[PATCH bpf-next v2 1/2] libbpf: Extend BPF_KSYSCALL documentation

[Ilya Leoshkevich <iii@linux.ibm.com>]

Explicitly list known quirks.
Mention that socket-related syscalls can be invoked via socketcall().

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 tools/lib/bpf/bpf_tracing.h | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/tools/lib/bpf/bpf_tracing.h b/tools/lib/bpf/bpf_tracing.h
index f4d3e1e2abe2..43ca3aff2292 100644
--- a/tools/lib/bpf/bpf_tracing.h
+++ b/tools/lib/bpf/bpf_tracing.h
@@ -523,10 +523,17 @@ static __always_inline typeof(name(0)) ____##name(struct pt_regs *ctx, ##args)
  * Original struct pt_regs * context is preserved as 'ctx' argument. This might
  * be necessary when using BPF helpers like bpf_perf_event_output().
  *
- * At the moment BPF_KSYSCALL does not handle all the calling convention
- * quirks for mmap(), clone() and compat syscalls transparrently. This may or
- * may not change in the future. User needs to take extra measures to handle
- * such quirks explicitly, if necessary.
+ * At the moment BPF_KSYSCALL does not transparently handle all the calling
+ * convention quirks for the following syscalls:
+ *
+ * - mmap(): __ARCH_WANT_SYS_OLD_MMAP.
+ * - clone(): CONFIG_CLONE_BACKWARDS, CONFIG_CLONE_BACKWARDS2 and
+ *            CONFIG_CLONE_BACKWARDS3.
+ * - socket-related syscalls: __ARCH_WANT_SYS_SOCKETCALL.
+ * - compat syscalls.
+ *
+ * This may or may not change in the future. User needs to take extra measures
+ * to handle such quirks explicitly, if necessary.
  *
  * This macro relies on BPF CO-RE support and virtual __kconfig externs.
  */
-- 
2.35.3