(int nr)
 {
-       int f = 0, c;
+       int f, c;
        FPU_REG *st_ptr;
 
        if (!NOT_EMPTY(0) || !NOT_EMPTY(nr)) {
@@ -235,12 +235,12 @@ static int compare_st_st(int nr)
                case COMP_No_Comp:
                        f = SW_C3 | SW_C2 | SW_C0;
                        break;
-#ifdef PARANOID
                default:
+#ifdef PARANOID
                        EXCEPTION(EX_INTERNAL | 0x122);
+#endif /* PARANOID */
                        f = SW_C3 | SW_C2 | SW_C0;
                        break;
-#endif /* PARANOID */
                }
        setcc(f);
        if (c & COMP_Denormal) {
@@ -283,12 +283,12 @@ static int compare_i_st_st(int nr)
        case COMP_No_Comp:
                f = X86_EFLAGS_ZF | X86_EFLAGS_PF | X86_EFLAGS_CF;
                break;
-#ifdef PARANOID
        default:
+#ifdef PARANOID
                EXCEPTION(EX_INTERNAL | 0x122);
+#endif /* PARANOID */
                f = 0;
                break;
-#endif /* PARANOID */
        }
        FPU_EFLAGS = (FPU_EFLAGS & ~(X86_EFLAGS_ZF | X86_EFLAGS_PF | X86_EFLAGS_CF)) | f;
        if (c & COMP_Denormal) {