[PATCH v2 14/17] tracing: probeevent: Add array type support

From: Masami Hiramatsu
Date: Wed Feb 21 2018 - 10:01:31 EST

Add array type support for probe events.
This allows user to get arraied types from memory address.
The array type syntax is

TYPE[N]

Where TYPE is one of types (u8/16/32/64,s8/16/32/64,
x8/16/32/64, symbol, string) and N is a fixed value less
than 64.

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 represents "char array",
but string array type represents "char * array". So, for example,
+0(%di):string[1] is equal to +0(+0(%di)):string.

Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
---
Changes in v2:
- Add array description in README file
- Fix to init s3 code out of loop.
- Fix to proceed code when the last code is OP_ARRAY.
- Add string array type and bitfield array type.
---
Documentation/trace/kprobetrace.txt | 13 ++++
kernel/trace/trace.c | 3 +
kernel/trace/trace_probe.c | 129 +++++++++++++++++++++++++++--------
kernel/trace/trace_probe.h | 14 ++++
kernel/trace/trace_probe_tmpl.h | 63 +++++++++++++++--
5 files changed, 183 insertions(+), 39 deletions(-)

diff --git a/Documentation/trace/kprobetrace.txt b/Documentation/trace/kprobetrace.txt
index 1d082f8ffeee..8bf752dfc072 100644
--- a/Documentation/trace/kprobetrace.txt
+++ b/Documentation/trace/kprobetrace.txt
@@ -65,9 +65,22 @@ in decimal ('s' and 'u') or hexadecimal ('x'). Without type casting, 'x32'
or 'x64' is used depends on the architecture (e.g. x86-32 uses x32, and
x86-64 uses x64).

+These value types can be an array. To record array data, you can add '[N]'
+(where N is a fixed number, less than 64) to the base type.
+E.g. 'x16[4]' means an array of x16 (2bytes hex) with 4 elements.
+Note that the array can be applied to memory type fetchargs, you can not
+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.
+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
+represents "char array", but string array type represents "char * array".
+So, for example, +0(%di):string[1] is equal to +0(+0(%di)):string.
+
Bitfield is another special type, which takes 3 parameters, bit-width, bit-
offset, and container-size (usually 32). The syntax is;

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 94423529b986..cdf3931cea57 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4610,7 +4610,8 @@ static const char readme_msg[] =
"\t fetcharg: %<register>, @<address>, @<symbol>[+|-<offset>],\n"
"\t $stack<index>, $stack, $retval, $comm, $arg<N>\n"
"\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>,\n"
+ "\t <type>[<array-size>]\n"
#endif
" events/\t\t- Directory containing all trace event subsystems:\n"
" enable\t\t- Write 0/1 to enable/disable tracing of all events\n"
diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index f4b83927d6c0..8b019125fbe4 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -365,9 +365,9 @@ static int __parse_bitfield_probe_arg(const char *bf,
int traceprobe_parse_probe_arg(char *arg, ssize_t *size,
struct probe_arg *parg, unsigned int flags)
{
- struct fetch_insn *code, *tmp = NULL;
- const char *t;
- int ret;
+ struct fetch_insn *code, *scode, *tmp = NULL;
+ char *t, *t2;
+ int ret, len;

if (strlen(arg) > MAX_ARGSTR_LEN) {
pr_info("Argument is too long.: %s\n", arg);
@@ -378,24 +378,42 @@ int traceprobe_parse_probe_arg(char *arg, ssize_t *size,
pr_info("Failed to allocate memory for command '%s'.\n", arg);
return -ENOMEM;
}
- t = strchr(parg->comm, ':');
+ t = strchr(arg, ':');
if (t) {
- arg[t - parg->comm] = '\0';
- t++;
+ *t = '\0';
+ t2 = strchr(++t, '[');
+ if (t2) {
+ *t2 = '\0';
+ parg->count = simple_strtoul(t2 + 1, &t2, 0);
+ if (strcmp(t2, "]") || parg->count == 0)
+ return -EINVAL;
+ if (parg->count > MAX_ARRAY_LEN)
+ return -E2BIG;
+ }
}
/*
* The default type of $comm should be "string", and it can't be
* dereferenced.
*/
if (!t && strcmp(arg, "$comm") == 0)
- t = "string";
- parg->type = find_fetch_type(t);
+ parg->type = find_fetch_type("string");
+ else
+ 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;
+ *size += parg->type->size * (parg->count ?: 1);
+
+ if (parg->count) {
+ len = strlen(parg->type->fmttype) + 6;
+ parg->fmt = kmalloc(len, GFP_KERNEL);
+ if (!parg->fmt)
+ return -ENOMEM;
+ snprintf(parg->fmt, len, "%s[%d]", parg->type->fmttype,
+ parg->count);
+ }

