Re: [PATCH v2 07/17] tracing: probeevent: Introduce new argument fetching code

[Namhyung Kim <namhyung@kernel.org>]

On Wed, Feb 21, 2018 at 11:57:36PM +0900, Masami Hiramatsu wrote:
> Replace {k,u}probe event argument fetching framework
> with switch-case based. Currently that is implemented
> with structures, macros and chain of function-pointers,
> which is more complicated than necessary and may get
> a performance penalty by retpoline.
> 
> This simplify that with an array of "fetch_insn" (opcode
> and oprands), and make process_fetch_insn() just
> interprets it. No function pointers are used.

I think it'd be nice to split this commit to 3 parts:

 * convert to the fetch_insn
 * remove fetch methods (now unused)
 * unify fetch type table

Thanks,
Namhyung


> 
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> ---
>  Changes in v2:
>   - Allow $comm:string.
> ---
>  kernel/trace/trace_kprobe.c     |  314 +++++++++++-----------------
>  kernel/trace/trace_probe.c      |  441 ++++++++++++---------------------------
>  kernel/trace/trace_probe.h      |  232 ++++-----------------
>  kernel/trace/trace_probe_tmpl.h |  120 +++++++++++
>  kernel/trace/trace_uprobe.c     |  150 +++++++------
>  5 files changed, 517 insertions(+), 740 deletions(-)
>  create mode 100644 kernel/trace/trace_probe_tmpl.h
> 
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index a96328dfc012..5dd2d470cc7e 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -24,6 +24,7 @@
>  #include <linux/error-injection.h>
>  
>  #include "trace_probe.h"
> +#include "trace_probe_tmpl.h"
>  
>  #define KPROBE_EVENT_SYSTEM "kprobes"
>  #define KRETPROBE_MAXACTIVE_MAX 4096
> @@ -121,184 +122,6 @@ static int kprobe_dispatcher(struct kprobe *kp, struct pt_regs *regs);
>  static int kretprobe_dispatcher(struct kretprobe_instance *ri,
>  				struct pt_regs *regs);
>  
> -/* Memory fetching by symbol */
> -struct symbol_cache {
> -	char		*symbol;
> -	long		offset;
> -	unsigned long	addr;
> -};
> -
> -unsigned long update_symbol_cache(struct symbol_cache *sc)
> -{
> -	sc->addr = (unsigned long)kallsyms_lookup_name(sc->symbol);
> -
> -	if (sc->addr)
> -		sc->addr += sc->offset;
> -
> -	return sc->addr;
> -}
> -
> -void free_symbol_cache(struct symbol_cache *sc)
> -{
> -	kfree(sc->symbol);
> -	kfree(sc);
> -}
> -
> -struct symbol_cache *alloc_symbol_cache(const char *sym, long offset)
> -{
> -	struct symbol_cache *sc;
> -
> -	if (!sym || strlen(sym) == 0)
> -		return NULL;
> -
> -	sc = kzalloc(sizeof(struct symbol_cache), GFP_KERNEL);
> -	if (!sc)
> -		return NULL;
> -
> -	sc->symbol = kstrdup(sym, GFP_KERNEL);
> -	if (!sc->symbol) {
> -		kfree(sc);
> -		return NULL;
> -	}
> -	sc->offset = offset;
> -	update_symbol_cache(sc);
> -
> -	return sc;
> -}
> -
> -/*
> - * Kprobes-specific fetch functions
> - */
> -#define DEFINE_FETCH_stack(type)					\
> -static void FETCH_FUNC_NAME(stack, type)(struct pt_regs *regs,		\
> -					  void *offset, void *dest)	\
> -{									\
> -	*(type *)dest = (type)regs_get_kernel_stack_nth(regs,		\
> -				(unsigned int)((unsigned long)offset));	\
> -}									\
> -NOKPROBE_SYMBOL(FETCH_FUNC_NAME(stack, type));
> -
> -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_memory(type)					\
> -static void FETCH_FUNC_NAME(memory, type)(struct pt_regs *regs,		\
> -					  void *addr, void *dest)	\
> -{									\
> -	type retval;							\
> -	if (probe_kernel_address(addr, retval))				\
> -		*(type *)dest = 0;					\
> -	else								\
> -		*(type *)dest = retval;					\
> -}									\
> -NOKPROBE_SYMBOL(FETCH_FUNC_NAME(memory, type));
> -
> -DEFINE_BASIC_FETCH_FUNCS(memory)
> -/*
> - * Fetch a null-terminated string. Caller MUST set *(u32 *)dest with max
> - * length and relative data location.
> - */
> -static void FETCH_FUNC_NAME(memory, string)(struct pt_regs *regs,
> -					    void *addr, void *dest)
> -{
> -	int maxlen = get_rloc_len(*(u32 *)dest);
> -	u8 *dst = get_rloc_data(dest);
> -	long ret;
> -
> -	if (!maxlen)
> -		return;
> -
> -	/*
> -	 * Try to get string again, since the string can be changed while
> -	 * probing.
> -	 */
> -	ret = strncpy_from_unsafe(dst, addr, maxlen);
> -
> -	if (ret < 0) {	/* Failed to fetch string */
> -		dst[0] = '\0';
> -		*(u32 *)dest = make_data_rloc(0, get_rloc_offs(*(u32 *)dest));
> -	} else {
> -		*(u32 *)dest = make_data_rloc(ret, get_rloc_offs(*(u32 *)dest));
> -	}
> -}
> -NOKPROBE_SYMBOL(FETCH_FUNC_NAME(memory, string));
> -
> -/* Return the length of string -- including null terminal byte */
> -static void FETCH_FUNC_NAME(memory, string_size)(struct pt_regs *regs,
> -						 void *addr, void *dest)
> -{
> -	mm_segment_t old_fs;
> -	int ret, len = 0;
> -	u8 c;
> -
> -	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;
> -}
> -NOKPROBE_SYMBOL(FETCH_FUNC_NAME(memory, string_size));
> -
> -#define DEFINE_FETCH_symbol(type)					\
> -void FETCH_FUNC_NAME(symbol, type)(struct pt_regs *regs, void *data, void *dest)\
> -{									\
> -	struct symbol_cache *sc = data;					\
> -	if (sc->addr)							\
> -		fetch_memory_##type(regs, (void *)sc->addr, dest);	\
> -	else								\
> -		*(type *)dest = 0;					\
> -}									\
> -NOKPROBE_SYMBOL(FETCH_FUNC_NAME(symbol, type));
> -
> -DEFINE_BASIC_FETCH_FUNCS(symbol)
> -DEFINE_FETCH_symbol(string)
> -DEFINE_FETCH_symbol(string_size)
> -
> -/* kprobes don't support file_offset fetch methods */
> -#define fetch_file_offset_u8		NULL
> -#define fetch_file_offset_u16		NULL
> -#define fetch_file_offset_u32		NULL
> -#define fetch_file_offset_u64		NULL
> -#define fetch_file_offset_string	NULL
> -#define fetch_file_offset_string_size	NULL
> -
> -/* Fetch type information table */
> -static const struct fetch_type kprobes_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),
> -	ASSIGN_FETCH_TYPE(u64, u64, 0),
> -	ASSIGN_FETCH_TYPE(s8,  u8,  1),
> -	ASSIGN_FETCH_TYPE(s16, u16, 1),
> -	ASSIGN_FETCH_TYPE(s32, u32, 1),
> -	ASSIGN_FETCH_TYPE(s64, u64, 1),
> -	ASSIGN_FETCH_TYPE_ALIAS(x8,  u8,  u8,  0),
> -	ASSIGN_FETCH_TYPE_ALIAS(x16, u16, u16, 0),
> -	ASSIGN_FETCH_TYPE_ALIAS(x32, u32, u32, 0),
> -	ASSIGN_FETCH_TYPE_ALIAS(x64, u64, u64, 0),
> -
> -	ASSIGN_FETCH_TYPE_END
> -};
> -
>  /*
>   * Allocate new trace_probe and initialize it (including kprobes).
