riscv: Extend patch_text for multiple instructions

Extend patch_text for multiple instructions. This is the preparaiton for
multiple instructions text patching in riscv BPF trampoline, and may be
useful for other scenario.

Signed-off-by: Pu Lehui <pulehui@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Björn Töpel <bjorn@rivosinc.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/bpf/20230215135205.1411105-2-pulehui@huaweicloud.com

Author: Pu Lehui

arch/riscv/include/asm/patch.h

@@ -7,6 +7,6 @@
 #define _ASM_RISCV_PATCH_H
 
 int patch_text_nosync(void *addr, const void *insns, size_t len);
-int patch_text(void *addr, u32 insn);
+int patch_text(void *addr, u32 *insns, int ninsns);
 
 #endif /* _ASM_RISCV_PATCH_H */

arch/riscv/kernel/patch.c

@@ -15,7 +15,8 @@
 
 struct patch_insn {
 	void *addr;
-	u32 insn;
+	u32 *insns;
+	int ninsns;
 	atomic_t cpu_count;
 };
 
@@ -102,12 +103,15 @@ NOKPROBE_SYMBOL(patch_text_nosync);
 static int patch_text_cb(void *data)
 {
 	struct patch_insn *patch = data;
-	int ret = 0;
+	unsigned long len;
+	int i, ret = 0;
 
 	if (atomic_inc_return(&patch->cpu_count) == num_online_cpus()) {
-		ret =
-		    patch_text_nosync(patch->addr, &patch->insn,
-					    GET_INSN_LENGTH(patch->insn));
+		for (i = 0; ret == 0 && i < patch->ninsns; i++) {
+			len = GET_INSN_LENGTH(patch->insns[i]);
+			ret = patch_text_nosync(patch->addr + i * len,
+						&patch->insns[i], len);
+		}
 		atomic_inc(&patch->cpu_count);
 	} else {
 		while (atomic_read(&patch->cpu_count) <= num_online_cpus())
@@ -119,11 +123,12 @@ static int patch_text_cb(void *data)
 }
 NOKPROBE_SYMBOL(patch_text_cb);
 
-int patch_text(void *addr, u32 insn)
+int patch_text(void *addr, u32 *insns, int ninsns)
 {
 	struct patch_insn patch = {
 		.addr = addr,
-		.insn = insn,
+		.insns = insns,
+		.ninsns = ninsns,
 		.cpu_count = ATOMIC_INIT(0),
 	};
 

arch/riscv/kernel/probes/kprobes.c

@@ -23,13 +23,14 @@ post_kprobe_handler(struct kprobe *, struct kprobe_ctlblk *, struct pt_regs *);
 
 static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
 {
+	u32 insn = __BUG_INSN_32;
 	unsigned long offset = GET_INSN_LENGTH(p->opcode);
 
 	p->ainsn.api.restore = (unsigned long)p->addr + offset;
 
-	patch_text(p->ainsn.api.insn, p->opcode);
+	patch_text(p->ainsn.api.insn, &p->opcode, 1);
 	patch_text((void *)((unsigned long)(p->ainsn.api.insn) + offset),
-		   __BUG_INSN_32);
+		   &insn, 1);
 }
 
 static void __kprobes arch_prepare_simulate(struct kprobe *p)
@@ -114,16 +115,16 @@ void *alloc_insn_page(void)
 /* install breakpoint in text */
 void __kprobes arch_arm_kprobe(struct kprobe *p)
 {
-	if ((p->opcode & __INSN_LENGTH_MASK) == __INSN_LENGTH_32)
-		patch_text(p->addr, __BUG_INSN_32);
-	else
-		patch_text(p->addr, __BUG_INSN_16);
+	u32 insn = (p->opcode & __INSN_LENGTH_MASK) == __INSN_LENGTH_32 ?
+		   __BUG_INSN_32 : __BUG_INSN_16;
+
+	patch_text(p->addr, &insn, 1);
 }
 
 /* remove breakpoint from text */
 void __kprobes arch_disarm_kprobe(struct kprobe *p)
 {
-	patch_text(p->addr, p->opcode);
+	patch_text(p->addr, &p->opcode, 1);
 }
 
 void __kprobes arch_remove_kprobe(struct kprobe *p)