tracing/kprobes: Support "string" type

Support string type tracing and printing in kprobe-tracer.

This allows user to trace string data in kernel including __user data. Note
that sometimes __user data may not be accessed if it is paged-out (sorry, but
kprobes operation should be done in atomic, we can not wait for page-in).

Commiter note: Fixed up conflicts with b7e2ece.

Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <20100519195724.2885.18788.stgit@localhost6.localdomain6>
Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 292 insertions, 78 deletions

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 3b831d8e201e..1b79d1c15726 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -30,6 +30,8 @@
 #include <linux/ptrace.h>
 #include <linux/perf_event.h>
 #include <linux/stringify.h>
+#include <linux/limits.h>
+#include <linux/uaccess.h>
 #include <asm/bitsperlong.h>
 
 #include "trace.h"
@@ -38,6 +40,7 @@
 #define MAX_TRACE_ARGS 128
 #define MAX_ARGSTR_LEN 63
 #define MAX_EVENT_NAME_LEN 64
+#define MAX_STRING_SIZE PATH_MAX
 #define KPROBE_EVENT_SYSTEM "kprobes"
 
 /* Reserved field names */
@@ -58,14 +61,16 @@ const char *reserved_field_names[] = {
 };
 
 /* Printing function type */
-typedef int (*print_type_func_t)(struct trace_seq *, const char *, void *);
+typedef int (*print_type_func_t)(struct trace_seq *, const char *, void *,
+                                 void *);
 #define PRINT_TYPE_FUNC_NAME(type)      print_type_##type
 #define PRINT_TYPE_FMT_NAME(type)       print_type_format_##type
 
 /* Printing  in basic type function template */
 #define DEFINE_BASIC_PRINT_TYPE_FUNC(type, fmt, cast)                   \
 static __kprobes int PRINT_TYPE_FUNC_NAME(type)(struct trace_seq *s,    \
-                                                const char *name, void *data)\
+                                                const char *name,       \
+                                                void *data, void *ent)\
 {                                                                       \
         return trace_seq_printf(s, " %s=" fmt, name, (cast)*(type *)data);\
 }                                                                       \
@@ -80,6 +85,49 @@ DEFINE_BASIC_PRINT_TYPE_FUNC(s16, "%d", int)
 DEFINE_BASIC_PRINT_TYPE_FUNC(s32, "%ld", long)
 DEFINE_BASIC_PRINT_TYPE_FUNC(s64, "%lld", long long)
 
+/* data_rloc: data relative location, compatible with u32 */
+#define make_data_rloc(len, roffs)      \
+        (((u32)(len) << 16) | ((u32)(roffs) & 0xffff))
+#define get_rloc_len(dl)        ((u32)(dl) >> 16)
+#define get_rloc_offs(dl)       ((u32)(dl) & 0xffff)
+
+static inline void *get_rloc_data(u32 *dl)
+{
+        return (u8 *)dl + get_rloc_offs(*dl);
+}
+
+/* For data_loc conversion */
+static inline void *get_loc_data(u32 *dl, void *ent)
+{
+        return (u8 *)ent + get_rloc_offs(*dl);
+}
+
+/*
+ * Convert data_rloc to data_loc:
+ *  data_rloc stores the offset from data_rloc itself, but data_loc
+ *  stores the offset from event entry.
+ */
+#define convert_rloc_to_loc(dl, offs)   ((u32)(dl) + (offs))
+
+/* For defining macros, define string/string_size types */
+typedef u32 string;
+typedef u32 string_size;
+
+/* Print type function for string type */
+static __kprobes int PRINT_TYPE_FUNC_NAME(string)(struct trace_seq *s,
+                                                  const char *name,
+                                                  void *data, void *ent)
+{
+        int len = *(u32 *)data >> 16;
+
+        if (!len)
+                return trace_seq_printf(s, " %s=(fault)", name);
+        else
+                return trace_seq_printf(s, " %s=\"%s\"", name,
+                                        (const char *)get_loc_data(data, ent));
+}
+static const char PRINT_TYPE_FMT_NAME(string)[] = "\\\"%s\\\"";
+
 /* Data fetch function type */
 typedef void (*fetch_func_t)(struct pt_regs *, void *, void *);
 
