tracing/kprobes: Make special variable names more self-explainable

Rename special variables to more self-explainable names as below:
- $rv to $retval
- $sa to $stack
- $aN to $argN
- $sN to $stackN

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>
Cc: Frank Ch. Eigler <fche@redhat.com>
LKML-Reference: <20091007222759.1684.3319.stgit@dhcp-100-2-132.bos.redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

2 files changed, 35 insertions, 39 deletions

diff --git a/Documentation/trace/kprobetrace.txt b/Documentation/trace/kprobetrace.txt
index 4208253b5a53..15415243a9a3 100644
--- a/Documentation/trace/kprobetrace.txt
+++ b/Documentation/trace/kprobetrace.txt
@@ -35,13 +35,13 @@ Synopsis of kprobe_events
  MEMADDR        : Address where the probe is inserted.
 
  FETCHARGS      : Arguments. Each probe can have up to 128 args.
-  %REG  : Fetch register REG
-  @ADDR : Fetch memory at ADDR (ADDR should be in kernel)
+  %REG          : Fetch register REG
+  @ADDR         : Fetch memory at ADDR (ADDR should be in kernel)
   @SYM[+|-offs] : Fetch memory at SYM +|- offs (SYM should be a data symbol)
-  $sN   : Fetch Nth entry of stack (N >= 0)
-  $sa   : Fetch stack address.
-  $aN   : Fetch function argument. (N >= 0)(*)
-  $rv   : Fetch return value.(**)
+  $stackN       : Fetch Nth entry of stack (N >= 0)
+  $stack        : Fetch stack address.
+  $argN         : Fetch function argument. (N >= 0)(*)
+  $retval       : Fetch return value.(**)
   +|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(***)
   NAME=FETCHARG: Set NAME as the argument name of FETCHARG.
 
@@ -84,13 +84,13 @@ Usage examples
 To add a probe as a new event, write a new definition to kprobe_events
 as below.
 
-  echo p:myprobe do_sys_open dfd=$a0 filename=$a1 flags=$a2 mode=$a3 > /sys/kernel/debug/tracing/kprobe_events
+  echo p:myprobe do_sys_open dfd=$arg0 filename=$arg1 flags=$arg2 mode=$arg3 > /sys/kernel/debug/tracing/kprobe_events
 
  This sets a kprobe on the top of do_sys_open() function with recording
 1st to 4th arguments as "myprobe" event. As this example shows, users can
 choose more familiar names for each arguments.
 
-  echo r:myretprobe do_sys_open $rv >> /sys/kernel/debug/tracing/kprobe_events
+  echo r:myretprobe do_sys_open $retval >> /sys/kernel/debug/tracing/kprobe_events
 
  This sets a kretprobe on the return point of do_sys_open() function with
 recording return value as "myretprobe" event.
@@ -137,11 +137,11 @@ events, you need to enable it.
 #           TASK-PID    CPU#    TIMESTAMP  FUNCTION
 #              | |       |          |         |
            <...>-1447  [001] 1038282.286875: myprobe: (do_sys_open+0x0/0xd6) dfd=3 filename=7fffd1ec4440 flags=8000 mode=0
-           <...>-1447  [001] 1038282.286878: myretprobe: (sys_openat+0xc/0xe <- do_sys_open) $rv=fffffffffffffffe
+           <...>-1447  [001] 1038282.286878: myretprobe: (sys_openat+0xc/0xe <- do_sys_open) $retval=fffffffffffffffe
            <...>-1447  [001] 1038282.286885: myprobe: (do_sys_open+0x0/0xd6) dfd=ffffff9c filename=40413c flags=8000 mode=1b6
-           <...>-1447  [001] 1038282.286915: myretprobe: (sys_open+0x1b/0x1d <- do_sys_open) $rv=3
+           <...>-1447  [001] 1038282.286915: myretprobe: (sys_open+0x1b/0x1d <- do_sys_open) $retval=3
            <...>-1447  [001] 1038282.286969: myprobe: (do_sys_open+0x0/0xd6) dfd=ffffff9c filename=4041c6 flags=98800 mode=10
-           <...>-1447  [001] 1038282.286976: myretprobe: (sys_open+0x1b/0x1d <- do_sys_open) $rv=3
+           <...>-1447  [001] 1038282.286976: myretprobe: (sys_open+0x1b/0x1d <- do_sys_open) $retval=3
 
