Re: [RFC][PATCH -tip 7/9] tracing: kprobe-tracer plugin supportsarguments

From: Frederic Weisbecker
Date: Thu Mar 19 2009 - 20:51:53 EST

On Thu, Mar 19, 2009 at 05:10:40PM -0400, Masami Hiramatsu wrote:
> Support probe arguments and add fetch functions.
>
> Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Cc: Ananth N Mavinakayanahalli <ananth@xxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxx>
> ---
> Documentation/ftrace.txt | 39 ++++--
> kernel/trace/trace_kprobe.c | 287 +++++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 305 insertions(+), 21 deletions(-)
>
> diff --git a/Documentation/ftrace.txt b/Documentation/ftrace.txt
> index a957adf..946c66f 100644
> --- a/Documentation/ftrace.txt
> +++ b/Documentation/ftrace.txt
> @@ -1329,17 +1329,30 @@ current_tracer, instead of that, just set probe points via
> /debug/tracing/kprobe_probes.
>
> Synopsis of kprobe_probes:
> - p SYMBOL[+offs|-offs]|MEMADDR : set a probe
> - r SYMBOL[+0] : set a return probe
> + p SYMBOL[+offs|-offs]|MEMADDR [FETCHARGS] : set a probe
> + r SYMBOL[+0] [FETCHARGS] : set a return probe
> +
> + FETCHARGS:
> + rN : Fetch Nth register (N >= 0)
> + sN : Fetch Nth entry of stack (N >= 0)
> + mADDR : Fetch memory at ADDR (ADDR should be in kernel)
> + aN : Fetch function argument. (N >= 1)(*)
> + rv : Fetch return value.(**)
> + rp : Fetch return address.(**)
> +
> + (*) aN may not correct on asmlinkaged functions and at function body.
> + (**) only for return probe.
>
> E.g.
> - echo p sys_open > /debug/tracing/kprobe_probes
> + echo p do_sys_open a1 a2 a3 a4 > /debug/tracing/kprobe_probes
>
> - This sets a kprobe on the top of sys_open() function.
> + This sets a kprobe on the top of do_sys_open() function with recording
> +1st to 3rd arguments.
>
> - echo r sys_open >> /debug/tracing/kprobe_probes
> + echo r do_sys_open rv rp >> /debug/tracing/kprobe_probes
>
> - This sets a kretprobe on the return point of sys_open() function.
> + This sets a kretprobe on the return point of do_sys_open() function with
> +recording return value and return address.
>
> echo > /debug/tracing/kprobe_probes
>
> @@ -1351,14 +1364,12 @@ E.g.
> #
> # TASK-PID CPU# TIMESTAMP FUNCTION
> # | | | | |
> - <...>-5117 [003] 416.481638: sys_open: @sys_open+0
> - <...>-5117 [003] 416.481662: syscall_call: <-sys_open+0
> - <...>-5117 [003] 416.481739: sys_open: @sys_open+0
> - <...>-5117 [003] 416.481762: sysenter_do_call: <-sys_open+0
> - <...>-5117 [003] 416.481818: sys_open: @sys_open+0
> - <...>-5117 [003] 416.481842: sysenter_do_call: <-sys_open+0
> - <...>-5117 [003] 416.481882: sys_open: @sys_open+0
> - <...>-5117 [003] 416.481905: sysenter_do_call: <-sys_open+0
> + <...>-2376 [001] 262.389131: do_sys_open: @do_sys_open+0 0xffffff9c 0x98db83e 0x8880 0x0
> + <...>-2376 [001] 262.391166: sys_open: <-do_sys_open+0 0x5 0xc06e8ebb
> + <...>-2376 [001] 264.384876: do_sys_open: @do_sys_open+0 0xffffff9c 0x98db83e 0x8880 0x0
> + <...>-2376 [001] 264.386880: sys_open: <-do_sys_open+0 0x5 0xc06e8ebb
> + <...>-2084 [001] 265.380330: do_sys_open: @do_sys_open+0 0xffffff9c 0x804be3e 0x0 0x1b6
> + <...>-2084 [001] 265.380399: sys_open: <-do_sys_open+0 0x3 0xc06e8ebb
>
> @SYMBOL means that kernel hits a probe, and <-SYMBOL means kernel returns
> from SYMBOL(e.g. "sysenter_do_call: <-sys_open+0" means kernel returns from
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index 33bb355..e801e8c 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -27,15 +27,124 @@
> #include <linux/types.h>
> #include <linux/string.h>
> #include <linux/ctype.h>
> +#include <linux/ptrace.h>
>
> #include <linux/ftrace.h>
> #include "trace.h"
>
> +/* TODO: Move these functions to arch/XXX/include/asm/ptrace.h */
> +#define STACK_MASK (THREAD_SIZE - 1)
> +#define valid_stack_addr(regs, addr) \
> + (((addr) & ~STACK_MASK) == (kernel_trap_sp(regs) & ~STACK_MASK))
> +
> +#if defined(__i386__)
> +#define MAX_REG_NUM 15
> +#elif defined(__x86_64__)
> +#define MAX_REG_NUM 21
> +#else
> +#define MAX_REG_NUM (sizeof(struct pt_regs)/sizeof(unsigned long))
> +#endif
> +
> +static unsigned long fetch_register(struct pt_regs *regs, void *num)
> +{
> + if (unlikely((unsigned)num > MAX_REG_NUM))
> + return 0;
> + return *((unsigned long *)regs + (unsigned)num);
> +}
> +
> +static unsigned long fetch_stack(struct pt_regs *regs, void *num)
> +{
> + unsigned long *addr = (unsigned long *)kernel_trap_sp(regs);
> + addr += (unsigned)num;
> + if (valid_stack_addr(regs, (unsigned long)addr))
> + return *addr;
> + else
> + return 0;
> +}
> +
> +static unsigned long fetch_memory(struct pt_regs *regs, void *addr)
> +{
> + unsigned long retval;
> + probe_kernel_address(addr, retval);
> + return retval;
> +}


