On Wed, Apr 14, 2021 at 10:10PM +0800, kernel test robot wrote:
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git perf/core
> head: 0da503cd07380952599b67ded6efe030d78ea42d
> commit: c7d4112e9f0e69edd649665836ce72008b95ab9f [18/22] perf: Add support for SIGTRAP on perf events
[...]
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <[email protected]>
[...]
> 6416 info.si_errno = event->attr.type;
> 6417 info.si_perf = event->attr.sig_data;
> > 6418 info.si_addr = (void *)event->sig_addr;
> 6419 force_sig_info(&info);
I think it wants the below (feel free to squash into "perf: Add support
for SIGTRAP on perf events").
Thanks,
-- Marco
------ >8 ------
From: Marco Elver <[email protected]>
Date: Wed, 14 Apr 2021 16:26:26 +0200
Subject: [PATCH] perf: Fix cast to void __user pointer
sparse let us know that si_addr is 'void __user *', therefore add the
missing __user attribute to the cast.
Reported-by: kernel test robot <[email protected]>
Signed-off-by: Marco Elver <[email protected]>
---
kernel/events/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 1d2077389c0c..2677438ed668 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6414,7 +6414,7 @@ static void perf_sigtrap(struct perf_event *event)
info.si_code = TRAP_PERF;
info.si_errno = event->attr.type;
info.si_perf = event->attr.sig_data;
- info.si_addr = (void *)event->sig_addr;
+ info.si_addr = (void __user *)event->sig_addr;
force_sig_info(&info);
}
--
2.31.1.295.g9ea45b61b8-goog
On Wed, Apr 14, 2021 at 04:33:22PM +0200, Marco Elver wrote:
> On Wed, Apr 14, 2021 at 10:10PM +0800, kernel test robot wrote:
> > tree: https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git perf/core
> > head: 0da503cd07380952599b67ded6efe030d78ea42d
> > commit: c7d4112e9f0e69edd649665836ce72008b95ab9f [18/22] perf: Add support for SIGTRAP on perf events
> [...]
> > If you fix the issue, kindly add following tag as appropriate
> > Reported-by: kernel test robot <[email protected]>
> [...]
> > 6416 info.si_errno = event->attr.type;
> > 6417 info.si_perf = event->attr.sig_data;
> > > 6418 info.si_addr = (void *)event->sig_addr;
> > 6419 force_sig_info(&info);
>
> I think it wants the below (feel free to squash into "perf: Add support
> for SIGTRAP on perf events").
>
> Thanks,
> -- Marco
>
> ------ >8 ------
>
> From: Marco Elver <[email protected]>
> Date: Wed, 14 Apr 2021 16:26:26 +0200
> Subject: [PATCH] perf: Fix cast to void __user pointer
>
> sparse let us know that si_addr is 'void __user *', therefore add the
> missing __user attribute to the cast.
>
> Reported-by: kernel test robot <[email protected]>
> Signed-off-by: Marco Elver <[email protected]>
> ---
> kernel/events/core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 1d2077389c0c..2677438ed668 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -6414,7 +6414,7 @@ static void perf_sigtrap(struct perf_event *event)
> info.si_code = TRAP_PERF;
> info.si_errno = event->attr.type;
> info.si_perf = event->attr.sig_data;
> - info.si_addr = (void *)event->sig_addr;
> + info.si_addr = (void __user *)event->sig_addr;
> force_sig_info(&info);
> }
Now the silly robot complains about:
CC kernel/events/core.o
../kernel/events/core.c: In function ‘perf_sigtrap’:
../kernel/events/core.c:6418:17: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
6418 | info.si_addr = (void __user *)event->sig_addr;
for all 32bit builds (because sig_addr is u64 and the pointer cast
truncates bits).
This had me look a little harder at sig_addr and I figured it should be
next to the pending fields for cache locality.
I've ended up with the below delta, does that work for you?
