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; /* 0 12 */
/* 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]; /* 24 48 */
/* --- 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; /* 0 12 */
/* XXX last struct has 3 bytes of padding */
int nr; /* 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 <asavkov@xxxxxxxxxx>
Acked-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
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
