tracing/probe: Add ustring type for user-space string

Add "ustring" type for fetching user-space string from kprobe event.
User can specify ustring type at uprobe event, and it is same as
"string" for uprobe.

Note that probe-event provides this option but it doesn't choose the
correct type automatically since we have not way to decide the address
is in user-space or not on some arch (and on some other arch, you can
fetch the string by "string" type). So user must carefully check the
target code (e.g. if you see __user on the target variable) and
use this new type.

Link: http://lkml.kernel.org/r/155789871009.26965.14167558859557329331.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>
This commit is contained in:
Masami Hiramatsu 2019-05-15 14:38:30 +09:00 committed by Steven Rostedt (VMware)
parent 3d7081822f
commit 88903c4643
7 changed files with 85 additions and 11 deletions

View File

@ -55,7 +55,8 @@ Synopsis of kprobe_events
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), hexadecimal types
(x8/x16/x32/x64), "string" and bitfield are supported.
(x8/x16/x32/x64), "string", "ustring" and bitfield
are supported.
(\*1) only for the probe on function entry (offs == 0).
(\*2) only for return probe.
@ -77,7 +78,11 @@ apply it to registers/stack-entries etc. (for example, '$stack1:x8[8]' is
wrong, but '+8($stack):x8[8]' is OK.)
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.
has been paged out. "ustring" type is an alternative of string for user-space.
Note that kprobe-event provides string/ustring types, but doesn't change it
automatically. So user has to decide if the targe string in kernel or in user
space carefully. On some arch, if you choose wrong one, it always fails to
record string data.
The string array type is a bit different from other types. For other base
types, <base-type>[1] is equal to <base-type> (e.g. +0(%di):x32[1] is same
as +0(%di):x32.) But string[1] is not equal to string. The string type itself

View File

@ -4847,7 +4847,7 @@ static const char readme_msg[] =
"\t $stack<index>, $stack, $retval, $comm\n"
#endif
"\t type: s8/16/32/64, u8/16/32/64, x8/16/32/64, string, symbol,\n"
"\t b<bit-width>@<bit-offset>/<container-size>,\n"
"\t b<bit-width>@<bit-offset>/<container-size>, ustring,\n"
"\t <type>\\[<array-size>\\]\n"
#ifdef CONFIG_HIST_TRIGGERS
"\t field: <stype> <name>;\n"

View File

@ -886,6 +886,15 @@ fetch_store_strlen(unsigned long addr)
return (ret < 0) ? ret : len;
}
/* Return the length of string -- including null terminal byte */
static nokprobe_inline int
fetch_store_strlen_user(unsigned long addr)
{
const void __user *uaddr = (__force const void __user *)addr;
return strnlen_unsafe_user(uaddr, MAX_STRING_SIZE);
}
/*
* Fetch a null-terminated string. Caller MUST set *(u32 *)buf with max
* length and relative data location.
@ -894,19 +903,46 @@ static nokprobe_inline int
fetch_store_string(unsigned long addr, void *dest, void *base)
{
int maxlen = get_loc_len(*(u32 *)dest);
u8 *dst = get_loc_data(dest, base);
void *__dest;
long ret;
if (unlikely(!maxlen))
return -ENOMEM;
__dest = get_loc_data(dest, base);
/*
* Try to get string again, since the string can be changed while
* probing.
*/
ret = strncpy_from_unsafe(dst, (void *)addr, maxlen);
ret = strncpy_from_unsafe(__dest, (void *)addr, maxlen);
if (ret >= 0)
*(u32 *)dest = make_data_loc(ret, (void *)dst - base);
*(u32 *)dest = make_data_loc(ret, __dest - base);
return ret;
}
/*
* Fetch a null-terminated string from user. Caller MUST set *(u32 *)buf
* with max length and relative data location.
*/
static nokprobe_inline int
fetch_store_string_user(unsigned long addr, void *dest, void *base)
{
const void __user *uaddr = (__force const void __user *)addr;
int maxlen = get_loc_len(*(u32 *)dest);
void *__dest;
long ret;
if (unlikely(!maxlen))
return -ENOMEM;
__dest = get_loc_data(dest, base);
ret = strncpy_from_unsafe_user(__dest, uaddr, maxlen);
if (ret >= 0)
*(u32 *)dest = make_data_loc(ret, __dest - base);
return ret;
}