>   */
> @@ -490,14 +313,11 @@ disable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file)
>  /* Internal register function - just handle k*probes and flags */
>  static int __register_trace_kprobe(struct trace_kprobe *tk)
>  {
> -	int i, ret;
> +	int ret;
>  
>  	if (trace_probe_is_registered(&tk->tp))
>  		return -EINVAL;
>  
> -	for (i = 0; i < tk->tp.nr_args; i++)
> -		traceprobe_update_arg(&tk->tp.args[i]);
> -
>  	/* Set/clear disabled flag according to tp->flag */
>  	if (trace_probe_is_enabled(&tk->tp))
>  		tk->rp.kp.flags &= ~KPROBE_FLAG_DISABLED;
> @@ -830,8 +650,7 @@ static int create_trace_kprobe(int argc, char **argv)
>  
>  		/* Parse fetch argument */
>  		ret = traceprobe_parse_probe_arg(arg, &tk->tp.size, parg,
> -						is_return, true,
> -						kprobes_fetch_type_table);
> +						 is_return, true);
>  		if (ret) {
>  			pr_info("Parse error at argument[%d]. (%d)\n", i, ret);
>  			goto error;
> @@ -985,6 +804,133 @@ static const struct file_operations kprobe_profile_ops = {
>  	.release        = seq_release,
>  };
>  
> +/* Kprobe specific fetch functions */
> +
> +/* Return the length of string -- including null terminal byte */
> +static nokprobe_inline void
> +fetch_store_strlen(unsigned long addr, void *dest)
> +{
> +	mm_segment_t old_fs;
> +	int ret, len = 0;
> +	u8 c;
> +
> +	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;
> +}
> +
> +/*
> + * Fetch a null-terminated string. Caller MUST set *(u32 *)buf with max
> + * length and relative data location.
> + */
> +static nokprobe_inline void
> +fetch_store_string(unsigned long addr, void *dest)
> +{
> +	int maxlen = get_rloc_len(*(u32 *)dest);
> +	u8 *dst = get_rloc_data(dest);
> +	long ret;
> +
> +	if (!maxlen)
> +		return;
> +
> +	/*
> +	 * Try to get string again, since the string can be changed while
> +	 * probing.
> +	 */
> +	ret = strncpy_from_unsafe(dst, (void *)addr, maxlen);
> +
> +	if (ret < 0) {	/* Failed to fetch string */
> +		dst[0] = '\0';
> +		*(u32 *)dest = make_data_rloc(0, get_rloc_offs(*(u32 *)dest));
> +	} else {
> +		*(u32 *)dest = make_data_rloc(ret, get_rloc_offs(*(u32 *)dest));
> +	}
> +}
> +
> +/* Note that we don't verify it, since the code does not come from user space */
> +static int
> +process_fetch_insn(struct fetch_insn *code, struct pt_regs *regs, void *dest,
> +		   bool pre)
> +{
> +	unsigned long val;
> +	int ret;
> +
> +	/* 1st stage: get value from context */
> +	switch (code->op) {
> +	case FETCH_OP_REG:
> +		val = regs_get_register(regs, code->param);
> +		break;
> +	case FETCH_OP_STACK:
> +		val = regs_get_kernel_stack_nth(regs, code->param);
> +		break;
> +	case FETCH_OP_STACKP:
> +		val = kernel_stack_pointer(regs);
> +		break;
> +	case FETCH_OP_RETVAL:
> +		val = regs_return_value(regs);
> +		break;
> +	case FETCH_OP_IMM:
> +		val = code->immediate;
> +		break;
> +	case FETCH_OP_COMM:
> +		val = (unsigned long)current->comm;
> +		break;
> +	default:
> +		return -EILSEQ;
> +	}
> +	code++;
> +
> +	/* 2nd stage: dereference memory if needed */
> +	while (code->op == FETCH_OP_DEREF) {
> +		ret = probe_kernel_read(&val, (void *)val + code->offset,
> +					sizeof(val));
> +		if (ret)
> +			return ret;
> +		code++;
> +	}
> +
> +	/* 3rd stage: store value to buffer */
> +	switch (code->op) {
> +	case FETCH_OP_ST_RAW:
> +		fetch_store_raw(val, code, dest);
> +		break;
> +	case FETCH_OP_ST_MEM:
> +		probe_kernel_read(dest, (void *)val + code->offset, code->size);
> +		break;
> +	case FETCH_OP_ST_STRING:
> +		if (pre)
> +			fetch_store_strlen(val + code->offset, dest);
> +		else
> +			fetch_store_string(val + code->offset, dest);
> +		break;
> +	default:
> +		return -EILSEQ;
> +	}
> +	code++;
> +
> +	/* 4th stage: modify stored value if needed */
> +	if (code->op == FETCH_OP_MOD_BF) {
> +		fetch_apply_bitfield(code, dest);
> +		code++;
> +	}
> +
> +	return code->op == FETCH_OP_END ? 0 : -EILSEQ;
> +}
> +NOKPROBE_SYMBOL(process_fetch_insn)
> +
>  /* Kprobe handler */
>  static nokprobe_inline void
>  __kprobe_trace_func(struct trace_kprobe *tk, struct pt_regs *regs,
> diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
> index 37bdd56b4988..cd87490b3492 100644
> --- a/kernel/trace/trace_probe.c
> +++ b/kernel/trace/trace_probe.c
> @@ -73,176 +73,29 @@ int PRINT_TYPE_FUNC_NAME(string)(struct trace_seq *s, void *data, void *ent)
>  
>  const char PRINT_TYPE_FMT_NAME(string)[] = "\\\"%s\\\"";
>  
> -#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)						\
> -void FETCH_FUNC_NAME(reg, type)(struct pt_regs *regs, void *offset, void *dest)	\
> -{									\
> -	*(type *)dest = (type)regs_get_register(regs,			\
> -				(unsigned int)((unsigned long)offset));	\
> -}									\
> -NOKPROBE_SYMBOL(FETCH_FUNC_NAME(reg, type));
> -DEFINE_BASIC_FETCH_FUNCS(reg)
> -/* No string on the register */
> -#define fetch_reg_string	NULL
> -#define fetch_reg_string_size	NULL
> -
> -#define DEFINE_FETCH_retval(type)					\
> -void FETCH_FUNC_NAME(retval, type)(struct pt_regs *regs,		\
> -				   void *dummy, void *dest)		\
> -{									\
> -	*(type *)dest = (type)regs_return_value(regs);			\
> -}									\
> -NOKPROBE_SYMBOL(FETCH_FUNC_NAME(retval, type));
