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authorAndre Przywara <andre.przywara@arm.com>2014-11-14 15:54:08 +0000
committerWill Deacon <will.deacon@arm.com>2014-11-25 13:46:36 +0000
commite039ee4ee3fcf174736f2cb0a2eed6cb908348a6 (patch)
tree65cb1ee1f7ad18726189954a4fd4d0f64420838a /arch/arm64/include
parent930da09f5e50dd22fb0a8600388da8677d62d671 (diff)
downloadlinux-e039ee4ee3fcf174736f2cb0a2eed6cb908348a6.tar.gz
arm64: add alternative runtime patching
With a blatant copy of some x86 bits we introduce the alternative runtime patching "framework" to arm64. This is quite basic for now and we only provide the functions we need at this time. This is connected to the newly introduced feature bits. Signed-off-by: Andre Przywara <andre.przywara@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/include')
-rw-r--r--arch/arm64/include/asm/alternative-asm.h16
-rw-r--r--arch/arm64/include/asm/alternative.h43
2 files changed, 59 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/alternative-asm.h b/arch/arm64/include/asm/alternative-asm.h
new file mode 100644
index 000000000000..5ee9340459b8
--- /dev/null
+++ b/arch/arm64/include/asm/alternative-asm.h
@@ -0,0 +1,16 @@
+#ifndef __ASM_ALTERNATIVE_ASM_H
+#define __ASM_ALTERNATIVE_ASM_H
+
+#ifdef __ASSEMBLY__
+
+.macro altinstruction_entry orig_offset alt_offset feature orig_len alt_len
+ .word \orig_offset - .
+ .word \alt_offset - .
+ .hword \feature
+ .byte \orig_len
+ .byte \alt_len
+.endm
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* __ASM_ALTERNATIVE_ASM_H */
diff --git a/arch/arm64/include/asm/alternative.h b/arch/arm64/include/asm/alternative.h
new file mode 100644
index 000000000000..f6d206e7f9e9
--- /dev/null
+++ b/arch/arm64/include/asm/alternative.h
@@ -0,0 +1,43 @@
+#ifndef __ASM_ALTERNATIVE_H
+#define __ASM_ALTERNATIVE_H
+
+#include <linux/types.h>
+#include <linux/stddef.h>
+#include <linux/stringify.h>
+
+struct alt_instr {
+ s32 orig_offset; /* offset to original instruction */
+ s32 alt_offset; /* offset to replacement instruction */
+ u16 cpufeature; /* cpufeature bit set for replacement */
+ u8 orig_len; /* size of original instruction(s) */
+ u8 alt_len; /* size of new instruction(s), <= orig_len */
+};
+
+void apply_alternatives(void);
+void free_alternatives_memory(void);
+
+#define ALTINSTR_ENTRY(feature) \
+ " .word 661b - .\n" /* label */ \
+ " .word 663f - .\n" /* new instruction */ \
+ " .hword " __stringify(feature) "\n" /* feature bit */ \
+ " .byte 662b-661b\n" /* source len */ \
+ " .byte 664f-663f\n" /* replacement len */
+
+/* alternative assembly primitive: */
+#define ALTERNATIVE(oldinstr, newinstr, feature) \
+ "661:\n\t" \
+ oldinstr "\n" \
+ "662:\n" \
+ ".pushsection .altinstructions,\"a\"\n" \
+ ALTINSTR_ENTRY(feature) \
+ ".popsection\n" \
+ ".pushsection .altinstr_replacement, \"a\"\n" \
+ "663:\n\t" \
+ newinstr "\n" \
+ "664:\n\t" \
+ ".popsection\n\t" \
+ ".if ((664b-663b) != (662b-661b))\n\t" \
+ " .error \"Alternatives instruction length mismatch\"\n\t"\
+ ".endif\n"
+
+#endif /* __ASM_ALTERNATIVE_H */