mm: add ksys_mmap_pgoff() helper; remove in-kernel calls to sys_mmap_pgoff()

Using this helper allows us to avoid the in-kernel calls to the
sys_mmap_pgoff() syscall. The ksys_ prefix denotes that this function is
meant as a drop-in replacement for the syscall. In particular, it uses the
same calling convention as sys_mmap_pgoff().

This patch is part of a series which removes in-kernel calls to syscalls.
On this basis, the syscall entry path can be streamlined. For details, see
http://lkml.kernel.org/r/20180325162527.GA17492@light.dominikbrodowski.net

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mm@kvack.org
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>

arch/alpha/kernel/osf_sys.c

@@ -189,7 +189,7 @@ SYSCALL_DEFINE6(osf_mmap, unsigned long, addr, unsigned long, len,
 		goto out;
 	if (off & ~PAGE_MASK)
 		goto out;
-	ret = sys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
+	ret = ksys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
  out:
 	return ret;
 }

arch/arm64/kernel/sys.c

@@ -34,7 +34,7 @@ asmlinkage long sys_mmap(unsigned long addr, unsigned long len,
 	if (offset_in_page(off) != 0)
 		return -EINVAL;
 
-	return sys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
+	return ksys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
 }
 
 SYSCALL_DEFINE1(arm64_personality, unsigned int, personality)

arch/ia64/kernel/sys_ia64.c

@@ -139,7 +139,7 @@ int ia64_mmap_check(unsigned long addr, unsigned long len,
 asmlinkage unsigned long
 sys_mmap2 (unsigned long addr, unsigned long len, int prot, int flags, int fd, long pgoff)
 {
-	addr = sys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
+	addr = ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
 	if (!IS_ERR((void *) addr))
 		force_successful_syscall_return();
 	return addr;
@@ -151,7 +151,7 @@ sys_mmap (unsigned long addr, unsigned long len, int prot, int flags, int fd, lo
 	if (offset_in_page(off) != 0)
 		return -EINVAL;
 
-	addr = sys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
+	addr = ksys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
 	if (!IS_ERR((void *) addr))
 		force_successful_syscall_return();
 	return addr;

arch/m68k/kernel/sys_m68k.c

@@ -46,7 +46,7 @@ asmlinkage long sys_mmap2(unsigned long addr, unsigned long len,
 	 * so we need to shift the argument down by 1; m68k mmap64(3)
 	 * (in libc) expects the last argument of mmap2 in 4Kb units.
 	 */
-	return sys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
+	return ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
 }
 
 /* Convert virtual (user) address VADDR to physical address PADDR */

arch/microblaze/kernel/sys_microblaze.c

@@ -40,7 +40,7 @@ SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len,
 	if (pgoff & ~PAGE_MASK)
 		return -EINVAL;
 
-	return sys_mmap_pgoff(addr, len, prot, flags, fd, pgoff >> PAGE_SHIFT);
+	return ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff >> PAGE_SHIFT);
 }
 
 SYSCALL_DEFINE6(mmap2, unsigned long, addr, unsigned long, len,
@@ -50,6 +50,6 @@ SYSCALL_DEFINE6(mmap2, unsigned long, addr, unsigned long, len,
 	if (pgoff & (~PAGE_MASK >> 12))
 		return -EINVAL;
 
-	return sys_mmap_pgoff(addr, len, prot, flags, fd,
+	return ksys_mmap_pgoff(addr, len, prot, flags, fd,
 			       pgoff >> (PAGE_SHIFT - 12));
 }

arch/mips/kernel/linux32.c

@@ -67,7 +67,7 @@ SYSCALL_DEFINE6(32_mmap2, unsigned long, addr, unsigned long, len,
 {
 	if (pgoff & (~PAGE_MASK >> 12))
 		return -EINVAL;
-	return sys_mmap_pgoff(addr, len, prot, flags, fd,
+	return ksys_mmap_pgoff(addr, len, prot, flags, fd,
 			       pgoff >> (PAGE_SHIFT-12));
 }
 

arch/mips/kernel/syscall.c

@@ -63,7 +63,8 @@ SYSCALL_DEFINE6(mips_mmap, unsigned long, addr, unsigned long, len,
 {
 	if (offset & ~PAGE_MASK)
 		return -EINVAL;
-	return sys_mmap_pgoff(addr, len, prot, flags, fd, offset >> PAGE_SHIFT);
+	return ksys_mmap_pgoff(addr, len, prot, flags, fd,
+			       offset >> PAGE_SHIFT);
 }
 
