#if __GNUC__ >= 4
extern void warn_pre_alternatives(void);
+extern bool __static_cpu_has_safe(u16 bit);
/*
* Static testing of CPU features. Used the same as boot_cpu_has().
__static_cpu_has(bit) : \
boot_cpu_has(bit) \
)
+
+static __always_inline __pure bool _static_cpu_has_safe(u16 bit)
+{
+#if __GNUC__ > 4 || __GNUC_MINOR__ >= 5
+/*
+ * We need to spell the jumps to the compiler because, depending on the offset,
+ * the replacement jump can be bigger than the original jump, and this we cannot
+ * have. Thus, we force the jump to the widest, 4-byte, signed relative
+ * offset even though the last would often fit in less bytes.
+ */
+ asm goto("1: .byte 0xe9\n .long %l[t_dynamic] - 2f\n"
+ "2:\n"
+ ".section .altinstructions,\"a\"\n"
+ " .long 1b - .\n" /* src offset */
+ " .long 3f - .\n" /* repl offset */
+ " .word %P1\n" /* always replace */
+ " .byte 2b - 1b\n" /* src len */
+ " .byte 4f - 3f\n" /* repl len */
+ ".previous\n"
+ ".section .altinstr_replacement,\"ax\"\n"
+ "3: .byte 0xe9\n .long %l[t_no] - 2b\n"
+ "4:\n"
+ ".previous\n"
+ ".section .altinstructions,\"a\"\n"
+ " .long 1b - .\n" /* src offset */
+ " .long 0\n" /* no replacement */
+ " .word %P0\n" /* feature bit */
+ " .byte 2b - 1b\n" /* src len */
+ " .byte 0\n" /* repl len */
+ ".previous\n"
+ : : "i" (bit), "i" (X86_FEATURE_ALWAYS)
+ : : t_dynamic, t_no);
+ return true;
+ t_no:
+ return false;
+ t_dynamic:
+ return __static_cpu_has_safe(bit);
+#else /* GCC_VERSION >= 40500 */
+ u8 flag;
+ /* Open-coded due to __stringify() in ALTERNATIVE() */
+ asm volatile("1: movb $2,%0\n"
+ "2:\n"
+ ".section .altinstructions,\"a\"\n"
+ " .long 1b - .\n" /* src offset */
+ " .long 3f - .\n" /* repl offset */
+ " .word %P2\n" /* always replace */
+ " .byte 2b - 1b\n" /* source len */
+ " .byte 4f - 3f\n" /* replacement len */
+ ".previous\n"
+ ".section .discard,\"aw\",@progbits\n"
+ " .byte 0xff + (4f-3f) - (2b-1b)\n" /* size check */
+ ".previous\n"
+ ".section .altinstr_replacement,\"ax\"\n"
+ "3: movb $0,%0\n"
+ "4:\n"
+ ".previous\n"
+ ".section .altinstructions,\"a\"\n"
+ " .long 1b - .\n" /* src offset */
+ " .long 5f - .\n" /* repl offset */
+ " .word %P1\n" /* feature bit */
+ " .byte 4b - 3b\n" /* src len */
+ " .byte 6f - 5f\n" /* repl len */
+ ".previous\n"
+ ".section .discard,\"aw\",@progbits\n"
+ " .byte 0xff + (6f-5f) - (4b-3b)\n" /* size check */
+ ".previous\n"
+ ".section .altinstr_replacement,\"ax\"\n"
+ "5: movb $1,%0\n"
+ "6:\n"
+ ".previous\n"
+ : "=qm" (flag)
+ : "i" (bit), "i" (X86_FEATURE_ALWAYS));
+ return (flag == 2 ? __static_cpu_has_safe(bit) : flag);
+#endif
+}
+
+#define static_cpu_has_safe(bit) \
+( \
+ __builtin_constant_p(boot_cpu_has(bit)) ? \
+ boot_cpu_has(bit) : \
+ _static_cpu_has_safe(bit) \
+)
#else
/*
* gcc 3.x is too stupid to do the static test; fall back to dynamic.
*/
-#define static_cpu_has(bit) boot_cpu_has(bit)
+#define static_cpu_has(bit) boot_cpu_has(bit)
+#define static_cpu_has_safe(bit) boot_cpu_has(bit)
#endif
#define cpu_has_bug(c, bit) cpu_has(c, (bit))