diff options
Diffstat (limited to 'drivers/lguest/interrupts_and_traps.c')
| -rw-r--r-- | drivers/lguest/interrupts_and_traps.c | 49 |
1 files changed, 48 insertions, 1 deletions
diff --git a/drivers/lguest/interrupts_and_traps.c b/drivers/lguest/interrupts_and_traps.c index fdefc0a..a57d757 100644 --- a/drivers/lguest/interrupts_and_traps.c +++ b/drivers/lguest/interrupts_and_traps.c @@ -12,8 +12,14 @@ * them first, so we also have a way of "reflecting" them into the Guest as if * they had been delivered to it directly. :*/ #include <linux/uaccess.h> +#include <linux/interrupt.h> +#include <linux/module.h> #include "lg.h" +/* Allow Guests to use a non-128 (ie. non-Linux) syscall trap. */ +static unsigned int syscall_vector = SYSCALL_VECTOR; +module_param(syscall_vector, uint, 0444); + /* The address of the interrupt handler is split into two bits: */ static unsigned long idt_address(u32 lo, u32 hi) { @@ -183,6 +189,47 @@ void maybe_do_interrupt(struct lguest *lg) * timer interrupt. */ write_timestamp(lg); } +/*:*/ + +/* Linux uses trap 128 for system calls. Plan9 uses 64, and Ron Minnich sent + * me a patch, so we support that too. It'd be a big step for lguest if half + * the Plan 9 user base were to start using it. + * + * Actually now I think of it, it's possible that Ron *is* half the Plan 9 + * userbase. Oh well. */ +static bool could_be_syscall(unsigned int num) +{ + /* Normal Linux SYSCALL_VECTOR or reserved vector? */ + return num == SYSCALL_VECTOR || num == syscall_vector; +} + +/* The syscall vector it wants must be unused by Host. */ +bool check_syscall_vector(struct lguest *lg) +{ + u32 vector; + + if (get_user(vector, &lg->lguest_data->syscall_vec)) + return false; + + return could_be_syscall(vector); +} + +int init_interrupts(void) +{ + /* If they want some strange system call vector, reserve it now */ + if (syscall_vector != SYSCALL_VECTOR + && test_and_set_bit(syscall_vector, used_vectors)) { + printk("lg: couldn't reserve syscall %u\n", syscall_vector); + return -EBUSY; + } + return 0; +} + +void free_interrupts(void) +{ + if (syscall_vector != SYSCALL_VECTOR) + clear_bit(syscall_vector, used_vectors); +} /*H:220 Now we've got the routines to deliver interrupts, delivering traps * like page fault is easy. The only trick is that Intel decided that some @@ -224,7 +271,7 @@ static int direct_trap(unsigned int num) { /* Hardware interrupts don't go to the Guest at all (except system * call). */ - if (num >= FIRST_EXTERNAL_VECTOR && num != SYSCALL_VECTOR) + if (num >= FIRST_EXTERNAL_VECTOR && !could_be_syscall(num)) return 0; /* The Host needs to see page faults (for shadow paging and to save the |