Messages in this thread Patch in this message | | | Date | Tue, 21 Dec 2021 17:03:48 +0000 | Subject | [PATCH v2 2/2] kcov: properly handle subsequent mmap calls | From | Aleksandr Nogikh <> |
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Allocate the kcov buffer during KCOV_MODE_INIT in order to untie mmapping of a kcov instance and the actual coverage collection process. Modify kcov_mmap, so that it can be reliably used any number of times once KCOV_MODE_INIT has succeeded.
These changes to the user-facing interface of the tool only weaken the preconditions, so all existing user space code should remain compatible with the new version.
Signed-off-by: Aleksandr Nogikh <nogikh@google.com> --- kernel/kcov.c | 49 +++++++++++++++++++++++++------------------------ 1 file changed, 25 insertions(+), 24 deletions(-)
diff --git a/kernel/kcov.c b/kernel/kcov.c index 5d87b4e0126f..d6a522fc6f36 100644 --- a/kernel/kcov.c +++ b/kernel/kcov.c @@ -459,37 +459,28 @@ void kcov_task_exit(struct task_struct *t) static int kcov_mmap(struct file *filep, struct vm_area_struct *vma) { int res = 0; - void *area; struct kcov *kcov = vma->vm_file->private_data; unsigned long size, off; struct page *page; unsigned long flags; - area = vmalloc_user(vma->vm_end - vma->vm_start); - if (!area) - return -ENOMEM; - spin_lock_irqsave(&kcov->lock, flags); size = kcov->size * sizeof(unsigned long); - if (kcov->mode != KCOV_MODE_INIT || vma->vm_pgoff != 0 || + if (kcov->area == NULL || vma->vm_pgoff != 0 || vma->vm_end - vma->vm_start != size) { res = -EINVAL; goto exit; } - if (!kcov->area) { - kcov->area = area; - vma->vm_flags |= VM_DONTEXPAND; - spin_unlock_irqrestore(&kcov->lock, flags); - for (off = 0; off < size; off += PAGE_SIZE) { - page = vmalloc_to_page(kcov->area + off); - if (vm_insert_page(vma, vma->vm_start + off, page)) - WARN_ONCE(1, "vm_insert_page() failed"); - } - return 0; + spin_unlock_irqrestore(&kcov->lock, flags); + vma->vm_flags |= VM_DONTEXPAND; + for (off = 0; off < size; off += PAGE_SIZE) { + page = vmalloc_to_page(kcov->area + off); + if (vm_insert_page(vma, vma->vm_start + off, page)) + WARN_ONCE(1, "vm_insert_page() failed"); } + return 0; exit: spin_unlock_irqrestore(&kcov->lock, flags); - vfree(area); return res; } @@ -671,25 +662,35 @@ static int kcov_ioctl_unlocked(struct kcov *kcov, unsigned int cmd, { unsigned long size, flags; int res; + void *area; switch (cmd) { case KCOV_INIT_TRACE: /* * Enable kcov in trace mode and setup buffer size. * Must happen before anything else. - */ - if (kcov->mode != KCOV_MODE_DISABLED) - return -EBUSY; - /* - * Size must be at least 2 to hold current position and one PC. - * Later we allocate size * sizeof(unsigned long) memory, - * that must not overflow. + * + * First check the size argument - it must be at least 2 + * to hold the current position and one PC. */ size = arg; if (size < 2 || size > INT_MAX / sizeof(unsigned long)) return -EINVAL; + + area = vmalloc_user(size * sizeof(unsigned long)); + if (area == NULL) + return -ENOMEM; + + spin_lock_irqsave(&kcov->lock, flags); + if (kcov->mode != KCOV_MODE_DISABLED) { + spin_unlock_irqrestore(&kcov->lock, flags); + vfree(area); + return -EBUSY; + } + kcov->area = area; kcov->size = size; kcov->mode = KCOV_MODE_INIT; + spin_unlock_irqrestore(&kcov->lock, flags); return 0; default: /* -- 2.34.1.307.g9b7440fafd-goog
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