linux-kernel - [PATCH 24/28] x86: math-emu: possible uninitialized variable use

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Date:   Tue, 18 Oct 2016 00:16:12 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     x86@...nel.org
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        Bill Metzenthen <billm@...bpc.org.au>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH 24/28] x86: math-emu: 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.

Cc: x86@...nel.org
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 arch/x86/math-emu/Makefile      |  4 ++--
 arch/x86/math-emu/reg_compare.c | 16 ++++++++--------
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/arch/x86/math-emu/Makefile b/arch/x86/math-emu/Makefile
index 9b0c63b..1b2dac1 100644
--- 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..19b33b50 100644
--- 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) {
-- 
2.9.0