@@ -94,32 +142,38 @@ static __kprobes void call_fetch(struct fetch_param *fprm,
         return fprm->fn(regs, fprm->data, dest);
 }
 
-#define FETCH_FUNC_NAME(kind, type)     fetch_##kind##_##type
+#define FETCH_FUNC_NAME(method, type)   fetch_##method##_##type
 /*
  * Define macro for basic types - we don't need to define s* types, because
  * we have to care only about bitwidth at recording time.
  */
-#define DEFINE_BASIC_FETCH_FUNCS(kind)  \
-DEFINE_FETCH_##kind(u8)                 \
-DEFINE_FETCH_##kind(u16)                \
-DEFINE_FETCH_##kind(u32)                \
-DEFINE_FETCH_##kind(u64)
-
-#define CHECK_BASIC_FETCH_FUNCS(kind, fn)       \
-        ((FETCH_FUNC_NAME(kind, u8) == fn) ||   \
-         (FETCH_FUNC_NAME(kind, u16) == fn) ||  \
-         (FETCH_FUNC_NAME(kind, u32) == fn) ||  \
-         (FETCH_FUNC_NAME(kind, u64) == fn))
+#define DEFINE_BASIC_FETCH_FUNCS(method) \
+DEFINE_FETCH_##method(u8)               \
+DEFINE_FETCH_##method(u16)              \
+DEFINE_FETCH_##method(u32)              \
+DEFINE_FETCH_##method(u64)
+
+#define CHECK_FETCH_FUNCS(method, fn)                   \
+        (((FETCH_FUNC_NAME(method, u8) == fn) ||        \
+          (FETCH_FUNC_NAME(method, u16) == fn) ||       \
+          (FETCH_FUNC_NAME(method, u32) == fn) ||       \
+          (FETCH_FUNC_NAME(method, u64) == fn) ||       \
+          (FETCH_FUNC_NAME(method, string) == fn) ||    \
+          (FETCH_FUNC_NAME(method, string_size) == fn)) \
+         && (fn != NULL))
 
 /* Data fetch function templates */
 #define DEFINE_FETCH_reg(type)                                          \
 static __kprobes void FETCH_FUNC_NAME(reg, type)(struct pt_regs *regs,  \
-                                          void *offset, void *dest)     \
+                                        void *offset, void *dest)       \
 {                                                                       \
         *(type *)dest = (type)regs_get_register(regs,                   \
                                 (unsigned int)((unsigned long)offset)); \
 }
 DEFINE_BASIC_FETCH_FUNCS(reg)
+/* No string on the register */
+#define fetch_reg_string NULL
+#define fetch_reg_string_size NULL
 
 #define DEFINE_FETCH_stack(type)                                        \
 static __kprobes void FETCH_FUNC_NAME(stack, type)(struct pt_regs *regs,\
@@ -129,6 +183,9 @@ static __kprobes void FETCH_FUNC_NAME(stack, type)(struct pt_regs *regs,\
                                 (unsigned int)((unsigned long)offset)); \
 }
 DEFINE_BASIC_FETCH_FUNCS(stack)
+/* No string on the stack entry */
+#define fetch_stack_string NULL
+#define fetch_stack_string_size NULL
 
 #define DEFINE_FETCH_retval(type)                                       \
 static __kprobes void FETCH_FUNC_NAME(retval, type)(struct pt_regs *regs,\
@@ -137,6 +194,9 @@ static __kprobes void FETCH_FUNC_NAME(retval, type)(struct pt_regs *regs,\
         *(type *)dest = (type)regs_return_value(regs);                  \
 }
 DEFINE_BASIC_FETCH_FUNCS(retval)
+/* No string on the retval */
+#define fetch_retval_string NULL
+#define fetch_retval_string_size NULL
 
