Re: [RFC PATCH bpf-next] bpf: change syscall_nr type to int in struct syscall_tp_t
On Fri, 13 Oct 2023 12:43:18 -0700 Andrii Nakryiko wrote: > > Correct. My Ack is based on the current way things are done upstream. > > It was just that linux-rt showed the issue, where the code was not as > > robust as it should have been. To me this was a correctness issue, not > > an issue that had to do with how things are done in linux-rt. > > I think we should at least add some BUILD_BUG_ON() that validates > offsets in syscall_tp_t matches the ones in syscall_trace_enter and > syscall_trace_exit, to fail more loudly if there is any mismatch in > the future. WDYT? If you want to, feel free to send a patch. > > > > > As for the changes in linux-rt, they are not upstream yet. I'll have my > > comments on that code when that happens. > > Ah, ok, cool. I'd appreciate you cc'ing b...@vger.kernel.org in that > discussion, thank you! If I remember ;-) -- Steve
Re: [PATCH bpf-next] bpf: change syscall_nr type to int in struct syscall_tp_t
Hello:
This patch was applied to bpf/bpf-next.git (master)
by Andrii Nakryiko :
On Fri, 13 Oct 2023 07:42:19 +0200 you wrote:
> linux-rt-devel tree contains a patch (b1773eac3f29c ("sched: Add support
> for lazy preemption")) that adds an extra member to struct trace_entry.
> This causes the offset of args field in struct trace_event_raw_sys_enter
> be different from the one in struct syscall_trace_enter:
>
> struct trace_event_raw_sys_enter {
> struct trace_entry ent; /* 012 */
>
> [...]
Here is the summary with links:
- [bpf-next] bpf: change syscall_nr type to int in struct syscall_tp_t
https://git.kernel.org/bpf/bpf-next/c/ba8ea72388a1
You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
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Re: [RFC PATCH bpf-next] bpf: change syscall_nr type to int in struct syscall_tp_t
On Fri, Oct 13, 2023 at 7:00 AM Steven Rostedt wrote: > > On Fri, 13 Oct 2023 08:01:34 +0200 > Artem Savkov wrote: > > > > But looking at [0] and briefly reading some of the discussions you, > > > Steven, had. I'm just wondering if it would be best to avoid > > > increasing struct trace_entry altogether? It seems like preempt_count > > > is actually a 4-bit field in trace context, so it doesn't seem like we > > > really need to allocate an entire byte for both preempt_count and > > > preempt_lazy_count. Why can't we just combine them and not waste 8 > > > extra bytes for each trace event in a ring buffer? > > > > > > [0] > > > https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git/commit/?id=b1773eac3f29cbdcdfd16e0339f1a164066e9f71 > > > > I agree that avoiding increase in struct trace_entry size would be very > > desirable, but I have no knowledge whether rt developers had reasons to > > do it like this. > > > > Nevertheless I think the issue with verifier running against a wrong > > struct still needs to be addressed. > > Correct. My Ack is based on the current way things are done upstream. > It was just that linux-rt showed the issue, where the code was not as > robust as it should have been. To me this was a correctness issue, not > an issue that had to do with how things are done in linux-rt. I think we should at least add some BUILD_BUG_ON() that validates offsets in syscall_tp_t matches the ones in syscall_trace_enter and syscall_trace_exit, to fail more loudly if there is any mismatch in the future. WDYT? > > As for the changes in linux-rt, they are not upstream yet. I'll have my > comments on that code when that happens. Ah, ok, cool. I'd appreciate you cc'ing b...@vger.kernel.org in that discussion, thank you! > > -- Steve
Re: [RFC PATCH bpf-next] bpf: change syscall_nr type to int in struct syscall_tp_t
