tracing: probeevent: Return consumed bytes of dynamic area

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.

Link: http://lkml.kernel.org/r/152465874163.26224.12125143907501289031.stgit@devbox

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 30 insertions, 31 deletions

diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 7772fec84c12..08ad51c8ebc0 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -111,43 +111,38 @@ 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;
+	if (unlikely(!maxlen))
+		return -ENOMEM;
 
 	ret = strncpy_from_user(dst, src, maxlen);
-	if (ret == maxlen)
-		dst[--ret] = '\0';
-
-	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));
+	if (ret >= 0) {
+		if (ret == maxlen)
+			dst[ret - 1] = '\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)
@@ -164,10 +159,10 @@ 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) {
@@ -204,18 +199,22 @@ 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;
@@ -228,7 +227,7 @@ 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)
 
@@ -1300,7 +1299,7 @@ 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);
@@ -1335,7 +1334,7 @@ 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);