From 4378a7d4be30ec6994702b19936f7d1465193541 Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Wed, 11 Jul 2018 14:56:56 +0100 Subject: arm64: implement syscall wrappers 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 --- arch/arm64/include/asm/syscall.h | 4 +- arch/arm64/include/asm/syscall_wrapper.h | 80 ++++++++++++++++++++++++++++++++ 2 files changed, 81 insertions(+), 3 deletions(-) create mode 100644 arch/arm64/include/asm/syscall_wrapper.h (limited to 'arch/arm64/include') diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h index b83d0e6980a3..ad8be16a39c9 100644 --- a/arch/arm64/include/asm/syscall.h +++ b/arch/arm64/include/asm/syscall.h @@ -20,9 +20,7 @@ #include #include -typedef long (*syscall_fn_t)(unsigned long, unsigned long, - unsigned long, unsigned long, - unsigned long, unsigned long); +typedef long (*syscall_fn_t)(struct pt_regs *regs); extern const syscall_fn_t sys_call_table[]; diff --git a/arch/arm64/include/asm/syscall_wrapper.h b/arch/arm64/include/asm/syscall_wrapper.h new file mode 100644 index 000000000000..a4477e515b79 --- /dev/null +++ b/arch/arm64/include/asm/syscall_wrapper.h @@ -0,0 +1,80 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * syscall_wrapper.h - arm64 specific wrappers to syscall definitions + * + * Based on arch/x86/include/asm_syscall_wrapper.h + */ + +#ifndef __ASM_SYSCALL_WRAPPER_H +#define __ASM_SYSCALL_WRAPPER_H + +#define SC_ARM64_REGS_TO_ARGS(x, ...) \ + __MAP(x,__SC_ARGS \ + ,,regs->regs[0],,regs->regs[1],,regs->regs[2] \ + ,,regs->regs[3],,regs->regs[4],,regs->regs[5]) + +#ifdef CONFIG_COMPAT + +#define COMPAT_SYSCALL_DEFINEx(x, name, ...) \ + asmlinkage long __arm64_compat_sys##name(const struct pt_regs *regs); \ + ALLOW_ERROR_INJECTION(__arm64_compat_sys##name, ERRNO); \ + static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \ + static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)); \ + asmlinkage long __arm64_compat_sys##name(const struct pt_regs *regs) \ + { \ + return __se_compat_sys##name(SC_ARM64_REGS_TO_ARGS(x,__VA_ARGS__)); \ + } \ + static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \ + { \ + return __do_compat_sys##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__)); \ + } \ + static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) + +#define COMPAT_SYSCALL_DEFINE0(sname) \ + asmlinkage long __arm64_compat_sys_##sname(void); \ + ALLOW_ERROR_INJECTION(__arm64_compat_sys_##sname, ERRNO); \ + asmlinkage long __arm64_compat_sys_##sname(void) + +#define COND_SYSCALL_COMPAT(name) \ + cond_syscall(__arm64_compat_sys_##name); + +#define COMPAT_SYS_NI(name) \ + SYSCALL_ALIAS(__arm64_compat_sys_##name, sys_ni_posix_timers); + +#endif /* CONFIG_COMPAT */ + +#define __SYSCALL_DEFINEx(x, name, ...) \ + asmlinkage long __arm64_sys##name(const struct pt_regs *regs); \ + ALLOW_ERROR_INJECTION(__arm64_sys##name, ERRNO); \ + static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \ + static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)); \ + asmlinkage long __arm64_sys##name(const struct pt_regs *regs) \ + { \ + return __se_sys##name(SC_ARM64_REGS_TO_ARGS(x,__VA_ARGS__)); \ + } \ + static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \ + { \ + long ret = __do_sys##name(__MAP(x,__SC_CAST,__VA_ARGS__)); \ + __MAP(x,__SC_TEST,__VA_ARGS__); \ + __PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__)); \ + return ret; \ + } \ + static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) + +#ifndef SYSCALL_DEFINE0 +#define SYSCALL_DEFINE0(sname) \ + SYSCALL_METADATA(_##sname, 0); \ + asmlinkage long __arm64_sys_##sname(void); \ + ALLOW_ERROR_INJECTION(__arm64_sys_##sname, ERRNO); \ + asmlinkage long __arm64_sys_##sname(void) +#endif + +#ifndef COND_SYSCALL +#define COND_SYSCALL(name) cond_syscall(__arm64_sys_##name) +#endif + +#ifndef SYS_NI +#define SYS_NI(name) SYSCALL_ALIAS(__arm64_sys_##name, sys_ni_posix_timers); +#endif + +#endif /* __ASM_SYSCALL_WRAPPER_H */ -- cgit v1.2.3