Messages in this thread | | | Date | Tue, 15 Mar 2011 13:10:20 -0600 | From | Jonathan Corbet <> | Subject | Re: [PATCH v2 2.6.38-rc8-tip 11/20] 11: uprobes: slot allocation for uprobes |
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Just a couple of minor notes while I was looking at this code...
> +static struct uprobes_xol_area *xol_alloc_area(void) > +{ > + struct uprobes_xol_area *area = NULL; > + > + area = kzalloc(sizeof(*area), GFP_USER); > + if (unlikely(!area)) > + return NULL; > + > + area->bitmap = kzalloc(BITS_TO_LONGS(UINSNS_PER_PAGE) * sizeof(long), > + GFP_USER);
Why GFP_USER? That causes extra allocation limits to be enforced. Given that in part 14 you have:
+/* Prepare to single-step probed instruction out of line. */ +static int pre_ssout(struct uprobe *uprobe, struct pt_regs *regs, + unsigned long vaddr) +{ + xol_get_insn_slot(uprobe, vaddr); + BUG_ON(!current->utask->xol_vaddr);
It seems to me that you really don't want those allocations to fail.
back to xol_alloc_area():
> + if (!area->bitmap) > + goto fail; > + > + spin_lock_init(&area->slot_lock); > + if (!xol_add_vma(area) && !current->mm->uprobes_xol_area) { > + task_lock(current); > + if (!current->mm->uprobes_xol_area) { > + current->mm->uprobes_xol_area = area; > + task_unlock(current); > + return area; > + } > + task_unlock(current); > + } > + > +fail: > + if (area) { > + if (area->bitmap) > + kfree(area->bitmap); > + kfree(area); > + }
You've already checked area against NULL, and kfree() can handle null pointers, so both of those tests are unneeded.
> + return current->mm->uprobes_xol_area; > +}
jon
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