 #define DEFINE_FETCH_memory(type)                                       \
 static __kprobes void FETCH_FUNC_NAME(memory, type)(struct pt_regs *regs,\
@@ -149,6 +209,62 @@ static __kprobes void FETCH_FUNC_NAME(memory, type)(struct pt_regs *regs,\
                 *(type *)dest = retval;                                 \
 }
 DEFINE_BASIC_FETCH_FUNCS(memory)
+/*
+ * Fetch a null-terminated string. Caller MUST set *(u32 *)dest with max
+ * length and relative data location.
+ */
+static __kprobes void FETCH_FUNC_NAME(memory, string)(struct pt_regs *regs,
+                                                      void *addr, void *dest)
+{
+        long ret;
+        int maxlen = get_rloc_len(*(u32 *)dest);
+        u8 *dst = get_rloc_data(dest);
+        u8 *src = addr;
+        mm_segment_t old_fs = get_fs();
+        if (!maxlen)
+                return;
+        /*
+         * Try to get string again, since the string can be changed while
+         * probing.
+         */
+        set_fs(KERNEL_DS);
+        pagefault_disable();
+        do
+                ret = __copy_from_user_inatomic(dst++, src++, 1);
+        while (dst[-1] && ret == 0 && src - (u8 *)addr < maxlen);
+        dst[-1] = '\0';
+        pagefault_enable();
+        set_fs(old_fs);
+
+        if (ret < 0) {  /* Failed to fetch string */
+                ((u8 *)get_rloc_data(dest))[0] = '\0';
+                *(u32 *)dest = make_data_rloc(0, get_rloc_offs(*(u32 *)dest));
+        } else
+                *(u32 *)dest = make_data_rloc(src - (u8 *)addr,
+                                              get_rloc_offs(*(u32 *)dest));
+}
+/* Return the length of string -- including null terminal byte */
+static __kprobes void FETCH_FUNC_NAME(memory, string_size)(struct pt_regs *regs,
+                                                        void *addr, void *dest)
+{
+        int ret, len = 0;
+        u8 c;
+        mm_segment_t old_fs = get_fs();
+
+        set_fs(KERNEL_DS);
+        pagefault_disable();
+        do {
+                ret = __copy_from_user_inatomic(&c, (u8 *)addr + len, 1);
+                len++;
+        } while (c && ret == 0 && len < MAX_STRING_SIZE);
+        pagefault_enable();
+        set_fs(old_fs);
+
+        if (ret < 0)    /* Failed to check the length */
+                *(u32 *)dest = 0;
+        else
+                *(u32 *)dest = len;
+}
 
 /* Memory fetching by symbol */
 struct symbol_cache {
@@ -203,6 +319,8 @@ static __kprobes void FETCH_FUNC_NAME(symbol, type)(struct pt_regs *regs,\
                 *(type *)dest = 0;                                      \
 }
 DEFINE_BASIC_FETCH_FUNCS(symbol)
+DEFINE_FETCH_symbol(string)
+DEFINE_FETCH_symbol(string_size)
 
 /* Dereference memory access function */
 struct deref_fetch_param {
@@ -224,12 +342,14 @@ static __kprobes void FETCH_FUNC_NAME(deref, type)(struct pt_regs *regs,\
                 *(type *)dest = 0;                                      \
 }
 DEFINE_BASIC_FETCH_FUNCS(deref)
+DEFINE_FETCH_deref(string)
+DEFINE_FETCH_deref(string_size)
 
 static __kprobes void free_deref_fetch_param(struct deref_fetch_param *data)
 {
-        if (CHECK_BASIC_FETCH_FUNCS(deref, data->orig.fn))
+        if (CHECK_FETCH_FUNCS(deref, data->orig.fn))
                 free_deref_fetch_param(data->orig.data);
-        else if (CHECK_BASIC_FETCH_FUNCS(symbol, data->orig.fn))
+        else if (CHECK_FETCH_FUNCS(symbol, data->orig.fn))
                 free_symbol_cache(data->orig.data);
         kfree(data);
 }
@@ -240,23 +360,43 @@ static __kprobes void free_deref_fetch_param(struct deref_fetch_param *data)
 #define DEFAULT_FETCH_TYPE _DEFAULT_FETCH_TYPE(BITS_PER_LONG)
 #define DEFAULT_FETCH_TYPE_STR __stringify(DEFAULT_FETCH_TYPE)
 
