syscalls/core: Introduce CONFIG_ARCH_HAS_SYSCALL_WRAPPER=y
It may be useful for an architecture to override the definitions of the SYSCALL_DEFINE0() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>, in particular to use a different calling convention for syscalls. This patch provides a mechanism to do so: It introduces CONFIG_ARCH_HAS_SYSCALL_WRAPPER. If it is enabled, <asm/sycall_wrapper.h> is included in <linux/syscalls.h> and may be used to define the macros mentioned above. Moreover, as the syscall calling convention may be different if CONFIG_ARCH_HAS_SYSCALL_WRAPPER is set, the syscall function prototypes in <linux/syscalls.h> are #ifndef'd out in that case. 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/20180405095307.3730-3-linux@dominikbrodowski.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -81,6 +81,17 @@ union bpf_attr;
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#include <linux/key.h>
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#include <trace/syscall.h>
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#ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
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/*
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* It may be useful for an architecture to override the definitions of the
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* SYSCALL_DEFINE0() and __SYSCALL_DEFINEx() macros, in particular to use a
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* different calling convention for syscalls. To allow for that, the prototypes
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* for the sys_*() functions below will *not* be included if
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* CONFIG_ARCH_HAS_SYSCALL_WRAPPER is enabled.
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*/
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#include <asm/syscall_wrapper.h>
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#endif /* CONFIG_ARCH_HAS_SYSCALL_WRAPPER */
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/*
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* __MAP - apply a macro to syscall arguments
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* __MAP(n, m, t1, a1, t2, a2, ..., tn, an) will expand to
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@ -189,11 +200,13 @@ static inline int is_syscall_trace_event(struct trace_event_call *tp_event)
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}
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#endif
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#ifndef SYSCALL_DEFINE0
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#define SYSCALL_DEFINE0(sname) \
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SYSCALL_METADATA(_##sname, 0); \
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asmlinkage long sys_##sname(void); \
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ALLOW_ERROR_INJECTION(sys_##sname, ERRNO); \
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asmlinkage long sys_##sname(void)
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#endif /* SYSCALL_DEFINE0 */
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#define SYSCALL_DEFINE1(name, ...) SYSCALL_DEFINEx(1, _##name, __VA_ARGS__)
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#define SYSCALL_DEFINE2(name, ...) SYSCALL_DEFINEx(2, _##name, __VA_ARGS__)
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@ -209,6 +222,8 @@ static inline int is_syscall_trace_event(struct trace_event_call *tp_event)
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__SYSCALL_DEFINEx(x, sname, __VA_ARGS__)
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#define __PROTECT(...) asmlinkage_protect(__VA_ARGS__)
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#ifndef __SYSCALL_DEFINEx
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#define __SYSCALL_DEFINEx(x, name, ...) \
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asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
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__attribute__((alias(__stringify(SyS##name)))); \
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@ -223,6 +238,7 @@ static inline int is_syscall_trace_event(struct trace_event_call *tp_event)
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return ret; \
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} \
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static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__))
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#endif /* __SYSCALL_DEFINEx */
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/*
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* Called before coming back to user-mode. Returning to user-mode with an
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@ -252,7 +268,12 @@ static inline void addr_limit_user_check(void)
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* Please note that these prototypes here are only provided for information
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* purposes, for static analysis, and for linking from the syscall table.
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* These functions should not be called elsewhere from kernel code.
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*
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* As the syscall calling convention may be different from the default
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* for architectures overriding the syscall calling convention, do not
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* include the prototypes if CONFIG_ARCH_HAS_SYSCALL_WRAPPER is enabled.
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*/
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#ifndef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
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asmlinkage long sys_io_setup(unsigned nr_reqs, aio_context_t __user *ctx);
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asmlinkage long sys_io_destroy(aio_context_t ctx);
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asmlinkage long sys_io_submit(aio_context_t, long,
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@ -1076,6 +1097,8 @@ asmlinkage long sys_old_mmap(struct mmap_arg_struct __user *arg);
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*/
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asmlinkage long sys_ni_syscall(void);
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#endif /* CONFIG_ARCH_HAS_SYSCALL_WRAPPER */
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/*
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* Kernel code should not call syscalls (i.e., sys_xyzyyz()) directly.
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@ -1923,3 +1923,10 @@ source "kernel/Kconfig.locks"
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config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
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bool
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# It may be useful for an architecture to override the definitions of the
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# SYSCALL_DEFINE() and __SYSCALL_DEFINEx() macros in <linux/syscalls.h>,
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# in particular to use a different calling convention for syscalls.
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config ARCH_HAS_SYSCALL_WRAPPER
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def_bool n
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depends on !COMPAT
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