 
  Each line shows when the kernel hits an event, and <- SYMBOL means kernel
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index ba6d3bd48889..3313fa74ce5f 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -215,22 +215,22 @@ static int probe_arg_string(char *buf, size_t n, struct fetch_func *ff)
         int ret = -EINVAL;
 
         if (ff->func == fetch_argument)
-                ret = snprintf(buf, n, "$a%lu", (unsigned long)ff->data);
+                ret = snprintf(buf, n, "$arg%lu", (unsigned long)ff->data);
         else if (ff->func == fetch_register) {
                 const char *name;
                 name = regs_query_register_name((unsigned int)((long)ff->data));
                 ret = snprintf(buf, n, "%%%s", name);
         } else if (ff->func == fetch_stack)
-                ret = snprintf(buf, n, "$s%lu", (unsigned long)ff->data);
+                ret = snprintf(buf, n, "$stack%lu", (unsigned long)ff->data);
         else if (ff->func == fetch_memory)
                 ret = snprintf(buf, n, "@0x%p", ff->data);
         else if (ff->func == fetch_symbol) {
                 struct symbol_cache *sc = ff->data;
                 ret = snprintf(buf, n, "@%s%+ld", sc->symbol, sc->offset);
         } else if (ff->func == fetch_retvalue)
-                ret = snprintf(buf, n, "$rv");
+                ret = snprintf(buf, n, "$retval");
         else if (ff->func == fetch_stack_address)
-                ret = snprintf(buf, n, "$sa");
+                ret = snprintf(buf, n, "$stack");
         else if (ff->func == fetch_indirect) {
                 struct indirect_fetch_data *id = ff->data;
                 size_t l = 0;
@@ -427,40 +427,36 @@ static int parse_probe_vars(char *arg, struct fetch_func *ff, int is_return)
         int ret = 0;
         unsigned long param;
 
-        switch (arg[0]) {
-        case 'a':       /* argument */
-                ret = strict_strtoul(arg + 1, 10, &param);
-                if (ret || param > PARAM_MAX_ARGS)
-                        ret = -EINVAL;
-                else {
-                        ff->func = fetch_argument;
-                        ff->data = (void *)param;
-                }
-                break;
-        case 'r':       /* retval or retaddr */
-                if (is_return && arg[1] == 'v') {
+        if (strcmp(arg, "retval") == 0) {
+                if (is_return) {
                         ff->func = fetch_retvalue;
                         ff->data = NULL;
                 } else
                         ret = -EINVAL;
-                break;
-        case 's':       /* stack */
-                if (arg[1] == 'a') {
+        } else if (strncmp(arg, "stack", 5) == 0) {
+                if (arg[5] == '\0') {
                         ff->func = fetch_stack_address;
                         ff->data = NULL;
-                } else {
-                        ret = strict_strtoul(arg + 1, 10, &param);
+                } else if (isdigit(arg[5])) {
+                        ret = strict_strtoul(arg + 5, 10, &param);
                         if (ret || param > PARAM_MAX_STACK)
                                 ret = -EINVAL;
                         else {
                                 ff->func = fetch_stack;
                                 ff->data = (void *)param;
                         }
+                } else
+                        ret = -EINVAL;
+        } else if (strncmp(arg, "arg", 3) == 0 && isdigit(arg[3])) {
+                ret = strict_strtoul(arg + 3, 10, &param);
+                if (ret || param > PARAM_MAX_ARGS)
+                        ret = -EINVAL;
+                else {
+                        ff->func = fetch_argument;
+                        ff->data = (void *)param;
                 }
-                break;
-        default:
+        } else
                 ret = -EINVAL;
-        }
         return ret;
 }
 
@@ -548,10 +544,10 @@ static int create_trace_probe(int argc, char **argv)
          *  - Add kprobe: p[:[GRP/]EVENT] KSYM[+OFFS]|KADDR [FETCHARGS]
          *  - Add kretprobe: r[:[GRP/]EVENT] KSYM[+0] [FETCHARGS]
          * Fetch args:
-         *  $aN : fetch Nth of function argument. (N:0-)
-         *  $rv : fetch return value
-         *  $sa : fetch stack address
-         *  $sN : fetch Nth of stack (N:0-)
+         *  $argN       : fetch Nth of function argument. (N:0-)
+         *  $retval     : fetch return value
+         *  $stack      : fetch stack address
+         *  $stackN     : fetch Nth of stack (N:0-)
          *  @ADDR       : fetch memory at ADDR (ADDR should be in kernel)
          *  @SYM[+|-offs] : fetch memory at SYM +|- offs (SYM is a data symbol)
          *  %REG        : fetch register REG