> -DEFINE_BASIC_FETCH_FUNCS(retval)
> -/* No string on the retval */
> -#define fetch_retval_string		NULL
> -#define fetch_retval_string_size	NULL
> -
> -/* Dereference memory access function */
> -struct deref_fetch_param {
> -	struct fetch_param	orig;
> -	long			offset;
> -	fetch_func_t		fetch;
> -	fetch_func_t		fetch_size;
> -};
> -
> -#define DEFINE_FETCH_deref(type)					\
> -void FETCH_FUNC_NAME(deref, type)(struct pt_regs *regs,			\
> -				  void *data, void *dest)		\
> -{									\
> -	struct deref_fetch_param *dprm = data;				\
> -	unsigned long addr;						\
> -	call_fetch(&dprm->orig, regs, &addr);				\
> -	if (addr) {							\
> -		addr += dprm->offset;					\
> -		dprm->fetch(regs, (void *)addr, dest);			\
> -	} else								\
> -		*(type *)dest = 0;					\
> -}									\
> -NOKPROBE_SYMBOL(FETCH_FUNC_NAME(deref, type));
> -DEFINE_BASIC_FETCH_FUNCS(deref)
> -DEFINE_FETCH_deref(string)
> -
> -void FETCH_FUNC_NAME(deref, string_size)(struct pt_regs *regs,
> -					 void *data, void *dest)
> -{
> -	struct deref_fetch_param *dprm = data;
> -	unsigned long addr;
> -
> -	call_fetch(&dprm->orig, regs, &addr);
> -	if (addr && dprm->fetch_size) {
> -		addr += dprm->offset;
> -		dprm->fetch_size(regs, (void *)addr, dest);
> -	} else
> -		*(string_size *)dest = 0;
> -}
> -NOKPROBE_SYMBOL(FETCH_FUNC_NAME(deref, string_size));
> -
> -static void update_deref_fetch_param(struct deref_fetch_param *data)
> -{
> -	if (CHECK_FETCH_FUNCS(deref, data->orig.fn))
> -		update_deref_fetch_param(data->orig.data);
> -	else if (CHECK_FETCH_FUNCS(symbol, data->orig.fn))
> -		update_symbol_cache(data->orig.data);
> -}
> -NOKPROBE_SYMBOL(update_deref_fetch_param);
> -
> -static void free_deref_fetch_param(struct deref_fetch_param *data)
> -{
> -	if (CHECK_FETCH_FUNCS(deref, data->orig.fn))
> -		free_deref_fetch_param(data->orig.data);
> -	else if (CHECK_FETCH_FUNCS(symbol, data->orig.fn))
> -		free_symbol_cache(data->orig.data);
> -	kfree(data);
> -}
> -NOKPROBE_SYMBOL(free_deref_fetch_param);
> -
> -/* Bitfield fetch function */
> -struct bitfield_fetch_param {
> -	struct fetch_param	orig;
> -	unsigned char		hi_shift;
> -	unsigned char		low_shift;
> +/* Fetch type information table */
> +static const struct fetch_type probe_fetch_types[] = {
> +	/* Special types */
> +	__ASSIGN_FETCH_TYPE("string", string, string, sizeof(u32), 1,
> +			    "__data_loc char[]"),
> +	/* Basic types */
> +	ASSIGN_FETCH_TYPE(u8,  u8,  0),
> +	ASSIGN_FETCH_TYPE(u16, u16, 0),
> +	ASSIGN_FETCH_TYPE(u32, u32, 0),
> +	ASSIGN_FETCH_TYPE(u64, u64, 0),
> +	ASSIGN_FETCH_TYPE(s8,  u8,  1),
> +	ASSIGN_FETCH_TYPE(s16, u16, 1),
> +	ASSIGN_FETCH_TYPE(s32, u32, 1),
> +	ASSIGN_FETCH_TYPE(s64, u64, 1),
> +	ASSIGN_FETCH_TYPE_ALIAS(x8,  u8,  u8,  0),
> +	ASSIGN_FETCH_TYPE_ALIAS(x16, u16, u16, 0),
> +	ASSIGN_FETCH_TYPE_ALIAS(x32, u32, u32, 0),
> +	ASSIGN_FETCH_TYPE_ALIAS(x64, u64, u64, 0),
> +
> +	ASSIGN_FETCH_TYPE_END
>  };
>  
> -#define DEFINE_FETCH_bitfield(type)					\
> -void FETCH_FUNC_NAME(bitfield, type)(struct pt_regs *regs,		\
> -				     void *data, void *dest)		\
> -{									\
> -	struct bitfield_fetch_param *bprm = data;			\
> -	type buf = 0;							\
> -	call_fetch(&bprm->orig, regs, &buf);				\
> -	if (buf) {							\
> -		buf <<= bprm->hi_shift;					\
> -		buf >>= bprm->low_shift;				\
> -	}								\
> -	*(type *)dest = buf;						\
> -}									\
> -NOKPROBE_SYMBOL(FETCH_FUNC_NAME(bitfield, type));
> -DEFINE_BASIC_FETCH_FUNCS(bitfield)
> -#define fetch_bitfield_string		NULL
> -#define fetch_bitfield_string_size	NULL
> -
> -static void
> -update_bitfield_fetch_param(struct bitfield_fetch_param *data)
> -{
> -	/*
> -	 * Don't check the bitfield itself, because this must be the
> -	 * last fetch function.
> -	 */
> -	if (CHECK_FETCH_FUNCS(deref, data->orig.fn))
> -		update_deref_fetch_param(data->orig.data);
> -	else if (CHECK_FETCH_FUNCS(symbol, data->orig.fn))
> -		update_symbol_cache(data->orig.data);
> -}
> -
> -static void
> -free_bitfield_fetch_param(struct bitfield_fetch_param *data)
> -{
> -	/*
> -	 * Don't check the bitfield itself, because this must be the
> -	 * last fetch function.
> -	 */
> -	if (CHECK_FETCH_FUNCS(deref, data->orig.fn))
> -		free_deref_fetch_param(data->orig.data);
> -	else if (CHECK_FETCH_FUNCS(symbol, data->orig.fn))
> -		free_symbol_cache(data->orig.data);
> -
> -	kfree(data);
> -}
> -
> -void FETCH_FUNC_NAME(comm, string)(struct pt_regs *regs,
> -					  void *data, void *dest)
> -{
> -	int maxlen = get_rloc_len(*(u32 *)dest);
> -	u8 *dst = get_rloc_data(dest);
> -	long ret;
> -
> -	if (!maxlen)
> -		return;
> -
> -	ret = strlcpy(dst, current->comm, maxlen);
> -	*(u32 *)dest = make_data_rloc(ret, get_rloc_offs(*(u32 *)dest));
> -}
> -NOKPROBE_SYMBOL(FETCH_FUNC_NAME(comm, string));
> -
> -void FETCH_FUNC_NAME(comm, string_size)(struct pt_regs *regs,
> -					       void *data, void *dest)
> -{
> -	*(u32 *)dest = strlen(current->comm) + 1;
> -}
> -NOKPROBE_SYMBOL(FETCH_FUNC_NAME(comm, string_size));
> -
> -static const struct fetch_type *find_fetch_type(const char *type,
> -						const struct fetch_type *ftbl)
> +static const struct fetch_type *find_fetch_type(const char *type)
>  {
>  	int i;
