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.netSigned-off-by: Ingo Molnar <mingo@kernel.org>

Documentation/process/adding-syscalls.rst

@@ -360,7 +360,7 @@ First, the entry in ``arch/x86/entry/syscalls/syscall_32.tbl`` gets an extra
 column to indicate that a 32-bit userspace program running on a 64-bit kernel
 should hit the compat entry point::
 
-    380   i386     xyzzy     sys_xyzzy    compat_sys_xyzzy
+    380   i386     xyzzy     sys_xyzzy    __ia32_compat_sys_xyzzy
 
 Second, you need to figure out what should happen for the x32 ABI version of
 the new system call.  There's a choice here: the layout of the arguments
@@ -373,7 +373,7 @@ the compatibility wrapper::
 
     333   64       xyzzy     sys_xyzzy
     ...
-    555   x32      xyzzy     compat_sys_xyzzy
+    555   x32      xyzzy     __x32_compat_sys_xyzzy
 
 If no pointers are involved, then it is preferable to re-use the 64-bit system
 call for the x32 ABI (and consequently the entry in

arch/x86/entry/syscalls/syscall_64.tbl

@@ -342,43 +342,43 @@
 
 #
 # x32-specific system call numbers start at 512 to avoid cache impact
-# for native 64-bit operation. The __compat_sys_x32 stubs are created
+# for native 64-bit operation. The __x32_compat_sys stubs are created
 # on-the-fly for compat_sys_*() compatibility system calls if X86_X32
 # is defined.
 #
-512	x32	rt_sigaction		__compat_sys_x32_rt_sigaction
+512	x32	rt_sigaction		__x32_compat_sys_rt_sigaction
 513	x32	rt_sigreturn		sys32_x32_rt_sigreturn
-514	x32	ioctl			__compat_sys_x32_ioctl
-515	x32	readv			__compat_sys_x32_readv
-516	x32	writev			__compat_sys_x32_writev
-517	x32	recvfrom		__compat_sys_x32_recvfrom
-518	x32	sendmsg			__compat_sys_x32_sendmsg
-519	x32	recvmsg			__compat_sys_x32_recvmsg
-520	x32	execve			__compat_sys_x32_execve/ptregs
-521	x32	ptrace			__compat_sys_x32_ptrace
-522	x32	rt_sigpending		__compat_sys_x32_rt_sigpending
-523	x32	rt_sigtimedwait		__compat_sys_x32_rt_sigtimedwait
-524	x32	rt_sigqueueinfo		__compat_sys_x32_rt_sigqueueinfo
-525	x32	sigaltstack		__compat_sys_x32_sigaltstack
-526	x32	timer_create		__compat_sys_x32_timer_create
-527	x32	mq_notify		__compat_sys_x32_mq_notify
-528	x32	kexec_load		__compat_sys_x32_kexec_load
-529	x32	waitid			__compat_sys_x32_waitid
-530	x32	set_robust_list		__compat_sys_x32_set_robust_list
-531	x32	get_robust_list		__compat_sys_x32_get_robust_list
-532	x32	vmsplice		__compat_sys_x32_vmsplice
-533	x32	move_pages		__compat_sys_x32_move_pages
-534	x32	preadv			__compat_sys_x32_preadv64
-535	x32	pwritev			__compat_sys_x32_pwritev64
-536	x32	rt_tgsigqueueinfo	__compat_sys_x32_rt_tgsigqueueinfo
-537	x32	recvmmsg		__compat_sys_x32_recvmmsg
-538	x32	sendmmsg		__compat_sys_x32_sendmmsg
-539	x32	process_vm_readv	__compat_sys_x32_process_vm_readv
-540	x32	process_vm_writev	__compat_sys_x32_process_vm_writev
-541	x32	setsockopt		__compat_sys_x32_setsockopt
-542	x32	getsockopt		__compat_sys_x32_getsockopt
-543	x32	io_setup		__compat_sys_x32_io_setup
-544	x32	io_submit		__compat_sys_x32_io_submit
-545	x32	execveat		__compat_sys_x32_execveat/ptregs
-546	x32	preadv2			__compat_sys_x32_preadv64v2
-547	x32	pwritev2		__compat_sys_x32_pwritev64v2
+514	x32	ioctl			__x32_compat_sys_ioctl
+515	x32	readv			__x32_compat_sys_readv
+516	x32	writev			__x32_compat_sys_writev
+517	x32	recvfrom		__x32_compat_sys_recvfrom
+518	x32	sendmsg			__x32_compat_sys_sendmsg
+519	x32	recvmsg			__x32_compat_sys_recvmsg
+520	x32	execve			__x32_compat_sys_execve/ptregs
+521	x32	ptrace			__x32_compat_sys_ptrace
+522	x32	rt_sigpending		__x32_compat_sys_rt_sigpending
+523	x32	rt_sigtimedwait		__x32_compat_sys_rt_sigtimedwait
+524	x32	rt_sigqueueinfo		__x32_compat_sys_rt_sigqueueinfo
+525	x32	sigaltstack		__x32_compat_sys_sigaltstack
+526	x32	timer_create		__x32_compat_sys_timer_create
+527	x32	mq_notify		__x32_compat_sys_mq_notify
+528	x32	kexec_load		__x32_compat_sys_kexec_load
+529	x32	waitid			__x32_compat_sys_waitid
+530	x32	set_robust_list		__x32_compat_sys_set_robust_list
+531	x32	get_robust_list		__x32_compat_sys_get_robust_list
+532	x32	vmsplice		__x32_compat_sys_vmsplice
+533	x32	move_pages		__x32_compat_sys_move_pages
+534	x32	preadv			__x32_compat_sys_preadv64
+535	x32	pwritev			__x32_compat_sys_pwritev64
+536	x32	rt_tgsigqueueinfo	__x32_compat_sys_rt_tgsigqueueinfo
+537	x32	recvmmsg		__x32_compat_sys_recvmmsg
+538	x32	sendmmsg		__x32_compat_sys_sendmmsg
+539	x32	process_vm_readv	__x32_compat_sys_process_vm_readv
+540	x32	process_vm_writev	__x32_compat_sys_process_vm_writev
+541	x32	setsockopt		__x32_compat_sys_setsockopt
+542	x32	getsockopt		__x32_compat_sys_getsockopt
+543	x32	io_setup		__x32_compat_sys_io_setup
+544	x32	io_submit		__x32_compat_sys_io_submit
+545	x32	execveat		__x32_compat_sys_execveat/ptregs
+546	x32	preadv2			__x32_compat_sys_preadv64v2
+547	x32	pwritev2		__x32_compat_sys_pwritev64v2