It will return a random value.


> +
> +#if defined(__i386__)
> +#define REGPARMS 3
> +static unsigned long fetch_argument(struct pt_regs *regs, void *data)
> +{
> + unsigned long n = (unsigned long)data;
> + if (n > REGPARMS) {
> + /*
> + * The typical case: arg n is on the stack.
> + * stack[0] = return address
> + */
> + return fetch_stack(regs, (void *)(n - REGPARMS));
> + } else {
> + switch (n) {
> + case 1: return regs->ax;
> + case 2: return regs->dx;
> + case 3: return regs->cx;
> + }
> + return 0;
> + }
> +}
> +#elif define(__x86_64__)
> +#define REGPARMS 6


These helpers could be defined in the appropriate arch directory.
They may even be reused by further debugging engines.


Frederic.


> +static unsigned long fetch_argument(struct pt_regs *regs, void *data)
> +{
> + unsigned long n = (unsigned long)data;
> + if (n > REGPARMS) {
> + /*
> + * The typical case: arg n is on the stack.
> + * stack[0] = return address
> + */
> + return fetch_stack(regs, (void *)(n - REGPARMS));
> + } else {
> + switch (n) {
> + case 1: return regs->di;
> + case 2: return regs->si;
> + case 3: return regs->dx;
> + case 4: return regs->cx;
> + case 5: return regs->r8;
> + case 6: return regs->r9;
> + }
> + return 0;
> + }
> +}
> +#else
> +static unsigned long fetch_argument(struct pt_regs *regs, void *data)
> +{
> + return fetch_stack(regs, data);
> +}
> +#endif
> +
> +static unsigned long fetch_retvalue(struct pt_regs *regs, void *dummy)
> +{
> + return regs_return_value(regs);
> +}
> +
> +static unsigned long fetch_ip(struct pt_regs *regs, void *dummy)
> +{
> + return instruction_pointer(regs);
> +}
> +
> +
> /**
> * kprobe_trace_core
> */
> #define TRACE_MAXARGS 6
>
> +struct fetch_func {
> + unsigned long (*func)(struct pt_regs *, void *);
> + void *data;
> +};
> +
> +static unsigned long call_fetch(struct fetch_func *f, struct pt_regs *regs)
> +{
> + return f->func(regs, f->data);
> +}
> +
> struct trace_probe {
> struct list_head list;
> union {
> @@ -43,6 +152,8 @@ struct trace_probe {
> struct kretprobe rp;
> };
> const char *symbol; /* symbol name */
> + unsigned int nr_args;
> + struct fetch_func args[TRACE_MAXARGS];
> };
>
> static void kprobe_trace_record(unsigned long ip, struct trace_probe *tp,
> @@ -152,17 +263,23 @@ static int create_trace_probe(int argc, char **argv)
> {
> /*
> * Argument syntax:
> - * - Add kprobe: p SYMBOL[+OFFS|-OFFS]|ADDRESS
> - * - Add kretprobe: r SYMBOL[+0]
> + * - Add kprobe: p SYMBOL[+OFFS|-OFFS]|ADDRESS [FETCHARGS]
> + * - Add kretprobe: r SYMBOL[+0] [FETCHARGS]
> + * Fetch args:
> + * aN : fetch Nth of function argument. (N:1-)
> + * rN : fetch Nth of register (pt_regs + N) (N:0-)
> + * sN : fetch Nth of stack (N:0-)
> + * mADDR : fetch memory at ADDR (ADDR should be in kernel)
> */
> struct trace_probe *tp;
> struct kprobe *kp;
> char *tmp;
> - int ret = 0;
> + int i, ret = 0;
> int is_return = 0;
> char *symbol = NULL;
> long offset = 0;
> void *addr = NULL;
> + unsigned long param;
>
> if (argc < 2)
> return -EINVAL;
> @@ -219,6 +336,63 @@ static int create_trace_probe(int argc, char **argv)
> } else
> kp->addr = addr;
>
> + /* parse arguments */
> + argc -= 2; argv += 2; ret = 0;
