[PATCH v6 10/21] tracing: probeevent: Return consumed bytes of dynamic area

Masami Hiramatsu
2018-03-17T12:45:36Z

Cleanup string fetching routine so that returns the consumed
bytes of dynamic area and store the string information as
data_loc format instead of data_rloc.
This simplifies the fetcharg loop.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
kernel/trace/trace_kprobe.c | 51 +++++++++++++++++++-------------------
kernel/trace/trace_probe.h | 26 ++++---------------
kernel/trace/trace_probe_tmpl.h | 52 +++++++++++++++++---------------------
kernel/trace/trace_uprobe.c | 53 ++++++++++++++++++++-------------------
4 files changed, 82 insertions(+), 100 deletions(-)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 0b73b1ee82c8..927299ff191c 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -807,8 +807,8 @@ static const struct file_operations kprobe_profile_ops = {
/* 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)
+static nokprobe_inline int
+fetch_store_strlen(unsigned long addr)
{
mm_segment_t old_fs;
int ret, len = 0;
@@ -826,25 +826,22 @@ fetch_store_strlen(unsigned long addr, void *dest)
pagefault_enable();
set_fs(old_fs);

- if (ret < 0) /* Failed to check the length */
- *(u32 *)dest = 0;
- else
- *(u32 *)dest = len;
+ return (ret < 0) ? ret : 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)
+static nokprobe_inline int
+fetch_store_string(unsigned long addr, void *dest, void *base)
{
- int maxlen = get_rloc_len(*(u32 *)dest);
- u8 *dst = get_rloc_data(dest);
+ int maxlen = get_loc_len(*(u32 *)dest);
+ u8 *dst = get_loc_data(dest, base);
long ret;

if (!maxlen)
- return;
+ return -ENOMEM;

/*
* Try to get string again, since the string can be changed while
@@ -854,19 +851,19 @@ fetch_store_string(unsigned long addr, void *dest)

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));
+ ret = 0;
}
+ *(u32 *)dest = make_data_loc(ret, (void *)dst - base);
+ return ret;
}

/* 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)
+ void *base)
{
unsigned long val;
- int ret;
+ int ret = 0;

/* 1st stage: get value from context */
switch (code->op) {
@@ -903,6 +900,13 @@ process_fetch_insn(struct fetch_insn *code, struct pt_regs *regs, void *dest,
}

/* 3rd stage: store value to buffer */
+ if (unlikely(!dest)) {
+ if (code->op == FETCH_OP_ST_STRING)
+ return fetch_store_strlen(val + code->offset);
+ else
+ return -EILSEQ;
+ }
+
switch (code->op) {
case FETCH_OP_ST_RAW:
fetch_store_raw(val, code, dest);
@@ -911,10 +915,7 @@ process_fetch_insn(struct fetch_insn *code, struct pt_regs *regs, void *dest,
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);
+ ret = fetch_store_string(val + code->offset, dest, base);
break;
default:
return -EILSEQ;
@@ -927,7 +928,7 @@ process_fetch_insn(struct fetch_insn *code, struct pt_regs *regs, void *dest,
code++;
}

- return code->op == FETCH_OP_END ? 0 : -EILSEQ;
+ return code->op == FETCH_OP_END ? ret : -EILSEQ;
}
NOKPROBE_SYMBOL(process_fetch_insn)

@@ -962,7 +963,7 @@ __kprobe_trace_func(struct trace_kprobe *tk, struct pt_regs *regs,

entry = ring_buffer_event_data(event);
entry->ip = (unsigned long)tk->rp.kp.addr;
- store_trace_args(sizeof(*entry), &tk->tp, regs, (u8 *)&entry[1], dsize);
+ store_trace_args(&entry[1], &tk->tp, regs, sizeof(*entry), dsize);

event_trigger_unlock_commit_regs(trace_file, buffer, event,
entry, irq_flags, pc, regs);
@@ -1011,7 +1012,7 @@ __kretprobe_trace_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,
entry = ring_buffer_event_data(event);
entry->func = (unsigned long)tk->rp.kp.addr;
entry->ret_ip = (unsigned long)ri->ret_addr;
- store_trace_args(sizeof(*entry), &tk->tp, regs, (u8 *)&entry[1], dsize);
+ store_trace_args(&entry[1], &tk->tp, regs, sizeof(*entry), dsize);

