[FIX] Save current uprobe state in stack (x86)

We cannot use per cpu vars here because when we make a singlestep
in userspace there is a chance our task is preempted and resumed
on another cpu. In that case we will not be able to restore its
normal execution.

Change-Id: I591ef52b52db8db0e741d81461903806ed00ef8e
Signed-off-by: Vyacheslav Cherkashin <v.cherkashin@samsung.com>
Signed-off-by: Vasiliy Ulyanov <v.ulyanov@samsung.com>

diff --git a/uprobe/arch/x86/swap-asm/swap_uprobes.c b/uprobe/arch/x86/swap-asm/swap_uprobes.c
index 1b0fbe8..f4f2272 100644 (file)
--- a/uprobe/arch/x86/swap-asm/swap_uprobes.c
+++ b/uprobe/arch/x86/swap-asm/swap_uprobes.c
@@ -54,32 +54,31 @@ static unsigned long trampoline_addr(struct uprobe *up)
                               UPROBES_TRAMP_RET_BREAK_IDX);
 }
 
-static DEFINE_PER_CPU(struct uprobe_ctlblk, ucb) = { 0, NULL };
-
-static struct kprobe *get_current_probe(void)
+static struct uprobe_ctlblk *current_ucb(void)
 {
-       return __get_cpu_var(ucb).p;
+       /* FIXME hardcoded offset */
+       return (struct uprobe_ctlblk *)(end_of_stack(current) + 20);
 }
 
-static void set_current_probe(struct kprobe *p)
+static struct kprobe *get_current_probe(void)
 {
-       __get_cpu_var(ucb).p = p;
+       return current_ucb()->p;
 }
 
-static void reset_current_probe(void)
+static void set_current_probe(struct kprobe *p)
 {
-       set_current_probe(NULL);
+       current_ucb()->p = p;
 }
 
 static void save_current_flags(struct pt_regs *regs)
 {
-       __get_cpu_var(ucb).flags = regs->EREG(flags);
+       current_ucb()->flags = regs->flags;
 }
 
-static void restore_current_flags(struct pt_regs *regs)
+static void restore_current_flags(struct pt_regs *regs, unsigned long flags)
 {
-       regs->EREG(flags) &= ~IF_MASK;
-       regs->EREG(flags) |= __get_cpu_var(ucb).flags & IF_MASK;
+       regs->flags &= ~IF_MASK;
+       regs->flags |= flags & IF_MASK;
 }
 
 /**
@@ -420,6 +419,27 @@ no_change:
        return;
 }
 
+static bool prepare_ss_addr(struct kprobe *p, struct pt_regs *regs)
+{
+       unsigned long *ss_addr = (long *)&p->ss_addr[smp_processor_id()];
+
+       if (*ss_addr) {
+               regs->ip = *ss_addr;
+               *ss_addr = 0;
+               return true;
+       } else {
+               regs->ip = (unsigned long)p->ainsn.insn;
+               return false;
+       }
+}
+
+static void prepare_ss(struct pt_regs *regs)
+{
+       /* set single step mode */
+       regs->flags |= TF_MASK;
+       regs->flags &= ~IF_MASK;
+}
+
 static int uprobe_handler(struct pt_regs *regs)
 {
        struct kprobe *p;
@@ -445,38 +465,38 @@ static int uprobe_handler(struct pt_regs *regs)
                return 1;
        } else {
                if (!p->pre_handler || !p->pre_handler(p, regs)) {
-
                        if (p->ainsn.boostable == 1 && !p->post_handler) {
-                               if (p->ss_addr[smp_processor_id()]) {
-                                       regs->EREG(ip) = (unsigned long)p->ss_addr[smp_processor_id()];
-                                       p->ss_addr[smp_processor_id()] = NULL;
-                               } else {
-                                       regs->EREG(ip) = (unsigned long)p->ainsn.insn;
-                               }
+                               prepare_ss_addr(p, regs);
                                return 1;
                        }
 
-                       prepare_singlestep(p, regs);
+                       if (prepare_ss_addr(p, regs) == false) {
+                               set_current_probe(p);
+                               prepare_ss(regs);
+                       }
                }
        }
 
-       set_current_probe(p);
-
        return 1;
 }
 
 static int post_uprobe_handler(struct pt_regs *regs)
 {
        struct kprobe *p = get_current_probe();
-       unsigned long flags = __get_cpu_var(ucb).flags;
+       unsigned long flags = current_ucb()->flags;
 
-       if (p == NULL)
+       if (p == NULL) {
+               printk("task[%u %u %s] current uprobe is not found\n",
+                      current->tgid, current->pid, current->comm);
                return 0;
+       }
 
        resume_execution(p, regs, flags);
-       restore_current_flags(regs);
+       restore_current_flags(regs, flags);
 
-       reset_current_probe();
+       /* clean stack */
+       current_ucb()->p = 0;
+       current_ucb()->flags = 0;
 
        return 1;
 }