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

Masami Hiramatsu
2017-04-13T03:09:31Z

On Wed, 12 Apr 2017 16:28:24 +0530
"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> wrote:

> 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.

Looks good to me.

Acked-by: Masami Hiramatsu <mhiramat@kernel.org>

Thanks!

>
> 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
>

--
Masami Hiramatsu <mhiramat@kernel.org>