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-rw-r--r--arch/arm64/include/asm/alternative.h41
-rw-r--r--arch/arm64/kernel/alternative.c43
2 files changed, 69 insertions, 15 deletions
diff --git a/arch/arm64/include/asm/alternative.h b/arch/arm64/include/asm/alternative.h
index 669028172fd6..a91933b1e2e6 100644
--- a/arch/arm64/include/asm/alternative.h
+++ b/arch/arm64/include/asm/alternative.h
@@ -5,6 +5,8 @@
#include <asm/cpucaps.h>
#include <asm/insn.h>
+#define ARM64_CB_PATCH ARM64_NCAPS
+
#ifndef __ASSEMBLY__
#include <linux/init.h>
@@ -22,12 +24,19 @@ struct alt_instr {
u8 alt_len; /* size of new instruction(s), <= orig_len */
};
+typedef void (*alternative_cb_t)(struct alt_instr *alt,
+ __le32 *origptr, __le32 *updptr, int nr_inst);
+
void __init apply_alternatives_all(void);
void apply_alternatives(void *start, size_t length);
-#define ALTINSTR_ENTRY(feature) \
+#define ALTINSTR_ENTRY(feature,cb) \
" .word 661b - .\n" /* label */ \
+ " .if " __stringify(cb) " == 0\n" \
" .word 663f - .\n" /* new instruction */ \
+ " .else\n" \
+ " .word " __stringify(cb) "- .\n" /* callback */ \
+ " .endif\n" \
" .hword " __stringify(feature) "\n" /* feature bit */ \
" .byte 662b-661b\n" /* source len */ \
" .byte 664f-663f\n" /* replacement len */
@@ -45,15 +54,18 @@ void apply_alternatives(void *start, size_t length);
* but most assemblers die if insn1 or insn2 have a .inst. This should
* be fixed in a binutils release posterior to 2.25.51.0.2 (anything
* containing commit 4e4d08cf7399b606 or c1baaddf8861).
+ *
+ * Alternatives with callbacks do not generate replacement instructions.
*/
-#define __ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg_enabled) \
+#define __ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg_enabled, cb) \
".if "__stringify(cfg_enabled)" == 1\n" \
"661:\n\t" \
oldinstr "\n" \
"662:\n" \
".pushsection .altinstructions,\"a\"\n" \
- ALTINSTR_ENTRY(feature) \
+ ALTINSTR_ENTRY(feature,cb) \
".popsection\n" \
+ " .if " __stringify(cb) " == 0\n" \
".pushsection .altinstr_replacement, \"a\"\n" \
"663:\n\t" \
newinstr "\n" \
@@ -61,11 +73,17 @@ void apply_alternatives(void *start, size_t length);
".popsection\n\t" \
".org . - (664b-663b) + (662b-661b)\n\t" \
".org . - (662b-661b) + (664b-663b)\n" \
+ ".else\n\t" \
+ "663:\n\t" \
+ "664:\n\t" \
+ ".endif\n" \
".endif\n"
#define _ALTERNATIVE_CFG(oldinstr, newinstr, feature, cfg, ...) \
- __ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg))
+ __ALTERNATIVE_CFG(oldinstr, newinstr, feature, IS_ENABLED(cfg), 0)
+#define ALTERNATIVE_CB(oldinstr, cb) \
+ __ALTERNATIVE_CFG(oldinstr, "NOT_AN_INSTRUCTION", ARM64_CB_PATCH, 1, cb)
#else
#include <asm/assembler.h>
@@ -132,6 +150,14 @@ void apply_alternatives(void *start, size_t length);
661:
.endm
+.macro alternative_cb cb
+ .set .Lasm_alt_mode, 0
+ .pushsection .altinstructions, "a"
+ altinstruction_entry 661f, \cb, ARM64_CB_PATCH, 662f-661f, 0
+ .popsection
+661:
+.endm
+
/*
* Provide the other half of the alternative code sequence.
*/
@@ -158,6 +184,13 @@ void apply_alternatives(void *start, size_t length);
.endm
/*
+ * Callback-based alternative epilogue
+ */
+.macro alternative_cb_end
+662:
+.endm
+
+/*
* Provides a trivial alternative or default sequence consisting solely
* of NOPs. The number of NOPs is chosen automatically to match the
* previous case.
diff --git a/arch/arm64/kernel/alternative.c b/arch/arm64/kernel/alternative.c
index 414288a558c8..5c4bce4ac381 100644
--- a/arch/arm64/kernel/alternative.c
+++ b/arch/arm64/kernel/alternative.c
@@ -107,32 +107,53 @@ static u32 get_alt_insn(struct alt_instr *alt, __le32 *insnptr, __le32 *altinsnp
return insn;
}
+static void patch_alternative(struct alt_instr *alt,
+ __le32 *origptr, __le32 *updptr, int nr_inst)
+{
+ __le32 *replptr;
+ int i;
+
+ replptr = ALT_REPL_PTR(alt);
+ for (i = 0; i < nr_inst; i++) {
+ u32 insn;
+
+ insn = get_alt_insn(alt, origptr + i, replptr + i);
+ updptr[i] = cpu_to_le32(insn);
+ }
+}
+
static void __apply_alternatives(void *alt_region, bool use_linear_alias)
{
struct alt_instr *alt;
struct alt_region *region = alt_region;
- __le32 *origptr, *replptr, *updptr;
+ __le32 *origptr, *updptr;
+ alternative_cb_t alt_cb;
for (alt = region->begin; alt < region->end; alt++) {
- u32 insn;
- int i, nr_inst;
+ int nr_inst;
- if (!cpus_have_cap(alt->cpufeature))
+ /* Use ARM64_CB_PATCH as an unconditional patch */
+ if (alt->cpufeature < ARM64_CB_PATCH &&
+ !cpus_have_cap(alt->cpufeature))
continue;
- BUG_ON(alt->alt_len != alt->orig_len);
+ if (alt->cpufeature == ARM64_CB_PATCH)
+ BUG_ON(alt->alt_len != 0);
+ else
+ BUG_ON(alt->alt_len != alt->orig_len);
pr_info_once("patching kernel code\n");
origptr = ALT_ORIG_PTR(alt);
- replptr = ALT_REPL_PTR(alt);
updptr = use_linear_alias ? lm_alias(origptr) : origptr;
- nr_inst = alt->alt_len / sizeof(insn);
+ nr_inst = alt->orig_len / AARCH64_INSN_SIZE;
- for (i = 0; i < nr_inst; i++) {
- insn = get_alt_insn(alt, origptr + i, replptr + i);
- updptr[i] = cpu_to_le32(insn);
- }
+ if (alt->cpufeature < ARM64_CB_PATCH)
+ alt_cb = patch_alternative;
+ else
+ alt_cb = ALT_REPL_PTR(alt);
+
+ alt_cb(alt, origptr, updptr, nr_inst);
flush_icache_range((uintptr_t)origptr,
(uintptr_t)(origptr + nr_inst));