[IMPROVE] call uprobe handlers from non-atomic context (for x86)

Change-Id: If7a9ca564d4caeecd1fbac3f4b1e55407e303adb
Signed-off-by: Vyacheslav Cherkashin <v.cherkashin@samsung.com>

diff --git a/uprobe/arch/x86/swap-asm/swap_uprobes.c b/uprobe/arch/x86/swap-asm/swap_uprobes.c
index 499f04d..2936f52 100644 (file)
--- a/uprobe/arch/x86/swap-asm/swap_uprobes.c
+++ b/uprobe/arch/x86/swap-asm/swap_uprobes.c
@@ -40,6 +40,13 @@
 #include "swap_uprobes.h"
 
 
+struct save_context {
+       struct pt_regs save_regs;
+       struct pt_regs *ptr_regs;
+       unsigned long val;
+       int (*handler)(struct pt_regs *);
+};
+
 /**
  * @struct uprobe_ctlblk
  * @brief Uprobe control block
@@ -47,6 +54,8 @@
 struct uprobe_ctlblk {
        unsigned long flags;            /**< Flags */
        struct uprobe *p;               /**< Pointer to the uprobe */
+
+       struct save_context ctx;
 };
 
 
@@ -69,6 +78,11 @@ static struct uprobe_ctlblk *current_ucb(void)
        return (struct uprobe_ctlblk *)swap_td_raw(&td_raw, current);
 }
 
+static struct save_context *current_ctx(void)
+{
+       return &current_ucb()->ctx;
+}
+
 static struct uprobe *get_current_probe(void)
 {
        return current_ucb()->p;
@@ -493,6 +507,61 @@ static int uprobe_handler(struct pt_regs *regs)
        return 1;
 }
 
+
+static unsigned long resume_userspace_addr;
+
+static void __used __up_handler(void)
+{
+       struct pt_regs *regs = current_ctx()->ptr_regs;
+       struct thread_info *tinfo = current_thread_info();
+       int (*handler)(struct pt_regs *) = current_ctx()->handler;
+
+       /* restore KS regs */
+       *regs = current_ctx()->save_regs;
+
+       /* call handler */
+       handler(regs);
+
+       /* resume_userspace */
+       asm volatile (
+               "movl %0, %%esp\n"
+               "movl %1, %%ebp\n"
+               "jmpl *%2\n"
+               : /* No outputs. */
+               : "r" (regs), "r" (tinfo) , "r" (resume_userspace_addr)
+       );
+}
+
+void up_handler(void);
+__asm(
+       "up_handler:\n"
+       /* skip hex tractor-driver bytes to make some free space (skip regs) */
+       "sub $0x300, %esp\n"
+       "jmp __up_handler\n"
+);
+
+static int exceptions_handler(struct pt_regs *regs,
+                             int (*handler)(struct pt_regs *))
+{
+       /* save regs */
+       current_ctx()->save_regs = *regs;
+       current_ctx()->ptr_regs = regs;
+
+       /* set handler */
+       current_ctx()->handler = handler;
+
+       /* setup regs to return to KS */
+       regs->ip = (unsigned long)up_handler;
+       regs->ds = __USER_DS;
+       regs->es = __USER_DS;
+       regs->fs = __KERNEL_PERCPU;
+       regs->cs = __KERNEL_CS | get_kernel_rpl();
+       regs->gs = 0;
+       regs->flags = X86_EFLAGS_IF | X86_EFLAGS_FIXED;
+
+       return 1;
+}
+
 static int post_uprobe_handler(struct pt_regs *regs)
 {
        struct uprobe *p = get_current_probe();
@@ -529,11 +598,11 @@ static int uprobe_exceptions_notify(struct notifier_block *self,
 #else
        case DIE_TRAP:
 #endif
-               if (uprobe_handler(args->regs))
+               if (exceptions_handler(args->regs, uprobe_handler))
                        ret = NOTIFY_STOP;
                break;
        case DIE_DEBUG:
-               if (post_uprobe_handler(args->regs))
+               if (exceptions_handler(args->regs, post_uprobe_handler))
                        ret = NOTIFY_STOP;
                break;
        default:
@@ -557,6 +626,12 @@ int swap_arch_init_uprobes(void)
 {
        int ret;
 
+       resume_userspace_addr = swap_ksyms("resume_userspace");
+       if (resume_userspace_addr == 0) {
+               pr_err("symbol 'resume_userspace' not found\n");
+               return -ESRCH;
+       }
+
        ret = swap_td_raw_reg(&td_raw, sizeof(struct uprobe_ctlblk));
        if (ret)
                return ret;