code = tmp = kzalloc(sizeof(*code) * FETCH_INSN_MAX, GFP_KERNEL);
if (!code)
@@ -415,10 +433,20 @@ int traceprobe_parse_probe_arg(char *arg, ssize_t *size,
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)
+ if (code->op != FETCH_OP_DEREF || parg->count) {
+ /*
+ * IMM and COMM is pointing actual address, those must
+ * be kept, and if parg->count != 0, this is an array
+ * of string pointers instead of string address itself.
+ */
code++;
+ if (code->op != FETCH_OP_NOP) {
+ ret = -E2BIG;
+ goto fail;
+ }
+ }
code->op = FETCH_OP_ST_STRING; /* In DEREF case, replace it */
+ code->size = parg->type->size;
parg->dynamic = true;
} else if (code->op == FETCH_OP_DEREF) {
code->op = FETCH_OP_ST_MEM;
@@ -432,12 +460,29 @@ int traceprobe_parse_probe_arg(char *arg, ssize_t *size,
code->op = FETCH_OP_ST_RAW;
code->size = parg->type->size;
}
+ scode = code;
/* Modify operation */
if (t != NULL) {
ret = __parse_bitfield_probe_arg(t, parg->type, &code);
if (ret)
goto fail;
}
+ /* Loop(Array) operation */
+ if (parg->count) {
+ if (scode->op != FETCH_OP_ST_MEM &&
+ scode->op != FETCH_OP_ST_STRING) {
+ pr_info("array only accepts memory or address\n");
+ ret = -EINVAL;
+ goto fail;
+ }
+ code++;
+ if (code->op != FETCH_OP_NOP) {
+ ret = -E2BIG;
+ goto fail;
+ }
+ code->op = FETCH_OP_LP_ARRAY;
+ code->param = parg->count;
+ }
code++;
code->op = FETCH_OP_END;

@@ -476,14 +521,17 @@ void traceprobe_free_probe_arg(struct probe_arg *arg)
kfree(arg->code);
kfree(arg->name);
kfree(arg->comm);
+ kfree(arg->fmt);
}

+/* When len=0, we just calculate the needed length */
+#define LEN_OR_ZERO (len ? len - pos : 0)
static int __set_print_fmt(struct trace_probe *tp, char *buf, int len,
bool is_return)
{
- int i;
+ struct probe_arg *parg;
+ int i, j;
int pos = 0;
-
const char *fmt, *arg;

if (!is_return) {
@@ -494,33 +542,49 @@ static int __set_print_fmt(struct trace_probe *tp, char *buf, int len,
arg = "REC->" FIELD_STRING_FUNC ", REC->" FIELD_STRING_RETIP;
}

- /* When len=0, we just calculate the needed length */
-#define LEN_OR_ZERO (len ? len - pos : 0)
-
pos += snprintf(buf + pos, LEN_OR_ZERO, "\"%s", fmt);

for (i = 0; i < tp->nr_args; i++) {
- pos += snprintf(buf + pos, LEN_OR_ZERO, " %s=%s",
- tp->args[i].name, tp->args[i].type->fmt);
+ parg = tp->args + i;
+ pos += snprintf(buf + pos, LEN_OR_ZERO, " %s=", parg->name);
+ if (parg->count) {
+ pos += snprintf(buf + pos, LEN_OR_ZERO, "{%s",
+ parg->type->fmt);
+ for (j = 1; j < parg->count; j++)
+ pos += snprintf(buf + pos, LEN_OR_ZERO, ",%s",
+ parg->type->fmt);
+ pos += snprintf(buf + pos, LEN_OR_ZERO, "}");
+ } else
+ pos += snprintf(buf + pos, LEN_OR_ZERO, "%s",
+ parg->type->fmt);
}

pos += snprintf(buf + pos, LEN_OR_ZERO, "\", %s", arg);

for (i = 0; i < tp->nr_args; i++) {
- if (strcmp(tp->args[i].type->name, "string") == 0)
+ parg = tp->args + i;
+ if (parg->count) {
+ if (strcmp(parg->type->name, "string") == 0)
+ fmt = ", __get_str(%s[%d])";
+ else
+ fmt = ", REC->%s[%d]";
+ for (j = 0; j < parg->count; j++)
+ pos += snprintf(buf + pos, LEN_OR_ZERO,
+ fmt, parg->name, j);
+ } else {
+ if (strcmp(parg->type->name, "string") == 0)
+ fmt = ", __get_str(%s)";
+ else
+ fmt = ", REC->%s";
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);
+ fmt, parg->name);
+ }
}

