[PATCH bpf-next v2 05/10] libbpf: Add PT_REGS_SYSCALL macro

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

Some architectures pass a pointer to struct pt_regs to syscall
handlers, others unpack it into individual function parameters.
Introduce a macro to describe what a particular arch does, using
`passing pt_regs *` as a default.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 tools/lib/bpf/bpf_tracing.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tools/lib/bpf/bpf_tracing.h b/tools/lib/bpf/bpf_tracing.h
index 30f0964f8c9e..400a4f002f77 100644
--- a/tools/lib/bpf/bpf_tracing.h
+++ b/tools/lib/bpf/bpf_tracing.h
@@ -334,6 +334,15 @@ struct pt_regs;
 
 #endif /* defined(bpf_target_defined) */
 
+/*
+ * When invoked from a syscall handler kprobe, returns a pointer to a
+ * struct pt_regs containing syscall arguments and suitable for passing to
+ * PT_REGS_PARMn_SYSCALL() and PT_REGS_PARMn_CORE_SYSCALL().
+ */
+#ifndef PT_REGS_SYSCALL
+#define PT_REGS_SYSCALL(ctx) ((struct pt_regs *)PT_REGS_PARM1(ctx))
+#endif
+
 #ifndef ___bpf_concat
 #define ___bpf_concat(a, b) a ## b
 #endif
-- 
2.34.1