syscalls/core, syscalls/x86: Clean up compat syscall stub naming convention

Tidy the naming convention for compat syscall subs. Hints which describe
the purpose of the stub go in front and receive a double underscore to
denote that they are generated on-the-fly by the COMPAT_SYSCALL_DEFINEx()
macro.

For the generic case, this means:

t            kernel_waitid	# common C function (see kernel/exit.c)

    __do_compat_sys_waitid	# inlined helper doing the actual work
				# (takes original parameters as declared)

T   __se_compat_sys_waitid	# sign-extending C function calling inlined
				# helper (takes parameters of type long,
				# casts them to unsigned long and then to
				# the declared type)

T        compat_sys_waitid      # alias to __se_compat_sys_waitid()
				# (taking parameters as declared), to
				# be included in syscall table

For x86, the naming is as follows:

t            kernel_waitid	# common C function (see kernel/exit.c)

    __do_compat_sys_waitid	# inlined helper doing the actual work
				# (takes original parameters as declared)

t   __se_compat_sys_waitid      # sign-extending C function calling inlined
				# helper (takes parameters of type long,
				# casts them to unsigned long and then to
				# the declared type)

T __ia32_compat_sys_waitid	# IA32_EMULATION 32-bit-ptregs -> C stub,
				# calls __se_compat_sys_waitid(); to be
				# included in syscall table

T  __x32_compat_sys_waitid	# x32 64-bit-ptregs -> C stub, calls
				# __se_compat_sys_waitid(); to be included
				# in syscall table

If only one of IA32_EMULATION and x32 is enabled, __se_compat_sys_waitid()
may be inlined into the stub __{ia32,x32}_compat_sys_waitid().

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
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: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20180409105145.5364-3-linux@dominikbrodowski.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 17 insertions, 12 deletions

diff --git a/include/linux/compat.h b/include/linux/compat.h
index 2d85ec5cfda2..aca050aac7b6 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -63,19 +63,24 @@
 #define COMPAT_SYSCALL_DEFINE6(name, ...) \
 	COMPAT_SYSCALL_DEFINEx(6, _##name, __VA_ARGS__)
 
+/*
+ * The asmlinkage stub is aliased to a function named __se_compat_sys_*() which
+ * sign-extends 32-bit ints to longs whenever needed. The actual work is
+ * done within __do_compat_sys_*().
+ */
 #ifndef COMPAT_SYSCALL_DEFINEx
-#define COMPAT_SYSCALL_DEFINEx(x, name, ...)				\
-	asmlinkage long compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
-	asmlinkage long compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))\
-		__attribute__((alias(__stringify(compat_SyS##name))));  \
-	ALLOW_ERROR_INJECTION(compat_sys##name, ERRNO);	\
-	static inline long C_SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
-	asmlinkage long compat_SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__));\
-	asmlinkage long compat_SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__))\
-	{								\
-		return C_SYSC##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));	\
-	}								\
-	static inline long C_SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__))
+#define COMPAT_SYSCALL_DEFINEx(x, name, ...)					\
+	asmlinkage long compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));	\
+	asmlinkage long compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))	\
+		__attribute__((alias(__stringify(__se_compat_sys##name))));	\
+	ALLOW_ERROR_INJECTION(compat_sys##name, ERRNO);				\
+	static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
+	asmlinkage long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__));	\
+	asmlinkage 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__))
 #endif /* COMPAT_SYSCALL_DEFINEx */
 
 #ifndef compat_user_stack_pointer