kprobes: Convert kprobe_lookup_name() to a function

The macro is now pretty long and ugly on powerpc. In the light of further
changes needed here, convert it to a __weak variant to be over-ridden with a
nicer looking function.

Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

2 files changed, 60 insertions, 2 deletions

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index fce05a38851c..e5f518a962c6 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -42,6 +42,64 @@ DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
 
 struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
 
+kprobe_opcode_t *kprobe_lookup_name(const char *name)
+{
+	kprobe_opcode_t *addr;
+
+#ifdef PPC64_ELF_ABI_v2
+	/* PPC64 ABIv2 needs local entry point */
+	addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
+	if (addr)
+		addr = (kprobe_opcode_t *)ppc_function_entry(addr);
+#elif defined(PPC64_ELF_ABI_v1)
+	/*
+	 * 64bit powerpc ABIv1 uses function descriptors:
+	 * - Check for the dot variant of the symbol first.
+	 * - If that fails, try looking up the symbol provided.
+	 *
+	 * This ensures we always get to the actual symbol and not
+	 * the descriptor.
+	 *
+	 * Also handle <module:symbol> format.
+	 */
+	char dot_name[MODULE_NAME_LEN + 1 + KSYM_NAME_LEN];
+	const char *modsym;
+	bool dot_appended = false;
+	if ((modsym = strchr(name, ':')) != NULL) {
+		modsym++;
+		if (*modsym != '\0' && *modsym != '.') {
+			/* Convert to <module:.symbol> */
+			strncpy(dot_name, name, modsym - name);
+			dot_name[modsym - name] = '.';
+			dot_name[modsym - name + 1] = '\0';
+			strncat(dot_name, modsym,
+				sizeof(dot_name) - (modsym - name) - 2);
+			dot_appended = true;
+		} else {
+			dot_name[0] = '\0';
+			strncat(dot_name, name, sizeof(dot_name) - 1);
+		}
+	} else if (name[0] != '.') {
+		dot_name[0] = '.';
+		dot_name[1] = '\0';
+		strncat(dot_name, name, KSYM_NAME_LEN - 2);
+		dot_appended = true;
+	} else {
+		dot_name[0] = '\0';
+		strncat(dot_name, name, KSYM_NAME_LEN - 1);
+	}
+	addr = (kprobe_opcode_t *)kallsyms_lookup_name(dot_name);
+	if (!addr && dot_appended) {
+		/* Let's try the original non-dot symbol lookup	*/
+		addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
+	}
+#else
+	addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
+#endif
+
+	return addr;
+}
+
 int __kprobes arch_prepare_kprobe(struct kprobe *p)
 {
 	int ret = 0;
diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
index 2282bf4e63cd..aefe076d00e0 100644
--- a/arch/powerpc/kernel/optprobes.c
+++ b/arch/powerpc/kernel/optprobes.c
@@ -243,8 +243,8 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
 	/*
 	 * 2. branch to optimized_callback() and emulate_step()
 	 */
-	kprobe_lookup_name("optimized_callback", op_callback_addr);
-	kprobe_lookup_name("emulate_step", emulate_step_addr);
+	op_callback_addr = kprobe_lookup_name("optimized_callback");
+	emulate_step_addr = kprobe_lookup_name("emulate_step");
 	if (!op_callback_addr || !emulate_step_addr) {
 		WARN(1, "kprobe_lookup_name() failed\n");
 		goto error;