> + for (i = 0; i < argc && i < TRACE_MAXARGS; i++) {
> + tmp = argv[i];
> + switch (*tmp) {
> + case 'a': /* argument */
> + ret = strict_strtoul(tmp + 1, 10, &param);
> + if (ret || param > PARAM_MAX_ARGS)
> + ret = -EINVAL;
> + else {
> + tp->args[i].func = fetch_argument;
> + tp->args[i].data = (void *)param;
> + }
> + break;
> + case 'r': /* register||retval||retip */
> + if (isdigit(tmp[1])) {
> + ret = strict_strtoul(tmp + 1, 10, &param);
> + if (ret || param > PARAM_MAX_REGS)
> + ret = -EINVAL;
> + else {
> + tp->args[i].func = fetch_register;
> + tp->args[i].data = (void *)param;
> + }
> + } else if (is_return && tmp[1] == 'v') {
> + tp->args[i].func = fetch_retvalue;
> + tp->args[i].data = NULL;
> + } else if (is_return && tmp[1] == 'p') {
> + tp->args[i].func = fetch_ip;
> + tp->args[i].data = NULL;
> + } else
> + ret = -EINVAL;
> + break;
> + case 's': /* stack */
> + ret = strict_strtoul(tmp + 1, 10, &param);
> + if (ret || param > PARAM_MAX_STACK)
> + ret = -EINVAL;
> + else {
> + tp->args[i].func = fetch_stack;
> + tp->args[i].data = (void *)param;
> + }
> + break;
> + case 'm': /* memory */
> + ret = strict_strtoul(tmp + 1, 0, &param);
> + if (!ret) {
> + tp->args[i].func = fetch_memory;
> + tp->args[i].data = (void *)param;
> + }
> + break;
> + default:
> + /* TODO: support custom handler */
> + ret = -EINVAL;
> + }
> + if (ret)
> + goto error;
> + }
> + tp->nr_args = i;
> +
> ret = register_trace_probe(tp);
> if (ret)
> goto error;
> @@ -278,18 +452,35 @@ static void probes_seq_stop(struct seq_file *m, void *v)
> static int probes_seq_show(struct seq_file *m, void *v)
> {
> struct trace_probe *tp = v;
> + int i;
>
> if (tp == NULL)
> return 0;
>
> if (tp->symbol)
> - seq_printf(m, "%c %s%+ld\n",
> + seq_printf(m, "%c %s%+ld ",
> probe_is_return(tp) ? 'r' : 'p',
> probe_symbol(tp), probe_offset(tp));
> else
> - seq_printf(m, "%c 0x%p\n",
> + seq_printf(m, "%c 0x%p ",
> probe_is_return(tp) ? 'r' : 'p',
> probe_address(tp));
> +
> + for (i = 0; i < tp->nr_args; i++) {
> + if (tp->args[i].func == fetch_argument)
> + seq_printf(m, " a%lu", (unsigned long)tp->args[i].data);
> + else if (tp->args[i].func == fetch_register)
> + seq_printf(m, " r%lu", (unsigned long)tp->args[i].data);
> + else if (tp->args[i].func == fetch_stack)
> + seq_printf(m, " s%lu", (unsigned long)tp->args[i].data);
> + else if (tp->args[i].func == fetch_memory)
> + seq_printf(m, " m0x%p", tp->args[i].data);
> + else if (tp->args[i].func == fetch_retvalue)
> + seq_printf(m, " rv");
> + else if (tp->args[i].func == fetch_ip)
> + seq_printf(m, " rp");
> + }
> + seq_printf(m, "\n");
> return 0;
> }
>
> @@ -380,13 +571,95 @@ static const struct file_operations kprobe_points_ops = {
> };
>
> /* event recording functions */
> -static void kprobe_trace_record(unsigned long ip, struct trace_probe *tp,
> - struct pt_regs *regs)
> +/* TODO: rewrite based on trace_vprintk(maybe, trace_vprintk_begin/end?) */
> +static void kprobe_trace_printk_0(unsigned long ip, struct trace_probe *tp,
> + struct pt_regs *regs)
> {
> __trace_printk(ip, "%s%s%+ld\n",
> probe_is_return(tp) ? "<-" : "@",
> probe_symbol(tp), probe_offset(tp));
> }
