arm64: use the correct function type in SYSCALL_DEFINE0

2019-06-22T06:09:13Z

[ Upstream commit 0e358bd7b7ebd27e491dabed938eae254c17fe3b ] Although a syscall defined using SYSCALL_DEFINE0 doesn't accept parameters, use the correct function type to avoid indirect call type mismatches with Control-Flow Integrity checking. Signed-off-by: Sami Tolvanen Signed-off-by: Will Deacon Signed-off-by: Sasha Levin

arm64: implement syscall wrappers

2018-07-12T13:49:48Z

To minimize the risk of userspace-controlled values being used under speculation, this patch adds pt_regs based syscall wrappers for arm64, which pass the minimum set of required userspace values to syscall implementations. For each syscall, a wrapper which takes a pt_regs argument is automatically generated, and this extracts the arguments before calling the "real" syscall implementation. Each syscall has three functions generated: * __do_sys_ is the "real" syscall implementation, with the expected prototype. * __se_sys_ is the sign-extension/narrowing wrapper, inherited from common code. This takes a series of long parameters, casting each to the requisite types required by the "real" syscall implementation in __do_sys_. This wrapper *may* not be necessary on arm64 given the AAPCS rules on unused register bits, but it seemed safer to keep the wrapper for now. * __arm64__sys_ takes a struct pt_regs pointer, and extracts *only* the relevant register values, passing these on to the __se_sys_ wrapper. The syscall invocation code is updated to handle the calling convention required by __arm64__sys_, and passes a single struct pt_regs pointer. The compiler can fold the syscall implementation and its wrappers, such that the overhead of this approach is minimized. Note that we play games with sys_ni_syscall(). It can't be defined with SYSCALL_DEFINE0() because we must avoid the possibility of error injection. Additionally, there are a couple of locations where we need to call it from C code, and we don't (currently) have a ksys_ni_syscall(). While it has no wrapper, passing in a redundant pt_regs pointer is benign per the AAPCS. When ARCH_HAS_SYSCALL_WRAPPER is selected, no prototype is defines for sys_ni_syscall(). Since we need to treat it differently for in-kernel calls and the syscall tables, the prototype is defined as-required. The wrappers are largely the same as their x86 counterparts, but simplified as we don't have a variety of compat calling conventions that require separate stubs. Unlike x86, we have some zero-argument compat syscalls, and must define COMPAT_SYSCALL_DEFINE0() to ensure that these are also given an __arm64_compat_sys_ prefix. Signed-off-by: Mark Rutland Reviewed-by: Dominik Brodowski Reviewed-by: Catalin Marinas Cc: Catalin Marinas Cc: Will Deacon Signed-off-by: Will Deacon

kernel/arch/arm64/include/asm/syscall_wrapper.h, branch linux-5.1.y

arm64: use the correct function type in SYSCALL_DEFINE0

arm64: implement syscall wrappers