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Introduce guest mem offset, static link example launcher

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In order to avoid problematic special linking of the Launcher, we give
the Host an offset: this means we can use any memory region in the
Launcher as Guest memory rather than insisting on mmap() at 0.

The result is quite pleasing: a number of casts are replaced with
simple additions.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell
2007-10-22 11:03:26 +10:00
parent 6649bb7af6
commit 3c6b5bfa3c
8 changed files with 162 additions and 139 deletions
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23
drivers/lguest/lguest_user.c
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@ -1,9 +1,9 @@
/*P:200 This contains all the /dev/lguest code, whereby the userspace launcher
* controls and communicates with the Guest. For example, the first write will
* tell us the memory size, pagetable, entry point and kernel address offset.
* A read will run the Guest until a signal is pending (-EINTR), or the Guest
* does a DMA out to the Launcher. Writes are also used to get a DMA buffer
* registered by the Guest and to send the Guest an interrupt. :*/
* tell us the Guest's memory layout, pagetable, entry point and kernel address
* offset. A read will run the Guest until something happens, such as a signal
* or the Guest doing a DMA out to the Launcher. Writes are also used to get a
* DMA buffer registered by the Guest and to send the Guest an interrupt. :*/
#include <linux/uaccess.h>
#include <linux/miscdevice.h>
#include <linux/fs.h>
@ -142,9 +142,11 @@ static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o)
return run_guest(lg, (unsigned long __user *)user);
}
/*L:020 The initialization write supplies 4 32-bit values (in addition to the
/*L:020 The initialization write supplies 5 32-bit values (in addition to the
* 32-bit LHREQ_INITIALIZE value). These are:
*
* base: The start of the Guest-physical memory inside the Launcher memory.
*
* pfnlimit: The highest (Guest-physical) page number the Guest should be
* allowed to access. The Launcher has to live in Guest memory, so it sets
* this to ensure the Guest can't reach it.
@ -166,7 +168,7 @@ static int initialize(struct file *file, const u32 __user *input)
* Guest. */
struct lguest *lg;
int err, i;
u32 args[4];
u32 args[5];
/* We grab the Big Lguest lock, which protects the global array
* "lguests" and multiple simultaneous initializations. */
@ -194,8 +196,9 @@ static int initialize(struct file *file, const u32 __user *input)
/* Populate the easy fields of our "struct lguest" */
lg->guestid = i;
lg->pfn_limit = args[0];
lg->page_offset = args[3];
lg->mem_base = (void __user *)(long)args[0];
lg->pfn_limit = args[1];
lg->page_offset = args[4];
/* We need a complete page for the Guest registers: they are accessible
* to the Guest and we can only grant it access to whole pages. */
@ -210,13 +213,13 @@ static int initialize(struct file *file, const u32 __user *input)
/* Initialize the Guest's shadow page tables, using the toplevel
* address the Launcher gave us. This allocates memory, so can
* fail. */
err = init_guest_pagetable(lg, args[1]);
err = init_guest_pagetable(lg, args[2]);
if (err)
goto free_regs;
/* Now we initialize the Guest's registers, handing it the start
* address. */
setup_regs(lg->regs, args[2]);
setup_regs(lg->regs, args[3]);
/* There are a couple of GDT entries the Guest expects when first
* booting. */