-#undef LEN_OR_ZERO
-
/* return the length of print_fmt */
return pos;
}
+#undef LEN_OR_ZERO

int traceprobe_set_print_fmt(struct trace_probe *tp, bool is_return)
{
@@ -548,11 +612,16 @@ int traceprobe_define_arg_fields(struct trace_event_call *event_call,
/* Set argument names as fields */
for (i = 0; i < tp->nr_args; i++) {
struct probe_arg *parg = &tp->args[i];
-
- ret = trace_define_field(event_call, parg->type->fmttype,
- parg->name,
+ const char *fmt = parg->type->fmttype;
+ int size = parg->type->size;
+
+ if (parg->fmt)
+ fmt = parg->fmt;
+ if (parg->count)
+ size *= parg->count;
+ ret = trace_define_field(event_call, fmt, parg->name,
offset + parg->offset,
- parg->type->size,
+ parg->type->size * parg->count,
parg->type->is_signed,
FILTER_OTHER);
if (ret)
diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index ff91faf70887..d256a19ee6d1 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -43,6 +43,7 @@

#define MAX_TRACE_ARGS 128
#define MAX_ARGSTR_LEN 63
+#define MAX_ARRAY_LEN 64
#define MAX_STRING_SIZE PATH_MAX

/* Reserved field names */
@@ -78,6 +79,14 @@ static nokprobe_inline void *get_loc_data(u32 *dl, void *ent)
return (u8 *)ent + get_loc_offs(*dl);
}

+static nokprobe_inline u32 update_data_loc(u32 loc, int consumed)
+{
+ u32 maxlen = get_loc_len(loc);
+ u32 offset = get_loc_offs(loc);
+
+ return make_data_loc(maxlen - consumed, offset + consumed);
+}
+
/* Printing function type */
typedef int (*print_type_func_t)(struct trace_seq *, void *, void *);

@@ -100,6 +109,8 @@ enum fetch_op {
FETCH_OP_ST_STRING, /* String: .offset, .size */
// Stage 4 (modify) op
FETCH_OP_MOD_BF, /* Bitfield: .basesize, .lshift, .rshift */
+ // Stage 5 (loop) op
+ FETCH_OP_LP_ARRAY, /* Array: .param = loop count */
FETCH_OP_END,
};

@@ -189,6 +200,7 @@ DECLARE_BASIC_PRINT_TYPE_FUNC(symbol);
_ASSIGN_FETCH_TYPE(#ptype, ptype, ftype, sizeof(ftype), sign, atype)

#define ASSIGN_FETCH_TYPE_END {}
+#define MAX_ARRAY_LEN 64

#ifdef CONFIG_KPROBE_EVENTS
bool trace_kprobe_on_func_entry(struct trace_event_call *call);
@@ -209,8 +221,10 @@ struct probe_arg {
struct fetch_insn *code;
bool dynamic;/* Dynamic array (string) is used */
unsigned int offset; /* Offset from argument entry */
+ unsigned int count; /* Array count */
const char *name; /* Name of this argument */
const char *comm; /* Command of this argument */
+ char *fmt; /* Format string if needed */
const struct fetch_type *type; /* Type of this argument */
};

diff --git a/kernel/trace/trace_probe_tmpl.h b/kernel/trace/trace_probe_tmpl.h
index 32ae2fc78190..edc09f2cd6b2 100644
--- a/kernel/trace/trace_probe_tmpl.h
+++ b/kernel/trace/trace_probe_tmpl.h
@@ -67,10 +67,15 @@ static nokprobe_inline int
process_fetch_insn_bottom(struct fetch_insn *code, unsigned long val,
void *dest, void *base)
{
- int ret = 0;
+ 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 */
while (code->op == FETCH_OP_DEREF) {
+ lval = val;
ret = probe_mem_read(&val, (void *)val + code->offset,
sizeof(val));
if (ret)
@@ -78,11 +83,15 @@ process_fetch_insn_bottom(struct fetch_insn *code, unsigned long val,
code++;
}

+ s3 = code;
+stage3:
/* 3rd stage: store value to buffer */
if (unlikely(!dest)) {
- if (code->op == FETCH_OP_ST_STRING)
- return fetch_store_strlen(val + code->offset);
- else
+ if (code->op == FETCH_OP_ST_STRING) {
+ ret += fetch_store_strlen(val + code->offset);
+ code++;
+ goto array;
+ } else
return -EILSEQ;
}

@@ -94,6 +103,7 @@ process_fetch_insn_bottom(struct fetch_insn *code, unsigned long val,
probe_mem_read(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;
default:
@@ -107,6 +117,29 @@ process_fetch_insn_bottom(struct fetch_insn *code, unsigned long val,
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) {
+ 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;
}

@@ -156,12 +189,26 @@ static inline int
print_probe_args(struct trace_seq *s, struct probe_arg *args, int nr_args,
u8 *data, void *field)
{
- int i;
+ void *p;
+ int i, j;

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;
+ 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;
}