On Fri, 13 Oct 2023 08:01:34 +0200 Artem Savkov wrote: > > But looking at [0] and briefly reading some of the discussions you, > > Steven, had. I'm just wondering if it would be best to avoid > > increasing struct trace_entry altogether? It seems like preempt_count > > is actually a 4-bit field in trace context, so it doesn't seem like we > > really need to allocate an entire byte for both preempt_count and > > preempt_lazy_count. Why can't we just combine them and not waste 8 > > extra bytes for each trace event in a ring buffer? > > > > [0] > > https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git/commit/?id=b1773eac3f29cbdcdfd16e0339f1a164066e9f71 > > > > I agree that avoiding increase in struct trace_entry size would be very > desirable, but I have no knowledge whether rt developers had reasons to > do it like this. > > Nevertheless I think the issue with verifier running against a wrong > struct still needs to be addressed. Correct. My Ack is based on the current way things are done upstream. It was just that linux-rt showed the issue, where the code was not as robust as it should have been. To me this was a correctness issue, not an issue that had to do with how things are done in linux-rt. As for the changes in linux-rt, they are not upstream yet. I'll have my comments on that code when that happens. -- Steve
Re: [RFC PATCH bpf-next] bpf: change syscall_nr type to int in struct syscall_tp_t
On Thu, Oct 12, 2023 at 04:32:51PM -0700, Andrii Nakryiko wrote:
> On Thu, Oct 12, 2023 at 6:43 AM Steven Rostedt wrote:
> >
> > On Thu, 12 Oct 2023 13:45:50 +0200
> > Artem Savkov wrote:
> >
> > > linux-rt-devel tree contains a patch (b1773eac3f29c ("sched: Add support
> > > for lazy preemption")) that adds an extra member to struct trace_entry.
> > > This causes the offset of args field in struct trace_event_raw_sys_enter
> > > be different from the one in struct syscall_trace_enter:
> > >
> > > struct trace_event_raw_sys_enter {
> > > struct trace_entry ent; /* 012 */
> > >
> > > /* XXX last struct has 3 bytes of padding */
> > > /* XXX 4 bytes hole, try to pack */
> > >
> > > long int id; /*16 8 */
> > > long unsigned int args[6]; /*2448 */
> > > /* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
> > > char __data[]; /*72 0 */
> > >
> > > /* size: 72, cachelines: 2, members: 4 */
> > > /* sum members: 68, holes: 1, sum holes: 4 */
> > > /* paddings: 1, sum paddings: 3 */
> > > /* last cacheline: 8 bytes */
> > > };
> > >
> > > struct syscall_trace_enter {
> > > struct trace_entry ent; /* 012 */
> > >
> > > /* XXX last struct has 3 bytes of padding */
> > >
> > > intnr; /*12 4 */
> > > long unsigned int args[]; /*16 0 */
> > >
> > > /* size: 16, cachelines: 1, members: 3 */
> > > /* paddings: 1, sum paddings: 3 */
> > > /* last cacheline: 16 bytes */
> > > };
> > >
> > > This, in turn, causes perf_event_set_bpf_prog() fail while running bpf
> > > test_profiler testcase because max_ctx_offset is calculated based on the
> > > former struct, while off on the latter:
> > >
> > > 10488 if (is_tracepoint || is_syscall_tp) {
> > > 10489 int off =
> > > trace_event_get_offsets(event->tp_event);
> > > 10490
> > > 10491 if (prog->aux->max_ctx_offset > off)
> > > 10492 return -EACCES;
> > > 10493 }
> > >
> > > What bpf program is actually getting is a pointer to struct
> > > syscall_tp_t, defined in kernel/trace/trace_syscalls.c. This patch fixes
> > > the problem by aligning struct syscall_tp_t with with struct
> > > syscall_trace_(enter|exit) and changing the tests to use these structs
> > > to dereference context.
> > >
> > > Signed-off-by: Artem Savkov
> >
>
> I think these changes make sense regardless, can you please resend the
> patch without RFC tag so that our CI can run tests for it?
Ok, didn't know it was set up like that.
> > Thanks for doing a proper fix.
> >
> > Acked-by: Steven Rostedt (Google)
>
> But looking at [0] and briefly reading some of the discussions you,
> Steven, had. I'm just wondering if it would be best to avoid
> increasing struct trace_entry altogether? It seems like preempt_count
> is actually a 4-bit field in trace context, so it doesn't seem like we
> really need to allocate an entire byte for both preempt_count and
> preempt_lazy_count. Why can't we just combine them and not waste 8
> extra bytes for each trace event in a ring buffer?
