[PATCH v4 1/5] powerpc/bpf: implement bpf_arch_text_copy

[Hari Bathini <hbathini@linux.ibm.com>]

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

Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
---
 arch/powerpc/net/bpf_jit_comp.c | 41 ++++++++++++++++++++++++++++++++-
 1 file changed, 40 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
index 37043dfc1add..4f896222c579 100644
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -13,9 +13,12 @@
 #include <linux/netdevice.h>
 #include <linux/filter.h>
 #include <linux/if_vlan.h>
-#include <asm/kprobes.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)
@@ -23,6 +26,28 @@ static void bpf_jit_fill_ill_insns(void *area, unsigned int size)
 	memset32(area, BREAKPOINT_INSTRUCTION, size / 4);
 }
 
+/*
+ * Patch 'len' bytes of instructions from opcode to addr, one instruction
+ * at a time. Returns addr on success. ERR_PTR(-EINVAL), otherwise.
+ */
+static void *bpf_patch_instructions(void *addr, void *opcode, size_t len, bool fill_insn)
+{
+	while (len > 0) {
+		ppc_inst_t insn = ppc_inst_read(opcode);
+		int ilen = ppc_inst_len(insn);
+
+		if (patch_instruction(addr, insn))
+			return ERR_PTR(-EINVAL);
+
+		len -= ilen;
+		addr = addr + ilen;
+		if (!fill_insn)
+			opcode = opcode + ilen;
+	}
+
+	return addr;
+}
+
 int bpf_jit_emit_exit_insn(u32 *image, struct codegen_context *ctx, int tmp_reg, long exit_addr)
 {
 	if (!exit_addr || is_offset_in_branch_range(exit_addr - (ctx->idx * 4))) {
@@ -274,3 +299,17 @@ 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)
+{
+	void *ret;
+
+	if (WARN_ON_ONCE(core_kernel_text((unsigned long)dst)))
+		return ERR_PTR(-EINVAL);
+
+	mutex_lock(&text_mutex);
+	ret = bpf_patch_instructions(dst, src, len, false);
+	mutex_unlock(&text_mutex);
+
+	return ret;
+}
-- 
2.41.0