[PATCH perf/core 1/3] uprobes/x86: Return error from uprobe syscall when not called from trampoline

Currently uprobe syscall handles all errors with forcing SIGILL to current
process. As suggested by Andrii it'd be helpful for uprobe syscall detection
to return error value for the !in_uprobe_trampoline check.

This way we could just call uprobe syscall and based on return value we will
find out if the kernel has it.

Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 arch/x86/kernel/uprobes.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 0a8c0a4a5423..845aeaf36b8d 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c

@@ -810,7 +810,7 @@ SYSCALL_DEFINE0(uprobe)
 
 	/* Allow execution only from uprobe trampolines. */
 	if (!in_uprobe_trampoline(regs->ip))
-		goto sigill;
+		return -ENXIO;
 
 	err = copy_from_user(&args, (void __user *)regs->sp, sizeof(args));
 	if (err)

-- 
2.51.0