>
> [0]
> https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git/commit/?id=b1773eac3f29cbdcdfd16e0339f1a164066e9f71
I agree that avoiding increase in struct trace_entry size would be very
desirable, but I have no knowledge whether rt developers had reasons to
do it like this.
Nevertheless I think the issue with verifier running against a wrong
struct still needs to be addressed.
--
Regards,
Artem
[PATCH bpf-next] bpf: change syscall_nr type to int in struct syscall_tp_t
linux-rt-devel tree contains a patch (b1773eac3f29c ("sched: Add support
for lazy preemption")) that adds an extra member to struct trace_entry.
This causes the offset of args field in struct trace_event_raw_sys_enter
be different from the one in struct syscall_trace_enter:
struct trace_event_raw_sys_enter {
struct trace_entry ent; /* 012 */
/* XXX last struct has 3 bytes of padding */
/* XXX 4 bytes hole, try to pack */
long int id; /*16 8 */
long unsigned int args[6]; /*2448 */
/* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
char __data[]; /*72 0 */
/* size: 72, cachelines: 2, members: 4 */
/* sum members: 68, holes: 1, sum holes: 4 */
/* paddings: 1, sum paddings: 3 */
/* last cacheline: 8 bytes */
};
struct syscall_trace_enter {
struct trace_entry ent; /* 012 */
/* XXX last struct has 3 bytes of padding */
intnr; /*12 4 */
long unsigned int args[]; /*16 0 */
/* size: 16, cachelines: 1, members: 3 */
/* paddings: 1, sum paddings: 3 */
/* last cacheline: 16 bytes */
};
This, in turn, causes perf_event_set_bpf_prog() fail while running bpf
test_profiler testcase because max_ctx_offset is calculated based on the
former struct, while off on the latter:
10488 if (is_tracepoint || is_syscall_tp) {
10489 int off = trace_event_get_offsets(event->tp_event);
10490
10491 if (prog->aux->max_ctx_offset > off)
10492 return -EACCES;
10493 }
What bpf program is actually getting is a pointer to struct
syscall_tp_t, defined in kernel/trace/trace_syscalls.c. This patch fixes
the problem by aligning struct syscall_tp_t with with struct
syscall_trace_(enter|exit) and changing the tests to use these structs
to dereference context.
Signed-off-by: Artem Savkov
Acked-by: Steven Rostedt (Google)
---
kernel/trace/trace_syscalls.c| 4 ++--
tools/testing/selftests/bpf/progs/profiler.inc.h | 2 +-
tools/testing/selftests/bpf/progs/test_vmlinux.c | 4 ++--
3 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index de753403cdafb..9c581d6da843a 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -556,7 +556,7 @@ static int perf_call_bpf_enter(struct trace_event_call
*call, struct pt_regs *re
{
struct syscall_tp_t {
struct trace_entry ent;
- unsigned long syscall_nr;
+ int syscall_nr;
unsigned long args[SYSCALL_DEFINE_MAXARGS];
} __aligned(8) param;
int i;
@@ -661,7 +661,7 @@ static int perf_call_bpf_exit(struct trace_event_call
*call, struct pt_regs *reg
{
struct syscall_tp_t {
struct trace_entry ent;
- unsigned long syscall_nr;
+ int syscall_nr;
unsigned long ret;
} __aligned(8) param;
diff --git a/tools/testing/selftests/bpf/progs/profiler.inc.h
b/tools/testing/selftests/bpf/progs/profiler.inc.h
index f799d87e87002..897061930cb76 100644
--- a/tools/testing/selftests/bpf/progs/profiler.inc.h
+++ b/tools/testing/selftests/bpf/progs/profiler.inc.h
@@ -609,7 +609,7 @@ ssize_t BPF_KPROBE(kprobe__proc_sys_write,
}
SEC("tracepoint/syscalls/sys_enter_kill")
