diff mbox series

[v6,bpf-next,06/11] bpf: Expose symbol's respective address

Message ID 20230628115329.248450-7-laoar.shao@gmail.com (mailing list archive)
State Changes Requested
Delegated to: BPF
Headers show
Series bpf: Support ->fill_link_info for kprobe_multi and perf_event links | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for bpf-next, async
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 12 this patch: 12
netdev/cc_maintainers success CCed 4 of 4 maintainers
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netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 12 this patch: 12
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 20 lines checked
netdev/kdoc success Errors and warnings before: 2 this patch: 2
netdev/source_inline success Was 0 now: 0
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Commit Message

Yafang Shao June 28, 2023, 11:53 a.m. UTC 
Since different symbols can share the same name, it is insufficient to only
expose the symbol name. It is essential to also expose the symbol address
so that users can accurately identify which one is being probed.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 kernel/trace/trace_kprobe.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

Comments

Daniel Borkmann July 5, 2023, 8:26 a.m. UTC | #1 
On 6/28/23 1:53 PM, Yafang Shao wrote:
> Since different symbols can share the same name, it is insufficient to only
> expose the symbol name. It is essential to also expose the symbol address
> so that users can accurately identify which one is being probed.
> 
> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> ---
>   kernel/trace/trace_kprobe.c | 10 +++++-----
>   1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index e4554dbfd113..17e17298e894 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -1547,15 +1547,15 @@ int bpf_get_kprobe_info(const struct perf_event *event, u32 *fd_type,
>   	if (tk->symbol) {
>   		*symbol = tk->symbol;
>   		*probe_offset = tk->rp.kp.offset;
> -		*probe_addr = 0;
>   	} else {
>   		*symbol = NULL;
>   		*probe_offset = 0;
> -		if (kallsyms_show_value(current_cred()))
> -			*probe_addr = (unsigned long)tk->rp.kp.addr;
> -		else
> -			*probe_addr = 0;
>   	}
> +
> +	if (kallsyms_show_value(current_cred()))
> +		*probe_addr = (unsigned long)tk->rp.kp.addr;
> +	else
> +		*probe_addr = 0;
>   	return 0;

Can't this be simplified further? If tk->symbol is NULL we assign NULL anyway:

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 1b3fa7b854aa..bf2872ca5aaf 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1544,15 +1544,10 @@ int bpf_get_kprobe_info(const struct perf_event *event, u32 *fd_type,

         *fd_type = trace_kprobe_is_return(tk) ? BPF_FD_TYPE_KRETPROBE
                                               : BPF_FD_TYPE_KPROBE;
-       if (tk->symbol) {
-               *symbol = tk->symbol;
-               *probe_offset = tk->rp.kp.offset;
-               *probe_addr = 0;
-       } else {
-               *symbol = NULL;
-               *probe_offset = 0;
-               *probe_addr = (unsigned long)tk->rp.kp.addr;
-       }
+       *probe_offset = tk->rp.kp.offset;
+       *probe_addr = kallsyms_show_value(current_cred()) ?
+                     (unsigned long)tk->rp.kp.addr : 0;
+       *symbol = tk->symbol;
         return 0;
  }
  #endif /* CONFIG_PERF_EVENTS */
Yafang Shao July 5, 2023, 10:01 a.m. UTC | #2 
On Wed, Jul 5, 2023 at 4:26 PM Daniel Borkmann <daniel@iogearbox.net> wrote:
>
> On 6/28/23 1:53 PM, Yafang Shao wrote:
> > Since different symbols can share the same name, it is insufficient to only
> > expose the symbol name. It is essential to also expose the symbol address
> > so that users can accurately identify which one is being probed.
> >
> > Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> > ---
> >   kernel/trace/trace_kprobe.c | 10 +++++-----
> >   1 file changed, 5 insertions(+), 5 deletions(-)
> >
> > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> > index e4554dbfd113..17e17298e894 100644
> > --- a/kernel/trace/trace_kprobe.c
> > +++ b/kernel/trace/trace_kprobe.c
> > @@ -1547,15 +1547,15 @@ int bpf_get_kprobe_info(const struct perf_event *event, u32 *fd_type,
> >       if (tk->symbol) {
> >               *symbol = tk->symbol;
> >               *probe_offset = tk->rp.kp.offset;
> > -             *probe_addr = 0;
> >       } else {
> >               *symbol = NULL;
> >               *probe_offset = 0;
> > -             if (kallsyms_show_value(current_cred()))
> > -                     *probe_addr = (unsigned long)tk->rp.kp.addr;
> > -             else
> > -                     *probe_addr = 0;
> >       }
> > +
> > +     if (kallsyms_show_value(current_cred()))
> > +             *probe_addr = (unsigned long)tk->rp.kp.addr;
> > +     else
> > +             *probe_addr = 0;
> >       return 0;
>
> Can't this be simplified further? If tk->symbol is NULL we assign NULL anyway:

Agree. Thanks.

>
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index 1b3fa7b854aa..bf2872ca5aaf 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -1544,15 +1544,10 @@ int bpf_get_kprobe_info(const struct perf_event *event, u32 *fd_type,
>
>          *fd_type = trace_kprobe_is_return(tk) ? BPF_FD_TYPE_KRETPROBE
>                                                : BPF_FD_TYPE_KPROBE;
> -       if (tk->symbol) {
> -               *symbol = tk->symbol;
> -               *probe_offset = tk->rp.kp.offset;
> -               *probe_addr = 0;
> -       } else {
> -               *symbol = NULL;
> -               *probe_offset = 0;
> -               *probe_addr = (unsigned long)tk->rp.kp.addr;
> -       }
> +       *probe_offset = tk->rp.kp.offset;
> +       *probe_addr = kallsyms_show_value(current_cred()) ?
> +                     (unsigned long)tk->rp.kp.addr : 0;
> +       *symbol = tk->symbol;
>          return 0;
>   }
>   #endif /* CONFIG_PERF_EVENTS */
>
diff mbox series

Patch

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index e4554dbfd113..17e17298e894 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1547,15 +1547,15 @@  int bpf_get_kprobe_info(const struct perf_event *event, u32 *fd_type,
 	if (tk->symbol) {
 		*symbol = tk->symbol;
 		*probe_offset = tk->rp.kp.offset;
-		*probe_addr = 0;
 	} else {
 		*symbol = NULL;
 		*probe_offset = 0;
-		if (kallsyms_show_value(current_cred()))
-			*probe_addr = (unsigned long)tk->rp.kp.addr;
-		else
-			*probe_addr = 0;
 	}
+
+	if (kallsyms_show_value(current_cred()))
+		*probe_addr = (unsigned long)tk->rp.kp.addr;
+	else
+		*probe_addr = 0;
 	return 0;
 }
 #endif	/* CONFIG_PERF_EVENTS */