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authorMark Rutland <mark.rutland@arm.com>2018-07-11 14:56:56 +0100
committerWill Deacon <will.deacon@arm.com>2018-07-12 14:49:48 +0100
commit4378a7d4be30ec6994702b19936f7d1465193541 (patch)
tree09bf8da3e6289b5944e81ea52a37bee40720f9fd /arch/arm64/include/asm/syscall_wrapper.h
parent55f849265af886aaf404cbf8a659b2c8d411fc3a (diff)
downloadlinux-4378a7d4be30ec6994702b19936f7d1465193541.tar.gz
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_<compat_>sys_<name> is the "real" syscall implementation, with the expected prototype. * __se_<compat_>sys_<name> 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_<compat_>sys_<name>. 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_<compat_>_sys_<name> takes a struct pt_regs pointer, and extracts *only* the relevant register values, passing these on to the __se_<compat_>sys_<name> wrapper. The syscall invocation code is updated to handle the calling convention required by __arm64_<compat_>_sys_<name>, 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 <mark.rutland@arm.com> Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/include/asm/syscall_wrapper.h')
-rw-r--r--arch/arm64/include/asm/syscall_wrapper.h80
1 files changed, 80 insertions, 0 deletions
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 */