syscalls/x86: Use 'struct pt_regs' based syscall calling for IA32_EMULATION and x32

Extend ARCH_HAS_SYSCALL_WRAPPER for i386 emulation and for x32 on 64-bit
x86.

For x32, all we need to do is to create an additional stub for each
compat syscall which decodes the parameters in x86-64 ordering, e.g.:

	asmlinkage long __compat_sys_x32_xyzzy(struct pt_regs *regs)
	{
		return c_SyS_xyzzy(regs->di, regs->si, regs->dx);
	}

For i386 emulation, we need to teach compat_sys_*() to take struct
pt_regs as its only argument, e.g.:

	asmlinkage long __compat_sys_ia32_xyzzy(struct pt_regs *regs)
	{
		return c_SyS_xyzzy(regs->bx, regs->cx, regs->dx);
	}

In addition, we need to create additional stubs for common syscalls
(that is, for syscalls which have the same parameters on 32-bit and
64-bit), e.g.:

	asmlinkage long __sys_ia32_xyzzy(struct pt_regs *regs)
	{
		return c_sys_xyzzy(regs->bx, regs->cx, regs->dx);
	}

This approach avoids leaking random user-provided register content down
the call chain.

This patch is based on an original proof-of-concept

 | From: Linus Torvalds <torvalds@linux-foundation.org>
 | Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

and was split up and heavily modified by me, in particular to base it on
ARCH_HAS_SYSCALL_WRAPPER.

Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20180405095307.3730-6-linux@dominikbrodowski.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 38 insertions, 36 deletions

diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index 5aef183e2f85..a83c0f7f462f 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -342,41 +342,43 @@
 
 #
 # x32-specific system call numbers start at 512 to avoid cache impact
-# for native 64-bit operation.
+# for native 64-bit operation. The __compat_sys_x32 stubs are created
+# on-the-fly for compat_sys_*() compatibility system calls if X86_X32
+# is defined.
 #
-512	x32	rt_sigaction		compat_sys_rt_sigaction
+512	x32	rt_sigaction		__compat_sys_x32_rt_sigaction
 513	x32	rt_sigreturn		sys32_x32_rt_sigreturn
-514	x32	ioctl			compat_sys_ioctl
-515	x32	readv			compat_sys_readv
-516	x32	writev			compat_sys_writev
-517	x32	recvfrom		compat_sys_recvfrom
-518	x32	sendmsg			compat_sys_sendmsg
-519	x32	recvmsg			compat_sys_recvmsg
-520	x32	execve			compat_sys_execve/ptregs
-521	x32	ptrace			compat_sys_ptrace
-522	x32	rt_sigpending		compat_sys_rt_sigpending
-523	x32	rt_sigtimedwait		compat_sys_rt_sigtimedwait
-524	x32	rt_sigqueueinfo		compat_sys_rt_sigqueueinfo
-525	x32	sigaltstack		compat_sys_sigaltstack
-526	x32	timer_create		compat_sys_timer_create
-527	x32	mq_notify		compat_sys_mq_notify
-528	x32	kexec_load		compat_sys_kexec_load
-529	x32	waitid			compat_sys_waitid
-530	x32	set_robust_list		compat_sys_set_robust_list
-531	x32	get_robust_list		compat_sys_get_robust_list
-532	x32	vmsplice		compat_sys_vmsplice
-533	x32	move_pages		compat_sys_move_pages
-534	x32	preadv			compat_sys_preadv64
-535	x32	pwritev			compat_sys_pwritev64
-536	x32	rt_tgsigqueueinfo	compat_sys_rt_tgsigqueueinfo
-537	x32	recvmmsg		compat_sys_recvmmsg
-538	x32	sendmmsg		compat_sys_sendmmsg
-539	x32	process_vm_readv	compat_sys_process_vm_readv
-540	x32	process_vm_writev	compat_sys_process_vm_writev
-541	x32	setsockopt		compat_sys_setsockopt
-542	x32	getsockopt		compat_sys_getsockopt
-543	x32	io_setup		compat_sys_io_setup
-544	x32	io_submit		compat_sys_io_submit
-545	x32	execveat		compat_sys_execveat/ptregs
-546	x32	preadv2			compat_sys_preadv64v2
-547	x32	pwritev2		compat_sys_pwritev64v2
+514	x32	ioctl			__compat_sys_x32_ioctl
+515	x32	readv			__compat_sys_x32_readv
+516	x32	writev			__compat_sys_x32_writev
+517	x32	recvfrom		__compat_sys_x32_recvfrom
+518	x32	sendmsg			__compat_sys_x32_sendmsg
+519	x32	recvmsg			__compat_sys_x32_recvmsg
+520	x32	execve			__compat_sys_x32_execve/ptregs
+521	x32	ptrace			__compat_sys_x32_ptrace
+522	x32	rt_sigpending		__compat_sys_x32_rt_sigpending
+523	x32	rt_sigtimedwait		__compat_sys_x32_rt_sigtimedwait
+524	x32	rt_sigqueueinfo		__compat_sys_x32_rt_sigqueueinfo
+525	x32	sigaltstack		__compat_sys_x32_sigaltstack
+526	x32	timer_create		__compat_sys_x32_timer_create
+527	x32	mq_notify		__compat_sys_x32_mq_notify
+528	x32	kexec_load		__compat_sys_x32_kexec_load
+529	x32	waitid			__compat_sys_x32_waitid
+530	x32	set_robust_list		__compat_sys_x32_set_robust_list
+531	x32	get_robust_list		__compat_sys_x32_get_robust_list
+532	x32	vmsplice		__compat_sys_x32_vmsplice
+533	x32	move_pages		__compat_sys_x32_move_pages
+534	x32	preadv			__compat_sys_x32_preadv64
+535	x32	pwritev			__compat_sys_x32_pwritev64
+536	x32	rt_tgsigqueueinfo	__compat_sys_x32_rt_tgsigqueueinfo
+537	x32	recvmmsg		__compat_sys_x32_recvmmsg
+538	x32	sendmmsg		__compat_sys_x32_sendmmsg
+539	x32	process_vm_readv	__compat_sys_x32_process_vm_readv
+540	x32	process_vm_writev	__compat_sys_x32_process_vm_writev
+541	x32	setsockopt		__compat_sys_x32_setsockopt
+542	x32	getsockopt		__compat_sys_x32_getsockopt
+543	x32	io_setup		__compat_sys_x32_io_setup
+544	x32	io_submit		__compat_sys_x32_io_submit
+545	x32	execveat		__compat_sys_x32_execveat/ptregs
+546	x32	preadv2			__compat_sys_x32_preadv64v2
+547	x32	pwritev2		__compat_sys_x32_pwritev64v2