>  
> @@ -263,58 +116,27 @@ static const struct fetch_type *find_fetch_type(const char *type,
>  
>  		switch (bs) {
>  		case 8:
> -			return find_fetch_type("u8", ftbl);
> +			return find_fetch_type("u8");
>  		case 16:
> -			return find_fetch_type("u16", ftbl);
> +			return find_fetch_type("u16");
>  		case 32:
> -			return find_fetch_type("u32", ftbl);
> +			return find_fetch_type("u32");
>  		case 64:
> -			return find_fetch_type("u64", ftbl);
> +			return find_fetch_type("u64");
>  		default:
>  			goto fail;
>  		}
>  	}
>  
> -	for (i = 0; ftbl[i].name; i++) {
> -		if (strcmp(type, ftbl[i].name) == 0)
> -			return &ftbl[i];
> +	for (i = 0; probe_fetch_types[i].name; i++) {
> +		if (strcmp(type, probe_fetch_types[i].name) == 0)
> +			return &probe_fetch_types[i];
>  	}
>  
>  fail:
>  	return NULL;
>  }
>  
> -/* Special function : only accept unsigned long */
> -static void fetch_kernel_stack_address(struct pt_regs *regs, void *dummy, void *dest)
> -{
> -	*(unsigned long *)dest = kernel_stack_pointer(regs);
> -}
> -NOKPROBE_SYMBOL(fetch_kernel_stack_address);
> -
> -static void fetch_user_stack_address(struct pt_regs *regs, void *dummy, void *dest)
> -{
> -	*(unsigned long *)dest = user_stack_pointer(regs);
> -}
> -NOKPROBE_SYMBOL(fetch_user_stack_address);
> -
> -static fetch_func_t get_fetch_size_function(const struct fetch_type *type,
> -					    fetch_func_t orig_fn,
> -					    const struct fetch_type *ftbl)
> -{
> -	int i;
> -
> -	if (type != &ftbl[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 ftbl[FETCH_TYPE_STRSIZE].fetch[i];
> -
> -	WARN_ON(1);	/* This should not happen */
> -
> -	return NULL;
> -}
> -
>  /* Split symbol and offset. */
>  int traceprobe_split_symbol_offset(char *symbol, long *offset)
>  {
> @@ -341,7 +163,7 @@ int traceprobe_split_symbol_offset(char *symbol, long *offset)
>  #define PARAM_MAX_STACK (THREAD_SIZE / sizeof(unsigned long))
>  
>  static int parse_probe_vars(char *arg, const struct fetch_type *t,
> -			    struct fetch_param *f, bool is_return,
> +			    struct fetch_insn *code, bool is_return,
>  			    bool is_kprobe)
>  {
>  	int ret = 0;
> @@ -349,33 +171,24 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t,
>  
>  	if (strcmp(arg, "retval") == 0) {
>  		if (is_return)
> -			f->fn = t->fetch[FETCH_MTD_retval];
> +			code->op = FETCH_OP_RETVAL;
>  		else
>  			ret = -EINVAL;
>  	} else if (strncmp(arg, "stack", 5) == 0) {
>  		if (arg[5] == '\0') {
> -			if (strcmp(t->name, DEFAULT_FETCH_TYPE_STR))
> -				return -EINVAL;
> -
> -			if (is_kprobe)
> -				f->fn = fetch_kernel_stack_address;
> -			else
> -				f->fn = fetch_user_stack_address;
> +			code->op = FETCH_OP_STACKP;
>  		} else if (isdigit(arg[5])) {
>  			ret = kstrtoul(arg + 5, 10, &param);
>  			if (ret || (is_kprobe && param > PARAM_MAX_STACK))
>  				ret = -EINVAL;
>  			else {
> -				f->fn = t->fetch[FETCH_MTD_stack];
> -				f->data = (void *)param;
> +				code->op = FETCH_OP_STACK;
> +				code->param = (unsigned int)param;
>  			}
>  		} else
>  			ret = -EINVAL;
>  	} else if (strcmp(arg, "comm") == 0) {
> -		if (strcmp(t->name, "string") != 0 &&
> -		    strcmp(t->name, "string_size") != 0)
> -			return -EINVAL;
> -		f->fn = t->fetch[FETCH_MTD_comm];
> +		code->op = FETCH_OP_COMM;
>  	} else
>  		ret = -EINVAL;
>  
> @@ -383,10 +196,12 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t,
>  }
>  
>  /* Recursive argument parser */
> -static int parse_probe_arg(char *arg, const struct fetch_type *t,
> -		     struct fetch_param *f, bool is_return, bool is_kprobe,
> -		     const struct fetch_type *ftbl)
> +static int
> +parse_probe_arg(char *arg, const struct fetch_type *type,
> +		struct fetch_insn **pcode, struct fetch_insn *end,
> +		bool is_return, bool is_kprobe)
>  {
> +	struct fetch_insn *code = *pcode;
>  	unsigned long param;
>  	long offset;
>  	char *tmp;
> @@ -394,14 +209,15 @@ static int parse_probe_arg(char *arg, const struct fetch_type *t,
>  
>  	switch (arg[0]) {
>  	case '$':
> -		ret = parse_probe_vars(arg + 1, t, f, is_return, is_kprobe);
> +		ret = parse_probe_vars(arg + 1, type, code,
> +					is_return, is_kprobe);
>  		break;
>  
>  	case '%':	/* named register */
>  		ret = regs_query_register_offset(arg + 1);
>  		if (ret >= 0) {
> -			f->fn = t->fetch[FETCH_MTD_reg];
> -			f->data = (void *)(unsigned long)ret;
> +			code->op = FETCH_OP_REG;
> +			code->param = (unsigned int)ret;
>  			ret = 0;
>  		}
>  		break;
> @@ -411,9 +227,9 @@ static int parse_probe_arg(char *arg, const struct fetch_type *t,
>  			ret = kstrtoul(arg + 1, 0, &param);
>  			if (ret)
>  				break;
> -
> -			f->fn = t->fetch[FETCH_MTD_memory];
> -			f->data = (void *)param;
> +			/* load address */
> +			code->op = FETCH_OP_IMM;
> +			code->immediate = param;
>  		} else if (arg[1] == '+') {
>  			/* kprobes don't support file offsets */
>  			if (is_kprobe)
> @@ -423,8 +239,8 @@ static int parse_probe_arg(char *arg, const struct fetch_type *t,
>  			if (ret)
>  				break;
>  
> -			f->fn = t->fetch[FETCH_MTD_file_offset];
> -			f->data = (void *)offset;
> +			code->op = FETCH_OP_FOFFS;
> +			code->immediate = (unsigned long)offset;  // imm64?