 SYSCALL_DEFINE6(mips_mmap2, unsigned long, addr, unsigned long, len,
@@ -73,7 +74,8 @@ SYSCALL_DEFINE6(mips_mmap2, unsigned long, addr, unsigned long, len,
 	if (pgoff & (~PAGE_MASK >> 12))
 		return -EINVAL;
 
-	return sys_mmap_pgoff(addr, len, prot, flags, fd, pgoff >> (PAGE_SHIFT-12));
+	return ksys_mmap_pgoff(addr, len, prot, flags, fd,
+			       pgoff >> (PAGE_SHIFT - 12));
 }
 
 save_static_function(sys_fork);

arch/parisc/kernel/sys_parisc.c

@@ -270,7 +270,7 @@ asmlinkage unsigned long sys_mmap2(unsigned long addr, unsigned long len,
 {
 	/* Make sure the shift for mmap2 is constant (12), no matter what PAGE_SIZE
 	   we have. */
-	return sys_mmap_pgoff(addr, len, prot, flags, fd,
+	return ksys_mmap_pgoff(addr, len, prot, flags, fd,
 			       pgoff >> (PAGE_SHIFT - 12));
 }
 
@@ -279,7 +279,7 @@ asmlinkage unsigned long sys_mmap(unsigned long addr, unsigned long len,
 		unsigned long offset)
 {
 	if (!(offset & ~PAGE_MASK)) {
-		return sys_mmap_pgoff(addr, len, prot, flags, fd,
+		return ksys_mmap_pgoff(addr, len, prot, flags, fd,
 					offset >> PAGE_SHIFT);
 	} else {
 		return -EINVAL;

arch/powerpc/kernel/syscalls.c

@@ -57,7 +57,7 @@ static inline long do_mmap2(unsigned long addr, size_t len,
 		off >>= shift;
 	}
 
-	ret = sys_mmap_pgoff(addr, len, prot, flags, fd, off);
+	ret = ksys_mmap_pgoff(addr, len, prot, flags, fd, off);
 out:
 	return ret;
 }

arch/riscv/kernel/sys_riscv.c

@@ -24,7 +24,7 @@ static long riscv_sys_mmap(unsigned long addr, unsigned long len,
 {
 	if (unlikely(offset & (~PAGE_MASK >> page_shift_offset)))
 		return -EINVAL;
-	return sys_mmap_pgoff(addr, len, prot, flags, fd,
+	return ksys_mmap_pgoff(addr, len, prot, flags, fd,
 			       offset >> (PAGE_SHIFT - page_shift_offset));
 }
 

arch/s390/kernel/compat_linux.c

@@ -442,7 +442,7 @@ COMPAT_SYSCALL_DEFINE1(s390_old_mmap, struct mmap_arg_struct_emu31 __user *, arg
 		return -EFAULT;
 	if (a.offset & ~PAGE_MASK)
 		return -EINVAL;
-	return sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
+	return ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
 			       a.offset >> PAGE_SHIFT);
 }
 
@@ -452,7 +452,7 @@ COMPAT_SYSCALL_DEFINE1(s390_mmap2, struct mmap_arg_struct_emu31 __user *, arg)
 
 	if (copy_from_user(&a, arg, sizeof(a)))
 		return -EFAULT;
-	return sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd, a.offset);
+	return ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd, a.offset);
 }
 
 COMPAT_SYSCALL_DEFINE3(s390_read, unsigned int, fd, char __user *, buf, compat_size_t, count)

arch/s390/kernel/sys_s390.c

@@ -53,7 +53,7 @@ SYSCALL_DEFINE1(mmap2, struct s390_mmap_arg_struct __user *, arg)
 
 	if (copy_from_user(&a, arg, sizeof(a)))
 		goto out;
-	error = sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd, a.offset);
+	error = ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd, a.offset);
 out:
 	return error;
 }

arch/sh/kernel/sys_sh.c

@@ -35,7 +35,7 @@ asmlinkage int old_mmap(unsigned long addr, unsigned long len,
 {
 	if (off & ~PAGE_MASK)
 		return -EINVAL;
-	return sys_mmap_pgoff(addr, len, prot, flags, fd, off>>PAGE_SHIFT);
+	return ksys_mmap_pgoff(addr, len, prot, flags, fd, off>>PAGE_SHIFT);
 }
 
 asmlinkage long sys_mmap2(unsigned long addr, unsigned long len,
@@ -51,7 +51,7 @@ asmlinkage long sys_mmap2(unsigned long addr, unsigned long len,
 
 	pgoff >>= PAGE_SHIFT - 12;
 
-	return sys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
+	return ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
 }
 
