powerpc/bpf: implement bpf_arch_text_copy

bpf_arch_text_copy is used to dump JITed binary to RX page, allowing
multiple BPF programs to share the same page. Use the newly introduced
patch_instructions() to implement it.

Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231020141358.643575-3-hbathini@linux.ibm.com

Author: hbathini

arch/powerpc/net/bpf_jit_comp.c

@@ -13,9 +13,13 @@
 #include <linux/netdevice.h>
 #include <linux/filter.h>
 #include <linux/if_vlan.h>
-#include <asm/kprobes.h>
+#include <linux/kernel.h>
+#include <linux/memory.h>
 #include <linux/bpf.h>
 
+#include <asm/kprobes.h>
+#include <asm/code-patching.h>
+
 #include "bpf_jit.h"
 
 static void bpf_jit_fill_ill_insns(void *area, unsigned int size)
@@ -274,3 +278,17 @@ int bpf_add_extable_entry(struct bpf_prog *fp, u32 *image, int pass, struct code
 	ctx->exentry_idx++;
 	return 0;
 }
+
+void *bpf_arch_text_copy(void *dst, void *src, size_t len)
+{
+	int err;
+
+	if (WARN_ON_ONCE(core_kernel_text((unsigned long)dst)))
+		return ERR_PTR(-EINVAL);
+
+	mutex_lock(&text_mutex);
+	err = patch_instructions(dst, src, len, false);
+	mutex_unlock(&text_mutex);
+
+	return err ? ERR_PTR(err) : dst;
+}