4 MK_FORMAT_EXTENSIONS?=no
7 # Warning flags for compiling the kernel and components of the kernel:
9 CWARNFLAGS?= -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes \
10 -Wmissing-prototypes -Wpointer-arith -Winline -Wcast-qual \
11 -Wundef -Wno-pointer-sign ${FORMAT_EXTENSIONS} \
12 -Wmissing-include-dirs -fdiagnostics-show-option \
15 # The following flags are next up for working on:
18 # Disable a few warnings for clang, since there are several places in the
19 # kernel where fixing them is more trouble than it is worth, or where there is
21 .if ${COMPILER_TYPE} == "clang"
22 NO_WCONSTANT_CONVERSION= -Wno-constant-conversion
23 NO_WARRAY_BOUNDS= -Wno-array-bounds
24 NO_WSHIFT_COUNT_NEGATIVE= -Wno-shift-count-negative
25 NO_WSHIFT_COUNT_OVERFLOW= -Wno-shift-count-overflow
26 NO_WUNUSED_VALUE= -Wno-unused-value
27 NO_WSELF_ASSIGN= -Wno-self-assign
28 NO_WFORMAT_SECURITY= -Wno-format-security
29 NO_WUNNEEDED_INTERNAL_DECL= -Wno-unneeded-internal-declaration
30 NO_WSOMETIMES_UNINITIALIZED= -Wno-error-sometimes-uninitialized
31 # Several other warnings which might be useful in some cases, but not severe
32 # enough to error out the whole kernel build. Display them anyway, so there is
33 # some incentive to fix them eventually.
34 CWARNEXTRA?= -Wno-error-tautological-compare -Wno-error-empty-body \
35 -Wno-error-parentheses-equality -Wno-unused-function \
39 # External compilers may not support our format extensions. Allow them
40 # to be disabled. WARNING: format checking is disabled in this case.
41 .if ${MK_FORMAT_EXTENSIONS} == "no"
42 NO_WFORMAT= -Wno-format
44 FORMAT_EXTENSIONS= -fformat-extensions
48 # On i386, do not align the stack to 16-byte boundaries. Otherwise GCC 2.95
49 # and above adds code to the entry and exit point of every function to align the
50 # stack to 16-byte boundaries -- thus wasting approximately 12 bytes of stack
51 # per function call. While the 16-byte alignment may benefit micro benchmarks,
52 # it is probably an overall loss as it makes the code bigger (less efficient
53 # use of code cache tag lines) and uses more stack (less efficient use of data
54 # cache tag lines). Explicitly prohibit the use of FPU, SSE and other SIMD
55 # operations inside the kernel itself. These operations are exclusively
56 # reserved for user applications.
59 # Setting -mno-mmx implies -mno-3dnow
60 # Setting -mno-sse implies -mno-sse2, -mno-sse3 and -mno-ssse3
63 # Setting -mno-mmx implies -mno-3dnow and -mno-3dnowa
64 # Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42
66 .if ${MACHINE_CPUARCH} == "i386"
67 .if ${COMPILER_TYPE} != "clang"
68 CFLAGS+= -mno-align-long-strings -mpreferred-stack-boundary=2
70 CFLAGS+= -mno-aes -mno-avx
72 CFLAGS+= -mno-mmx -mno-sse -msoft-float
76 .if ${MACHINE_CPUARCH} == "arm"
81 # For IA-64, we use r13 for the kernel globals pointer and we only use
82 # a very small subset of float registers for integer divides.
84 .if ${MACHINE_CPUARCH} == "ia64"
85 CFLAGS+= -ffixed-r13 -mfixed-range=f32-f127 -fpic #-mno-sdata
90 # For sparc64 we want the medany code model so modules may be located
91 # anywhere in the 64-bit address space. We also tell GCC to use floating
92 # point emulation. This avoids using floating point registers for integer
93 # operations which it has a tendency to do.
95 .if ${MACHINE_CPUARCH} == "sparc64"
96 CFLAGS+= -mcmodel=medany -msoft-float
101 # For AMD64, we explicitly prohibit the use of FPU, SSE and other SIMD
102 # operations inside the kernel itself. These operations are exclusively
103 # reserved for user applications.
106 # Setting -mno-mmx implies -mno-3dnow
107 # Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3 and -mfpmath=387
110 # Setting -mno-mmx implies -mno-3dnow and -mno-3dnowa
111 # Setting -mno-sse implies -mno-sse2, -mno-sse3, -mno-ssse3, -mno-sse41 and -mno-sse42
112 # (-mfpmath= is not supported)
114 .if ${MACHINE_CPUARCH} == "amd64"
115 .if ${COMPILER_TYPE} == "clang"
116 CFLAGS+= -mno-aes -mno-avx
118 CFLAGS+= -mcmodel=kernel -mno-red-zone -mno-mmx -mno-sse -msoft-float \
119 -fno-asynchronous-unwind-tables
124 # For PowerPC we tell gcc to use floating point emulation. This avoids using
125 # floating point registers for integer operations which it has a tendency to do.
126 # Also explicitly disable Altivec instructions inside the kernel.
128 .if ${MACHINE_CPUARCH} == "powerpc"
129 CFLAGS+= -msoft-float -mno-altivec
134 # Use dot symbols on powerpc64 to make ddb happy
136 .if ${MACHINE_ARCH} == "powerpc64"
137 CFLAGS+= -mcall-aixdesc
141 # For MIPS we also tell gcc to use floating point emulation
143 .if ${MACHINE_CPUARCH} == "mips"
144 CFLAGS+= -msoft-float
149 # GCC 3.0 and above like to do certain optimizations based on the
150 # assumption that the program is linked against libc. Stop this.
152 CFLAGS+= -ffreestanding
157 .if ${MK_SSP} != "no" && ${MACHINE_CPUARCH} != "ia64" && \
158 ${MACHINE_CPUARCH} != "arm" && ${MACHINE_CPUARCH} != "mips"
159 CFLAGS+= -fstack-protector