>  		} else {
>  			/* uprobes don't support symbols */
>  			if (!is_kprobe)
> @@ -434,10 +250,19 @@ static int parse_probe_arg(char *arg, const struct fetch_type *t,
>  			if (ret)
>  				break;
>  
> -			f->data = alloc_symbol_cache(arg + 1, offset);
> -			if (f->data)
> -				f->fn = t->fetch[FETCH_MTD_symbol];
> +			code->op = FETCH_OP_IMM;
> +			code->immediate =
> +				(unsigned long)kallsyms_lookup_name(arg + 1);
> +			if (!code->immediate)
> +				return -ENOENT;
> +			code->immediate += offset;
>  		}
> +		/* These are fetching from memory */
> +		if (++code == end)
> +			return -E2BIG;
> +		*pcode = code;
> +		code->op = FETCH_OP_DEREF;
> +		code->offset = offset;
>  		break;
>  
>  	case '+':	/* deref memory */
> @@ -445,11 +270,10 @@ static int parse_probe_arg(char *arg, const struct fetch_type *t,
>  	case '-':
>  		tmp = strchr(arg, '(');
>  		if (!tmp)
> -			break;
> +			return -EINVAL;
>  
>  		*tmp = '\0';
>  		ret = kstrtol(arg, 0, &offset);
> -
>  		if (ret)
>  			break;
>  
> @@ -457,36 +281,28 @@ static int parse_probe_arg(char *arg, const struct fetch_type *t,
>  		tmp = strrchr(arg, ')');
>  
>  		if (tmp) {
> -			struct deref_fetch_param	*dprm;
> -			const struct fetch_type		*t2;
> +			const struct fetch_type *t2 = find_fetch_type(NULL);
>  
> -			t2 = find_fetch_type(NULL, ftbl);
>  			*tmp = '\0';
> -			dprm = kzalloc(sizeof(struct deref_fetch_param), GFP_KERNEL);
> -
> -			if (!dprm)
> -				return -ENOMEM;
> -
> -			dprm->offset = offset;
> -			dprm->fetch = t->fetch[FETCH_MTD_memory];
> -			dprm->fetch_size = get_fetch_size_function(t,
> -							dprm->fetch, ftbl);
> -			ret = parse_probe_arg(arg, t2, &dprm->orig, is_return,
> -							is_kprobe, ftbl);
> +			ret = parse_probe_arg(arg, t2, &code, end, is_return,
> +					      is_kprobe);
>  			if (ret)
> -				kfree(dprm);
> -			else {
> -				f->fn = t->fetch[FETCH_MTD_deref];
> -				f->data = (void *)dprm;
> -			}
> +				break;
> +			if (code->op == FETCH_OP_COMM)
> +				return -EINVAL;
> +			if (++code == end)
> +				return -E2BIG;
> +			*pcode = code;
> +
> +			code->op = FETCH_OP_DEREF;
> +			code->offset = offset;
>  		}
>  		break;
>  	}
> -	if (!ret && !f->fn) {	/* Parsed, but do not find fetch method */
> -		pr_info("%s type has no corresponding fetch method.\n", t->name);
> +	if (!ret && code->op == FETCH_OP_NOP) {
> +		/* Parsed, but do not find fetch method */
>  		ret = -EINVAL;
>  	}
> -
>  	return ret;
>  }
>  
> @@ -495,22 +311,15 @@ static int parse_probe_arg(char *arg, const struct fetch_type *t,
>  /* Bitfield type needs to be parsed into a fetch function */
>  static int __parse_bitfield_probe_arg(const char *bf,
>  				      const struct fetch_type *t,
> -				      struct fetch_param *f)
> +				      struct fetch_insn **pcode)
>  {
> -	struct bitfield_fetch_param *bprm;
> +	struct fetch_insn *code = *pcode;
>  	unsigned long bw, bo;
>  	char *tail;
>  
>  	if (*bf != 'b')
>  		return 0;
>  
> -	bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
> -	if (!bprm)
> -		return -ENOMEM;
> -
> -	bprm->orig = *f;
> -	f->fn = t->fetch[FETCH_MTD_bitfield];
> -	f->data = (void *)bprm;
>  	bw = simple_strtoul(bf + 1, &tail, 0);	/* Use simple one */
>  
>  	if (bw == 0 || *tail != '@')
> @@ -521,18 +330,24 @@ static int __parse_bitfield_probe_arg(const char *bf,
>  
>  	if (tail == bf || *tail != '/')
>  		return -EINVAL;
> +	code++;
> +	if (code->op != FETCH_OP_NOP)
> +		return -E2BIG;
> +	*pcode = code;
>  
> -	bprm->hi_shift = BYTES_TO_BITS(t->size) - (bw + bo);
> -	bprm->low_shift = bprm->hi_shift + bo;
> +	code->op = FETCH_OP_MOD_BF;
> +	code->lshift = BYTES_TO_BITS(t->size) - (bw + bo);
> +	code->rshift = BYTES_TO_BITS(t->size) - bw;
> +	code->basesize = t->size;
>  
>  	return (BYTES_TO_BITS(t->size) < (bw + bo)) ? -EINVAL : 0;
>  }
>  
>  /* String length checking wrapper */
>  int traceprobe_parse_probe_arg(char *arg, ssize_t *size,
> -		struct probe_arg *parg, bool is_return, bool is_kprobe,
> -		const struct fetch_type *ftbl)
> +		struct probe_arg *parg, bool is_return, bool is_kprobe)
>  {
> +	struct fetch_insn *code, *tmp = NULL;
>  	const char *t;
>  	int ret;
>  
> @@ -556,25 +371,67 @@ int traceprobe_parse_probe_arg(char *arg, ssize_t *size,
>  	 */
>  	if (!t && strcmp(arg, "$comm") == 0)
>  		t = "string";
> -	parg->type = find_fetch_type(t, ftbl);
> +	parg->type = find_fetch_type(t);
>  	if (!parg->type) {
>  		pr_info("Unsupported type: %s\n", t);
>  		return -EINVAL;
>  	}
>  	parg->offset = *size;
>  	*size += parg->type->size;
> -	ret = parse_probe_arg(arg, parg->type, &parg->fetch, is_return,
> -			      is_kprobe, ftbl);
> -
> -	if (ret >= 0 && t != NULL)
> -		ret = __parse_bitfield_probe_arg(t, parg->type, &parg->fetch);
>  
> -	if (ret >= 0) {
> -		parg->fetch_size.fn = get_fetch_size_function(parg->type,
> -							      parg->fetch.fn,
> -							      ftbl);
> -		parg->fetch_size.data = parg->fetch.data;
> +	code = tmp = kzalloc(sizeof(*code) * FETCH_INSN_MAX, GFP_KERNEL);
> +	if (!code)
> +		return -ENOMEM;
> +	code[FETCH_INSN_MAX - 1].op = FETCH_OP_END;
> +
> +	ret = parse_probe_arg(arg, parg->type, &code, &code[FETCH_INSN_MAX - 1],
> +			      is_return, is_kprobe);
> +	if (ret)
> +		goto fail;
> +
> +	/* Store operation */
> +	if (!strcmp(parg->type->name, "string")) {
> +		if (code->op != FETCH_OP_DEREF && code->op != FETCH_OP_IMM &&
> +		    code->op != FETCH_OP_COMM) {
> +			pr_info("string only accepts memory or address.\n");
> +			ret = -EINVAL;
> +			goto fail;
> +		}
> +		/* Since IMM or COMM must be the 1st insn, this is safe */
> +		if (code->op == FETCH_OP_IMM || code->op == FETCH_OP_COMM)
> +			code++;
> +		code->op = FETCH_OP_ST_STRING;	/* In DEREF case, replace it */
> +		parg->dynamic = true;
> +	} else if (code->op == FETCH_OP_DEREF) {
> +		code->op = FETCH_OP_ST_MEM;
> +		code->size = parg->type->size;
> +	} else {
> +		code++;
> +		if (code->op != FETCH_OP_NOP) {
> +			ret = -E2BIG;
> +			goto fail;
> +		}
> +		code->op = FETCH_OP_ST_RAW;
> +		code->size = parg->type->size;
>  	}
> +	/* Modify operation */
> +	if (t != NULL) {
> +		ret = __parse_bitfield_probe_arg(t, parg->type, &code);
> +		if (ret)
> +			goto fail;
> +	}
> +	code++;
> +	code->op = FETCH_OP_END;
> +
> +	/* Shrink down the code buffer */
> +	parg->code = kzalloc(sizeof(*code) * (code - tmp + 1), GFP_KERNEL);
> +	if (!parg->code)
> +		ret = -ENOMEM;
> +	else
> +		memcpy(parg->code, tmp, sizeof(*code) * (code - tmp + 1));
> +
> +fail:
> +	kfree(tmp);
>  
>  	return ret;
>  }
> @@ -596,25 +453,9 @@ int traceprobe_conflict_field_name(const char *name,
>  	return 0;
>  }
>  
> -void traceprobe_update_arg(struct probe_arg *arg)
> -{
> -	if (CHECK_FETCH_FUNCS(bitfield, arg->fetch.fn))
> -		update_bitfield_fetch_param(arg->fetch.data);
> -	else if (CHECK_FETCH_FUNCS(deref, arg->fetch.fn))
