linux/kernel/trace/trace_probe_tmpl.h
Masami Hiramatsu e65f7ae7f4 tracing/probe: Support user-space dereference
Support user-space dereference syntax for probe event arguments
to dereference the data-structure or array in user-space.

The syntax is just adding 'u' before an offset value.

 +|-u<OFFSET>(<FETCHARG>)

e.g. +u8(%ax), +u0(+0(%si))

For example, if you probe do_sched_setscheduler(pid, policy,
param) and record param->sched_priority, you can add new
probe as below;

 p do_sched_setscheduler priority=+u0($arg3)

Note that kprobe event provides this and it doesn't change the
dereference method automatically because we do not know whether
the given address is in userspace or kernel on some archs.

So as same as "ustring", this is an option for user, who has to
carefully choose the dereference method.

Link: http://lkml.kernel.org/r/155789872187.26965.4468456816590888687.stgit@devnote2

Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2019-05-25 23:04:42 -04:00

243 lines
5.6 KiB
C

/* 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;
}
}
/*
* These functions must be defined for each callsite.
* Return consumed dynamic data size (>= 0), or error (< 0).
* If dest is NULL, don't store result and return required dynamic data size.
*/
static int
process_fetch_insn(struct fetch_insn *code, struct pt_regs *regs,
void *dest, void *base);
static nokprobe_inline int fetch_store_strlen(unsigned long addr);
static nokprobe_inline int
fetch_store_string(unsigned long addr, void *dest, void *base);
static nokprobe_inline int fetch_store_strlen_user(unsigned long addr);
static nokprobe_inline int
fetch_store_string_user(unsigned long addr, void *dest, void *base);
static nokprobe_inline int
probe_mem_read(void *dest, void *src, size_t size);
static nokprobe_inline int
probe_mem_read_user(void *dest, void *src, size_t size);
/* From the 2nd stage, routine is same */
static nokprobe_inline int
process_fetch_insn_bottom(struct fetch_insn *code, unsigned long val,
void *dest, void *base)
{
struct fetch_insn *s3 = NULL;
int total = 0, ret = 0, i = 0;
u32 loc = 0;
unsigned long lval = val;
stage2:
/* 2nd stage: dereference memory if needed */
do {
if (code->op == FETCH_OP_DEREF) {
lval = val;
ret = probe_mem_read(&val, (void *)val + code->offset,
sizeof(val));
} else if (code->op == FETCH_OP_UDEREF) {
lval = val;
ret = probe_mem_read_user(&val,
(void *)val + code->offset, sizeof(val));
} else
break;
if (ret)
return ret;
code++;
} while (1);
s3 = code;
stage3:
/* 3rd stage: store value to buffer */
if (unlikely(!dest)) {
if (code->op == FETCH_OP_ST_STRING) {
ret = fetch_store_strlen(val + code->offset);
code++;
goto array;
} else if (code->op == FETCH_OP_ST_USTRING) {
ret += fetch_store_strlen_user(val + code->offset);
code++;
goto array;
} else
return -EILSEQ;
}
switch (code->op) {
case FETCH_OP_ST_RAW:
fetch_store_raw(val, code, dest);
break;
case FETCH_OP_ST_MEM:
probe_mem_read(dest, (void *)val + code->offset, code->size);
break;
case FETCH_OP_ST_UMEM:
probe_mem_read_user(dest, (void *)val + code->offset, code->size);
break;
case FETCH_OP_ST_STRING:
loc = *(u32 *)dest;
ret = fetch_store_string(val + code->offset, dest, base);
break;
case FETCH_OP_ST_USTRING:
loc = *(u32 *)dest;
ret = fetch_store_string_user(val + code->offset, dest, base);
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++;
}
array:
/* the last stage: Loop on array */
if (code->op == FETCH_OP_LP_ARRAY) {
total += ret;
if (++i < code->param) {
code = s3;
if (s3->op != FETCH_OP_ST_STRING &&
s3->op != FETCH_OP_ST_USTRING) {
dest += s3->size;
val += s3->size;
goto stage3;
}
code--;
val = lval + sizeof(char *);
if (dest) {
dest += sizeof(u32);
*(u32 *)dest = update_data_loc(loc, ret);
}
goto stage2;
}
code++;
ret = total;
}
return code->op == FETCH_OP_END ? ret : -EILSEQ;
}
/* 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, len, ret = 0;
for (i = 0; i < tp->nr_args; i++) {
arg = tp->args + i;
if (unlikely(arg->dynamic)) {
len = process_fetch_insn(arg->code, regs, NULL, NULL);
if (len > 0)
ret += len;
}
}
return ret;
}
/* Store the value of each argument */
static nokprobe_inline void
store_trace_args(void *data, struct trace_probe *tp, struct pt_regs *regs,
int header_size, int maxlen)
{
struct probe_arg *arg;
void *base = data - header_size;
void *dyndata = data + tp->size;
u32 *dl; /* Data location */
int ret, i;
for (i = 0; i < tp->nr_args; i++) {
arg = tp->args + i;
dl = data + arg->offset;
/* Point the dynamic data area if needed */
if (unlikely(arg->dynamic))
*dl = make_data_loc(maxlen, dyndata - base);
ret = process_fetch_insn(arg->code, regs, dl, base);
if (unlikely(ret < 0 && arg->dynamic)) {
*dl = make_data_loc(0, dyndata - base);
} else {
dyndata += ret;
maxlen -= ret;
}
}
}
static inline int
print_probe_args(struct trace_seq *s, struct probe_arg *args, int nr_args,
u8 *data, void *field)
{
void *p;
int i, j;
for (i = 0; i < nr_args; i++) {
struct probe_arg *a = args + i;
trace_seq_printf(s, " %s=", a->name);
if (likely(!a->count)) {
if (!a->type->print(s, data + a->offset, field))
return -ENOMEM;
continue;
}
trace_seq_putc(s, '{');
p = data + a->offset;
for (j = 0; j < a->count; j++) {
if (!a->type->print(s, p, field))
return -ENOMEM;
trace_seq_putc(s, j == a->count - 1 ? '}' : ',');
p += a->type->size;
}
}
return 0;
}