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

Arnd Bergmann
2016-10-17T22:20:13Z

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@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.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