> -		update_deref_fetch_param(arg->fetch.data);
> -	else if (CHECK_FETCH_FUNCS(symbol, arg->fetch.fn))
> -		update_symbol_cache(arg->fetch.data);
> -}
> -
>  void traceprobe_free_probe_arg(struct probe_arg *arg)
>  {
> -	if (CHECK_FETCH_FUNCS(bitfield, arg->fetch.fn))
> -		free_bitfield_fetch_param(arg->fetch.data);
> -	else if (CHECK_FETCH_FUNCS(deref, arg->fetch.fn))
> -		free_deref_fetch_param(arg->fetch.data);
> -	else if (CHECK_FETCH_FUNCS(symbol, arg->fetch.fn))
> -		free_symbol_cache(arg->fetch.data);
> -
> +	kfree(arg->code);
>  	kfree(arg->name);
>  	kfree(arg->comm);
>  }
> diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
> index de928052926b..89d853ef5174 100644
> --- a/kernel/trace/trace_probe.h
> +++ b/kernel/trace/trace_probe.h
> @@ -91,25 +91,50 @@ static nokprobe_inline void *get_loc_data(u32 *dl, void *ent)
>  	return (u8 *)ent + get_rloc_offs(*dl);
>  }
>  
> -/* Data fetch function type */
> -typedef	void (*fetch_func_t)(struct pt_regs *, void *, void *);
>  /* Printing function type */
>  typedef int (*print_type_func_t)(struct trace_seq *, void *, void *);
>  
> -/* Fetch types */
> -enum {
> -	FETCH_MTD_reg = 0,
> -	FETCH_MTD_stack,
> -	FETCH_MTD_retval,
> -	FETCH_MTD_comm,
> -	FETCH_MTD_memory,
> -	FETCH_MTD_symbol,
> -	FETCH_MTD_deref,
> -	FETCH_MTD_bitfield,
> -	FETCH_MTD_file_offset,
> -	FETCH_MTD_END,
> +enum fetch_op {
> +	FETCH_OP_NOP = 0,
> +	// Stage 1 (load) ops
> +	FETCH_OP_REG,		/* Register : .param = offset */
> +	FETCH_OP_STACK,		/* Stack : .param = index */
> +	FETCH_OP_STACKP,	/* Stack pointer */
> +	FETCH_OP_RETVAL,	/* Return value */
> +	FETCH_OP_IMM,		/* Immediate : .immediate */
> +	FETCH_OP_COMM,		/* Current comm */
> +	FETCH_OP_FOFFS,		/* File offset: .immediate */
> +	// Stage 2 (dereference) op
> +	FETCH_OP_DEREF,		/* Dereference: .offset */
> +	// Stage 3 (store) ops
> +	FETCH_OP_ST_RAW,	/* Raw: .size */
> +	FETCH_OP_ST_MEM,	/* Mem: .offset, .size */
> +	FETCH_OP_ST_STRING,	/* String: .offset, .size */
> +	// Stage 4 (modify) op
> +	FETCH_OP_MOD_BF,	/* Bitfield: .basesize, .lshift, .rshift */
> +	FETCH_OP_END,
>  };
>  
> +struct fetch_insn {
> +	enum fetch_op op;
> +	union {
> +		unsigned int param;
> +		struct {
> +			unsigned int size;
> +			int offset;
> +		};
> +		struct {
> +			unsigned char basesize;
> +			unsigned char lshift;
> +			unsigned char rshift;
> +		};
> +		unsigned long immediate;
> +	};
> +};
> +
> +/* fetch + deref*N + store + mod + end <= 16, this allows N=12, enough */
> +#define FETCH_INSN_MAX	16
> +
>  /* Fetch type information table */
>  struct fetch_type {
>  	const char		*name;		/* Name of type */
> @@ -118,13 +143,6 @@ struct fetch_type {
>  	print_type_func_t	print;		/* Print functions */
>  	const char		*fmt;		/* Fromat string */
>  	const char		*fmttype;	/* Name in format file */
> -	/* Fetch functions */
> -	fetch_func_t		fetch[FETCH_MTD_END];
> -};
> -
> -struct fetch_param {
> -	fetch_func_t		fn;
> -	void 			*data;
>  };
>  
>  /* For defining macros, define string/string_size types */
> @@ -154,66 +172,12 @@ DECLARE_BASIC_PRINT_TYPE_FUNC(x64);
>  
>  DECLARE_BASIC_PRINT_TYPE_FUNC(string);
>  
> -#define FETCH_FUNC_NAME(method, type)	fetch_##method##_##type
> -
> -/* Declare macro for basic types */
> -#define DECLARE_FETCH_FUNC(method, type)				\
> -extern void FETCH_FUNC_NAME(method, type)(struct pt_regs *regs, 	\
> -					  void *data, void *dest)
> -
> -#define DECLARE_BASIC_FETCH_FUNCS(method) 	\
> -DECLARE_FETCH_FUNC(method, u8);			\
> -DECLARE_FETCH_FUNC(method, u16);		\
> -DECLARE_FETCH_FUNC(method, u32);		\
> -DECLARE_FETCH_FUNC(method, u64)
> -
> -DECLARE_BASIC_FETCH_FUNCS(reg);
> -#define fetch_reg_string			NULL
> -#define fetch_reg_string_size			NULL
> -
> -DECLARE_BASIC_FETCH_FUNCS(retval);
> -#define fetch_retval_string			NULL
> -#define fetch_retval_string_size		NULL
> -
> -DECLARE_BASIC_FETCH_FUNCS(symbol);
> -DECLARE_FETCH_FUNC(symbol, string);
> -DECLARE_FETCH_FUNC(symbol, string_size);
> -
> -DECLARE_BASIC_FETCH_FUNCS(deref);
> -DECLARE_FETCH_FUNC(deref, string);
> -DECLARE_FETCH_FUNC(deref, string_size);
> -
> -DECLARE_BASIC_FETCH_FUNCS(bitfield);
> -#define fetch_bitfield_string			NULL
> -#define fetch_bitfield_string_size		NULL
> -
> -/* comm only makes sense as a string */
> -#define fetch_comm_u8		NULL
> -#define fetch_comm_u16		NULL
> -#define fetch_comm_u32		NULL
> -#define fetch_comm_u64		NULL
> -DECLARE_FETCH_FUNC(comm, string);
> -DECLARE_FETCH_FUNC(comm, string_size);
> -
> -/*
> - * 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(method) \
> -DEFINE_FETCH_##method(u8)		\
> -DEFINE_FETCH_##method(u16)		\
> -DEFINE_FETCH_##method(u32)		\
> -DEFINE_FETCH_##method(u64)
> -
>  /* Default (unsigned long) fetch type */
>  #define __DEFAULT_FETCH_TYPE(t) x##t
>  #define _DEFAULT_FETCH_TYPE(t) __DEFAULT_FETCH_TYPE(t)
>  #define DEFAULT_FETCH_TYPE _DEFAULT_FETCH_TYPE(BITS_PER_LONG)
>  #define DEFAULT_FETCH_TYPE_STR __stringify(DEFAULT_FETCH_TYPE)
>  
> -#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,					\
> @@ -221,17 +185,6 @@ DEFINE_FETCH_##method(u64)
>  	 .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(comm, ftype),				\
> -ASSIGN_FETCH_FUNC(memory, ftype),			\
> -ASSIGN_FETCH_FUNC(symbol, ftype),			\
> -ASSIGN_FETCH_FUNC(deref, ftype),			\
> -ASSIGN_FETCH_FUNC(bitfield, ftype),			\
> -ASSIGN_FETCH_FUNC(file_offset, ftype),			\
> -	  }						\
>  	}
>  
>  #define ASSIGN_FETCH_TYPE(ptype, ftype, sign)			\
> @@ -243,42 +196,10 @@ ASSIGN_FETCH_FUNC(file_offset, ftype),			\
>  
>  #define ASSIGN_FETCH_TYPE_END {}
>  
> -#define FETCH_TYPE_STRING	0
> -#define FETCH_TYPE_STRSIZE	1
> -
>  #ifdef CONFIG_KPROBE_EVENTS
> -struct symbol_cache;
> -unsigned long update_symbol_cache(struct symbol_cache *sc);
> -void free_symbol_cache(struct symbol_cache *sc);
> -struct symbol_cache *alloc_symbol_cache(const char *sym, long offset);
>  bool trace_kprobe_on_func_entry(struct trace_event_call *call);
>  bool trace_kprobe_error_injectable(struct trace_event_call *call);
>  #else
> -/* uprobes do not support symbol fetch methods */
> -#define fetch_symbol_u8			NULL
> -#define fetch_symbol_u16		NULL
> -#define fetch_symbol_u32		NULL
> -#define fetch_symbol_u64		NULL
> -#define fetch_symbol_string		NULL
> -#define fetch_symbol_string_size	NULL
> -
> -struct symbol_cache {
> -};
> -static inline unsigned long __used update_symbol_cache(struct symbol_cache *sc)
> -{
> -	return 0;
> -}
> -
> -static inline void __used free_symbol_cache(struct symbol_cache *sc)
> -{
> -}
> -
> -static inline struct symbol_cache * __used
> -alloc_symbol_cache(const char *sym, long offset)
> -{
> -	return NULL;
> -}
> -
>  static inline bool trace_kprobe_on_func_entry(struct trace_event_call *call)
>  {
>  	return false;
> @@ -291,8 +212,8 @@ static inline bool trace_kprobe_error_injectable(struct trace_event_call *call)