-int tracepoint__syscalls__sys_enter_kill(struct trace_event_raw_sys_enter* ctx)
+int tracepoint__syscalls__sys_enter_kill(struct syscall_trace_enter* ctx)
{
struct bpf_func_stats_ctx stats_ctx;
diff --git a/tools/testing/selftests/bpf/progs/test_vmlinux.c
b/tools/testing/selftests/bpf/progs/test_vmlinux.c
index 4b8e37f7fd06c..78b23934d9f8f 100644
--- a/tools/testing/selftests/bpf/progs/test_vmlinux.c
+++ b/tools/testing/selftests/bpf/progs/test_vmlinux.c
@@ -16,12 +16,12 @@ bool kprobe_called = false;
bool fentry_called = false;
SEC("tp/syscalls/sys_enter_nanosleep")
-int handle__tp(struct trace_event_raw_sys_enter *args)
+int handle__tp(struct syscall_trace_enter *args)
{
struct __kernel_timespec *ts;
long tv_nsec;
- if (args->id != __NR_nanosleep)
+ if (args->nr != __NR_nanosleep)
return 0;
ts = (void *)args->args[0];
--
2.41.0
Re: [RFC PATCH bpf-next] bpf: change syscall_nr type to int in struct syscall_tp_t
For the novice with the RT kernel, Could somebody tell me what kernel
this bug was first introduced in and what kernel we need to install to
get the fix?
This could be the issue we have been experiencing in the Linuxcnc
community with excessive RT network latency (mostly with realtek
NIC's).
I had flagged Lazy preemption as being the possible changes causing
this issue. I thought Lazy Preemption was added Circa kernel 5.09 as
it affected Debian Bullseye on Kernel 5.10 which coincided with when
we first observed the problem.
Thanks in anticipation.
Rod Webster
Rod Webster
1300 896 832
+61 435 765 611
VMN®
www.vmn.com.au
Sole Queensland Distributor
On Thu, 12 Oct 2023 at 21:46, Artem Savkov wrote:
>
> linux-rt-devel tree contains a patch (b1773eac3f29c ("sched: Add support
> for lazy preemption")) that adds an extra member to struct trace_entry.
> This causes the offset of args field in struct trace_event_raw_sys_enter
> be different from the one in struct syscall_trace_enter:
>
> struct trace_event_raw_sys_enter {
> struct trace_entry ent; /* 012 */
>
> /* XXX last struct has 3 bytes of padding */
> /* XXX 4 bytes hole, try to pack */
>
> long int id; /*16 8 */
> long unsigned int args[6]; /*2448 */
> /* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
> char __data[]; /*72 0 */
>
> /* size: 72, cachelines: 2, members: 4 */
> /* sum members: 68, holes: 1, sum holes: 4 */
> /* paddings: 1, sum paddings: 3 */
> /* last cacheline: 8 bytes */
> };
>
> struct syscall_trace_enter {
> struct trace_entry ent; /* 012 */
>
> /* XXX last struct has 3 bytes of padding */
>
> intnr; /*12 4 */
> long unsigned int args[]; /*16 0 */
>
> /* size: 16, cachelines: 1, members: 3 */
> /* paddings: 1, sum paddings: 3 */
> /* last cacheline: 16 bytes */
> };
>
> This, in turn, causes perf_event_set_bpf_prog() fail while running bpf
> test_profiler testcase because max_ctx_offset is calculated based on the
> former struct, while off on the latter:
>
> 10488 if (is_tracepoint || is_syscall_tp) {
> 10489 int off = trace_event_get_offsets(event->tp_event);
> 10490
> 10491 if (prog->aux->max_ctx_offset > off)
> 10492 return -EACCES;
> 10493 }
>
> What bpf program is actually getting is a pointer to struct
> syscall_tp_t, defined in kernel/trace/trace_syscalls.c. This patch fixes
> the problem by aligning struct syscall_tp_t with with struct
> syscall_trace_(enter|exit) and changing the tests to use these structs
> to dereference context.
