syscalls/x86: Unconditionally enable 'struct pt_regs' based syscalls on x86_64

Removing CONFIG_SYSCALL_PTREGS from arch/x86/Kconfig and simply selecting
ARCH_HAS_SYSCALL_WRAPPER unconditionally on x86-64 allows us to simplify
several codepaths.

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/20180405095307.3730-7-linux@dominikbrodowski.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/Kconfig

@@ -29,6 +29,7 @@ config X86_64
 	select HAVE_ARCH_SOFT_DIRTY
 	select MODULES_USE_ELF_RELA
 	select X86_DEV_DMA_OPS
+	select ARCH_HAS_SYSCALL_WRAPPER
 
 #
 # Arch settings
@@ -2954,8 +2955,3 @@ source "crypto/Kconfig"
 source "arch/x86/kvm/Kconfig"
 
 source "lib/Kconfig"
-
-config SYSCALL_PTREGS
-	def_bool y
-	depends on X86_64
-	select ARCH_HAS_SYSCALL_WRAPPER

arch/x86/entry/common.c

@@ -284,13 +284,7 @@ __visible void do_syscall_64(unsigned long nr, struct pt_regs *regs)
 	nr &= __SYSCALL_MASK;
 	if (likely(nr < NR_syscalls)) {
 		nr = array_index_nospec(nr, NR_syscalls);
-#ifdef CONFIG_SYSCALL_PTREGS
 		regs->ax = sys_call_table[nr](regs);
-#else
-		regs->ax = sys_call_table[nr](
-			regs->di, regs->si, regs->dx,
-			regs->r10, regs->r8, regs->r9);
-#endif
 	}
 
 	syscall_return_slowpath(regs);
@@ -325,7 +319,7 @@ static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs)
 
 	if (likely(nr < IA32_NR_syscalls)) {
 		nr = array_index_nospec(nr, IA32_NR_syscalls);
-#ifdef CONFIG_SYSCALL_PTREGS
+#ifdef CONFIG_IA32_EMULATION
 		regs->ax = ia32_sys_call_table[nr](regs);
 #else
 		/*
@@ -338,7 +332,7 @@ static __always_inline void do_syscall_32_irqs_on(struct pt_regs *regs)
 			(unsigned int)regs->bx, (unsigned int)regs->cx,
 			(unsigned int)regs->dx, (unsigned int)regs->si,
 			(unsigned int)regs->di, (unsigned int)regs->bp);
-#endif /* CONFIG_SYSCALL_PTREGS */
+#endif /* CONFIG_IA32_EMULATION */
 	}
 
 	syscall_return_slowpath(regs);

arch/x86/entry/syscall_32.c

@@ -7,17 +7,17 @@
 #include <asm/asm-offsets.h>
 #include <asm/syscall.h>
 
-#ifdef CONFIG_SYSCALL_PTREGS
+#ifdef CONFIG_IA32_EMULATION
 /* On X86_64, we use struct pt_regs * to pass parameters to syscalls */
 #define __SYSCALL_I386(nr, sym, qual) extern asmlinkage long sym(const struct pt_regs *);
 
 /* this is a lie, but it does not hurt as sys_ni_syscall just returns -EINVAL */
 extern asmlinkage long sys_ni_syscall(const struct pt_regs *);
 
-#else /* CONFIG_SYSCALL_PTREGS */
+#else /* CONFIG_IA32_EMULATION */
 #define __SYSCALL_I386(nr, sym, qual) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
 extern asmlinkage long sys_ni_syscall(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
-#endif /* CONFIG_SYSCALL_PTREGS */
+#endif /* CONFIG_IA32_EMULATION */
 
 #include <asm/syscalls_32.h>
 #undef __SYSCALL_I386

arch/x86/entry/syscall_64.c

@@ -7,14 +7,9 @@
 #include <asm/asm-offsets.h>
 #include <asm/syscall.h>
 
-#ifdef CONFIG_SYSCALL_PTREGS
 /* this is a lie, but it does not hurt as sys_ni_syscall just returns -EINVAL */
 extern asmlinkage long sys_ni_syscall(const struct pt_regs *);
 #define __SYSCALL_64(nr, sym, qual) extern asmlinkage long sym(const struct pt_regs *);
-#else /* CONFIG_SYSCALL_PTREGS */
-extern asmlinkage long sys_ni_syscall(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
-#define __SYSCALL_64(nr, sym, qual) extern asmlinkage long sym(unsigned long, unsigned long, unsigned long, unsigned long, unsigned long, unsigned long);
-#endif /* CONFIG_SYSCALL_PTREGS */
 #include <asm/syscalls_64.h>
 #undef __SYSCALL_64
 

arch/x86/entry/vsyscall/vsyscall_64.c

@@ -127,9 +127,7 @@ bool emulate_vsyscall(struct pt_regs *regs, unsigned long address)
 	int vsyscall_nr, syscall_nr, tmp;
 	int prev_sig_on_uaccess_err;
 	long ret;
-#ifdef CONFIG_SYSCALL_PTREGS
 	unsigned long orig_dx;
-#endif
 
