tracing/kprobes: Add bitfield type

Add bitfield type for tracing arguments on kprobe-tracer.  The syntax of
a bitfield type is:

 b<bit-size>@<bit-offset>/<container-size>

e.g.

Accessing 2 bits-width field with 4 bits-offset in 32 bits-width data at
4 bytes offseted from the address pointed by AX register:

 +4(%ax):b2@4/32

Since the width of container data depends on the arch, so I just added
the container-size at the end.

Cc: 2nddept-manager@sdl.hitachi.co.jp
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <20110204125205.9507.11363.stgit@ltc236.sdl.hitachi.co.jp>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Masami Hiramatsu 2011-02-04 21:52:05 +09:00 committed by Arnaldo Carvalho de Melo
parent e374536998
commit 1ff511e35e
2 changed files with 118 additions and 2 deletions

View file

@ -42,11 +42,25 @@ Synopsis of kprobe_events
+|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(**)
NAME=FETCHARG : Set NAME as the argument name of FETCHARG.
FETCHARG:TYPE : Set TYPE as the type of FETCHARG. Currently, basic types
(u8/u16/u32/u64/s8/s16/s32/s64) and string are supported.
(u8/u16/u32/u64/s8/s16/s32/s64), "string" and bitfield
are supported.
(*) only for return probe.
(**) this is useful for fetching a field of data structures.
Types
-----
Several types are supported for fetch-args. Kprobe tracer will access memory
by given type. Prefix 's' and 'u' means those types are signed and unsigned
respectively. Traced arguments are shown in decimal (signed) or hex (unsigned).
String type is a special type, which fetches a "null-terminated" string from
kernel space. This means it will fail and store NULL if the string container
has been paged out.
Bitfield is another special type, which takes 3 parameters, bit-width, bit-
offset, and container-size (usually 32). The syntax is;
b<bit-width>@<bit-offset>/<container-size>
Per-Probe Event Filtering
-------------------------

View file

@ -353,6 +353,43 @@ static __kprobes void free_deref_fetch_param(struct deref_fetch_param *data)
kfree(data);
}
/* Bitfield fetch function */
struct bitfield_fetch_param {
struct fetch_param orig;
unsigned char hi_shift;
unsigned char low_shift;
};
#define DEFINE_FETCH_bitfield(type) \
static __kprobes 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; \
}
DEFINE_BASIC_FETCH_FUNCS(bitfield)
#define fetch_bitfield_string NULL
#define fetch_bitfield_string_size NULL
static __kprobes 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);
}
/* Default (unsigned long) fetch type */
#define __DEFAULT_FETCH_TYPE(t) u##t
#define _DEFAULT_FETCH_TYPE(t) __DEFAULT_FETCH_TYPE(t)
@ -367,6 +404,7 @@ enum {
FETCH_MTD_memory,
FETCH_MTD_symbol,
FETCH_MTD_deref,
FETCH_MTD_bitfield,
FETCH_MTD_END,
};
@ -387,6 +425,7 @@ ASSIGN_FETCH_FUNC(retval, ftype), \
ASSIGN_FETCH_FUNC(memory, ftype), \
ASSIGN_FETCH_FUNC(symbol, ftype), \
ASSIGN_FETCH_FUNC(deref, ftype), \
ASSIGN_FETCH_FUNC(bitfield, ftype), \
} \
}
@ -430,9 +469,33 @@ static const struct fetch_type *find_fetch_type(const char *type)
if (!type)
type = DEFAULT_FETCH_TYPE_STR;
/* Special case: bitfield */
if (*type == 'b') {
unsigned long bs;
type = strchr(type, '/');
if (!type)
goto fail;
type++;
if (strict_strtoul(type, 0, &bs))
goto fail;
switch (bs) {
case 8:
return find_fetch_type("u8");
case 16:
return find_fetch_type("u16");
case 32:
return find_fetch_type("u32");
case 64:
return find_fetch_type("u64");
default:
goto fail;
}
}
for (i = 0; i < ARRAY_SIZE(fetch_type_table); i++)
if (strcmp(type, fetch_type_table[i].name) == 0)
return &fetch_type_table[i];
fail:
return NULL;
}
@ -586,7 +649,9 @@ error:
static void free_probe_arg(struct probe_arg *arg)
{
if (CHECK_FETCH_FUNCS(deref, arg->fetch.fn))
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);
@ -806,6 +871,41 @@ static int __parse_probe_arg(char *arg, const struct fetch_type *t,
return ret;
}
#define BYTES_TO_BITS(nb) ((BITS_PER_LONG * (nb)) / sizeof(long))
/* 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 bitfield_fetch_param *bprm;
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 != '@')
return -EINVAL;
bf = tail + 1;
bo = simple_strtoul(bf, &tail, 0);
if (tail == bf || *tail != '/')
return -EINVAL;
bprm->hi_shift = BYTES_TO_BITS(t->size) - (bw + bo);
bprm->low_shift = bprm->hi_shift + bo;
return (BYTES_TO_BITS(t->size) < (bw + bo)) ? -EINVAL : 0;
}
/* String length checking wrapper */
static int parse_probe_arg(char *arg, struct trace_probe *tp,
struct probe_arg *parg, int is_return)
@ -835,6 +935,8 @@ static int parse_probe_arg(char *arg, struct trace_probe *tp,
parg->offset = tp->size;
tp->size += parg->type->size;
ret = __parse_probe_arg(arg, parg->type, &parg->fetch, is_return);
if (ret >= 0)
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);