---
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -735,6 +735,7 @@ struct perf_event {
int pending_wakeup;
int pending_kill;
int pending_disable;
+ unsigned long pending_addr; /* SIGTRAP */
struct irq_work pending;
atomic_t event_limit;
@@ -778,9 +779,6 @@ struct perf_event {
void *security;
#endif
struct list_head sb_list;
-
- /* Address associated with event, which can be passed to siginfo_t. */
- u64 sig_addr;
#endif /* CONFIG_PERF_EVENTS */
};
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6415,7 +6415,7 @@ static void perf_sigtrap(struct perf_eve
info.si_code = TRAP_PERF;
info.si_errno = event->attr.type;
info.si_perf = event->attr.sig_data;
- info.si_addr = (void __user *)event->sig_addr;
+ info.si_addr = (void __user *)event->pending_addr;
force_sig_info(&info);
}
@@ -9137,7 +9137,7 @@ static int __perf_event_overflow(struct
if (events && atomic_dec_and_test(&event->event_limit)) {
ret = 1;
event->pending_kill = POLL_HUP;
- event->sig_addr = data->addr;
+ event->pending_addr = data->addr;
perf_event_disable_inatomic(event);
}
On Thu, Apr 15, 2021 at 10:48AM +0200, Peter Zijlstra wrote:
> On Wed, Apr 14, 2021 at 04:33:22PM +0200, Marco Elver wrote:
> > On Wed, Apr 14, 2021 at 10:10PM +0800, kernel test robot wrote:
> > > tree: https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git perf/core
> > > head: 0da503cd07380952599b67ded6efe030d78ea42d
> > > commit: c7d4112e9f0e69edd649665836ce72008b95ab9f [18/22] perf: Add support for SIGTRAP on perf events
> > [...]
> > > If you fix the issue, kindly add following tag as appropriate
> > > Reported-by: kernel test robot <[email protected]>
> > [...]
> > > 6416 info.si_errno = event->attr.type;
> > > 6417 info.si_perf = event->attr.sig_data;
> > > > 6418 info.si_addr = (void *)event->sig_addr;
> > > 6419 force_sig_info(&info);
> >
> > I think it wants the below (feel free to squash into "perf: Add support
> > for SIGTRAP on perf events").
> >
> > Thanks,
> > -- Marco
> >
[...]
>
> Now the silly robot complains about:
>
> CC kernel/events/core.o
> ../kernel/events/core.c: In function ‘perf_sigtrap’:
> ../kernel/events/core.c:6418:17: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
> 6418 | info.si_addr = (void __user *)event->sig_addr;
>
> for all 32bit builds (because sig_addr is u64 and the pointer cast
> truncates bits).
>
> This had me look a little harder at sig_addr and I figured it should be
> next to the pending fields for cache locality.
>
> I've ended up with the below delta, does that work for you?
Thanks, that works for me. Do note that I explicitly chose u64 for
sig_addr/pending_addr because data->addr is u64. There might be a new
warning about the u64 to unsigned long assignment on 32 bit arches.
Perhaps it needs something ugly like this:
info.si_addr = (void __user *)(unsigned long)event->pending_addr;
if pending_addr wants to be u64. Or just
event->pending_addr = (unsigned long)data->addr;
if data->addr being u64 on 32 bit arches is simply overkill.
Thanks,
-- Marco
> ---
>
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -735,6 +735,7 @@ struct perf_event {
> int pending_wakeup;
> int pending_kill;
> int pending_disable;
> + unsigned long pending_addr; /* SIGTRAP */
> struct irq_work pending;
>
> atomic_t event_limit;
> @@ -778,9 +779,6 @@ struct perf_event {
> void *security;
> #endif
> struct list_head sb_list;
> -
> - /* Address associated with event, which can be passed to siginfo_t. */
> - u64 sig_addr;
> #endif /* CONFIG_PERF_EVENTS */
> };
>
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -6415,7 +6415,7 @@ static void perf_sigtrap(struct perf_eve
> info.si_code = TRAP_PERF;
> info.si_errno = event->attr.type;
> info.si_perf = event->attr.sig_data;
> - info.si_addr = (void __user *)event->sig_addr;
> + info.si_addr = (void __user *)event->pending_addr;
> force_sig_info(&info);
> }
>
> @@ -9137,7 +9137,7 @@ static int __perf_event_overflow(struct
> if (events && atomic_dec_and_test(&event->event_limit)) {
> ret = 1;
> event->pending_kill = POLL_HUP;
> - event->sig_addr = data->addr;
> + event->pending_addr = data->addr;
>
> perf_event_disable_inatomic(event);
> }
On Thu, Apr 15, 2021 at 11:03:09AM +0200, Marco Elver wrote:
> On Thu, Apr 15, 2021 at 10:48AM +0200, Peter Zijlstra wrote:
> > I've ended up with the below delta, does that work for you?
>
> Thanks, that works for me. Do note that I explicitly chose u64 for
> sig_addr/pending_addr because data->addr is u64. There might be a new
> warning about the u64 to unsigned long assignment on 32 bit arches.
My local i386-defconfig build seemed happy now. Mostly I think you're
allowed to silently truncate between base integer types. We'll see..
maybe some other compiler.
> Perhaps it needs something ugly like this:
>
> info.si_addr = (void __user *)(unsigned long)event->pending_addr;
>
> if pending_addr wants to be u64. Or just
>
> event->pending_addr = (unsigned long)data->addr;
>
> if data->addr being u64 on 32 bit arches is simply overkill.
Yeah it is. It's u64 for data layout purposes, the perf buffer works in
u64 chunks.