>  #endif /* CONFIG_KPROBE_EVENTS */
>  
>  struct probe_arg {
> -	struct fetch_param	fetch;
> -	struct fetch_param	fetch_size;
> +	struct fetch_insn	*code;
> +	bool			dynamic;/* Dynamic array (string) is used */
>  	unsigned int		offset;	/* Offset from argument entry */
>  	const char		*name;	/* Name of this argument */
>  	const char		*comm;	/* Command of this argument */
> @@ -324,12 +245,6 @@ static inline bool trace_probe_is_registered(struct trace_probe *tp)
>  	return !!(tp->flags & TP_FLAG_REGISTERED);
>  }
>  
> -static nokprobe_inline void call_fetch(struct fetch_param *fprm,
> -				 struct pt_regs *regs, void *dest)
> -{
> -	return fprm->fn(regs, fprm->data, dest);
> -}
> -
>  /* Check the name is good for event/group/fields */
>  static inline bool is_good_name(const char *name)
>  {
> @@ -355,8 +270,7 @@ find_event_file_link(struct trace_probe *tp, struct trace_event_file *file)
>  }
>  
>  extern int traceprobe_parse_probe_arg(char *arg, ssize_t *size,
> -		   struct probe_arg *parg, bool is_return, bool is_kprobe,
> -		   const struct fetch_type *ftbl);
> +		   struct probe_arg *parg, bool is_return, bool is_kprobe);
>  
>  extern int traceprobe_conflict_field_name(const char *name,
>  			       struct probe_arg *args, int narg);
> @@ -366,68 +280,6 @@ extern void traceprobe_free_probe_arg(struct probe_arg *arg);
>  
>  extern int traceprobe_split_symbol_offset(char *symbol, long *offset);
>  
> -/* Sum up total data length for dynamic arraies (strings) */
> -static nokprobe_inline 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 nokprobe_inline 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);
> -	}
> -}
> -
> -static inline int
> -print_probe_args(struct trace_seq *s, struct probe_arg *args, int nr_args,
> -		 u8 *data, void *field)
> -{
> -	int i;
> -
> -	for (i = 0; i < nr_args; i++) {
> -		trace_seq_printf(s, " %s=", args[i].name);
> -		if (!args[i].type->print(s, data + args[i].offset, field))
> -			return -ENOMEM;
> -	}
> -	return 0;
> -}
> -
>  extern int set_print_fmt(struct trace_probe *tp, bool is_return);
>  
>  #ifdef CONFIG_PERF_EVENTS
> diff --git a/kernel/trace/trace_probe_tmpl.h b/kernel/trace/trace_probe_tmpl.h
> new file mode 100644
> index 000000000000..c8a5272abf01
> --- /dev/null
> +++ b/kernel/trace/trace_probe_tmpl.h
> @@ -0,0 +1,120 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Traceprobe fetch helper inlines
> + */
> +
> +static nokprobe_inline void
> +fetch_store_raw(unsigned long val, struct fetch_insn *code, void *buf)
> +{
> +	switch (code->size) {
> +	case 1:
> +		*(u8 *)buf = (u8)val;
> +		break;
> +	case 2:
> +		*(u16 *)buf = (u16)val;
> +		break;
> +	case 4:
> +		*(u32 *)buf = (u32)val;
> +		break;
> +	case 8:
> +		//TBD: 32bit signed
> +		*(u64 *)buf = (u64)val;
> +		break;
> +	default:
> +		*(unsigned long *)buf = val;
> +	}
> +}
> +
> +static nokprobe_inline void
> +fetch_apply_bitfield(struct fetch_insn *code, void *buf)
> +{
> +	switch (code->basesize) {
> +	case 1:
> +		*(u8 *)buf <<= code->lshift;
> +		*(u8 *)buf >>= code->rshift;
> +		break;
> +	case 2:
> +		*(u16 *)buf <<= code->lshift;
> +		*(u16 *)buf >>= code->rshift;
> +		break;
> +	case 4:
> +		*(u32 *)buf <<= code->lshift;
> +		*(u32 *)buf >>= code->rshift;
> +		break;
> +	case 8:
> +		*(u64 *)buf <<= code->lshift;
> +		*(u64 *)buf >>= code->rshift;
> +		break;
> +	}
> +}
> +
> +/* Define this for each callsite */
> +static int
> +process_fetch_insn(struct fetch_insn *code, struct pt_regs *regs,
> +		   void *dest, bool pre);
> +
> +/* Sum up total data length for dynamic arraies (strings) */
> +static nokprobe_inline int
> +__get_data_size(struct trace_probe *tp, struct pt_regs *regs)
> +{
> +	struct probe_arg *arg;
> +	int i, ret = 0;
> +	u32 len;
> +
> +	for (i = 0; i < tp->nr_args; i++) {
> +		arg = tp->args + i;
> +		if (unlikely(arg->dynamic)) {
> +			process_fetch_insn(arg->code, regs, &len, true);
> +			ret += len;
> +		}
> +	}
> +
> +	return ret;
> +}
> +
> +/* Store the value of each argument */
> +static nokprobe_inline void
> +store_trace_args(int ent_size, struct trace_probe *tp, struct pt_regs *regs,
> +		 u8 *data, int maxlen)
> +{
> +	struct probe_arg *arg;
> +	u32 end = tp->size;
> +	u32 *dl;	/* Data (relative) location */
> +	int i;
> +
> +	for (i = 0; i < tp->nr_args; i++) {
> +		arg = tp->args + i;
> +		if (unlikely(arg->dynamic)) {
> +			/*
> +			 * First, we set the relative location and
> +			 * maximum data length to *dl
> +			 */
> +			dl = (u32 *)(data + arg->offset);
> +			*dl = make_data_rloc(maxlen, end - arg->offset);
> +			/* Then try to fetch string or dynamic array data */
> +			process_fetch_insn(arg->code, regs, dl, false);
> +			/* 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 + arg->offset);
> +		} else
> +			/* Just fetching data normally */
> +			process_fetch_insn(arg->code, regs, data + arg->offset,
> +					   false);
> +	}
> +}
> +
> +static inline int
> +print_probe_args(struct trace_seq *s, struct probe_arg *args, int nr_args,
> +		 u8 *data, void *field)
> +{
> +	int i;
> +
> +	for (i = 0; i < nr_args; i++) {
> +		trace_seq_printf(s, " %s=", args[i].name);
> +		if (!args[i].type->print(s, data + args[i].offset, field))
> +			return -ENOMEM;
> +	}
> +	return 0;
> +}
> diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
> index 887da2bb63aa..9fc0123c721f 100644
> --- a/kernel/trace/trace_uprobe.c
> +++ b/kernel/trace/trace_uprobe.c
> @@ -27,6 +27,7 @@
>  #include <linux/rculist.h>
>  
>  #include "trace_probe.h"
> +#include "trace_probe_tmpl.h"
>  
>  #define UPROBE_EVENT_SYSTEM	"uprobes"
>  
> @@ -109,37 +110,19 @@ static unsigned long get_user_stack_nth(struct pt_regs *regs, unsigned int n)
>  /*
>   * Uprobes-specific fetch functions
>   */
> -#define DEFINE_FETCH_stack(type)					\
> -static void FETCH_FUNC_NAME(stack, type)(struct pt_regs *regs,		\
> -					 void *offset, void *dest)	\
> -{									\
> -	*(type *)dest = (type)get_user_stack_nth(regs,			\
> -					      ((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_memory(type)					\
> -static void FETCH_FUNC_NAME(memory, type)(struct pt_regs *regs,		\
> -					  void *addr, void *dest)	\
> -{									\
> -	type retval;							\
> -	void __user *vaddr = (void __force __user *) addr;		\
> -									\
> -	if (copy_from_user(&retval, vaddr, sizeof(type)))		\
> -		*(type *)dest = 0;					\
> -	else								\
> -		*(type *) dest = retval;				\
> +static nokprobe_inline int
> +probe_user_read(void *dest, void *src, size_t size)
> +{
> +	void __user *vaddr = (void __force __user *)src;
> +
> +	return copy_from_user(dest, vaddr, size);
>  }
> -DEFINE_BASIC_FETCH_FUNCS(memory)
>  /*
>   * Fetch a null-terminated string. Caller MUST set *(u32 *)dest with max
>   * length and relative data location.