arch/x86/include/asm/syscall_wrapper.h

@@ -29,11 +29,11 @@
  * case as well.
  */
 #define COMPAT_SC_IA32_STUBx(x, name, ...)				\
-	asmlinkage long __compat_sys_ia32##name(const struct pt_regs *regs);\
-	ALLOW_ERROR_INJECTION(__compat_sys_ia32##name, ERRNO);		\
-	asmlinkage long __compat_sys_ia32##name(const struct pt_regs *regs)\
+	asmlinkage long __ia32_compat_sys##name(const struct pt_regs *regs);\
+	ALLOW_ERROR_INJECTION(__ia32_compat_sys##name, ERRNO);		\
+	asmlinkage long __ia32_compat_sys##name(const struct pt_regs *regs)\
 	{								\
-		return c_SyS##name(SC_IA32_REGS_TO_ARGS(x,__VA_ARGS__));\
+		return __se_compat_sys##name(SC_IA32_REGS_TO_ARGS(x,__VA_ARGS__));\
 	}								\
 
 #define SC_IA32_WRAPPERx(x, name, ...)					\
@@ -65,11 +65,11 @@
  * with x86_64 obviously do not need such care.
  */
 #define COMPAT_SC_X32_STUBx(x, name, ...)				\
-	asmlinkage long __compat_sys_x32##name(const struct pt_regs *regs);\
-	ALLOW_ERROR_INJECTION(__compat_sys_x32##name, ERRNO);		\
-	asmlinkage long __compat_sys_x32##name(const struct pt_regs *regs)\
+	asmlinkage long __x32_compat_sys##name(const struct pt_regs *regs);\
+	ALLOW_ERROR_INJECTION(__x32_compat_sys##name, ERRNO);		\
+	asmlinkage long __x32_compat_sys##name(const struct pt_regs *regs)\
 	{								\
-		return c_SyS##name(SC_X86_64_REGS_TO_ARGS(x,__VA_ARGS__));\
+		return __se_compat_sys##name(SC_X86_64_REGS_TO_ARGS(x,__VA_ARGS__));\
 	}								\
 
 #else /* CONFIG_X86_X32 */
@@ -85,15 +85,15 @@
  * unused on x86.
  */
 #define COMPAT_SYSCALL_DEFINEx(x, name, ...)					\
-	static long c_SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__));	\
-	static inline long C_SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
+	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__));\
 	COMPAT_SC_IA32_STUBx(x, name, __VA_ARGS__)				\
 	COMPAT_SC_X32_STUBx(x, name, __VA_ARGS__)				\
-	static long c_SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__))		\
+	static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))	\
 	{									\
-		return C_SYSC##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));	\
+		return __do_compat_sys##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));\
 	}									\
-	static inline long C_SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__))
+	static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
 
 /*
  * As some compat syscalls may not be implemented, we need to expand
@@ -101,12 +101,12 @@
  * kernel/time/posix-stubs.c to cover this case as well.
  */
 #define COND_SYSCALL_COMPAT(name) 					\
-	cond_syscall(__compat_sys_ia32_##name);				\
-	cond_syscall(__compat_sys_x32_##name)
+	cond_syscall(__ia32_compat_sys_##name);				\
+	cond_syscall(__x32_compat_sys_##name)
 
 #define COMPAT_SYS_NI(name)						\
-	SYSCALL_ALIAS(__compat_sys_ia32_##name, sys_ni_posix_timers);	\
-	SYSCALL_ALIAS(__compat_sys_x32_##name, sys_ni_posix_timers)
+	SYSCALL_ALIAS(__ia32_compat_sys_##name, sys_ni_posix_timers);	\
+	SYSCALL_ALIAS(__x32_compat_sys_##name, sys_ni_posix_timers)
 
 #endif /* CONFIG_COMPAT */
 

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))));  \
+	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 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__))\
+	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 C_SYSC##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));	\
+		return __do_compat_sys##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));\
 	}									\
-	static inline long C_SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__))
+	static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
 #endif /* COMPAT_SYSCALL_DEFINEx */
 
 #ifndef compat_user_stack_pointer

scripts/bloat-o-meter

@@ -31,7 +31,7 @@ def getsizes(file, format):
                 # strip generated symbols
                 if name.startswith("__mod_"): continue
                 if name.startswith("__se_sys"): continue
-                if name.startswith("compat_SyS_"): continue
+                if name.startswith("__se_compat_sys"): continue
                 if name == "linux_banner": continue
                 # statics and some other optimizations adds random .NUMBER
                 name = re_NUMBER.sub('', name)