Impelment bpf_arch_text_poke() for arm64, so bpf trampoline code can use
it to replace nop with jump, or replace jump with nop.

Signed-off-by: Xu Kuohai <redacted>
Acked-by: Song Liu <redacted>
---
 arch/arm64/net/bpf_jit_comp.c | 63 +++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)

diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 8ab4035dea27..3f9bdfec54c4 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c

@@ -9,6 +9,7 @@
 
 #include <linux/bitfield.h>
 #include <linux/bpf.h>
+#include <linux/memory.h>
 #include <linux/filter.h>
 #include <linux/printk.h>
 #include <linux/slab.h>

@@ -18,6 +19,7 @@
 #include <asm/cacheflush.h>
 #include <asm/debug-monitors.h>
 #include <asm/insn.h>
+#include <asm/patching.h>
 #include <asm/set_memory.h>
 
 #include "bpf_jit.h"

@@ -1529,3 +1531,64 @@ void bpf_jit_free_exec(void *addr)
 {
 	return vfree(addr);
 }
+
+static int gen_branch_or_nop(enum aarch64_insn_branch_type type, void *ip,
+			     void *addr, u32 *insn)
+{
+	if (!addr)
+		*insn = aarch64_insn_gen_nop();
+	else
+		*insn = aarch64_insn_gen_branch_imm((unsigned long)ip,
+						    (unsigned long)addr,
+						    type);
+
+	return *insn != AARCH64_BREAK_FAULT ? 0 : -EFAULT;
+}
+
+int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type poke_type,
+		       void *old_addr, void *new_addr)
+{
+	int ret;
+	u32 old_insn;
+	u32 new_insn;
+	u32 replaced;
+	enum aarch64_insn_branch_type branch_type;
+
+	if (!is_bpf_text_address((long)ip))
+		/* Only poking bpf text is supported. Since kernel function
+		 * entry is set up by ftrace, we reply on ftrace to poke kernel
+		 * functions. For kernel funcitons, bpf_arch_text_poke() is only
+		 * called after a failed poke with ftrace. In this case, there
+		 * is probably something wrong with fentry, so there is nothing
+		 * we can do here. See register_fentry, unregister_fentry and
+		 * modify_fentry for details.
+		 */
+		return -EINVAL;