event_trigger_unlock_commit_regs(trace_file, buffer, event,
entry, irq_flags, pc, regs);
@@ -1162,7 +1163,7 @@ kprobe_perf_func(struct trace_kprobe *tk, struct pt_regs *regs)

entry->ip = (unsigned long)tk->rp.kp.addr;
memset(&entry[1], 0, dsize);
- store_trace_args(sizeof(*entry), &tk->tp, regs, (u8 *)&entry[1], dsize);
+ store_trace_args(&entry[1], &tk->tp, regs, sizeof(*entry), dsize);
perf_trace_buf_submit(entry, size, rctx, call->event.type, 1, regs,
head, NULL);
return 0;
@@ -1198,7 +1199,7 @@ kretprobe_perf_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,

entry->func = (unsigned long)tk->rp.kp.addr;
entry->ret_ip = (unsigned long)ri->ret_addr;
- store_trace_args(sizeof(*entry), &tk->tp, regs, (u8 *)&entry[1], dsize);
+ store_trace_args(&entry[1], &tk->tp, regs, sizeof(*entry), dsize);
perf_trace_buf_submit(entry, size, rctx, call->event.type, 1, regs,
head, NULL);
}
diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index 89d853ef5174..d1b8bd74bf56 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -66,29 +66,15 @@
#define TP_FLAG_PROFILE 2
#define TP_FLAG_REGISTERED 4

+/* data_loc: data location, compatible with u32 */
+#define make_data_loc(len, offs) \
+ (((u32)(len) << 16) | ((u32)(offs) & 0xffff))
+#define get_loc_len(dl) ((u32)(dl) >> 16)
+#define get_loc_offs(dl) ((u32)(dl) & 0xffff)

-/* data_rloc: data relative location, compatible with u32 */
-#define make_data_rloc(len, roffs) \
- (((u32)(len) << 16) | ((u32)(roffs) & 0xffff))
-#define get_rloc_len(dl) ((u32)(dl) >> 16)
-#define get_rloc_offs(dl) ((u32)(dl) & 0xffff)
-
-/*
- * Convert data_rloc to data_loc:
- * data_rloc stores the offset from data_rloc itself, but data_loc
- * stores the offset from event entry.
- */
-#define convert_rloc_to_loc(dl, offs) ((u32)(dl) + (offs))
-
-static nokprobe_inline void *get_rloc_data(u32 *dl)
-{
- return (u8 *)dl + get_rloc_offs(*dl);
-}
-
-/* For data_loc conversion */
static nokprobe_inline void *get_loc_data(u32 *dl, void *ent)
{
- return (u8 *)ent + get_rloc_offs(*dl);
+ return (u8 *)ent + get_loc_offs(*dl);
}

/* Printing function type */
diff --git a/kernel/trace/trace_probe_tmpl.h b/kernel/trace/trace_probe_tmpl.h
index c8a5272abf01..d9aebd395a9d 100644
--- a/kernel/trace/trace_probe_tmpl.h
+++ b/kernel/trace/trace_probe_tmpl.h
@@ -48,24 +48,28 @@ fetch_apply_bitfield(struct fetch_insn *code, void *buf)
}
}

-/* Define this for each callsite */
+/*
+ * This 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, bool pre);
+ void *dest, void *base);

/* 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;
+ int i, len, ret = 0;

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;
+ len = process_fetch_insn(arg->code, regs, NULL, NULL);
+ if (len > 0)
+ ret += len;
}
}

@@ -74,34 +78,24 @@ __get_data_size(struct trace_probe *tp, struct pt_regs *regs)

