From: Joerg Roedel <[email protected]>
This patch extends the alternative instruction framework to support an
arbitrary number of alternatives on the i386 architecture.
Signed-off-by: Joerg Roedel <[email protected]>
--
Joerg Roedel
Operating System Research Center
AMD Saxony LLC & Co. KG
diff --git a/arch/i386/kernel/alternative.c b/arch/i386/kernel/alternative.c
index 9eca21b..2dedf4b 100644
--- a/arch/i386/kernel/alternative.c
+++ b/arch/i386/kernel/alternative.c
@@ -149,19 +149,38 @@ extern u8 __smp_alt_begin[], __smp_alt_end[];
self modifying code. This implies that assymetric systems where
APs have less capabilities than the boot processor are not handled.
Tough. Make sure you disable such features by hand. */
-
void apply_alternatives(struct alt_instr *start, struct alt_instr *end)
{
struct alt_instr *a;
- u8 *instr;
+ u8 *instr = NULL, *new_instr = NULL;
+ u8 instr_len = 0, new_instr_len = 0;
int diff;
DPRINTK("%s: alt table %p -> %p\n", __FUNCTION__, start, end);
for (a = start; a < end; a++) {
- BUG_ON(a->replacementlen > a->instrlen);
- if (!boot_cpu_has(a->cpuid))
+
+ if (a->used == 0) {
+ instr = a->instr;
+ instr_len = a->instrlen;
+ new_instr =
+ boot_cpu_has(a->cpuid) ? a->replacement : NULL;
+ new_instr_len =
+ boot_cpu_has(a->cpuid) ? a->replacementlen : 0;
+ } else if (a->used >= 1 && boot_cpu_has(a->instr_cpuid)) {
+ BUG_ON(instr == NULL);
+ new_instr = a->instr;
+ new_instr_len = a->instrlen;
+ } else if (a->used == 2 && boot_cpu_has(a->cpuid)) {
+ BUG_ON(instr == NULL);
+ new_instr = a->replacement;
+ new_instr_len = a->replacementlen;
+ }
+
+ if (instr == NULL || new_instr == NULL)
continue;
- instr = a->instr;
+
+ BUG_ON(new_instr_len > instr_len);
+
#ifdef CONFIG_X86_64
/* vsyscall code is not mapped yet. resolve it manually. */
if (instr >= (u8 *)VSYSCALL_START && instr < (u8*)VSYSCALL_END) {
@@ -170,9 +189,10 @@ void apply_alternatives(struct alt_instr *start, struct alt_instr *end)
__FUNCTION__, a->instr, instr);
}
#endif
- memcpy(instr, a->replacement, a->replacementlen);
- diff = a->instrlen - a->replacementlen;
- nop_out(instr + a->replacementlen, diff);
+ memcpy(instr, new_instr, new_instr_len);
+ diff = instr_len - new_instr_len;
+ nop_out(instr + new_instr_len, diff);
+ instr = new_instr = NULL;
}
}
diff --git a/include/asm-i386/alternative.h b/include/asm-i386/alternative.h
index b8fa955..b899e61 100644
--- a/include/asm-i386/alternative.h
+++ b/include/asm-i386/alternative.h
@@ -7,14 +7,31 @@
#include <linux/stddef.h>
#include <linux/types.h>
+/* struct alt_instr - define replacement sequences
+ *
+ * this struct is used in 2 ways:
+ * - as the first entry for a replace sequence (used == 0)
+ * In this case *instr points to the original instruction and
+ * instr_cpuid is ignored
+ * - as a following entry in a replace sequence (used == [1|2])
+ * In this case *instr is used as a replacement pointer too
+ * (supporting up to two replacements per struct) and
+ * instr_cpuid is its cpuid value
+ *
+ * The first matching replacement in a sequence is used
+ */
struct alt_instr {
u8 *instr; /* original instruction */
u8 *replacement;
+ u8 used; /* count the number of replacements in
+ this struct (only for succeeding entries) */
+ u8 instr_cpuid; /* cpuid bit set if instr is used
+ as replacement */
u8 cpuid; /* cpuid bit set for replacement */
u8 instrlen; /* length of original instruction */
u8 replacementlen; /* length of new instruction, <= instrlen */
- u8 pad;
-};
+ u8 pad[3];
+} __attribute__ ((packed));
extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
@@ -36,6 +53,12 @@ static inline void alternatives_smp_switch(int smp) {}
#endif
/*
+ * Use or extend the following macros if you need more than one
+ * output argument in the alternative_io() macro
+ */
+#define ALTERNATIVE_OUTPUT2(a,b) a,b
+
+/*
* Alternative instructions for different CPU types or capabilities.