-#define ASSIGN_FETCH_FUNC(kind, type)   \
-        .kind = FETCH_FUNC_NAME(kind, type)
-
-#define ASSIGN_FETCH_TYPE(ptype, ftype, sign)   \
-        {.name = #ptype,                        \
-         .size = sizeof(ftype),                 \
-         .is_signed = sign,                     \
-         .print = PRINT_TYPE_FUNC_NAME(ptype),  \
-         .fmt = PRINT_TYPE_FMT_NAME(ptype),     \
-ASSIGN_FETCH_FUNC(reg, ftype),                  \
-ASSIGN_FETCH_FUNC(stack, ftype),                \
-ASSIGN_FETCH_FUNC(retval, ftype),               \
-ASSIGN_FETCH_FUNC(memory, ftype),               \
-ASSIGN_FETCH_FUNC(symbol, ftype),               \
-ASSIGN_FETCH_FUNC(deref, ftype),                \
+/* Fetch types */
+enum {
+        FETCH_MTD_reg = 0,
+        FETCH_MTD_stack,
+        FETCH_MTD_retval,
+        FETCH_MTD_memory,
+        FETCH_MTD_symbol,
+        FETCH_MTD_deref,
+        FETCH_MTD_END,
+};
+
+#define ASSIGN_FETCH_FUNC(method, type) \
+        [FETCH_MTD_##method] = FETCH_FUNC_NAME(method, type)
+
+#define __ASSIGN_FETCH_TYPE(_name, ptype, ftype, _size, sign, _fmttype) \
+        {.name = _name,                         \
+         .size = _size,                                 \
+         .is_signed = sign,                             \
+         .print = PRINT_TYPE_FUNC_NAME(ptype),          \
+         .fmt = PRINT_TYPE_FMT_NAME(ptype),             \
+         .fmttype = _fmttype,                           \
+         .fetch = {                                     \
+ASSIGN_FETCH_FUNC(reg, ftype),                          \
+ASSIGN_FETCH_FUNC(stack, ftype),                        \
+ASSIGN_FETCH_FUNC(retval, ftype),                       \
+ASSIGN_FETCH_FUNC(memory, ftype),                       \
+ASSIGN_FETCH_FUNC(symbol, ftype),                       \
+ASSIGN_FETCH_FUNC(deref, ftype),                        \
+          }                                             \
         }
 
+#define ASSIGN_FETCH_TYPE(ptype, ftype, sign)                   \
+        __ASSIGN_FETCH_TYPE(#ptype, ptype, ftype, sizeof(ftype), sign, #ptype)
+
+#define FETCH_TYPE_STRING 0
+#define FETCH_TYPE_STRSIZE 1
+
 /* Fetch type information table */
 static const struct fetch_type {
         const char      *name;          /* Name of type */
@@ -264,14 +404,16 @@ static const struct fetch_type {
         int             is_signed;      /* Signed flag */
         print_type_func_t       print;  /* Print functions */
         const char      *fmt;           /* Fromat string */
+        const char      *fmttype;       /* Name in format file */
         /* Fetch functions */
-        fetch_func_t    reg;
-        fetch_func_t    stack;
-        fetch_func_t    retval;
-        fetch_func_t    memory;
-        fetch_func_t    symbol;
-        fetch_func_t    deref;
+        fetch_func_t    fetch[FETCH_MTD_END];
 } fetch_type_table[] = {
+        /* Special types */
+        [FETCH_TYPE_STRING] = __ASSIGN_FETCH_TYPE("string", string, string,
+                                        sizeof(u32), 1, "__data_loc char[]"),
+        [FETCH_TYPE_STRSIZE] = __ASSIGN_FETCH_TYPE("string_size", u32,
+                                        string_size, sizeof(u32), 0, "u32"),
+        /* Basic types */
         ASSIGN_FETCH_TYPE(u8,  u8,  0),
         ASSIGN_FETCH_TYPE(u16, u16, 0),
         ASSIGN_FETCH_TYPE(u32, u32, 0),
@@ -302,12 +444,28 @@ static __kprobes void fetch_stack_address(struct pt_regs *regs,
         *(unsigned long *)dest = kernel_stack_pointer(regs);
 }
 
