syscalls/core, syscalls/x86: Clean up 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 SYSCALL_DEFINEx() macro.

For the generic case, this means (0xffffffff prefix removed):

 810f08d0 t     kernel_waitid	# common C function (see kernel/exit.c)

 <inline>     __do_sys_waitid	# inlined helper doing the actual work
				# (takes original parameters as declared)

 810f1aa0 T   __se_sys_waitid	# sign-extending C function calling inlined
				# helper (takes parameters of type long;
				# casts them to the declared type)

 810f1aa0 T        sys_waitid	# alias to __se_sys_waitid() (taking
				# parameters as declared), to be included
				# in syscall table

For x86, the naming is as follows:

 810efc70 t     kernel_waitid	# common C function (see kernel/exit.c)

 <inline>     __do_sys_waitid	# inlined helper doing the actual work
				# (takes original parameters as declared)

 810efd60 t   __se_sys_waitid	# sign-extending C function calling inlined
				# helper (takes parameters of type long;
				# casts them to the declared type)

 810f1140 T __ia32_sys_waitid	# IA32_EMULATION 32-bit-ptregs -> C stub,
				# calls __se_sys_waitid(); to be included
				# in syscall table

 810f1110 T        sys_waitid	# x86 64-bit-ptregs -> C stub, calls
				# __se_sys_waitid(); to be included in
				# syscall table

For x86, sys_waitid() will be re-named to __x64_sys_waitid in a follow-up
patch.
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/20180409105145.5364-2-linux@dominikbrodowski.netSigned-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/syscall_wrapper.h

@@ -22,7 +22,7 @@
 #ifdef CONFIG_IA32_EMULATION
 /*
  * For IA32 emulation, we need to handle "compat" syscalls *and* create
- * additional wrappers (aptly named __sys_ia32_sys_xyzzy) which decode the
+ * additional wrappers (aptly named __ia32_sys_xyzzy) which decode the
  * ia32 regs in the proper order for shared or "common" syscalls. As some
  * syscalls may not be implemented, we need to expand COND_SYSCALL in
  * kernel/sys_ni.c and SYS_NI in kernel/time/posix-stubs.c to cover this
@@ -37,20 +37,20 @@
 	}								\
 
 #define SC_IA32_WRAPPERx(x, name, ...)					\
-	asmlinkage long __sys_ia32##name(const struct pt_regs *regs);	\
-	ALLOW_ERROR_INJECTION(__sys_ia32##name, ERRNO);			\
-	asmlinkage long __sys_ia32##name(const struct pt_regs *regs)	\
+	asmlinkage long __ia32_sys##name(const struct pt_regs *regs);	\
+	ALLOW_ERROR_INJECTION(__ia32_sys##name, ERRNO);			\
+	asmlinkage long __ia32_sys##name(const struct pt_regs *regs)	\
 	{								\
-		return SyS##name(SC_IA32_REGS_TO_ARGS(x,__VA_ARGS__));	\
+		return __se_sys##name(SC_IA32_REGS_TO_ARGS(x,__VA_ARGS__));\
 	}
 
 #define COND_SYSCALL(name)						\
 	cond_syscall(sys_##name);					\
-	cond_syscall(__sys_ia32_##name)
+	cond_syscall(__ia32_sys_##name)
 
 #define SYS_NI(name)							\
 	SYSCALL_ALIAS(sys_##name, sys_ni_posix_timers);			\
-	SYSCALL_ALIAS(__sys_ia32_##name, sys_ni_posix_timers)
+	SYSCALL_ALIAS(__ia32_sys_##name, sys_ni_posix_timers)
 
 #else /* CONFIG_IA32_EMULATION */
 #define COMPAT_SC_IA32_STUBx(x, name, ...)
@@ -115,9 +115,10 @@
  * Instead of the generic __SYSCALL_DEFINEx() definition, this macro takes
  * struct pt_regs *regs as the only argument of the syscall stub named
  * sys_*(). It decodes just the registers it needs and passes them on to
- * the SyS_*() wrapper and then to the SYSC_*() function doing the actual job.
- * These wrappers and functions are inlined, meaning that the assembly looks
- * as follows (slightly re-ordered):
+ * the __se_sys_*() wrapper performing sign extension and then to the
+ * __do_sys_*() function doing the actual job. These wrappers and functions
+ * are inlined (at least in very most cases), meaning that the assembly looks
+ * as follows (slightly re-ordered for better readability):
  *
  * <sys_recv>:			<-- syscall with 4 parameters
  *	callq	<__fentry__>
@@ -140,7 +141,7 @@
  * the call chain.
  *
  * If IA32_EMULATION is enabled, this macro generates an additional wrapper
- * named __sys_ia32_*() which decodes the struct pt_regs *regs according
+ * named __ia32_sys_*() which decodes the struct pt_regs *regs according
  * to the i386 calling convention (bx, cx, dx, si, di, bp).
  *
  * As the generic SYSCALL_DEFINE0() macro does not decode any parameters for
@@ -151,21 +152,21 @@
 #define __SYSCALL_DEFINEx(x, name, ...)					\
 	asmlinkage long sys##name(const struct pt_regs *regs);		\
 	ALLOW_ERROR_INJECTION(sys##name, ERRNO);			\
-	static long SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__));		\
-	static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__));	\
+	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 sys##name(const struct pt_regs *regs)		\
 	{								\
-		return SyS##name(SC_X86_64_REGS_TO_ARGS(x,__VA_ARGS__));\
+		return __se_sys##name(SC_X86_64_REGS_TO_ARGS(x,__VA_ARGS__));\
 	}								\
 	SC_IA32_WRAPPERx(x, name, __VA_ARGS__)				\
-	static long SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__))		\
+	static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))	\
 	{								\
-		long ret = SYSC##name(__MAP(x,__SC_CAST,__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 SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__))
+	static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
 
 /*
  * For VSYSCALLS, we need to declare these three syscalls with the new

include/linux/syscalls.h

@@ -223,21 +223,26 @@ static inline int is_syscall_trace_event(struct trace_event_call *tp_event)
 
 #define __PROTECT(...) asmlinkage_protect(__VA_ARGS__)
 
+/*
+ * The asmlinkage stub is aliased to a function named __se_sys_*() which
+ * sign-extends 32-bit ints to longs whenever needed. The actual work is
+ * done within __do_sys_*().
+ */
 #ifndef __SYSCALL_DEFINEx
 #define __SYSCALL_DEFINEx(x, name, ...)					\
 	asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))	\
-		__attribute__((alias(__stringify(SyS##name))));		\
+		__attribute__((alias(__stringify(__se_sys##name))));	\
 	ALLOW_ERROR_INJECTION(sys##name, ERRNO);			\
-	static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__));	\
-	asmlinkage long SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__));	\
-	asmlinkage long SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__))	\
+	static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
+	asmlinkage long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__));	\
+	asmlinkage long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))	\
 	{								\
-		long ret = SYSC##name(__MAP(x,__SC_CAST,__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 SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__))
+	static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
 #endif /* __SYSCALL_DEFINEx */
 
 /*

scripts/bloat-o-meter

@@ -30,7 +30,7 @@ def getsizes(file, format):
             if type in format:
                 # strip generated symbols
                 if name.startswith("__mod_"): continue
-                if name.startswith("SyS_"): continue
+                if name.startswith("__se_sys"): continue
                 if name.startswith("compat_SyS_"): continue
                 if name == "linux_banner": continue
                 # statics and some other optimizations adds random .NUMBER