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[PATCH] Return probe redesign: x86_64 specific changes 

The following patch contains the x86_64 specific changes for the new
return probe design.  Changes include:
 * Removing the architecture specific functions for querying a return probe
   instance off a stack address
 * Complete rework onf arch_prepare_kretprobe() and trampoline_probe_handler()
 * Removing trampoline_post_handler()
 * Adding arch_init() so that now we handle registering the return probe
   trampoline instead of kernel/kprobes.c doing it

NOTE:
Note that with this new design, the dependency on calculating a pointer to
the task off the stack pointer no longer exist (resolving the problem of
interruption stacks as pointed out in the original feedback to this port.)

Signed-off-by: Rusty Lynch <rusty.lynch@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Rusty Lynch 2005-06-27 15:17:10 -07:00 committed by Linus Torvalds
parent 4bdbd37f6d
commit ba8af12f43
1 changed files with 67 additions and 60 deletions
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127
arch/x86_64/kernel/kprobes.c
View File

@ -272,48 +272,23 @@ static void prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
regs->rip = (unsigned long)p->ainsn.insn;
}
struct task_struct *arch_get_kprobe_task(void *ptr)
{
return ((struct thread_info *) (((unsigned long) ptr) &
(~(THREAD_SIZE -1))))->task;
}
void arch_prepare_kretprobe(struct kretprobe *rp, struct pt_regs *regs)
{
unsigned long *sara = (unsigned long *)regs->rsp;
struct kretprobe_instance *ri;
static void *orig_ret_addr;
struct kretprobe_instance *ri;
/*
* Save the return address when the return probe hits
* the first time, and use it to populate the (krprobe
* instance)->ret_addr for subsequent return probes at
* the same addrress since stack address would have
* the kretprobe_trampoline by then.
*/
if (((void*) *sara) != kretprobe_trampoline)
orig_ret_addr = (void*) *sara;
if ((ri = get_free_rp_inst(rp)) != NULL) {
ri->rp = rp;
ri->task = current;
ri->ret_addr = (kprobe_opcode_t *) *sara;
if ((ri = get_free_rp_inst(rp)) != NULL) {
ri->rp = rp;
ri->stack_addr = sara;
ri->ret_addr = orig_ret_addr;
add_rp_inst(ri);
/* Replace the return addr with trampoline addr */
*sara = (unsigned long) &kretprobe_trampoline;
} else {
rp->nmissed++;
}
}
void arch_kprobe_flush_task(struct task_struct *tk)
{
struct kretprobe_instance *ri;
while ((ri = get_rp_inst_tsk(tk)) != NULL) {
*((unsigned long *)(ri->stack_addr)) =
(unsigned long) ri->ret_addr;
recycle_rp_inst(ri);
}
add_rp_inst(ri);
} else {
rp->nmissed++;
}
}
/*
@ -426,36 +401,59 @@ no_kprobe:
*/
int trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
{
struct task_struct *tsk;
struct kretprobe_instance *ri;
struct hlist_head *head;
struct hlist_node *node;
unsigned long *sara = (unsigned long *)regs->rsp - 1;
struct kretprobe_instance *ri = NULL;
struct hlist_head *head;
struct hlist_node *node, *tmp;
unsigned long orig_ret_address = 0;
unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
tsk = arch_get_kprobe_task(sara);
head = kretprobe_inst_table_head(tsk);
head = kretprobe_inst_table_head(current);
hlist_for_each_entry(ri, node, head, hlist) {
if (ri->stack_addr == sara && ri->rp) {
if (ri->rp->handler)
ri->rp->handler(ri, regs);
}
}
return 0;
}
/*
* It is possible to have multiple instances associated with a given
* task either because an multiple functions in the call path
* have a return probe installed on them, and/or more then one return
* return probe was registered for a target function.
*
* We can handle this because:
* - instances are always inserted at the head of the list
* - when multiple return probes are registered for the same
* function, the first instance's ret_addr will point to the
* real return address, and all the rest will point to
* kretprobe_trampoline
*/
hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
if (ri->task != current)
/* another task is sharing our hash bucket */
continue;
void trampoline_post_handler(struct kprobe *p, struct pt_regs *regs,
unsigned long flags)
{
struct kretprobe_instance *ri;
/* RA already popped */
unsigned long *sara = ((unsigned long *)regs->rsp) - 1;
if (ri->rp && ri->rp->handler)
ri->rp->handler(ri, regs);
while ((ri = get_rp_inst(sara))) {
regs->rip = (unsigned long)ri->ret_addr;
orig_ret_address = (unsigned long)ri->ret_addr;
recycle_rp_inst(ri);
if (orig_ret_address != trampoline_address)
/*
* This is the real return address. Any other
* instances associated with this task are for
* other calls deeper on the call stack
*/
break;
}
regs->eflags &= ~TF_MASK;
BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address));
regs->rip = orig_ret_address;
unlock_kprobes();
preempt_enable_no_resched();
/*
* By returning a non-zero value, we are telling
* kprobe_handler() that we have handled unlocking
* and re-enabling preemption.
*/
return 1;
}
/*
@ -548,8 +546,7 @@ int post_kprobe_handler(struct pt_regs *regs)
current_kprobe->post_handler(current_kprobe, regs, 0);
}
if (current_kprobe->post_handler != trampoline_post_handler)
resume_execution(current_kprobe, regs);
resume_execution(current_kprobe, regs);
regs->eflags |= kprobe_saved_rflags;
/* Restore the original saved kprobes variables and continue. */
@ -679,3 +676,13 @@ int longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
}
return 0;
}
static struct kprobe trampoline_p = {
.addr = (kprobe_opcode_t *) &kretprobe_trampoline,
.pre_handler = trampoline_probe_handler
};
int __init arch_init(void)
{
return register_kprobe(&trampoline_p);
}