Linux Virtualization - May 2007 - [PATCH 1/3] Documentation and example updates

1) Example code: old libc headers don't have SIOCBRADDIF, and old zlibs
   don't have gzdirect() -- it's a sanity check anyway.
2) Some people don't build in their source directories, so .config
   isn't there (thanks to Tony Breeds <tony@bakeyournoodle.com>).
3) Point out that guest and host kernel are usually the same.
4) Set the "no checksum" option on the tun device as a minor
optimization.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

---
 Documentation/lguest/Makefile   |    9 ++++++++-
 Documentation/lguest/lguest.c   |    6 ++++--
 Documentation/lguest/lguest.txt |    8 ++++++--
 3 files changed, 18 insertions(+), 5 deletions(-)

==================================================================---
a/Documentation/lguest/Makefile
+++ b/Documentation/lguest/Makefile
@@ -1,7 +1,14 @@
 # This creates the demonstration utility "lguest" which runs a Linux
guest.
 
+# For those people that have a separate object dir, look there for .config
+KBUILD_OUTPUT := ../..
+ifdef O
+  ifeq ("$(origin O)", "command line")
+    KBUILD_OUTPUT := $(O)
+  endif
+endif
 # We rely on CONFIG_PAGE_OFFSET to know where to put lguest binary.
-include ../../.config
+include $(KBUILD_OUTPUT)/.config
 LGUEST_GUEST_TOP := ($(CONFIG_PAGE_OFFSET) - 0x08000000)
 
 CFLAGS:=-Wall -Wmissing-declarations -Wmissing-prototypes -O3 \
==================================================================---
a/Documentation/lguest/lguest.c
+++ b/Documentation/lguest/lguest.c
@@ -40,6 +40,9 @@ typedef uint8_t u8;
 #define PAGE_PRESENT 0x7 	/* Present, RW, Execute */
 #define NET_PEERNUM 1
 #define BRIDGE_PFX "bridge:"
+#ifndef SIOCBRADDIF
+#define SIOCBRADDIF	0x89a2		/* add interface to bridge      */
+#endif
 
 static bool verbose;
 #define verbose(args...) \
@@ -166,8 +169,6 @@ static unsigned long unpack_bzimage(int 
 	void *img = (void *)0x100000;
 
 	f = gzdopen(fd, "rb");
-	if (gzdirect(f))
-		errx(1, "did not find correct gzip header");
 	while ((ret = gzread(f, img + len, 65536)) > 0)
 		len += ret;
 	if (ret < 0)
@@ -820,6 +821,7 @@ static void setup_tun_net(const char *ar
 	strcpy(ifr.ifr_name, "tap%d");
 	if (ioctl(netfd, TUNSETIFF, &ifr) != 0)
 		err(1, "configuring /dev/net/tun");
+	ioctl(netfd, TUNSETNOCSUM, 1);
 
 	/* You will be peer 1: we should create enough jitter to randomize */
 	dev = new_device(devices, LGUEST_DEVICE_T_NET, 1,
==================================================================---
a/Documentation/lguest/lguest.txt
+++ b/Documentation/lguest/lguest.txt
@@ -23,7 +23,10 @@ Developer features:
 
 Running Lguest:
 
-- You will need to configure your kernel with the following options:
+- Lguest runs the same kernel as guest and host.  You can configure
+  them differently, but usually it's easiest not to.
+
+  You will need to configure your kernel with the following options:
 
   CONFIG_HIGHMEM64G=n ("High Memory Support" "64GB")[1]
   CONFIG_TUN=y/m ("Universal TUN/TAP device driver support")
@@ -35,7 +38,8 @@ Running Lguest:
   CONFIG_HZ=100 ("Timer frequency")[2]
 
 - A tool called "lguest" is available in this directory: type
"make"
-  to build it.
+  to build it.  If you didn't build your kernel in-tree, use "make
+  O=<builddir>".
 
 - Create or find a root disk image.  There are several useful ones
   around, such as the xm-test tiny root image at

I've long disliked Linux's user access functions.  Nonetheless,
let's
stop the warnings.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

---
 drivers/lguest/core.c                 |    8 +++++---
 drivers/lguest/hypercalls.c           |   33 ++++++++++++++++++++++-----------
 drivers/lguest/interrupts_and_traps.c |   17 ++++++++++++-----
 3 files changed, 39 insertions(+), 19 deletions(-)

==================================================================---
a/drivers/lguest/core.c
+++ b/drivers/lguest/core.c
@@ -303,8 +303,9 @@ int run_guest(struct lguest *lg, char *_
 		/* Hypercalls first: we might have been out to userspace */
 		do_hypercalls(lg);
 		if (lg->dma_is_pending) {
-			put_user(lg->pending_dma, (unsigned long *)user);
-			put_user(lg->pending_key, (unsigned long *)user+1);
+			if (put_user(lg->pending_dma, (unsigned long *)user) ||
+			    put_user(lg->pending_key, (unsigned long *)user+1))
+				return -EFAULT;
 			return sizeof(unsigned long)*2;
 		}
 
@@ -350,7 +351,8 @@ int run_guest(struct lguest *lg, char *_
 				continue;
 
 			/* If lguest_data is NULL, this won't hurt. */
-			put_user(cr2, &lg->lguest_data->cr2);
+			if (put_user(cr2, &lg->lguest_data->cr2))
+				kill_guest(lg, "Writing cr2");
 			break;
 		case 7: /* We've intercepted a Device Not Available fault. */
 			/* If they don't want to know, just absorb it. */
==================================================================---
a/drivers/lguest/hypercalls.c
+++ b/drivers/lguest/hypercalls.c
@@ -102,7 +102,9 @@ static void do_async_hcalls(struct lgues
 	unsigned int i;
 	u8 st[LHCALL_RING_SIZE];
 