>
> Signed-off-by: Artem Savkov
> ---
> kernel/trace/trace_syscalls.c| 4 ++--
> tools/testing/selftests/bpf/progs/profiler.inc.h | 2 +-
> tools/testing/selftests/bpf/progs/test_vmlinux.c | 4 ++--
> 3 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
> index de753403cdafb..9c581d6da843a 100644
> --- a/kernel/trace/trace_syscalls.c
> +++ b/kernel/trace/trace_syscalls.c
> @@ -556,7 +556,7 @@ static int perf_call_bpf_enter(struct trace_event_call
> *call, struct pt_regs *re
> {
> struct syscall_tp_t {
> struct trace_entry ent;
> - unsigned long syscall_nr;
> + int syscall_nr;
> unsigned long args[SYSCALL_DEFINE_MAXARGS];
> } __aligned(8) param;
> int i;
> @@ -661,7 +661,7 @@ static int perf_call_bpf_exit(struct trace_event_call
> *call, struct pt_regs *reg
> {
> struct syscall_tp_t {
> struct trace_entry ent;
> - unsigned long syscall_nr;
> + int syscall_nr;
> unsigned long ret;
> } __aligned(8) param;
>
> diff --git a/tools/testing/selftests/bpf/progs/profiler.inc.h
> b/tools/testing/selftests/bpf/progs/profiler.inc.h
> index f799d87e87002..897061930cb76 100644
> --- a/tools/testing/selftests/bpf/progs/profiler.inc.h
> +++ b/tools/testing/selftests/bpf/progs/profiler.inc.h
> @@ -609,7 +609,7 @@ ssize_t BPF_KPROBE(kprobe__proc_sys_write,
> }
>
> SEC("tracepoint/syscalls/sys_enter_kill")
> -int tracepoint__syscalls__sys_enter_kill(struct trace_event_raw_sys_enter*
> ctx)
> +int tracepoint__syscalls__sys_enter_kill(struct syscall_trace_enter* ctx)
> {
> struct bpf_func_stats_ctx stats_ctx;
>
> diff --git a/tools/testing/selftests/bpf/progs/test_vmlinux.c
> b/tools/testing/selftests/bpf/progs/test_vmlinux.c
> index 4b8e37f7fd06c..78b23934d9f8f 100644
> --- a/tools/testing/selftests/bpf/progs/test_vmlinux.c
> +++
Re: [RFC PATCH bpf-next] bpf: change syscall_nr type to int in struct syscall_tp_t
On Thu, Oct 12, 2023 at 6:43 AM Steven Rostedt wrote:
>
> On Thu, 12 Oct 2023 13:45:50 +0200
> Artem Savkov wrote:
>
> > linux-rt-devel tree contains a patch (b1773eac3f29c ("sched: Add support
> > for lazy preemption")) that adds an extra member to struct trace_entry.
> > This causes the offset of args field in struct trace_event_raw_sys_enter
> > be different from the one in struct syscall_trace_enter:
> >
> > struct trace_event_raw_sys_enter {
> > struct trace_entry ent; /* 012 */
> >
> > /* XXX last struct has 3 bytes of padding */
> > /* XXX 4 bytes hole, try to pack */
> >
> > long int id; /*16 8 */
> > long unsigned int args[6]; /*2448 */
> > /* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
> > char __data[]; /*72 0 */
> >
> > /* size: 72, cachelines: 2, members: 4 */
> > /* sum members: 68, holes: 1, sum holes: 4 */
> > /* paddings: 1, sum paddings: 3 */
> > /* last cacheline: 8 bytes */
> > };
> >
> > struct syscall_trace_enter {
> > struct trace_entry ent; /* 012 */
> >
> > /* XXX last struct has 3 bytes of padding */
> >
> > intnr; /*12 4 */
> > long unsigned int args[]; /*16 0 */
> >
> > /* size: 16, cachelines: 1, members: 3 */
> > /* paddings: 1, sum paddings: 3 */
> > /* last cacheline: 16 bytes */
> > };
> >
> > This, in turn, causes perf_event_set_bpf_prog() fail while running bpf
> > test_profiler testcase because max_ctx_offset is calculated based on the
> > former struct, while off on the latter:
> >
> > 10488 if (is_tracepoint || is_syscall_tp) {
> > 10489 int off = trace_event_get_offsets(event->tp_event);
> > 10490
> > 10491 if (prog->aux->max_ctx_offset > off)
> > 10492 return -EACCES;
> > 10493 }
> >
> > What bpf program is actually getting is a pointer to struct
> > syscall_tp_t, defined in kernel/trace/trace_syscalls.c. This patch fixes
> > the problem by aligning struct syscall_tp_t with with struct
> > syscall_trace_(enter|exit) and changing the tests to use these structs
> > to dereference context.
