4 # Warning flags for compiling the kernel and components of the kernel:
6 CWARNFLAGS?= -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes \
7 -Wmissing-prototypes -Wpointer-arith -Winline -Wcast-qual \
8 -Wundef -Wno-pointer-sign -fformat-extensions \
9 -Wmissing-include-dirs -fdiagnostics-show-option \
12 # The following flags are next up for working on:
15 # Disable a few warnings for clang, since there are several places in the
16 # kernel where fixing them is more trouble than it is worth, or where there is
18 .if ${CC:T:Mclang} == "clang"
19 NO_WCONSTANT_CONVERSION= -Wno-constant-conversion
20 NO_WARRAY_BOUNDS= -Wno-array-bounds
21 NO_WSHIFT_COUNT_NEGATIVE= -Wno-shift-count-negative
22 NO_WSHIFT_COUNT_OVERFLOW= -Wno-shift-count-overflow
23 NO_WUNUSED_VALUE= -Wno-unused-value
24 NO_WSELF_ASSIGN= -Wno-self-assign
25 # Several other warnings which might be useful in some cases, but not severe
26 # enough to error out the whole kernel build. Display them anyway, so there is
27 # some incentive to fix them eventually.
28 CWARNEXTRA?= -Wno-error-tautological-compare -Wno-error-empty-body \
29 -Wno-error-parentheses-equality
33 # On i386, do not align the stack to 16-byte boundaries. Otherwise GCC 2.95
34 # and above adds code to the entry and exit point of every function to align the
35 # stack to 16-byte boundaries -- thus wasting approximately 12 bytes of stack
36 # per function call. While the 16-byte alignment may benefit micro benchmarks,
37 # it is probably an overall loss as it makes the code bigger (less efficient
38 # use of code cache tag lines) and uses more stack (less efficient use of data
39 # cache tag lines). Explicitly prohibit the use of FPU, SSE and other SIMD
40 # operations inside the kernel itself. These operations are exclusively
41 # reserved for user applications.
44 # Setting -mno-mmx implies -mno-3dnow
45 # Setting -mno-sse implies -mno-sse2, -mno-sse3 and -mno-ssse3
48 # Setting -mno-mmx implies -mno-3dnow, -mno-3dnowa, -mno-sse, -mno-sse2,
49 # -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42
51 .if ${MACHINE_CPUARCH} == "i386"
52 .if ${CC:T:Mclang} != "clang"
53 CFLAGS+= -mno-align-long-strings -mpreferred-stack-boundary=2 -mno-sse
55 CFLAGS+= -mno-aes -mno-avx
57 CFLAGS+= -mno-mmx -msoft-float
61 .if ${MACHINE_CPUARCH} == "arm"
66 # For IA-64, we use r13 for the kernel globals pointer and we only use
67 # a very small subset of float registers for integer divides.
69 .if ${MACHINE_CPUARCH} == "ia64"
70 CFLAGS+= -ffixed-r13 -mfixed-range=f32-f127 -fpic #-mno-sdata
75 # For sparc64 we want the medany code model so modules may be located
76 # anywhere in the 64-bit address space. We also tell GCC to use floating
77 # point emulation. This avoids using floating point registers for integer
78 # operations which it has a tendency to do.
80 .if ${MACHINE_CPUARCH} == "sparc64"
81 CFLAGS+= -mcmodel=medany -msoft-float
86 # For AMD64, we explicitly prohibit the use of FPU, SSE and other SIMD
87 # operations inside the kernel itself. These operations are exclusively
88 # reserved for user applications.
91 # Setting -mno-mmx implies -mno-3dnow
92 # Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3 and -mfpmath=387
95 # Setting -mno-mmx implies -mno-3dnow, -mno-3dnowa, -mno-sse, -mno-sse2,
96 # -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42
97 # (-mfpmath= is not supported)
99 .if ${MACHINE_CPUARCH} == "amd64"
100 .if ${CC:T:Mclang} != "clang"
103 CFLAGS+= -mno-aes -mno-avx
105 CFLAGS+= -mcmodel=kernel -mno-red-zone -mno-mmx -msoft-float \
106 -fno-asynchronous-unwind-tables
111 # For PowerPC we tell gcc to use floating point emulation. This avoids using
112 # floating point registers for integer operations which it has a tendency to do.
113 # Also explicitly disable Altivec instructions inside the kernel.
115 .if ${MACHINE_CPUARCH} == "powerpc"
116 CFLAGS+= -msoft-float -mno-altivec
121 # Use dot symbols on powerpc64 to make ddb happy
123 .if ${MACHINE_ARCH} == "powerpc64"
124 CFLAGS+= -mcall-aixdesc
128 # For MIPS we also tell gcc to use floating point emulation
130 .if ${MACHINE_CPUARCH} == "mips"
131 CFLAGS+= -msoft-float
136 # GCC 3.0 and above like to do certain optimizations based on the
137 # assumption that the program is linked against libc. Stop this.
139 CFLAGS+= -ffreestanding
144 .if ${MK_SSP} != "no" && ${MACHINE_CPUARCH} != "ia64" && \
145 ${MACHINE_CPUARCH} != "arm" && ${MACHINE_CPUARCH} != "mips"
146 CFLAGS+= -fstack-protector