 /* sys_cacheflush -- flush (part of) the processor cache.  */

arch/sparc/kernel/sys_sparc_32.c

@@ -104,7 +104,7 @@ asmlinkage long sys_mmap2(unsigned long addr, unsigned long len,
 {
 	/* Make sure the shift for mmap2 is constant (12), no matter what PAGE_SIZE
 	   we have. */
-	return sys_mmap_pgoff(addr, len, prot, flags, fd,
+	return ksys_mmap_pgoff(addr, len, prot, flags, fd,
 			       pgoff >> (PAGE_SHIFT - 12));
 }
 
@@ -113,7 +113,7 @@ asmlinkage long sys_mmap(unsigned long addr, unsigned long len,
 	unsigned long off)
 {
 	/* no alignment check? */
-	return sys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
+	return ksys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
 }
 
 long sparc_remap_file_pages(unsigned long start, unsigned long size,

arch/sparc/kernel/sys_sparc_64.c

@@ -458,7 +458,7 @@ SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len,
 		goto out;
 	if (off & ~PAGE_MASK)
 		goto out;
-	retval = sys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
+	retval = ksys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
 out:
 	return retval;
 }

arch/um/kernel/syscall.c

@@ -22,7 +22,7 @@ long old_mmap(unsigned long addr, unsigned long len,
 	if (offset & ~PAGE_MASK)
 		goto out;
 
-	err = sys_mmap_pgoff(addr, len, prot, flags, fd, offset >> PAGE_SHIFT);
+	err = ksys_mmap_pgoff(addr, len, prot, flags, fd, offset >> PAGE_SHIFT);
  out:
 	return err;
 }

arch/x86/ia32/sys_ia32.c

@@ -166,7 +166,7 @@ COMPAT_SYSCALL_DEFINE1(x86_mmap, struct mmap_arg_struct32 __user *, arg)
 	if (a.offset & ~PAGE_MASK)
 		return -EINVAL;
 
-	return sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
+	return ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
 			       a.offset>>PAGE_SHIFT);
 }
 

arch/x86/kernel/sys_x86_64.c

@@ -97,7 +97,7 @@ SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len,
 	if (off & ~PAGE_MASK)
 		goto out;
 
-	error = sys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
+	error = ksys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
 out:
 	return error;
 }

include/linux/syscalls.h

@@ -979,6 +979,9 @@ static inline int ksys_fadvise64_64(int fd, loff_t offset, loff_t len,
 	return -EINVAL;
 }
 #endif
+unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
+			      unsigned long prot, unsigned long flags,
+			      unsigned long fd, unsigned long pgoff);
 
 /*
  * The following kernel syscall equivalents are just wrappers to fs-internal

mm/mmap.c

@@ -1488,9 +1488,9 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
 	return addr;
 }
 
-SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
-		unsigned long, prot, unsigned long, flags,
-		unsigned long, fd, unsigned long, pgoff)
+unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
+			      unsigned long prot, unsigned long flags,
+			      unsigned long fd, unsigned long pgoff)
 {
 	struct file *file = NULL;
 	unsigned long retval;
@@ -1537,6 +1537,13 @@ SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
 	return retval;
 }
 
+SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
+		unsigned long, prot, unsigned long, flags,
+		unsigned long, fd, unsigned long, pgoff)
+{
+	return ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
+}
+
 #ifdef __ARCH_WANT_SYS_OLD_MMAP
 struct mmap_arg_struct {
 	unsigned long addr;
@@ -1556,7 +1563,7 @@ SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
 	if (offset_in_page(a.offset))
 		return -EINVAL;
 
-	return sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
+	return ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
 			       a.offset >> PAGE_SHIFT);
 }
 #endif /* __ARCH_WANT_SYS_OLD_MMAP */

mm/nommu.c

@@ -1423,9 +1423,9 @@ unsigned long do_mmap(struct file *file,
 	return -ENOMEM;
 }
 
-SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
-		unsigned long, prot, unsigned long, flags,
-		unsigned long, fd, unsigned long, pgoff)
+unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
+			      unsigned long prot, unsigned long flags,
+			      unsigned long fd, unsigned long pgoff)
 {
 	struct file *file = NULL;
 	unsigned long retval = -EBADF;
@@ -1447,6 +1447,13 @@ SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
 	return retval;
 }
 
+SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
+		unsigned long, prot, unsigned long, flags,
+		unsigned long, fd, unsigned long, pgoff)
+{
+	return ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
+}
+
 #ifdef __ARCH_WANT_SYS_OLD_MMAP
 struct mmap_arg_struct {
 	unsigned long addr;
@@ -1466,7 +1473,7 @@ SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
 	if (offset_in_page(a.offset))
 		return -EINVAL;
 
-	return sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
+	return ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
 			       a.offset >> PAGE_SHIFT);
 }
 #endif /* __ARCH_WANT_SYS_OLD_MMAP */