[RFC PATCH 2/3] powerpc/bpf: implement bpf_arch_text_invalidate for bpf_prog_pack

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

Implement bpf_arch_text_invalidate and use it to fill unused part of
the bpf_prog_pack with trap instructions when a BPF program is freed.

Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
---
 arch/powerpc/net/bpf_jit_comp.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
index 7383e0effad2..f925755cd249 100644
--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c
@@ -26,6 +26,33 @@ static void bpf_jit_fill_ill_insns(void *area, unsigned int size)
 	memset32(area, BREAKPOINT_INSTRUCTION, size / 4);
 }
 
+/*
+ * Patch 'len' bytes with trap instruction at addr, one instruction
+ * at a time. Returns addr on success. ERR_PTR(-EINVAL), otherwise.
+ */
+static void *bpf_patch_ill_insns(void *addr, size_t len)
+{
+	void *ret = ERR_PTR(-EINVAL);
+	size_t patched = 0;
+	u32 *start = addr;
+
+	if (WARN_ON_ONCE(core_kernel_text((unsigned long)addr)))
+		return ret;
+
+	mutex_lock(&text_mutex);
+	while (patched < len) {
+		if (patch_instruction(start++, ppc_inst(PPC_RAW_TRAP())))
+			goto error;
+
+		patched += 4;
+	}
+
+	ret = addr;
+error:
+	mutex_unlock(&text_mutex);
+	return ret;
+}
+
 /*
  * Patch 'len' bytes of instructions from opcode to addr, one instruction
  * at a time. Returns addr on success. ERR_PTR(-EINVAL), otherwise.
@@ -394,3 +421,8 @@ void *bpf_arch_text_copy(void *dst, void *src, size_t len)
 {
 	return bpf_patch_instructions(dst, src, len);
 }
+
+int bpf_arch_text_invalidate(void *dst, size_t len)
+{
+	return IS_ERR(bpf_patch_ill_insns(dst, len));
+}
-- 
2.37.3