View File

@ -78,6 +78,8 @@ static const struct fetch_type probe_fetch_types[] = {
/* Special types */
__ASSIGN_FETCH_TYPE("string", string, string, sizeof(u32), 1,
"__data_loc char[]"),
__ASSIGN_FETCH_TYPE("ustring", string, string, sizeof(u32), 1,
"__data_loc char[]"),
/* Basic types */
ASSIGN_FETCH_TYPE(u8, u8, 0),
ASSIGN_FETCH_TYPE(u16, u16, 0),
@ -569,7 +571,8 @@ static int traceprobe_parse_probe_arg_body(char *arg, ssize_t *size,
goto fail;
/* Store operation */
if (!strcmp(parg->type->name, "string")) {
if (!strcmp(parg->type->name, "string") ||
!strcmp(parg->type->name, "ustring")) {
if (code->op != FETCH_OP_DEREF && code->op != FETCH_OP_IMM &&
code->op != FETCH_OP_COMM) {
trace_probe_log_err(offset + (t ? (t - arg) : 0),
@ -590,7 +593,11 @@ static int traceprobe_parse_probe_arg_body(char *arg, ssize_t *size,
goto fail;
}
}
code->op = FETCH_OP_ST_STRING; /* In DEREF case, replace it */
/* If op == DEREF, replace it with STRING */
if (!strcmp(parg->type->name, "ustring"))
code->op = FETCH_OP_ST_USTRING;
else
code->op = FETCH_OP_ST_STRING;
code->size = parg->type->size;
parg->dynamic = true;
} else if (code->op == FETCH_OP_DEREF) {
@ -618,7 +625,8 @@ static int traceprobe_parse_probe_arg_body(char *arg, ssize_t *size,
/* Loop(Array) operation */
if (parg->count) {
if (scode->op != FETCH_OP_ST_MEM &&
scode->op != FETCH_OP_ST_STRING) {
scode->op != FETCH_OP_ST_STRING &&
scode->op != FETCH_OP_ST_USTRING) {
trace_probe_log_err(offset + (t ? (t - arg) : 0),
BAD_STRING);
ret = -EINVAL;

View File

@ -96,6 +96,7 @@ enum fetch_op {
FETCH_OP_ST_RAW, /* Raw: .size */
FETCH_OP_ST_MEM, /* Mem: .offset, .size */
FETCH_OP_ST_STRING, /* String: .offset, .size */
FETCH_OP_ST_USTRING, /* User String: .offset, .size */
// Stage 4 (modify) op
FETCH_OP_MOD_BF, /* Bitfield: .basesize, .lshift, .rshift */
// Stage 5 (loop) op

View File

@ -59,6 +59,9 @@ process_fetch_insn(struct fetch_insn *code, struct pt_regs *regs,
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);
@ -91,6 +94,10 @@ stage3:
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;
}
@ -106,6 +113,10 @@ stage3:
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;
}
@ -123,7 +134,8 @@ array:
total += ret;
if (++i < code->param) {
code = s3;
if (s3->op != FETCH_OP_ST_STRING) {
if (s3->op != FETCH_OP_ST_STRING &&
s3->op != FETCH_OP_ST_USTRING) {
dest += s3->size;
val += s3->size;
goto stage3;

View File

@ -176,6 +176,12 @@ fetch_store_string(unsigned long addr, void *dest, void *base)
return ret;
}
static nokprobe_inline int
fetch_store_string_user(unsigned long addr, void *dest, void *base)
{
return fetch_store_string(addr, dest, base);
}
/* Return the length of string -- including null terminal byte */
static nokprobe_inline int
fetch_store_strlen(unsigned long addr)
@ -191,6 +197,12 @@ fetch_store_strlen(unsigned long addr)
return (len > MAX_STRING_SIZE) ? 0 : len;
}
static nokprobe_inline int
fetch_store_strlen_user(unsigned long addr)
{
return fetch_store_strlen(addr);
}
static unsigned long translate_user_vaddr(unsigned long file_offset)
{
unsigned long base_addr;