/* 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)
+store_trace_args(void *data, struct trace_probe *tp, struct pt_regs *regs,
+ int header_size, int maxlen)
{
struct probe_arg *arg;
- u32 end = tp->size;
- u32 *dl; /* Data (relative) location */
- int i;
+ 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;
- 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);
+ 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 (ret > 0)
+ dyndata += ret;
}
}

diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 9fc0123c721f..de4f91bb313a 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -121,41 +121,38 @@ probe_user_read(void *dest, void *src, size_t size)
* Fetch a null-terminated string. Caller MUST set *(u32 *)dest with max
* length and relative data location.
*/
-static nokprobe_inline void
-fetch_store_string(unsigned long addr, void *dest)
+static nokprobe_inline int
+fetch_store_string(unsigned long addr, void *dest, void *base)
{
long ret;
- u32 rloc = *(u32 *)dest;
- int maxlen = get_rloc_len(rloc);
- u8 *dst = get_rloc_data(dest);
+ u32 loc = *(u32 *)dest;
+ int maxlen = get_loc_len(loc);
+ u8 *dst = get_loc_data(dest, base);
void __user *src = (void __force __user *) addr;

if (!maxlen)
- return;
+ return -ENOMEM;

ret = strncpy_from_user(dst, src, maxlen);

if (ret < 0) { /* Failed to fetch string */
- ((u8 *)get_rloc_data(dest))[0] = '\0';
- *(u32 *)dest = make_data_rloc(0, get_rloc_offs(rloc));
- } else {
- *(u32 *)dest = make_data_rloc(ret, get_rloc_offs(rloc));
+ dst[0] = '\0';
+ ret = 0;
}
+ *(u32 *)dest = make_data_loc(ret, (void *)dst - base);
+ return ret;
}

/* Return the length of string -- including null terminal byte */
-static nokprobe_inline void
-fetch_store_strlen(unsigned long addr, void *dest)
+static nokprobe_inline int
+fetch_store_strlen(unsigned long addr)
{
int len;
void __user *vaddr = (void __force __user *) addr;

len = strnlen_user(vaddr, MAX_STRING_SIZE);

- if (len == 0 || len > MAX_STRING_SIZE) /* Failed to check length */
- *(u32 *)dest = 0;
- else
- *(u32 *)dest = len;
+ return (len > MAX_STRING_SIZE) ? 0 : len;
}

static unsigned long translate_user_vaddr(unsigned long file_offset)
@@ -172,10 +169,10 @@ static unsigned long translate_user_vaddr(unsigned long file_offset)
/* 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)
+ void *base)
{
unsigned long val;
- int ret;
+ int ret = 0;

/* 1st stage: get value from context */
switch (code->op) {
@@ -212,18 +209,22 @@ process_fetch_insn(struct fetch_insn *code, struct pt_regs *regs, void *dest,
}

/* 3rd stage: store value to buffer */
+ if (unlikely(!dest)) {
+ if (code->op == FETCH_OP_ST_STRING)
+ return fetch_store_strlen(val + code->offset);
+ else
+ return -EILSEQ;
+ }
+
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);
+ 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);
+ ret = fetch_store_string(val + code->offset, dest, base);
break;
default:
return -EILSEQ;
@@ -236,7 +237,7 @@ process_fetch_insn(struct fetch_insn *code, struct pt_regs *regs, void *dest,
code++;
}

- return code->op == FETCH_OP_END ? 0 : -EILSEQ;
+ return code->op == FETCH_OP_END ? ret : -EILSEQ;
}
NOKPROBE_SYMBOL(process_fetch_insn)

@@ -1242,7 +1243,7 @@ static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs *regs)
esize = SIZEOF_TRACE_ENTRY(is_ret_probe(tu));

ucb = uprobe_buffer_get();
- store_trace_args(esize, &tu->tp, regs, ucb->buf, dsize);
+ store_trace_args(ucb->buf, &tu->tp, regs, esize, dsize);

if (tu->tp.flags & TP_FLAG_TRACE)
ret |= uprobe_trace_func(tu, regs, ucb, dsize);
@@ -1277,7 +1278,7 @@ static int uretprobe_dispatcher(struct uprobe_consumer *con,
esize = SIZEOF_TRACE_ENTRY(is_ret_probe(tu));

ucb = uprobe_buffer_get();
- store_trace_args(esize, &tu->tp, regs, ucb->buf, dsize);
+ store_trace_args(ucb->buf, &tu->tp, regs, esize, dsize);

if (tu->tp.flags & TP_FLAG_TRACE)
uretprobe_trace_func(tu, func, regs, ucb, dsize);