From: Jason Baron <redacted>

Add core support to event tracing for compat syscalls. The basic idea is that we
check if we have a compat task via 'is_compat_task()'. If so, we lookup in the
new compat_syscalls_metadata table, the corresponding struct syscall_metadata, to
check syscall arguments and whether or not we are enabled.

Signed-off-by: Jason Baron <redacted>
Signed-off-by: Ian Munsie <redacted>
---
 include/linux/compat.h        |    2 +
 include/trace/syscall.h       |    4 ++
 kernel/trace/trace.h          |    2 +
 kernel/trace/trace_syscalls.c |   86 +++++++++++++++++++++++++++++++++++++----
 4 files changed, 86 insertions(+), 8 deletions(-)

diff --git a/include/linux/compat.h b/include/linux/compat.h
index ab638e9..a94f13d 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h

@@ -363,6 +363,8 @@ extern ssize_t compat_rw_copy_check_uvector(int type,
 
 #else /* CONFIG_COMPAT */
 
+#define NR_syscalls_compat 0
+
 static inline int is_compat_task(void)
 {
 	return 0;

diff --git a/include/trace/syscall.h b/include/trace/syscall.h
index 75f3dce..67d4e64 100644
--- a/include/trace/syscall.h
+++ b/include/trace/syscall.h

@@ -22,6 +22,7 @@
 struct syscall_metadata {
 	const char	*name;
 	int		syscall_nr;
+	int		compat_syscall_nr;

 	int		nb_args;
 	const char	**types;
 	const char	**args;

@@ -38,6 +39,9 @@ struct syscall_metadata {
 
 #ifdef CONFIG_FTRACE_SYSCALLS
 extern unsigned long arch_syscall_addr(int nr);
+#ifdef CONFIG_COMPAT
+extern unsigned long arch_compat_syscall_addr(int nr);
+#endif
 extern int init_syscall_trace(struct ftrace_event_call *call);
 
 extern int reg_event_syscall_enter(struct ftrace_event_call *call);

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 01ce088..53ace4b 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h

@@ -79,12 +79,14 @@ enum trace_type {
 struct syscall_trace_enter {
 	struct trace_entry	ent;
 	int			nr;
+	int			compat;