+static fetch_func_t get_fetch_size_function(const struct fetch_type *type,
+                                            fetch_func_t orig_fn)
+{
+        int i;
+
+        if (type != &fetch_type_table[FETCH_TYPE_STRING])
+                return NULL;    /* Only string type needs size function */
+        for (i = 0; i < FETCH_MTD_END; i++)
+                if (type->fetch[i] == orig_fn)
+                        return fetch_type_table[FETCH_TYPE_STRSIZE].fetch[i];
+
+        WARN_ON(1);     /* This should not happen */
+        return NULL;
+}
+
 /**
  * Kprobe event core functions
  */
 
 struct probe_arg {
         struct fetch_param      fetch;
+        struct fetch_param      fetch_size;
         unsigned int            offset; /* Offset from argument entry */
         const char              *name;  /* Name of this argument */
         const char              *comm;  /* Command of this argument */
@@ -429,9 +587,9 @@ error:
 
 static void free_probe_arg(struct probe_arg *arg)
 {
-        if (CHECK_BASIC_FETCH_FUNCS(deref, arg->fetch.fn))
+        if (CHECK_FETCH_FUNCS(deref, arg->fetch.fn))
                 free_deref_fetch_param(arg->fetch.data);
-        else if (CHECK_BASIC_FETCH_FUNCS(symbol, arg->fetch.fn))
+        else if (CHECK_FETCH_FUNCS(symbol, arg->fetch.fn))
                 free_symbol_cache(arg->fetch.data);
         kfree(arg->name);
         kfree(arg->comm);
@@ -548,7 +706,7 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t,
 
         if (strcmp(arg, "retval") == 0) {
                 if (is_return)
-                        f->fn = t->retval;
+                        f->fn = t->fetch[FETCH_MTD_retval];
                 else
                         ret = -EINVAL;
         } else if (strncmp(arg, "stack", 5) == 0) {
@@ -562,7 +720,7 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t,
                         if (ret || param > PARAM_MAX_STACK)
                                 ret = -EINVAL;
                         else {
-                                f->fn = t->stack;
+                                f->fn = t->fetch[FETCH_MTD_stack];
                                 f->data = (void *)param;
                         }
                 } else
@@ -588,7 +746,7 @@ static int __parse_probe_arg(char *arg, const struct fetch_type *t,
         case '%':       /* named register */
                 ret = regs_query_register_offset(arg + 1);
                 if (ret >= 0) {
-                        f->fn = t->reg;
+                        f->fn = t->fetch[FETCH_MTD_reg];
                         f->data = (void *)(unsigned long)ret;
                         ret = 0;
                 }
@@ -598,7 +756,7 @@ static int __parse_probe_arg(char *arg, const struct fetch_type *t,
                         ret = strict_strtoul(arg + 1, 0, &param);
                         if (ret)
                                 break;
-                        f->fn = t->memory;
+                        f->fn = t->fetch[FETCH_MTD_memory];
                         f->data = (void *)param;
                 } else {
                         ret = split_symbol_offset(arg + 1, &offset);
@@ -606,7 +764,7 @@ static int __parse_probe_arg(char *arg, const struct fetch_type *t,
                                 break;
                         f->data = alloc_symbol_cache(arg + 1, offset);
                         if (f->data)
-                                f->fn = t->symbol;
+                                f->fn = t->fetch[FETCH_MTD_symbol];
                 }
                 break;
         case '+':       /* deref memory */
@@ -636,14 +794,17 @@ static int __parse_probe_arg(char *arg, const struct fetch_type *t,
                         if (ret)
                                 kfree(dprm);
                         else {
-                                f->fn = t->deref;
+                                f->fn = t->fetch[FETCH_MTD_deref];
                                 f->data = (void *)dprm;
                         }
                 }
                 break;
         }
-        if (!ret && !f->fn)
+        if (!ret && !f->fn) {   /* Parsed, but do not find fetch method */
+                pr_info("%s type has no corresponding fetch method.\n",
+                        t->name);
                 ret = -EINVAL;
+        }
         return ret;
 }
 
