Commit 6203deb0 authored by Dominik Brodowski's avatar Dominik Brodowski
Browse files

kernel: add do_compat_sigaltstack() helper; remove in-kernel call to compat syscall 

Using this helper allows us to avoid the in-kernel call to the
compat_sys_sigaltstack() syscall.

This patch is part of a series which removes in-kernel calls to syscalls.
On this basis, the syscall entry path can be streamlined. For details, see
http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net



Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarDominik Brodowski <linux@dominikbrodowski.net>
parent 192c5807

kernel/signal.c

+10 −4
Original line number Diff line number Diff line
@@ -3573,9 +3573,8 @@ int __save_altstack(stack_t __user *uss, unsigned long sp) 
}



#ifdef CONFIG_COMPAT

COMPAT_SYSCALL_DEFINE2(sigaltstack,

			const compat_stack_t __user *, uss_ptr,

			compat_stack_t __user *, uoss_ptr)

static int do_compat_sigaltstack(const compat_stack_t __user *uss_ptr,

				 compat_stack_t __user *uoss_ptr)

{

	stack_t uss, uoss;

	int ret;
@@ -3602,9 +3601,16 @@ COMPAT_SYSCALL_DEFINE2(sigaltstack, 
	return ret;

}



COMPAT_SYSCALL_DEFINE2(sigaltstack,

			const compat_stack_t __user *, uss_ptr,

			compat_stack_t __user *, uoss_ptr)

{

	return do_compat_sigaltstack(uss_ptr, uoss_ptr);

}



int compat_restore_altstack(const compat_stack_t __user *uss)

{

	int err = compat_sys_sigaltstack(uss, NULL);

	int err = do_compat_sigaltstack(uss, NULL);

	/* squash all but -EFAULT for now */

	return err == -EFAULT ? err : 0;

}