Re: [PATCH 15/17] tracing/uprobes: Add support for full argumentaccess methods

From: Steven Rostedt
Date: Thu Jan 02 2014 - 15:58:38 EST

On Mon, 16 Dec 2013 13:32:14 +0900
Namhyung Kim <namhyung@xxxxxxxxxx> wrote:

> From: Namhyung Kim <namhyung.kim@xxxxxxx>
>
> Enable to fetch other types of argument for the uprobes. IOW, we can
> access stack, memory, deref, bitfield and retval from uprobes now.
>
> The format for the argument types are same as kprobes (but @SYMBOL
> type is not supported for uprobes), i.e:
>
> @ADDR : Fetch memory at ADDR
> $stackN : Fetch Nth entry of stack (N >= 0)
> $stack : Fetch stack address
> $retval : Fetch return value
> +|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address
>
> Note that the retval only can be used with uretprobes.
>
> Original-patch-by: Hyeoncheol Lee <cheol.lee@xxxxxxx>

Where was the original patch posted? And can we get Hyeoncheol's SOB for
this?

Thanks!

-- Steve

> Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
> Cc: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
> Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
> Cc: zhangwei(Jovi) <jovi.zhangwei@xxxxxxxxxx>
> Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
> ---
> Documentation/trace/uprobetracer.txt | 25 +++++++++++++++++++++++++
> kernel/trace/trace_probe.c | 34 ++++++++++++++++++++++------------
> 2 files changed, 47 insertions(+), 12 deletions(-)
>
> diff --git a/Documentation/trace/uprobetracer.txt b/Documentation/trace/uprobetracer.txt
> index 8f1a8b8956fc..6e5cff263e2b 100644
> --- a/Documentation/trace/uprobetracer.txt
> +++ b/Documentation/trace/uprobetracer.txt
> @@ -31,6 +31,31 @@ Synopsis of uprobe_tracer
>
> FETCHARGS : Arguments. Each probe can have up to 128 args.
> %REG : Fetch register REG
> + @ADDR : Fetch memory at ADDR (ADDR should be in userspace)
> + $stackN : Fetch Nth entry of stack (N >= 0)
> + $stack : Fetch stack address.
> + $retval : Fetch return value.(*)
> + +|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(**)
> + 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), "string" and bitfield
> + are supported.
> +
> + (*) only for return probe.
> + (**) this is useful for fetching a field of data structures.
> +
> +Types
> +-----
> +Several types are supported for fetch-args. Uprobe tracer will access memory
> +by given type. Prefix 's' and 'u' means those types are signed and unsigned
> +respectively. Traced arguments are shown in decimal (signed) or hex (unsigned).
> +String type is a special type, which fetches a "null-terminated" string from
> +user space.
> +Bitfield is another special type, which takes 3 parameters, bit-width, bit-
> +offset, and container-size (usually 32). The syntax is;
> +
> + b<bit-width>@<bit-offset>/<container-size>
> +
>
> Event Profiling
> ---------------
> diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
> index 8f7a2b6d389d..a130d612e705 100644
> --- a/kernel/trace/trace_probe.c
> +++ b/kernel/trace/trace_probe.c
> @@ -255,12 +255,18 @@ fail:
> }
>
> /* Special function : only accept unsigned long */
> -static __kprobes void fetch_stack_address(struct pt_regs *regs,
> - void *dummy, void *dest)
> +static __kprobes void fetch_kernel_stack_address(struct pt_regs *regs,
> + void *dummy, void *dest)
> {
> *(unsigned long *)dest = kernel_stack_pointer(regs);
> }
>
> +static __kprobes void fetch_user_stack_address(struct pt_regs *regs,
> + void *dummy, void *dest)
> +{
> + *(unsigned long *)dest = user_stack_pointer(regs);
> +}
> +
> static fetch_func_t get_fetch_size_function(const struct fetch_type *type,
> fetch_func_t orig_fn,
> const struct fetch_type *ftbl)
> @@ -305,7 +311,8 @@ int traceprobe_split_symbol_offset(char *symbol, unsigned long *offset)
> #define PARAM_MAX_STACK (THREAD_SIZE / sizeof(unsigned long))
>
> static int parse_probe_vars(char *arg, const struct fetch_type *t,
> - struct fetch_param *f, bool is_return)
> + struct fetch_param *f, bool is_return,
> + bool is_kprobe)
> {
> int ret = 0;
> unsigned long param;
> @@ -317,13 +324,16 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t,
> ret = -EINVAL;
> } else if (strncmp(arg, "stack", 5) == 0) {
> if (arg[5] == '\0') {
> - if (strcmp(t->name, DEFAULT_FETCH_TYPE_STR) == 0)
> - f->fn = fetch_stack_address;
> + if (strcmp(t->name, DEFAULT_FETCH_TYPE_STR))
> + return -EINVAL;
> +
> + if (is_kprobe)
> + f->fn = fetch_kernel_stack_address;
> else
> - ret = -EINVAL;
> + f->fn = fetch_user_stack_address;
> } else if (isdigit(arg[5])) {
> ret = kstrtoul(arg + 5, 10, &param);
> - if (ret || param > PARAM_MAX_STACK)
> + if (ret || (is_kprobe && param > PARAM_MAX_STACK))
> ret = -EINVAL;
> else {
> f->fn = t->fetch[FETCH_MTD_stack];
> @@ -350,13 +360,9 @@ static int parse_probe_arg(char *arg, const struct fetch_type *t,
> ftbl = is_kprobe ? kprobes_fetch_type_table : uprobes_fetch_type_table;
> BUG_ON(ftbl == NULL);
>
> - /* Until uprobe_events supports only reg arguments */
> - if (!is_kprobe && arg[0] != '%')
> - return -EINVAL;
> -
> switch (arg[0]) {
> case '$':
> - ret = parse_probe_vars(arg + 1, t, f, is_return);
> + ret = parse_probe_vars(arg + 1, t, f, is_return, is_kprobe);
> break;
>
> case '%': /* named register */
> @@ -377,6 +383,10 @@ static int parse_probe_arg(char *arg, const struct fetch_type *t,
> f->fn = t->fetch[FETCH_MTD_memory];
> f->data = (void *)param;
> } else {
> + /* uprobes don't support symbols */
> + if (!is_kprobe)
> + return -EINVAL;
> +
> ret = traceprobe_split_symbol_offset(arg + 1, &offset);
> if (ret)
> break;

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/