@@ -652,6 +813,7 @@ static int parse_probe_arg(char *arg, struct trace_probe *tp,
                            struct probe_arg *parg, int is_return)
 {
         const char *t;
+        int ret;
 
         if (strlen(arg) > MAX_ARGSTR_LEN) {
                 pr_info("Argument is too long.: %s\n",  arg);
@@ -674,7 +836,13 @@ static int parse_probe_arg(char *arg, struct trace_probe *tp,
         }
         parg->offset = tp->size;
         tp->size += parg->type->size;
-        return __parse_probe_arg(arg, parg->type, &parg->fetch, is_return);
+        ret = __parse_probe_arg(arg, parg->type, &parg->fetch, is_return);
+        if (ret >= 0) {
+                parg->fetch_size.fn = get_fetch_size_function(parg->type,
+                                                              parg->fetch.fn);
+                parg->fetch_size.data = parg->fetch.data;
+        }
+        return ret;
 }
 
 /* Return 1 if name is reserved or already used by another argument */
@@ -1043,6 +1211,54 @@ static const struct file_operations kprobe_profile_ops = {
         .release        = seq_release,
 };
 
+/* Sum up total data length for dynamic arraies (strings) */
+static __kprobes int __get_data_size(struct trace_probe *tp,
+                                     struct pt_regs *regs)
+{
+        int i, ret = 0;
+        u32 len;
+
+        for (i = 0; i < tp->nr_args; i++)
+                if (unlikely(tp->args[i].fetch_size.fn)) {
+                        call_fetch(&tp->args[i].fetch_size, regs, &len);
+                        ret += len;
+                }
+
+        return ret;
+}
+
+/* Store the value of each argument */
+static __kprobes void store_trace_args(int ent_size, struct trace_probe *tp,
+                                       struct pt_regs *regs,
+                                       u8 *data, int maxlen)
+{
+        int i;
+        u32 end = tp->size;
+        u32 *dl;        /* Data (relative) location */
+
+        for (i = 0; i < tp->nr_args; i++) {
+                if (unlikely(tp->args[i].fetch_size.fn)) {
+                        /*
+                         * First, we set the relative location and
+                         * maximum data length to *dl
+                         */
+                        dl = (u32 *)(data + tp->args[i].offset);
+                        *dl = make_data_rloc(maxlen, end - tp->args[i].offset);
+                        /* Then try to fetch string or dynamic array data */
+                        call_fetch(&tp->args[i].fetch, regs, dl);
+                        /* Reduce maximum length */
+                        end += get_rloc_len(*dl);
+                        maxlen -= get_rloc_len(*dl);
+                        /* Trick here, convert data_rloc to data_loc */
+                        *dl = convert_rloc_to_loc(*dl,
+                                 ent_size + tp->args[i].offset);
+                } else
+                        /* Just fetching data normally */
+                        call_fetch(&tp->args[i].fetch, regs,
+                                   data + tp->args[i].offset);
+        }
+}
+
 /* Kprobe handler */
 static __kprobes void kprobe_trace_func(struct kprobe *kp, struct pt_regs *regs)
 {
@@ -1050,8 +1266,7 @@ static __kprobes void kprobe_trace_func(struct kprobe *kp, struct pt_regs *regs)
         struct kprobe_trace_entry_head *entry;
         struct ring_buffer_event *event;
         struct ring_buffer *buffer;
-        u8 *data;
-        int size, i, pc;
+        int size, dsize, pc;
         unsigned long irq_flags;
         struct ftrace_event_call *call = &tp->call;
 
@@ -1060,7 +1275,8 @@ static __kprobes void kprobe_trace_func(struct kprobe *kp, struct pt_regs *regs)
         local_save_flags(irq_flags);
         pc = preempt_count();
 
