diff options
Diffstat (limited to 'drivers/lguest/hypercalls.c')
| -rw-r--r-- | drivers/lguest/hypercalls.c | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/drivers/lguest/hypercalls.c b/drivers/lguest/hypercalls.c index 5ecd60b54201..02e67b49ea4f 100644 --- a/drivers/lguest/hypercalls.c +++ b/drivers/lguest/hypercalls.c @@ -205,16 +205,19 @@ static void initialize(struct lguest *lg) tsc_speed = 0; /* The pointer to the Guest's "struct lguest_data" is the only - * argument. */ - lg->lguest_data = (struct lguest_data __user *)lg->regs->edx; - /* If we check the address they gave is OK now, we can simply - * copy_to_user/from_user from now on rather than using lgread/lgwrite. - * I put this in to show that I'm not immune to writing stupid - * optimizations. */ + * argument. We check that address now. */ if (!lguest_address_ok(lg, lg->regs->edx, sizeof(*lg->lguest_data))) { kill_guest(lg, "bad guest page %p", lg->lguest_data); return; } + + /* Having checked it, we simply set lg->lguest_data to point straight + * into the Launcher's memory at the right place and then use + * copy_to_user/from_user from now on, instead of lgread/write. I put + * this in to show that I'm not immune to writing stupid + * optimizations. */ + lg->lguest_data = lg->mem_base + lg->regs->edx; + /* The Guest tells us where we're not to deliver interrupts by putting * the range of addresses into "struct lguest_data". */ if (get_user(lg->noirq_start, &lg->lguest_data->noirq_start) |