From 31dc1e9681e109a04459d9059874264f4925605d Mon Sep 17 00:00:00 2001
From: John Baldwin <jhb@FreeBSD.org>
Date: Fri, 14 Oct 2016 20:01:07 +0000
Subject: [PATCH] Drop support for using mmap() with /dev/kmem.

Using the device pager with /dev/kmem is not stable since KVA mappings
are transient, but the device pager caches the PA associated with a
given offset forever.  Interestingly, mips' implementation of
memmap() already refused requests for /dev/kmem.

Note that kvm_read/kvm_write do not use mmap, but use read and write on
/dev/kmem, so this should not affect libkvm users.

Reviewed by:	kib
MFC after:	2 months
---
 sys/amd64/amd64/mem.c     | 7 +++----
 sys/arm/arm/mem.c         | 9 ++++-----
 sys/arm64/arm64/mem.c     | 9 ++++-----
 sys/i386/i386/mem.c       | 9 ++++-----
 sys/powerpc/powerpc/mem.c | 2 --
 5 files changed, 15 insertions(+), 21 deletions(-)

diff --git a/sys/amd64/amd64/mem.c b/sys/amd64/amd64/mem.c
index 716fcfb118d..51f46507436 100644
--- a/sys/amd64/amd64/mem.c
+++ b/sys/amd64/amd64/mem.c
@@ -172,10 +172,9 @@ memmmap(struct cdev *dev, vm_ooffset_t offset, vm_paddr_t *paddr,
 		if (offset >= (1ULL << cpu_maxphyaddr))
 			return (-1);
 		*paddr = offset;
-	} else if (dev2unit(dev) == CDEV_MINOR_KMEM)
-        	*paddr = vtophys(offset);
-	/* else panic! */
-	return (0);
+		return (0);
+	}
+	return (-1);
 }
 
 /*
diff --git a/sys/arm/arm/mem.c b/sys/arm/arm/mem.c
index 096988dc0b7..c2cf320b2b6 100644
--- a/sys/arm/arm/mem.c
+++ b/sys/arm/arm/mem.c
@@ -161,10 +161,9 @@ int
 memmmap(struct cdev *dev, vm_ooffset_t offset, vm_paddr_t *paddr,
     int prot __unused, vm_memattr_t *memattr __unused)
 {
-	if (dev2unit(dev) == CDEV_MINOR_MEM)
+	if (dev2unit(dev) == CDEV_MINOR_MEM) {
 		*paddr = offset;
-	else if (dev2unit(dev) == CDEV_MINOR_KMEM)
-        	*paddr = vtophys(offset);
-	/* else panic! */
-	return (0);
+		return (0);
+	}
+	return (-1);
 }
diff --git a/sys/arm64/arm64/mem.c b/sys/arm64/arm64/mem.c
index 9044fb3ba7f..e0ea4889cb5 100644
--- a/sys/arm64/arm64/mem.c
+++ b/sys/arm64/arm64/mem.c
@@ -123,10 +123,9 @@ int
 memmmap(struct cdev *dev, vm_ooffset_t offset, vm_paddr_t *paddr,
     int prot __unused, vm_memattr_t *memattr __unused)
 {
-	if (dev2unit(dev) == CDEV_MINOR_MEM)
+	if (dev2unit(dev) == CDEV_MINOR_MEM) {
 		*paddr = offset;
-	else if (dev2unit(dev) == CDEV_MINOR_KMEM)
-		*paddr = vtophys(offset);
-	/* else panic! */
-	return (0);
+		return (0);
+	}
+	return (-1);
 }
diff --git a/sys/i386/i386/mem.c b/sys/i386/i386/mem.c
index b036bd3ec3c..43fb99451f7 100644
--- a/sys/i386/i386/mem.c
+++ b/sys/i386/i386/mem.c
@@ -161,12 +161,11 @@ int
 memmmap(struct cdev *dev, vm_ooffset_t offset, vm_paddr_t *paddr,
     int prot __unused, vm_memattr_t *memattr __unused)
 {
-	if (dev2unit(dev) == CDEV_MINOR_MEM)
+	if (dev2unit(dev) == CDEV_MINOR_MEM) {
 		*paddr = offset;
-	else if (dev2unit(dev) == CDEV_MINOR_KMEM)
-        	*paddr = vtophys(offset);
-	/* else panic! */
-	return (0);
+		return (0);
+	}
+	return (-1);
 }
 
 /*
diff --git a/sys/powerpc/powerpc/mem.c b/sys/powerpc/powerpc/mem.c
index a7fbfa3edf8..2bc89fd4b5a 100644
--- a/sys/powerpc/powerpc/mem.c
+++ b/sys/powerpc/powerpc/mem.c
@@ -179,8 +179,6 @@ memmmap(struct cdev *dev, vm_ooffset_t offset, vm_paddr_t *paddr,
 
 	if (dev2unit(dev) == CDEV_MINOR_MEM)
 		*paddr = offset;
-	else if (dev2unit(dev) == CDEV_MINOR_KMEM)
-		*paddr = vtophys(offset);
 	else
 		return (EFAULT);