> >
> > Signed-off-by: Artem Savkov
>
I think these changes make sense regardless, can you please resend the
patch without RFC tag so that our CI can run tests for it?
> Thanks for doing a proper fix.
>
> Acked-by: Steven Rostedt (Google)
But looking at [0] and briefly reading some of the discussions you,
Steven, had. I'm just wondering if it would be best to avoid
increasing struct trace_entry altogether? It seems like preempt_count
is actually a 4-bit field in trace context, so it doesn't seem like we
really need to allocate an entire byte for both preempt_count and
preempt_lazy_count. Why can't we just combine them and not waste 8
extra bytes for each trace event in a ring buffer?
[0]
https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git/commit/?id=b1773eac3f29cbdcdfd16e0339f1a164066e9f71
>
> -- Steve
Re: [RFC PATCH bpf-next] bpf: change syscall_nr type to int in struct syscall_tp_t
On Thu, 12 Oct 2023 13:45:50 +0200
Artem Savkov wrote:
> linux-rt-devel tree contains a patch (b1773eac3f29c ("sched: Add support
> for lazy preemption")) that adds an extra member to struct trace_entry.
> This causes the offset of args field in struct trace_event_raw_sys_enter
> be different from the one in struct syscall_trace_enter:
>
> struct trace_event_raw_sys_enter {
> struct trace_entry ent; /* 012 */
>
> /* XXX last struct has 3 bytes of padding */
> /* XXX 4 bytes hole, try to pack */
>
> long int id; /*16 8 */
> long unsigned int args[6]; /*2448 */
> /* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
> char __data[]; /*72 0 */
>
> /* size: 72, cachelines: 2, members: 4 */
> /* sum members: 68, holes: 1, sum holes: 4 */
> /* paddings: 1, sum paddings: 3 */
> /* last cacheline: 8 bytes */
> };
>
> struct syscall_trace_enter {
> struct trace_entry ent; /* 012 */
>
> /* XXX last struct has 3 bytes of padding */
>
> intnr; /*12 4 */
> long unsigned int args[]; /*16 0 */
>
> /* size: 16, cachelines: 1, members: 3 */
> /* paddings: 1, sum paddings: 3 */
> /* last cacheline: 16 bytes */
> };
>
> This, in turn, causes perf_event_set_bpf_prog() fail while running bpf
> test_profiler testcase because max_ctx_offset is calculated based on the
> former struct, while off on the latter:
>
> 10488 if (is_tracepoint || is_syscall_tp) {
> 10489 int off = trace_event_get_offsets(event->tp_event);
> 10490
> 10491 if (prog->aux->max_ctx_offset > off)
> 10492 return -EACCES;
> 10493 }
>
> What bpf program is actually getting is a pointer to struct
> syscall_tp_t, defined in kernel/trace/trace_syscalls.c. This patch fixes
> the problem by aligning struct syscall_tp_t with with struct
> syscall_trace_(enter|exit) and changing the tests to use these structs
> to dereference context.
>
> Signed-off-by: Artem Savkov
Thanks for doing a proper fix.
Acked-by: Steven Rostedt (Google)
-- Steve
[RFC PATCH bpf-next] bpf: change syscall_nr type to int in struct syscall_tp_t
linux-rt-devel tree contains a patch (b1773eac3f29c ("sched: Add support
for lazy preemption")) that adds an extra member to struct trace_entry.
