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@@ -73,6 +73,17 @@ struct uprobe {
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struct inode *inode; /* Also hold a ref to inode */
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loff_t offset;
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unsigned long flags;
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+
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+ /*
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+ * The generic code assumes that it has two members of unknown type
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+ * owned by the arch-specific code:
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+ *
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+ * insn - copy_insn() saves the original instruction here for
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+ * arch_uprobe_analyze_insn().
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+ *
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+ * ixol - potentially modified instruction to execute out of
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+ * line, copied to xol_area by xol_get_insn_slot().
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+ */
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struct arch_uprobe arch;
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};
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@@ -85,6 +96,29 @@ struct return_instance {
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struct return_instance *next; /* keep as stack */
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};
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+/*
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+ * Execute out of line area: anonymous executable mapping installed
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+ * by the probed task to execute the copy of the original instruction
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+ * mangled by set_swbp().
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+ *
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+ * On a breakpoint hit, thread contests for a slot. It frees the
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+ * slot after singlestep. Currently a fixed number of slots are
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+ * allocated.
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+ */
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+struct xol_area {
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+ wait_queue_head_t wq; /* if all slots are busy */
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+ atomic_t slot_count; /* number of in-use slots */
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+ unsigned long *bitmap; /* 0 = free slot */
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+ struct page *page;
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+
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+ /*
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+ * We keep the vma's vm_start rather than a pointer to the vma
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+ * itself. The probed process or a naughty kernel module could make
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+ * the vma go away, and we must handle that reasonably gracefully.
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+ */
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+ unsigned long vaddr; /* Page(s) of instruction slots */
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+};
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+
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/*
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* valid_vma: Verify if the specified vma is an executable vma
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* Relax restrictions while unregistering: vm_flags might have
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@@ -330,7 +364,7 @@ int __weak set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned
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int __weak
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set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
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{
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- return uprobe_write_opcode(mm, vaddr, *(uprobe_opcode_t *)auprobe->insn);
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+ return uprobe_write_opcode(mm, vaddr, *(uprobe_opcode_t *)&auprobe->insn);
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}
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static int match_uprobe(struct uprobe *l, struct uprobe *r)
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@@ -529,8 +563,8 @@ static int copy_insn(struct uprobe *uprobe, struct file *filp)
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{
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struct address_space *mapping = uprobe->inode->i_mapping;
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loff_t offs = uprobe->offset;
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- void *insn = uprobe->arch.insn;
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- int size = MAX_UINSN_BYTES;
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+ void *insn = &uprobe->arch.insn;
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+ int size = sizeof(uprobe->arch.insn);
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int len, err = -EIO;
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/* Copy only available bytes, -EIO if nothing was read */
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@@ -569,7 +603,7 @@ static int prepare_uprobe(struct uprobe *uprobe, struct file *file,
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goto out;
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ret = -ENOTSUPP;
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- if (is_trap_insn((uprobe_opcode_t *)uprobe->arch.insn))
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+ if (is_trap_insn((uprobe_opcode_t *)&uprobe->arch.insn))
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goto out;
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ret = arch_uprobe_analyze_insn(&uprobe->arch, mm, vaddr);
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@@ -1264,7 +1298,7 @@ static unsigned long xol_get_insn_slot(struct uprobe *uprobe)
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/* Initialize the slot */
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copy_to_page(area->page, xol_vaddr,
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- uprobe->arch.ixol, sizeof(uprobe->arch.ixol));
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+ &uprobe->arch.ixol, sizeof(uprobe->arch.ixol));
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/*
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* We probably need flush_icache_user_range() but it needs vma.
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* This should work on supported architectures too.
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@@ -1403,12 +1437,10 @@ static void uprobe_warn(struct task_struct *t, const char *msg)
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static void dup_xol_work(struct callback_head *work)
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{
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- kfree(work);
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-
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if (current->flags & PF_EXITING)
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return;
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- if (!__create_xol_area(current->utask->vaddr))
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+ if (!__create_xol_area(current->utask->dup_xol_addr))
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uprobe_warn(current, "dup xol area");
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}
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@@ -1419,7 +1451,6 @@ void uprobe_copy_process(struct task_struct *t, unsigned long flags)
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{
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struct uprobe_task *utask = current->utask;
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struct mm_struct *mm = current->mm;
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- struct callback_head *work;
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struct xol_area *area;
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t->utask = NULL;
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@@ -1441,14 +1472,9 @@ void uprobe_copy_process(struct task_struct *t, unsigned long flags)
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if (mm == t->mm)
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return;
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- /* TODO: move it into the union in uprobe_task */
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- work = kmalloc(sizeof(*work), GFP_KERNEL);
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- if (!work)
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- return uprobe_warn(t, "dup xol area");
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-
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- t->utask->vaddr = area->vaddr;
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- init_task_work(work, dup_xol_work);
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- task_work_add(t, work, true);
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+ t->utask->dup_xol_addr = area->vaddr;
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+ init_task_work(&t->utask->dup_xol_work, dup_xol_work);
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+ task_work_add(t, &t->utask->dup_xol_work, true);
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}
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/*
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Ingo Molnar