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Diffstat (limited to 'kernel/events/uprobes.c')
-rw-r--r--kernel/events/uprobes.c64
1 files changed, 47 insertions, 17 deletions
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 24b7d6ca871..307d87c0991 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -73,6 +73,17 @@ struct uprobe {
struct inode *inode; /* Also hold a ref to inode */
loff_t offset;
unsigned long flags;
+
+ /*
+ * The generic code assumes that it has two members of unknown type
+ * owned by the arch-specific code:
+ *
+ * insn - copy_insn() saves the original instruction here for
+ * arch_uprobe_analyze_insn().
+ *
+ * ixol - potentially modified instruction to execute out of
+ * line, copied to xol_area by xol_get_insn_slot().
+ */
struct arch_uprobe arch;
};
@@ -86,6 +97,29 @@ struct return_instance {
};
/*
+ * Execute out of line area: anonymous executable mapping installed
+ * by the probed task to execute the copy of the original instruction
+ * mangled by set_swbp().
+ *
+ * On a breakpoint hit, thread contests for a slot. It frees the
+ * slot after singlestep. Currently a fixed number of slots are
+ * allocated.
+ */
+struct xol_area {
+ wait_queue_head_t wq; /* if all slots are busy */
+ atomic_t slot_count; /* number of in-use slots */
+ unsigned long *bitmap; /* 0 = free slot */
+ struct page *page;
+
+ /*
+ * We keep the vma's vm_start rather than a pointer to the vma
+ * itself. The probed process or a naughty kernel module could make
+ * the vma go away, and we must handle that reasonably gracefully.
+ */
+ unsigned long vaddr; /* Page(s) of instruction slots */
+};
+
+/*
* valid_vma: Verify if the specified vma is an executable vma
* Relax restrictions while unregistering: vm_flags might have
* changed after breakpoint was inserted.
@@ -330,7 +364,7 @@ int __weak set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned
int __weak
set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
{
- return uprobe_write_opcode(mm, vaddr, *(uprobe_opcode_t *)auprobe->insn);
+ return uprobe_write_opcode(mm, vaddr, *(uprobe_opcode_t *)&auprobe->insn);
}
static int match_uprobe(struct uprobe *l, struct uprobe *r)
@@ -529,8 +563,8 @@ static int copy_insn(struct uprobe *uprobe, struct file *filp)
{
struct address_space *mapping = uprobe->inode->i_mapping;
loff_t offs = uprobe->offset;
- void *insn = uprobe->arch.insn;
- int size = MAX_UINSN_BYTES;
+ void *insn = &uprobe->arch.insn;
+ int size = sizeof(uprobe->arch.insn);
int len, err = -EIO;
/* Copy only available bytes, -EIO if nothing was read */
@@ -569,7 +603,7 @@ static int prepare_uprobe(struct uprobe *uprobe, struct file *file,
goto out;
ret = -ENOTSUPP;
- if (is_trap_insn((uprobe_opcode_t *)uprobe->arch.insn))
+ if (is_trap_insn((uprobe_opcode_t *)&uprobe->arch.insn))
goto out;
ret = arch_uprobe_analyze_insn(&uprobe->arch, mm, vaddr);
@@ -1264,7 +1298,7 @@ static unsigned long xol_get_insn_slot(struct uprobe *uprobe)
/* Initialize the slot */
copy_to_page(area->page, xol_vaddr,
- uprobe->arch.ixol, sizeof(uprobe->arch.ixol));
+ &uprobe->arch.ixol, sizeof(uprobe->arch.ixol));
/*
* We probably need flush_icache_user_range() but it needs vma.
* This should work on supported architectures too.
@@ -1403,12 +1437,10 @@ static void uprobe_warn(struct task_struct *t, const char *msg)
static void dup_xol_work(struct callback_head *work)
{
- kfree(work);
-
if (current->flags & PF_EXITING)
return;
- if (!__create_xol_area(current->utask->vaddr))
+ if (!__create_xol_area(current->utask->dup_xol_addr))
uprobe_warn(current, "dup xol area");
}
@@ -1419,7 +1451,6 @@ void uprobe_copy_process(struct task_struct *t, unsigned long flags)
{
struct uprobe_task *utask = current->utask;
struct mm_struct *mm = current->mm;
- struct callback_head *work;
struct xol_area *area;
t->utask = NULL;
@@ -1441,14 +1472,9 @@ void uprobe_copy_process(struct task_struct *t, unsigned long flags)
if (mm == t->mm)
return;
- /* TODO: move it into the union in uprobe_task */
- work = kmalloc(sizeof(*work), GFP_KERNEL);
- if (!work)
- return uprobe_warn(t, "dup xol area");
-
- t->utask->vaddr = area->vaddr;
- init_task_work(work, dup_xol_work);
- task_work_add(t, work, true);
+ t->utask->dup_xol_addr = area->vaddr;
+ init_task_work(&t->utask->dup_xol_work, dup_xol_work);
+ task_work_add(t, &t->utask->dup_xol_work, true);
}
/*
@@ -1828,6 +1854,10 @@ static void handle_swbp(struct pt_regs *regs)
if (unlikely(!test_bit(UPROBE_COPY_INSN, &uprobe->flags)))
goto out;
+ /* Tracing handlers use ->utask to communicate with fetch methods */
+ if (!get_utask())
+ goto out;
+
handler_chain(uprobe, regs);
if (can_skip_sstep(uprobe, regs))
goto out;