-        size = sizeof(*entry) + tp->size;
+        dsize = __get_data_size(tp, regs);
+        size = sizeof(*entry) + tp->size + dsize;
 
         event = trace_current_buffer_lock_reserve(&buffer, call->event.type,
                                                   size, irq_flags, pc);
@@ -1069,9 +1285,7 @@ static __kprobes void kprobe_trace_func(struct kprobe *kp, struct pt_regs *regs)
 
         entry = ring_buffer_event_data(event);
         entry->ip = (unsigned long)kp->addr;
-        data = (u8 *)&entry[1];
-        for (i = 0; i < tp->nr_args; i++)
-                call_fetch(&tp->args[i].fetch, regs, data + tp->args[i].offset);
+        store_trace_args(sizeof(*entry), tp, regs, (u8 *)&entry[1], dsize);
 
         if (!filter_current_check_discard(buffer, call, entry, event))
                 trace_nowake_buffer_unlock_commit(buffer, event, irq_flags, pc);
@@ -1085,15 +1299,15 @@ static __kprobes void kretprobe_trace_func(struct kretprobe_instance *ri,
         struct kretprobe_trace_entry_head *entry;
         struct ring_buffer_event *event;
         struct ring_buffer *buffer;
-        u8 *data;
-        int size, i, pc;
+        int size, pc, dsize;
         unsigned long irq_flags;
         struct ftrace_event_call *call = &tp->call;
 
         local_save_flags(irq_flags);
         pc = preempt_count();
 
-        size = sizeof(*entry) + tp->size;
+        dsize = __get_data_size(tp, regs);
+        size = sizeof(*entry) + tp->size + dsize;
 
         event = trace_current_buffer_lock_reserve(&buffer, call->event.type,
                                                   size, irq_flags, pc);
@@ -1103,9 +1317,7 @@ static __kprobes void kretprobe_trace_func(struct kretprobe_instance *ri,
         entry = ring_buffer_event_data(event);
         entry->func = (unsigned long)tp->rp.kp.addr;
         entry->ret_ip = (unsigned long)ri->ret_addr;
-        data = (u8 *)&entry[1];
-        for (i = 0; i < tp->nr_args; i++)
-                call_fetch(&tp->args[i].fetch, regs, data + tp->args[i].offset);
+        store_trace_args(sizeof(*entry), tp, regs, (u8 *)&entry[1], dsize);
 
         if (!filter_current_check_discard(buffer, call, entry, event))
                 trace_nowake_buffer_unlock_commit(buffer, event, irq_flags, pc);
@@ -1137,7 +1349,7 @@ print_kprobe_event(struct trace_iterator *iter, int flags,
         data = (u8 *)&field[1];
         for (i = 0; i < tp->nr_args; i++)
                 if (!tp->args[i].type->print(s, tp->args[i].name,
-                                             data + tp->args[i].offset))
+                                             data + tp->args[i].offset, field))
                         goto partial;
 
         if (!trace_seq_puts(s, "\n"))
@@ -1179,7 +1391,7 @@ print_kretprobe_event(struct trace_iterator *iter, int flags,
         data = (u8 *)&field[1];
         for (i = 0; i < tp->nr_args; i++)
                 if (!tp->args[i].type->print(s, tp->args[i].name,
-                                             data + tp->args[i].offset))
+                                             data + tp->args[i].offset, field))
                         goto partial;
 