 	/*
 	 * No point in checking CS -- the only way to get here is a user mode
@@ -230,38 +228,22 @@ bool emulate_vsyscall(struct pt_regs *regs, unsigned long address)
 	ret = -EFAULT;
 	switch (vsyscall_nr) {
 	case 0:
-#ifdef CONFIG_SYSCALL_PTREGS
 		/* this decodes regs->di and regs->si on its own */
 		ret = sys_gettimeofday(regs);
-#else
-		ret = sys_gettimeofday(
-			(struct timeval __user *)regs->di,
-			(struct timezone __user *)regs->si);
-#endif /* CONFIG_SYSCALL_PTREGS */
 		break;
 
 	case 1:
-#ifdef CONFIG_SYSCALL_PTREGS
 		/* this decodes regs->di on its own */
 		ret = sys_time(regs);
-#else
-		ret = sys_time((time_t __user *)regs->di);
-#endif /* CONFIG_SYSCALL_PTREGS */
 		break;
 
 	case 2:
-#ifdef CONFIG_SYSCALL_PTREGS
 		/* while we could clobber regs->dx, we didn't in the past... */
 		orig_dx = regs->dx;
 		regs->dx = 0;
 		/* this decodes regs->di, regs->si and regs->dx on its own */
 		ret = sys_getcpu(regs);
 		regs->dx = orig_dx;
-#else
-		ret = sys_getcpu((unsigned __user *)regs->di,
-				 (unsigned __user *)regs->si,
-				 NULL);
-#endif /* CONFIG_SYSCALL_PTREGS */
 		break;
 	}
 

arch/x86/include/asm/syscall.h

@@ -20,13 +20,13 @@
 #include <asm/thread_info.h>	/* for TS_COMPAT */
 #include <asm/unistd.h>
 
-#ifdef CONFIG_SYSCALL_PTREGS
+#ifdef CONFIG_X86_64
 typedef asmlinkage long (*sys_call_ptr_t)(const struct pt_regs *);
 #else
 typedef asmlinkage long (*sys_call_ptr_t)(unsigned long, unsigned long,
 					  unsigned long, unsigned long,
 					  unsigned long, unsigned long);
-#endif /* CONFIG_SYSCALL_PTREGS */
+#endif /* CONFIG_X86_64 */
 extern const sys_call_ptr_t sys_call_table[];
 
 #if defined(CONFIG_X86_32)

arch/x86/include/asm/syscalls.h

@@ -19,10 +19,10 @@
 /* kernel/ioport.c */
 long ksys_ioperm(unsigned long from, unsigned long num, int turn_on);
 
-#ifndef CONFIG_SYSCALL_PTREGS
-/*
- * If CONFIG_SYSCALL_PTREGS is enabled, a different syscall calling convention
- * is used. Do not include these -- invalid -- prototypes then
+#ifdef CONFIG_X86_32
+/* 
+ * These definitions are only valid on pure 32-bit systems; x86-64 uses a
+ * different syscall calling convention
  */
 asmlinkage long sys_ioperm(unsigned long, unsigned long, int);
 asmlinkage long sys_iopl(unsigned int);
@@ -38,7 +38,6 @@ asmlinkage long sys_set_thread_area(struct user_desc __user *);
 asmlinkage long sys_get_thread_area(struct user_desc __user *);
 
 /* X86_32 only */
-#ifdef CONFIG_X86_32
 
 /* kernel/signal.c */
 asmlinkage long sys_sigreturn(void);
@@ -48,16 +47,5 @@ struct vm86_struct;
 asmlinkage long sys_vm86old(struct vm86_struct __user *);
 asmlinkage long sys_vm86(unsigned long, unsigned long);
 
-#else /* CONFIG_X86_32 */
-
-/* X86_64 only */
-/* kernel/process_64.c */
-asmlinkage long sys_arch_prctl(int, unsigned long);
-
-/* kernel/sys_x86_64.c */
-asmlinkage long sys_mmap(unsigned long, unsigned long, unsigned long,
-			 unsigned long, unsigned long, unsigned long);
-
 #endif /* CONFIG_X86_32 */
-#endif /* CONFIG_SYSCALL_PTREGS */
 #endif /* _ASM_X86_SYSCALLS_H */