[PATCH v4 2/3] perf: kretprobes: offset from reloc_sym if kernel supports it
Masami Hiramatsu
mhiramat at kernel.org
Tue Mar 7 08:06:38 AEDT 2017
On Mon, 6 Mar 2017 23:19:09 +0530
"Naveen N. Rao" <naveen.n.rao at linux.vnet.ibm.com> wrote:
> Masami,
> Your patch works, thanks! However, I felt we could refactor and reuse
> some of the code across kprobes.c for this purpose. Can you please see
> if the below patch is fine?
OK, looks good to me:)
Acked-by: Masami Hiramatsu <mhiramat at kernel.org>
Thanks!
>
> Thanks,
> Naveen
>
> --
> trace/kprobes: fix check for kretprobe offset within function entry
>
> perf specifies an offset from _text and since this offset is fed
> directly into the arch-specific helper, kprobes tracer rejects
> installation of kretprobes through perf. Fix this by looking up the
> actual offset from a function for the specified sym+offset.
>
> Refactor and reuse existing routines to limit code duplication -- we
> repurpose kprobe_addr() for determining final kprobe address and we
> split out the function entry offset determination into a separate
> generic helper.
>
> Before patch:
>
> naveen at ubuntu:~/linux/tools/perf$ sudo ./perf probe -v do_open%return
> probe-definition(0): do_open%return
> symbol:do_open file:(null) line:0 offset:0 return:1 lazy:(null)
> 0 arguments
> Looking at the vmlinux_path (8 entries long)
> Using /boot/vmlinux for symbols
> Open Debuginfo file: /boot/vmlinux
> Try to find probe point from debuginfo.
> Matched function: do_open [2d0c7ff]
> Probe point found: do_open+0
> Matched function: do_open [35d76dc]
> found inline addr: 0xc0000000004ba9c4
> Failed to find "do_open%return",
> because do_open is an inlined function and has no return point.
> An error occurred in debuginfo analysis (-22).
> Trying to use symbols.
> Opening /sys/kernel/debug/tracing//README write=0
> Opening /sys/kernel/debug/tracing//kprobe_events write=1
> Writing event: r:probe/do_open _text+4469776
> Failed to write event: Invalid argument
> Error: Failed to add events. Reason: Invalid argument (Code: -22)
> naveen at ubuntu:~/linux/tools/perf$ dmesg | tail
> <snip>
> [ 33.568656] Given offset is not valid for return probe.
>
> After patch:
>
> naveen at ubuntu:~/linux/tools/perf$ sudo ./perf probe -v do_open%return
> probe-definition(0): do_open%return
> symbol:do_open file:(null) line:0 offset:0 return:1 lazy:(null)
> 0 arguments
> Looking at the vmlinux_path (8 entries long)
> Using /boot/vmlinux for symbols
> Open Debuginfo file: /boot/vmlinux
> Try to find probe point from debuginfo.
> Matched function: do_open [2d0c7d6]
> Probe point found: do_open+0
> Matched function: do_open [35d76b3]
> found inline addr: 0xc0000000004ba9e4
> Failed to find "do_open%return",
> because do_open is an inlined function and has no return point.
> An error occurred in debuginfo analysis (-22).
> Trying to use symbols.
> Opening /sys/kernel/debug/tracing//README write=0
> Opening /sys/kernel/debug/tracing//kprobe_events write=1
> Writing event: r:probe/do_open _text+4469808
> Writing event: r:probe/do_open_1 _text+4956344
> Added new events:
> probe:do_open (on do_open%return)
> probe:do_open_1 (on do_open%return)
>
> You can now use it in all perf tools, such as:
>
> perf record -e probe:do_open_1 -aR sleep 1
>
> naveen at ubuntu:~/linux/tools/perf$ sudo cat /sys/kernel/debug/kprobes/list
> c000000000041370 k kretprobe_trampoline+0x0 [OPTIMIZED]
> c0000000004ba0b8 r do_open+0x8 [DISABLED]
> c000000000443430 r do_open+0x0 [DISABLED]
>
> Signed-off-by: Naveen N. Rao <naveen.n.rao at linux.vnet.ibm.com>
> ---
> include/linux/kprobes.h | 1 +
> kernel/kprobes.c | 40 ++++++++++++++++++++++++++--------------
> kernel/trace/trace_kprobe.c | 2 +-
> 3 files changed, 28 insertions(+), 15 deletions(-)
>
> diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
> index 862f87adcbb4..6888c9f29cb6 100644
> --- a/include/linux/kprobes.h
> +++ b/include/linux/kprobes.h
> @@ -267,6 +267,7 @@ extern void show_registers(struct pt_regs *regs);
> extern void kprobes_inc_nmissed_count(struct kprobe *p);
> extern bool arch_within_kprobe_blacklist(unsigned long addr);
> extern bool arch_function_offset_within_entry(unsigned long offset);
> +extern bool function_offset_within_entry(kprobe_opcode_t *addr, const char *sym, unsigned long offset);
>
> extern bool within_kprobe_blacklist(unsigned long addr);
>
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 524766563896..49f870ea4070 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1391,21 +1391,19 @@ bool within_kprobe_blacklist(unsigned long addr)
> * This returns encoded errors if it fails to look up symbol or invalid
> * combination of parameters.