         if (!trace_seq_puts(s, "\n"))
@@ -1234,7 +1446,7 @@ static int kprobe_event_define_fields(struct ftrace_event_call *event_call)
         DEFINE_FIELD(unsigned long, ip, FIELD_STRING_IP, 0);
         /* Set argument names as fields */
         for (i = 0; i < tp->nr_args; i++) {
-                ret = trace_define_field(event_call, tp->args[i].type->name,
+                ret = trace_define_field(event_call, tp->args[i].type->fmttype,
                                          tp->args[i].name,
                                          sizeof(field) + tp->args[i].offset,
                                          tp->args[i].type->size,
@@ -1256,7 +1468,7 @@ static int kretprobe_event_define_fields(struct ftrace_event_call *event_call)
         DEFINE_FIELD(unsigned long, ret_ip, FIELD_STRING_RETIP, 0);
         /* Set argument names as fields */
         for (i = 0; i < tp->nr_args; i++) {
-                ret = trace_define_field(event_call, tp->args[i].type->name,
+                ret = trace_define_field(event_call, tp->args[i].type->fmttype,
                                          tp->args[i].name,
                                          sizeof(field) + tp->args[i].offset,
                                          tp->args[i].type->size,
@@ -1296,8 +1508,13 @@ static int __set_print_fmt(struct trace_probe *tp, char *buf, int len)
         pos += snprintf(buf + pos, LEN_OR_ZERO, "\", %s", arg);
 
         for (i = 0; i < tp->nr_args; i++) {
-                pos += snprintf(buf + pos, LEN_OR_ZERO, ", REC->%s",
-                                tp->args[i].name);
+                if (strcmp(tp->args[i].type->name, "string") == 0)
+                        pos += snprintf(buf + pos, LEN_OR_ZERO,
+                                        ", __get_str(%s)",
+                                        tp->args[i].name);
+                else
+                        pos += snprintf(buf + pos, LEN_OR_ZERO, ", REC->%s",
+                                        tp->args[i].name);
         }
 
 #undef LEN_OR_ZERO
@@ -1334,11 +1551,11 @@ static __kprobes void kprobe_perf_func(struct kprobe *kp,
         struct ftrace_event_call *call = &tp->call;
         struct kprobe_trace_entry_head *entry;
         struct hlist_head *head;
-        u8 *data;
-        int size, __size, i;
+        int size, __size, dsize;
         int rctx;
 
-        __size = sizeof(*entry) + tp->size;
+        dsize = __get_data_size(tp, regs);
+        __size = sizeof(*entry) + tp->size + dsize;
         size = ALIGN(__size + sizeof(u32), sizeof(u64));
         size -= sizeof(u32);
         if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,
@@ -1350,9 +1567,8 @@ static __kprobes void kprobe_perf_func(struct kprobe *kp,
                 return;
 
         entry->ip = (unsigned long)kp->addr;
-        data = (u8 *)&entry[1];
-        for (i = 0; i < tp->nr_args; i++)
-                call_fetch(&tp->args[i].fetch, regs, data + tp->args[i].offset);
+        memset(&entry[1], 0, dsize);
+        store_trace_args(sizeof(*entry), tp, regs, (u8 *)&entry[1], dsize);
 
         head = this_cpu_ptr(call->perf_events);
         perf_trace_buf_submit(entry, size, rctx, entry->ip, 1, regs, head);
@@ -1366,11 +1582,11 @@ static __kprobes void kretprobe_perf_func(struct kretprobe_instance *ri,
         struct ftrace_event_call *call = &tp->call;
         struct kretprobe_trace_entry_head *entry;
         struct hlist_head *head;
-        u8 *data;
-        int size, __size, i;
+        int size, __size, dsize;
         int rctx;
 
-        __size = sizeof(*entry) + tp->size;
+        dsize = __get_data_size(tp, regs);
+        __size = sizeof(*entry) + tp->size + dsize;
         size = ALIGN(__size + sizeof(u32), sizeof(u64));
         size -= sizeof(u32);
         if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,
@@ -1383,9 +1599,7 @@ static __kprobes void kretprobe_perf_func(struct kretprobe_instance *ri,
 
         entry->func = (unsigned long)tp->rp.kp.addr;
         entry->ret_ip = (unsigned long)ri->ret_addr;
-        data = (u8 *)&entry[1];
-        for (i = 0; i < tp->nr_args; i++)
-                call_fetch(&tp->args[i].fetch, regs, data + tp->args[i].offset);
+        store_trace_args(sizeof(*entry), tp, regs, (u8 *)&entry[1], dsize);
 
         head = this_cpu_ptr(call->perf_events);
         perf_trace_buf_submit(entry, size, rctx, entry->ret_ip, 1, regs, head);