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Date: Fri, 18 Oct 2013 23:19:56 +0800
From: Jiang Liu <liuj97@...il.com>
To: Steven Rostedt <rostedt@...dmis.org>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will.deacon@....com>,
Sandeepa Prabhu <sandeepa.prabhu@...aro.org>,
Jiang Liu <jiang.liu@...wei.com>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc: Jiang Liu <liuj97@...il.com>
Subject: [PATCH v5 2/7] arm64: introduce interfaces to hotpatch kernel and module code
From: Jiang Liu <jiang.liu@...wei.com>
Introduce three interfaces to patch kernel and module code:
aarch64_insn_patch_text_nosync():
patch code without synchronization, it's caller's responsibility
to synchronize all CPUs if needed.
aarch64_insn_patch_text_sync():
patch code and always synchronize with stop_machine()
aarch64_insn_patch_text():
patch code and synchronize with stop_machine() if needed
Signed-off-by: Jiang Liu <jiang.liu@...wei.com>
Cc: Jiang Liu <liuj97@...il.com>
---
arch/arm64/include/asm/insn.h | 19 ++++++++-
arch/arm64/kernel/insn.c | 91 +++++++++++++++++++++++++++++++++++++++++++
2 files changed, 109 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/insn.h b/arch/arm64/include/asm/insn.h
index 7499490..7a69491 100644
--- a/arch/arm64/include/asm/insn.h
+++ b/arch/arm64/include/asm/insn.h
@@ -71,8 +71,25 @@ enum aarch64_insn_hint_op {
bool aarch64_insn_is_nop(u32 insn);
-enum aarch64_insn_encoding_class aarch64_get_insn_class(u32 insn);
+/*
+ * In ARMv8-A, A64 instructions have a fixed length of 32 bits and are always
+ * little-endian.
+ */
+static __always_inline u32 aarch64_insn_read(void *addr)
+{
+ return le32_to_cpu(*(u32 *)addr);
+}
+static __always_inline void aarch64_insn_write(void *addr, u32 insn)
+{
+ *(u32 *)addr = cpu_to_le32(insn);
+}
+
+enum aarch64_insn_encoding_class aarch64_get_insn_class(u32 insn);
bool aarch64_insn_hotpatch_safe(u32 old_insn, u32 new_insn);
+int aarch64_insn_patch_text_nosync(void *addr, u32 insn);
+int aarch64_insn_patch_text_sync(void *addrs[], u32 insns[], int cnt);
+int aarch64_insn_patch_text(void *addrs[], u32 insns[], int cnt);
+
#endif /* __ASM_INSN_H */
diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
index f5b779f..3879db4 100644
--- a/arch/arm64/kernel/insn.c
+++ b/arch/arm64/kernel/insn.c
@@ -16,6 +16,9 @@
*/
#include <linux/compiler.h>
#include <linux/kernel.h>
+#include <linux/smp.h>
+#include <linux/stop_machine.h>
+#include <asm/cacheflush.h>
#include <asm/insn.h>
static int aarch64_insn_encoding_class[] = {
@@ -88,3 +91,91 @@ bool __kprobes aarch64_insn_hotpatch_safe(u32 old_insn, u32 new_insn)
return __aarch64_insn_hotpatch_safe(old_insn) &&
__aarch64_insn_hotpatch_safe(new_insn);
}
+
+int __kprobes aarch64_insn_patch_text_nosync(void *addr, u32 insn)
+{
+ u32 *tp = addr;
+
+ /* A64 instructions must be word aligned */
+ if ((uintptr_t)tp & 0x3)
+ return -EINVAL;
+
+ aarch64_insn_write(tp, insn);
+ flush_icache_range((uintptr_t)tp, (uintptr_t)tp + sizeof(u32));
+
+ return 0;
+}
+
+struct aarch64_insn_patch {
+ void **text_addrs;
+ u32 *new_insns;
+ int insn_cnt;
+};
+
+static DEFINE_MUTEX(text_patch_lock);
+static atomic_t text_patch_id;
+
+static int __kprobes aarch64_insn_patch_text_cb(void *arg)
+{
+ int i, ret = 0;
+ struct aarch64_insn_patch *pp = arg;
+
+ if (atomic_read(&text_patch_id) == smp_processor_id()) {
+ for (i = 0; ret == 0 && i < pp->insn_cnt; i++)
+ ret = aarch64_insn_patch_text_nosync(pp->text_addrs[i],
+ pp->new_insns[i]);
+ /* Let other CPU continue */
+ atomic_set(&text_patch_id, -1);
+ } else {
+ while (atomic_read(&text_patch_id) != -1)
+ cpu_relax();
+ isb();
+ }
+
+ return ret;
+}
+
+int __kprobes aarch64_insn_patch_text_sync(void *addrs[], u32 insns[], int cnt)
+{
+ int ret;
+ struct aarch64_insn_patch patch = {
+ .text_addrs = addrs,
+ .new_insns = insns,
+ .insn_cnt = cnt,
+ };
+
+ if (cnt <= 0)
+ return -EINVAL;
+
+ mutex_lock(&text_patch_lock);
+ atomic_set(&text_patch_id, smp_processor_id());
+ ret = stop_machine(aarch64_insn_patch_text_cb, &patch, cpu_online_mask);
+ mutex_unlock(&text_patch_lock);
+
+ return ret;
+}
+
+int __kprobes aarch64_insn_patch_text(void *addrs[], u32 insns[], int cnt)
+{
+ int ret;
+ bool safe = false;
+
+ if (cnt == 1)
+ safe = aarch64_insn_hotpatch_safe(aarch64_insn_read(addrs[0]),
+ insns[0]);
+
+ if (safe) {
+ /*
+ * ARMv8 architecture doesn't guarantee all CPUs see the new
+ * instruction after returning from function
+ * aarch64_insn_patch_text_nosync(). So send a IPI to all other
+ * CPUs to achieve instruction synchronization.
+ */
+ ret = aarch64_insn_patch_text_nosync(addrs[0], insns[0]);
+ kick_all_cpus_sync();
+ } else {
+ ret = aarch64_insn_patch_text_sync(addrs, insns, cnt);
+ }
+
+ return ret;
+}
--
1.8.1.2
--
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