syscalls: Remove start and number from syscall_get_arguments() args

At Linux Plumbers, Andy Lutomirski approached me and pointed out that the
function call syscall_get_arguments() implemented in x86 was horribly
written and not optimized for the standard case of passing in 0 and 6 for
the starting index and the number of system calls to get. When looking at
all the users of this function, I discovered that all instances pass in only
0 and 6 for these arguments. Instead of having this function handle
different cases that are never used, simply rewrite it to return the first 6
arguments of a system call.

This should help out the performance of tracing system calls by ptrace,
ftrace and perf.

Link: http://lkml.kernel.org/r/[email protected]

Cc: Oleg Nesterov <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Dominik Brodowski <[email protected]>
Cc: Dave Martin <[email protected]>
Cc: "Dmitry V. Levin" <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Acked-by: Paul Burton <[email protected]> # MIPS parts
Acked-by: Max Filippov <[email protected]> # For xtensa changes
Acked-by: Will Deacon <[email protected]> # For the arm64 bits
Reviewed-by: Thomas Gleixner <[email protected]> # for x86
Reviewed-by: Dmitry V. Levin <[email protected]>
Reported-by: Andy Lutomirski <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/syscall.c b/lib/syscall.c
index e8467e17b9a2..fb328e7ccb08 100644
--- a/lib/syscall.c
+++ b/lib/syscall.c
@@ -27,7 +27,7 @@ static int collect_syscall(struct task_struct *target, struct syscall_info *info
 
 	info->data.nr = syscall_get_nr(target, regs);
 	if (info->data.nr != -1L)
-		syscall_get_arguments(target, regs, 0, 6,
+		syscall_get_arguments(target, regs,
 				      (unsigned long *)&info->data.args[0]);
 
 	put_task_stack(target);