> +static void kprobe_trace_printk_1(unsigned long ip, struct trace_probe *tp,
> + struct pt_regs *regs)
> +{
> + __trace_printk(ip, "%s%s%+ld 0x%lx\n",
> + probe_is_return(tp) ? "<-" : "@",
> + probe_symbol(tp), probe_offset(tp),
> + call_fetch(&tp->args[0], regs));
> +}
> +static void kprobe_trace_printk_2(unsigned long ip, struct trace_probe *tp,
> + struct pt_regs *regs)
> +{
> + __trace_printk(ip, "%s%s%+ld 0x%lx 0x%lx\n",
> + probe_is_return(tp) ? "<-" : "@", probe_symbol(tp),
> + probe_offset(tp),
> + call_fetch(&tp->args[0], regs),
> + call_fetch(&tp->args[1], regs));
> +}
> +static void kprobe_trace_printk_3(unsigned long ip, struct trace_probe *tp,
> + struct pt_regs *regs)
> +{
> + __trace_printk(ip, "%s%s%+ld 0x%lx 0x%lx 0x%lx\n",
> + probe_is_return(tp) ? "<-" : "@", probe_symbol(tp),
> + probe_offset(tp),
> + call_fetch(&tp->args[0], regs),
> + call_fetch(&tp->args[1], regs),
> + call_fetch(&tp->args[2], regs));
> +}
> +static void kprobe_trace_printk_4(unsigned long ip, struct trace_probe *tp,
> + struct pt_regs *regs)
> +{
> + __trace_printk(ip, "%s%s%+ld 0x%lx 0x%lx 0x%lx 0x%lx\n",
> + probe_is_return(tp) ? "<-" : "@", probe_symbol(tp),
> + probe_offset(tp),
> + call_fetch(&tp->args[0], regs),
> + call_fetch(&tp->args[1], regs),
> + call_fetch(&tp->args[2], regs),
> + call_fetch(&tp->args[3], regs));
> +}
> +static void kprobe_trace_printk_5(unsigned long ip, struct trace_probe *tp,
> + struct pt_regs *regs)
> +{
> + __trace_printk(ip, "%s%s%+ld 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx\n",
> + probe_is_return(tp) ? "<-" : "@", probe_symbol(tp),
> + probe_offset(tp),
> + call_fetch(&tp->args[0], regs),
> + call_fetch(&tp->args[1], regs),
> + call_fetch(&tp->args[2], regs),
> + call_fetch(&tp->args[3], regs),
> + call_fetch(&tp->args[4], regs));
> +}
> +static void kprobe_trace_printk_6(unsigned long ip, struct trace_probe *tp,
> + struct pt_regs *regs)
> +{
> + __trace_printk(ip, "%s%s%+ld 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx\n",
> + probe_is_return(tp) ? "<-" : "@", probe_symbol(tp),
> + probe_offset(tp),
> + call_fetch(&tp->args[0], regs),
> + call_fetch(&tp->args[1], regs),
> + call_fetch(&tp->args[2], regs),
> + call_fetch(&tp->args[3], regs),
> + call_fetch(&tp->args[4], regs),
> + call_fetch(&tp->args[5], regs));
> +}
> +
> +static void (*kprobe_trace_printk_n[TRACE_MAXARGS + 1])(unsigned long ip,
> + struct trace_probe *,
> + struct pt_regs *) = {
> + [0] = kprobe_trace_printk_0,
> + [1] = kprobe_trace_printk_1,
> + [2] = kprobe_trace_printk_2,
> + [3] = kprobe_trace_printk_3,
> + [4] = kprobe_trace_printk_4,
> + [5] = kprobe_trace_printk_5,
> + [6] = kprobe_trace_printk_6,
> +};
> +
> +static void kprobe_trace_record(unsigned long ip, struct trace_probe *tp,
> + struct pt_regs *regs)
> +{
> + kprobe_trace_printk_n[tp->nr_args](ip, tp, regs);
> +}
>
> /* Make a debugfs interface for controling probe points */
> static __init int init_kprobe_trace(void)
> --
> Masami Hiramatsu
>
> Software Engineer
> Hitachi Computer Products (America) Inc.
> Software Solutions Division
>
> e-mail: mhiramat@xxxxxxxxxx
>
>
> --
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