From: Matthew Wilcox (Oracle) <willy@infradead.org>
Date: Mon, 10 Aug 2020 12:51:44 +0000 (-0400)
Subject: mshare: Add new system call
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=10b0ae3004c577d0b190c907ee7c0f15a341f27f;p=users%2Fwilly%2Flinux.git

mshare: Add new system call

[wired up x86-64 only, fix before submission]

Almost no implementation here; just return a file descriptor that can't
actually do anything.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---

diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index 78847b32e137..05abbdc34a10 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -360,6 +360,7 @@
 437	common	openat2			sys_openat2
 438	common	pidfd_getfd		sys_pidfd_getfd
 439	common	faccessat2		sys_faccessat2
+449	common	mshare			sys_mshare
 
 #
 # x32-specific system call numbers start at 512 to avoid cache impact
diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
index f4a01305d9a6..69bed18e23f5 100644
--- a/include/uapi/asm-generic/unistd.h
+++ b/include/uapi/asm-generic/unistd.h
@@ -859,7 +859,7 @@ __SYSCALL(__NR_pidfd_getfd, sys_pidfd_getfd)
 __SYSCALL(__NR_faccessat2, sys_faccessat2)
 
 #undef __NR_syscalls
-#define __NR_syscalls 440
+#define __NR_syscalls 450
 
 /*
  * 32 bit systems traditionally used different
diff --git a/mm/Makefile b/mm/Makefile
index 6e9d46b2efc9..01a75d90d352 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -35,7 +35,7 @@ CFLAGS_init-mm.o += $(call cc-disable-warning, override-init)
 CFLAGS_init-mm.o += $(call cc-disable-warning, initializer-overrides)
 
 mmu-y			:= nommu.o
-mmu-$(CONFIG_MMU)	:= highmem.o memory.o mincore.o \
+mmu-$(CONFIG_MMU)	:= highmem.o memory.o mincore.o mshare.o \
 			   mlock.o mmap.o mmu_gather.o mprotect.o mremap.o \
 			   msync.o page_vma_mapped.o pagewalk.o \
 			   pgtable-generic.o rmap.o vmalloc.o
diff --git a/mm/mshare.c b/mm/mshare.c
new file mode 100644
index 000000000000..72af82683fdb
--- /dev/null
+++ b/mm/mshare.c
@@ -0,0 +1,19 @@
+#include <linux/anon_inodes.h>
+#include <linux/fs.h>
+#include <linux/syscalls.h>
+
+static const struct file_operations mshare_fops = {
+};
+
+SYSCALL_DEFINE3(mshare, unsigned long, addr, unsigned long, len,
+		unsigned long, flags)
+{
+	int fd;
+
+	if ((addr | len) & (PGDIR_SIZE - 1))
+		return -EINVAL;
+
+	fd = anon_inode_getfd("mshare", &mshare_fops, NULL, O_RDWR);
+
+	return fd;
+}