*
* This allows to use optimized instructions even on generic binary
@@ -53,6 +76,8 @@ static inline void alternatives_smp_switch(int smp) {}
" .align 4\n" \
" .long 661b\n" /* label */ \
" .long 663f\n" /* new instruction */ \
+ " .byte 0x00\n" /* used count */ \
+ " .byte 0x00\n" /* instr_cpuid */ \
" .byte %c0\n" /* feature bit */ \
" .byte 662b-661b\n" /* sourcelen */ \
" .byte 664f-663f\n" /* replacementlen */ \
@@ -77,6 +102,8 @@ static inline void alternatives_smp_switch(int smp) {}
" .align 4\n" \
" .long 661b\n" /* label */ \
" .long 663f\n" /* new instruction */ \
+ " .byte 0x00\n" /* used count */ \
+ " .byte 0x00\n" /* instr_cpuid */ \
" .byte %c0\n" /* feature bit */ \
" .byte 662b-661b\n" /* sourcelen */ \
" .byte 664f-663f\n" /* replacementlen */ \
@@ -85,6 +112,62 @@ static inline void alternatives_smp_switch(int smp) {}
"663:\n\t" newinstr "\n664:\n" /* replacement */\
".previous" :: "i" (feature), ##input)
+/* Like alternative_input, but with a single output argument */
+#define alternative_io(oldinstr, newinstr, feature, output, input...) \
+ asm volatile ("661:\n\t" oldinstr "\n662:\n" \
+ ".section .altinstructions,\"a\"\n" \
+ " .align 4\n" \
+ " .long 661b\n" /* label */ \
+ " .long 663f\n" /* new instruction */ \
+ " .byte 0x00\n" /* first entry */ \
+ " .byte 0x00\n" /* zero for first entry */ \
+ " .byte %c[feat]\n" /* feature bit */ \
+ " .byte 662b-661b\n" /* sourcelen */ \
+ " .byte 664f-663f\n" /* replacementlen */ \
+ ".previous\n" \
+ ".section .altinstr_replacement,\"ax\"\n" \
+ "663:\n\t" newinstr "\n664:\n" /* replacement */ \
+ ".previous" : output : [feat] "i" (feature), ##input)
+
+/*
+ * additional alternatives
+ *
+ * In the case where more than one alternative for an instruction exist,
+ * the two following macros could be used. They must appear immediately
+ * after the use alternative_io, alternative_input or alternative macros.
+ */
+
+#define alternative_add_one(newinstr2, feature2) \
+ asm volatile(".section .altinstructions,\"a\"\n" \
+ " .align 4\n" \
+ " .long 661f\n" \
+ " .long 0x00\n" \
+ " .byte 0x01\n" \
+ " .byte %c[feat2]\n" \
+ " .byte 0x00\n" \
+ " .byte 662f-661f\n" \
+ " .byte 0x00\n" \
+ ".previous\n" \
+ ".section .altinstr_replacement,\"ax\"\n" \
+ "661:\n\t" newinstr2 "\n662:\n" \
+ ".previous" : : [feat2] "i" (feature2) )
+
+#define alternative_add_two(newinstr2, feature2, newinstr3, feature3) \
+ asm volatile(".section .altinstructions,\"a\"\n" \
+ " .align 4\n" \
+ " .long 661f\n" \
+ " .long 663f\n" \
+ " .byte 0x02\n" \
+ " .byte %c[feat2]\n" \
+ " .byte %c[feat3]\n" \
+ " .byte 662f-661f\n" \
+ " .byte 664f-663f\n" \
+ ".previous\n" \
+ ".section .altinstr_replacement,\"ax\"\n" \
+ "661:\n\t" newinstr2 "\n662:\n" \
+ "663:\n\t" newinstr3 "\n664:\n" \
+ ".previous" : : [feat2] "i" (feature2), [feat3] "i" (feature3))
+
/*
* Alternative inline assembly for SMP.
*
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