[PATCH v2 1/5] kprobes: convert kprobe_lookup_name() to a function

Naveen N. Rao
2017-04-12T10:59:52Z

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>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
---
arch/powerpc/include/asm/kprobes.h | 53 ----------------------------------
arch/powerpc/kernel/kprobes.c | 58 ++++++++++++++++++++++++++++++++++++++
arch/powerpc/kernel/optprobes.c | 4 +--
include/linux/kprobes.h | 1 +
kernel/kprobes.c | 20 ++++++-------
5 files changed, 69 insertions(+), 67 deletions(-)

diff --git a/arch/powerpc/include/asm/kprobes.h b/arch/powerpc/include/asm/kprobes.h
index 0503c98b2117..a843884aafaf 100644
--- a/arch/powerpc/include/asm/kprobes.h
+++ b/arch/powerpc/include/asm/kprobes.h
@@ -61,59 +61,6 @@ extern kprobe_opcode_t optprobe_template_end[];
#define MAX_OPTINSN_SIZE (optprobe_template_end - optprobe_template_entry)
#define RELATIVEJUMP_SIZE sizeof(kprobe_opcode_t) /* 4 bytes */

-#ifdef PPC64_ELF_ABI_v2
-/* PPC64 ABIv2 needs local entry point */
-#define kprobe_lookup_name(name, addr) \
-{ \
- 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.
- */
-#define kprobe_lookup_name(name, addr) \
-{ \
- 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); \
- } \
-}
-#endif
-
#define flush_insn_slot(p) do { } while (0)
#define kretprobe_blacklist_size 0

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 331751701fed..a7aa7394954d 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(dot_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;
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index c328e4f7dcad..16f153c84646 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -379,6 +379,7 @@ static inline struct kprobe_ctlblk *get_kprobe_ctlblk(void)
return this_cpu_ptr(&kprobe_ctlblk);
}

+kprobe_opcode_t *kprobe_lookup_name(const char *name);
int register_kprobe(struct kprobe *p);
void unregister_kprobe(struct kprobe *p);
int register_kprobes(struct kprobe **kps, int num);
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 699c5bc51a92..f3421b6b47a3 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -58,15 +58,6 @@
#define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS)

-/*
- * Some oddball architectures like 64bit powerpc have function descriptors
- * so this must be overridable.
- */
-#ifndef kprobe_lookup_name
-#define kprobe_lookup_name(name, addr) \
- addr = ((kprobe_opcode_t *)(kallsyms_lookup_name(name)))
-#endif
-
static int kprobes_initialized;
static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE];
static struct hlist_head kretprobe_inst_table[KPROBE_TABLE_SIZE];
@@ -81,6 +72,11 @@ static struct {
raw_spinlock_t lock ____cacheline_aligned_in_smp;
} kretprobe_table_locks[KPROBE_TABLE_SIZE];

+kprobe_opcode_t * __weak kprobe_lookup_name(const char *name)
+{
+ return ((kprobe_opcode_t *)(kallsyms_lookup_name(name)));
+}
+
static raw_spinlock_t *kretprobe_table_lock_ptr(unsigned long hash)
{
return &(kretprobe_table_locks[hash].lock);
@@ -1400,7 +1396,7 @@ static kprobe_opcode_t *kprobe_addr(struct kprobe *p)
goto invalid;

if (p->symbol_name) {
- kprobe_lookup_name(p->symbol_name, addr);
+ addr = kprobe_lookup_name(p->symbol_name);
if (!addr)
return ERR_PTR(-ENOENT);
}
@@ -2192,8 +2188,8 @@ static int __init init_kprobes(void)
if (kretprobe_blacklist_size) {
/* lookup the function address from its name */
for (i = 0; kretprobe_blacklist[i].name != NULL; i++) {
- kprobe_lookup_name(kretprobe_blacklist[i].name,
- kretprobe_blacklist[i].addr);
+ kretprobe_blacklist[i].addr =
+ kprobe_lookup_name(kretprobe_blacklist[i].name);
if (!kretprobe_blacklist[i].addr)
printk("kretprobe: lookup failed: %s\n",
kretprobe_blacklist[i].name);
--
2.12.1