[PATCH 2/2] um: remove copy_from_kernel_nofault_allowed

[Benjamin Berg]

From: Benjamin Berg <benjamin.berg at intel.com>

There is no need to override the default version of this function
anymore as UML now has proper _nofault memory access functions.

Doing this also fixes the fact that the implementation was incorrect as
using mincore() will incorrectly flag pages as inaccessible if they were
swapped out by the host.

Fixes: f75b1b1bedfb ("um: Implement probe_kernel_read()")
Signed-off-by: Benjamin Berg <benjamin.berg at intel.com>
---
 arch/um/include/shared/os.h |  1 -
 arch/um/kernel/Makefile     |  2 +-
 arch/um/kernel/maccess.c    | 19 --------------
 arch/um/os-Linux/process.c  | 51 -------------------------------------
 4 files changed, 1 insertion(+), 72 deletions(-)
 delete mode 100644 arch/um/kernel/maccess.c

diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index 5babad8c5f75..bc02767f0639 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -213,7 +213,6 @@ extern int os_protect_memory(void *addr, unsigned long len,
 extern int os_unmap_memory(void *addr, int len);
 extern int os_drop_memory(void *addr, int length);
 extern int can_drop_memory(void);
-extern int os_mincore(void *addr, unsigned long len);
 
 void os_set_pdeathsig(void);
 
diff --git a/arch/um/kernel/Makefile b/arch/um/kernel/Makefile
index f8567b933ffa..4df1cd0d2017 100644
--- a/arch/um/kernel/Makefile
+++ b/arch/um/kernel/Makefile
@@ -17,7 +17,7 @@ extra-y := vmlinux.lds
 obj-y = config.o exec.o exitcode.o irq.o ksyms.o mem.o \
 	physmem.o process.o ptrace.o reboot.o sigio.o \
 	signal.o sysrq.o time.o tlb.o trap.o \
-	um_arch.o umid.o maccess.o kmsg_dump.o capflags.o skas/
+	um_arch.o umid.o kmsg_dump.o capflags.o skas/
 obj-y += load_file.o
 
 obj-$(CONFIG_BLK_DEV_INITRD) += initrd.o
diff --git a/arch/um/kernel/maccess.c b/arch/um/kernel/maccess.c
deleted file mode 100644
index 8ccd56813f68..000000000000
--- a/arch/um/kernel/maccess.c
+++ /dev/null
@@ -1,19 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * Copyright (C) 2013 Richard Weinberger <richrd at nod.at>
- */
-
-#include <linux/uaccess.h>
-#include <linux/kernel.h>
-#include <os.h>
-
-bool copy_from_kernel_nofault_allowed(const void *src, size_t size)
-{
-	void *psrc = (void *)rounddown((unsigned long)src, PAGE_SIZE);
-
-	if ((unsigned long)src < PAGE_SIZE || size <= 0)
-		return false;
-	if (os_mincore(psrc, size + src - psrc) <= 0)
-		return false;
-	return true;
-}
diff --git a/arch/um/os-Linux/process.c b/arch/um/os-Linux/process.c
index 9f086f939420..184566edeee9 100644
--- a/arch/um/os-Linux/process.c
+++ b/arch/um/os-Linux/process.c
@@ -142,57 +142,6 @@ int __init can_drop_memory(void)
 	return ok;
 }
 
-static int os_page_mincore(void *addr)
-{
-	char vec[2];
-	int ret;
-
-	ret = mincore(addr, UM_KERN_PAGE_SIZE, vec);
-	if (ret < 0) {
-		if (errno == ENOMEM || errno == EINVAL)
-			return 0;
-		else
-			return -errno;
-	}
-
-	return vec[0] & 1;
-}
-
-int os_mincore(void *addr, unsigned long len)
-{
-	char *vec;
-	int ret, i;
-
-	if (len <= UM_KERN_PAGE_SIZE)
-		return os_page_mincore(addr);
-
-	vec = calloc(1, (len + UM_KERN_PAGE_SIZE - 1) / UM_KERN_PAGE_SIZE);
-	if (!vec)
-		return -ENOMEM;
-
-	ret = mincore(addr, UM_KERN_PAGE_SIZE, vec);
-	if (ret < 0) {
-		if (errno == ENOMEM || errno == EINVAL)
-			ret = 0;
-		else
-			ret = -errno;
-
-		goto out;
-	}
-
-	for (i = 0; i < ((len + UM_KERN_PAGE_SIZE - 1) / UM_KERN_PAGE_SIZE); i++) {
-		if (!(vec[i] & 1)) {
-			ret = 0;
-			goto out;
-		}
-	}
-
-	ret = 1;
-out:
-	free(vec);
-	return ret;
-}
-
 void init_new_thread_signals(void)
 {
 	set_handler(SIGSEGV);
-- 
2.48.1