> */
> -static kprobe_opcode_t *kprobe_addr(struct kprobe *p)
> +static kprobe_opcode_t *_kprobe_addr(kprobe_opcode_t *addr,
> + const char *symbol_name, unsigned int offset)
> {
> - kprobe_opcode_t *addr = p->addr;
> -
> - if ((p->symbol_name && p->addr) ||
> - (!p->symbol_name && !p->addr))
> + if ((symbol_name && addr) || (!symbol_name && !addr))
> goto invalid;
>
> - if (p->symbol_name) {
> - kprobe_lookup_name(p->symbol_name, addr);
> + if (symbol_name) {
> + kprobe_lookup_name(symbol_name, addr);
> if (!addr)
> return ERR_PTR(-ENOENT);
> }
>
> - addr = (kprobe_opcode_t *)(((char *)addr) + p->offset);
> + addr = (kprobe_opcode_t *)(((char *)addr) + offset);
> if (addr)
> return addr;
>
> @@ -1413,6 +1411,11 @@ static kprobe_opcode_t *kprobe_addr(struct kprobe *p)
> return ERR_PTR(-EINVAL);
> }
>
> +static kprobe_opcode_t *kprobe_addr(struct kprobe *p)
> +{
> + return _kprobe_addr(p->addr, p->symbol_name, p->offset);
> +}
> +
> /* Check passed kprobe is valid and return kprobe in kprobe_table. */
> static struct kprobe *__get_valid_kprobe(struct kprobe *p)
> {
> @@ -1874,19 +1877,28 @@ bool __weak arch_function_offset_within_entry(unsigned long offset)
> return !offset;
> }
>
> +bool function_offset_within_entry(kprobe_opcode_t *addr, const char *sym, unsigned long offset)
> +{
> + kprobe_opcode_t *kp_addr = _kprobe_addr(addr, sym, offset);
> +
> + if (IS_ERR(kp_addr))
> + return false;
> +
> + if (!kallsyms_lookup_size_offset((unsigned long)kp_addr, NULL, &offset) ||
> + !arch_function_offset_within_entry(offset))
> + return false;
> +
> + return true;
> +}
> +
> int register_kretprobe(struct kretprobe *rp)
> {
> int ret = 0;
> struct kretprobe_instance *inst;
> int i;
> void *addr;
> - unsigned long offset;
> -
> - addr = kprobe_addr(&rp->kp);
> - if (!kallsyms_lookup_size_offset((unsigned long)addr, NULL, &offset))
> - return -EINVAL;
>
> - if (!arch_function_offset_within_entry(offset))
> + if (!function_offset_within_entry(rp->kp.addr, rp->kp.symbol_name, rp->kp.offset))
> return -EINVAL;
>
> if (kretprobe_blacklist_size) {
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index c60f9dc4610e..828ef31a1c27 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -695,7 +695,7 @@ static int create_trace_kprobe(int argc, char **argv)
> return ret;
> }
> if (offset && is_return &&
> - !arch_function_offset_within_entry(offset)) {
> + !function_offset_within_entry(NULL, symbol, offset)) {
> pr_info("Given offset is not valid for return probe.\n");
> return -EINVAL;
> }
> --
> 2.11.1
>
--
Masami Hiramatsu <mhiramat at kernel.org>
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