-	copy_from_user(&st, &lg->lguest_data->hcall_status, sizeof(st));
+	if (copy_from_user(&st, &lg->lguest_data->hcall_status,
sizeof(st)))
+		return;
+
 	for (i = 0; i < ARRAY_SIZE(st); i++) {
 		struct lguest_regs regs;
 		unsigned int n = lg->next_hcall;
@@ -113,12 +115,20 @@ static void do_async_hcalls(struct lgues
 		if (++lg->next_hcall == LHCALL_RING_SIZE)
 			lg->next_hcall = 0;
 
-		get_user(regs.eax, &lg->lguest_data->hcalls[n].eax);
-		get_user(regs.edx, &lg->lguest_data->hcalls[n].edx);
-		get_user(regs.ecx, &lg->lguest_data->hcalls[n].ecx);
-		get_user(regs.ebx, &lg->lguest_data->hcalls[n].ebx);
+		if (get_user(regs.eax, &lg->lguest_data->hcalls[n].eax)
+		    || get_user(regs.edx, &lg->lguest_data->hcalls[n].edx)
+		    || get_user(regs.ecx, &lg->lguest_data->hcalls[n].ecx)
+		    || get_user(regs.ebx, &lg->lguest_data->hcalls[n].ebx)) {
+			kill_guest(lg, "Fetching async hypercalls");
+			break;
+		}
+
 		do_hcall(lg, &regs);
-		put_user(0xFF, &lg->lguest_data->hcall_status[n]);
+		if (put_user(0xFF, &lg->lguest_data->hcall_status[n])) {
+			kill_guest(lg, "Writing result for async hypercall");
+			break;
+		}
+
 		if (lg->dma_is_pending)
 			break;
 	}
@@ -139,11 +149,12 @@ static void initialize(struct lguest *lg
 		kill_guest(lg, "bad guest page %p", lg->lguest_data);
 		return;
 	}
-	get_user(lg->noirq_start, &lg->lguest_data->noirq_start);
-	get_user(lg->noirq_end, &lg->lguest_data->noirq_end);
-	/* We reserve the top pgd entry. */
-	put_user(4U*1024*1024, &lg->lguest_data->reserve_mem);
-	put_user(lg->guestid, &lg->lguest_data->guestid);
+	if (get_user(lg->noirq_start, &lg->lguest_data->noirq_start)
+	    || get_user(lg->noirq_end, &lg->lguest_data->noirq_end)
+	    /* We reserve the top pgd entry. */
+	    || put_user(4U*1024*1024, &lg->lguest_data->reserve_mem)
+	    || put_user(lg->guestid, &lg->lguest_data->guestid))
+		kill_guest(lg, "bad guest page %p", lg->lguest_data);
 
 	/* This is the one case where the above accesses might have
 	 * been the first write to a Guest page.  This may have caused
==================================================================---
a/drivers/lguest/interrupts_and_traps.c
+++ b/drivers/lguest/interrupts_and_traps.c
@@ -40,7 +40,8 @@ static void set_guest_interrupt(struct l
 	/* We use IF bit in eflags to indicate whether irqs were disabled
 	   (it's always 0, since irqs are enabled when guest is running). */
 	eflags = lg->regs->eflags;
-	get_user(irq_enable, &lg->lguest_data->irq_enabled);
+	if (get_user(irq_enable, &lg->lguest_data->irq_enabled))
+		irq_enable = 0;
 	eflags |= (irq_enable & X86_EFLAGS_IF);
 
 	push_guest_stack(lg, &gstack, eflags);
@@ -58,7 +59,8 @@ static void set_guest_interrupt(struct l
 
 	/* Disable interrupts for an interrupt gate. */
 	if (idt_type(lo, hi) == 0xE)
-		put_user(0, &lg->lguest_data->irq_enabled);
+		if (put_user(0, &lg->lguest_data->irq_enabled))
+			kill_guest(lg, "Disabling interrupts");
 }
 
 void maybe_do_interrupt(struct lguest *lg)
@@ -75,7 +77,10 @@ void maybe_do_interrupt(struct lguest *l
 		set_bit(0, lg->irqs_pending);
 
 	/* Mask out any interrupts they have blocked. */
-	copy_from_user(&blk, lg->lguest_data->blocked_interrupts,
sizeof(blk));
+	if (copy_from_user(&blk, lg->lguest_data->blocked_interrupts,
+			   sizeof(blk)))
+		return;
+
 	bitmap_andnot(blk, lg->irqs_pending, blk, LGUEST_IRQS);
 
 	irq = find_first_bit(blk, LGUEST_IRQS);
@@ -88,12 +93,14 @@ void maybe_do_interrupt(struct lguest *l
 	/* If they're halted, we re-enable interrupts. */
 	if (lg->halted) {
 		/* Re-enable interrupts. */
-		put_user(X86_EFLAGS_IF, &lg->lguest_data->irq_enabled);
+		if (put_user(X86_EFLAGS_IF, &lg->lguest_data->irq_enabled))
+			kill_guest(lg, "Re-enabling interrupts");
 		lg->halted = 0;
 	} else {
 		/* Maybe they have interrupts disabled? */
 		u32 irq_enabled;
-		get_user(irq_enabled, &lg->lguest_data->irq_enabled);
+		if (get_user(irq_enabled, &lg->lguest_data->irq_enabled))
+			irq_enabled = 0;
 		if (!irq_enabled)
 			return;
 	}