>   */
> -static void FETCH_FUNC_NAME(memory, string)(struct pt_regs *regs,
> -					    void *addr, void *dest)
> +static nokprobe_inline void
> +fetch_store_string(unsigned long addr, void *dest)
>  {
>  	long ret;
>  	u32 rloc = *(u32 *)dest;
> @@ -160,8 +143,9 @@ static void FETCH_FUNC_NAME(memory, string)(struct pt_regs *regs,
>  	}
>  }
>  
> -static void FETCH_FUNC_NAME(memory, string_size)(struct pt_regs *regs,
> -						 void *addr, void *dest)
> +/* Return the length of string -- including null terminal byte */
> +static nokprobe_inline void
> +fetch_store_strlen(unsigned long addr, void *dest)
>  {
>  	int len;
>  	void __user *vaddr = (void __force __user *) addr;
> @@ -174,7 +158,7 @@ static void FETCH_FUNC_NAME(memory, string_size)(struct pt_regs *regs,
>  		*(u32 *)dest = len;
>  }
>  
> -static unsigned long translate_user_vaddr(void *file_offset)
> +static unsigned long translate_user_vaddr(unsigned long file_offset)
>  {
>  	unsigned long base_addr;
>  	struct uprobe_dispatch_data *udd;
> @@ -182,44 +166,79 @@ static unsigned long translate_user_vaddr(void *file_offset)
>  	udd = (void *) current->utask->vaddr;
>  
>  	base_addr = udd->bp_addr - udd->tu->offset;
> -	return base_addr + (unsigned long)file_offset;
> +	return base_addr + file_offset;
>  }
>  
> -#define DEFINE_FETCH_file_offset(type)					\
> -static void FETCH_FUNC_NAME(file_offset, type)(struct pt_regs *regs,	\
> -					       void *offset, void *dest)\
> -{									\
> -	void *vaddr = (void *)translate_user_vaddr(offset);		\
> -									\
> -	FETCH_FUNC_NAME(memory, type)(regs, vaddr, dest);		\
> +/* Note that we don't verify it, since the code does not come from user space */
> +static int
> +process_fetch_insn(struct fetch_insn *code, struct pt_regs *regs, void *dest,
> +		   bool pre)
> +{
> +	unsigned long val;
> +	int ret;
> +
> +	/* 1st stage: get value from context */
> +	switch (code->op) {
> +	case FETCH_OP_REG:
> +		val = regs_get_register(regs, code->param);
> +		break;
> +	case FETCH_OP_STACK:
> +		val = get_user_stack_nth(regs, code->param);
> +		break;
> +	case FETCH_OP_STACKP:
> +		val = user_stack_pointer(regs);
> +		break;
> +	case FETCH_OP_RETVAL:
> +		val = regs_return_value(regs);
> +		break;
> +	case FETCH_OP_IMM:
> +		val = code->immediate;
> +		break;
> +	case FETCH_OP_FOFFS:
> +		val = translate_user_vaddr(code->immediate);
> +		break;
> +	default:
> +		return -EILSEQ;
> +	}
> +	code++;
> +
> +	/* 2nd stage: dereference memory if needed */
> +	while (code->op == FETCH_OP_DEREF) {
> +		ret = probe_user_read(&val, (void *)val + code->offset,
> +				      sizeof(val));
> +		if (ret)
> +			return ret;
> +		code++;
> +	}
> +
> +	/* 3rd stage: store value to buffer */
> +	switch (code->op) {
> +	case FETCH_OP_ST_RAW:
> +		fetch_store_raw(val, code, dest);
> +		break;
> +	case FETCH_OP_ST_MEM:
> +		probe_user_read(dest, (void *)val + code->offset, code->size);
> +		break;
> +	case FETCH_OP_ST_STRING:
> +		if (pre)
> +			fetch_store_strlen(val + code->offset, dest);
> +		else
> +			fetch_store_string(val + code->offset, dest);
> +		break;
> +	default:
> +		return -EILSEQ;
> +	}
> +	code++;
> +
> +	/* 4th stage: modify stored value if needed */
> +	if (code->op == FETCH_OP_MOD_BF) {
> +		fetch_apply_bitfield(code, dest);
> +		code++;
> +	}
> +
> +	return code->op == FETCH_OP_END ? 0 : -EILSEQ;
>  }
> -DEFINE_BASIC_FETCH_FUNCS(file_offset)
> -DEFINE_FETCH_file_offset(string)
> -DEFINE_FETCH_file_offset(string_size)
> -
> -/* Fetch type information table */
> -static const struct fetch_type uprobes_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),
> -	ASSIGN_FETCH_TYPE(u64, u64, 0),
> -	ASSIGN_FETCH_TYPE(s8,  u8,  1),
> -	ASSIGN_FETCH_TYPE(s16, u16, 1),
> -	ASSIGN_FETCH_TYPE(s32, u32, 1),
> -	ASSIGN_FETCH_TYPE(s64, u64, 1),
> -	ASSIGN_FETCH_TYPE_ALIAS(x8,  u8,  u8,  0),
> -	ASSIGN_FETCH_TYPE_ALIAS(x16, u16, u16, 0),
> -	ASSIGN_FETCH_TYPE_ALIAS(x32, u32, u32, 0),
> -	ASSIGN_FETCH_TYPE_ALIAS(x64, u64, u64, 0),
> -
> -	ASSIGN_FETCH_TYPE_END
> -};
> +NOKPROBE_SYMBOL(process_fetch_insn)
>  
>  static inline void init_trace_uprobe_filter(struct trace_uprobe_filter *filter)
>  {
> @@ -538,8 +557,7 @@ static int create_trace_uprobe(int argc, char **argv)
>  
>  		/* Parse fetch argument */
>  		ret = traceprobe_parse_probe_arg(arg, &tu->tp.size, parg,
> -						 is_return, false,
> -						 uprobes_fetch_type_table);
> +						 is_return, false);
>  		if (ret) {
>  			pr_info("Parse error at argument[%d]. (%d)\n", i, ret);
>  			goto error;
>