This causes the offset of args field in struct trace_event_raw_sys_enter
be different from the one in struct syscall_trace_enter:
struct trace_event_raw_sys_enter {
struct trace_entry ent; /* 012 */
/* XXX last struct has 3 bytes of padding */
/* XXX 4 bytes hole, try to pack */
long int id; /*16 8 */
long unsigned int args[6]; /*2448 */
/* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
char __data[]; /*72 0 */
/* size: 72, cachelines: 2, members: 4 */
/* sum members: 68, holes: 1, sum holes: 4 */
/* paddings: 1, sum paddings: 3 */
/* last cacheline: 8 bytes */
};
struct syscall_trace_enter {
struct trace_entry ent; /* 012 */
/* XXX last struct has 3 bytes of padding */
intnr; /*12 4 */
long unsigned int args[]; /*16 0 */
/* size: 16, cachelines: 1, members: 3 */
/* paddings: 1, sum paddings: 3 */
/* last cacheline: 16 bytes */
};
This, in turn, causes perf_event_set_bpf_prog() fail while running bpf
test_profiler testcase because max_ctx_offset is calculated based on the
former struct, while off on the latter:
10488 if (is_tracepoint || is_syscall_tp) {
10489 int off = trace_event_get_offsets(event->tp_event);
10490
10491 if (prog->aux->max_ctx_offset > off)
10492 return -EACCES;
10493 }
What bpf program is actually getting is a pointer to struct
syscall_tp_t, defined in kernel/trace/trace_syscalls.c. This patch fixes
the problem by aligning struct syscall_tp_t with with struct
syscall_trace_(enter|exit) and changing the tests to use these structs
to dereference context.
Signed-off-by: Artem Savkov
---
kernel/trace/trace_syscalls.c| 4 ++--
tools/testing/selftests/bpf/progs/profiler.inc.h | 2 +-
tools/testing/selftests/bpf/progs/test_vmlinux.c | 4 ++--
3 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index de753403cdafb..9c581d6da843a 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -556,7 +556,7 @@ static int perf_call_bpf_enter(struct trace_event_call
*call, struct pt_regs *re
{
struct syscall_tp_t {
struct trace_entry ent;
- unsigned long syscall_nr;
+ int syscall_nr;
unsigned long args[SYSCALL_DEFINE_MAXARGS];
} __aligned(8) param;
int i;
@@ -661,7 +661,7 @@ static int perf_call_bpf_exit(struct trace_event_call
*call, struct pt_regs *reg
{
struct syscall_tp_t {
struct trace_entry ent;
- unsigned long syscall_nr;
+ int syscall_nr;
unsigned long ret;
} __aligned(8) param;
diff --git a/tools/testing/selftests/bpf/progs/profiler.inc.h
b/tools/testing/selftests/bpf/progs/profiler.inc.h
index f799d87e87002..897061930cb76 100644
--- a/tools/testing/selftests/bpf/progs/profiler.inc.h
+++ b/tools/testing/selftests/bpf/progs/profiler.inc.h
@@ -609,7 +609,7 @@ ssize_t BPF_KPROBE(kprobe__proc_sys_write,
}
SEC("tracepoint/syscalls/sys_enter_kill")
-int tracepoint__syscalls__sys_enter_kill(struct trace_event_raw_sys_enter* ctx)
+int tracepoint__syscalls__sys_enter_kill(struct syscall_trace_enter* ctx)
{
struct bpf_func_stats_ctx stats_ctx;
diff --git a/tools/testing/selftests/bpf/progs/test_vmlinux.c
b/tools/testing/selftests/bpf/progs/test_vmlinux.c
index 4b8e37f7fd06c..78b23934d9f8f 100644
--- a/tools/testing/selftests/bpf/progs/test_vmlinux.c
+++ b/tools/testing/selftests/bpf/progs/test_vmlinux.c
@@ -16,12 +16,12 @@ bool kprobe_called = false;
bool fentry_called = false;
SEC("tp/syscalls/sys_enter_nanosleep")
-int handle__tp(struct trace_event_raw_sys_enter *args)
+int handle__tp(struct syscall_trace_enter *args)
{
struct __kernel_timespec *ts;
long tv_nsec;
- if (args->id != __NR_nanosleep)
+ if (args->nr != __NR_nanosleep)
return 0;
ts = (void *)args->args[0];
--
2.41.0
