[haiku-bugs] Re: [Haiku] #5118: Haiku panics on HDA sound card
- From: "bonefish" <trac@xxxxxxxxxxxx>
- Date: Sun, 13 Dec 2009 22:09:37 -0000
#5118: Haiku panics on HDA sound card
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Reporter: flaggy | Owner: nobody
Type: bug | Status: new
Priority: normal | Milestone: Unscheduled
Component: Audio & Video | Version: R1/Development
Keywords: | Blockedby:
Platform: x86 | Blocking:
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Comment(by bonefish):
Replying to [comment:4 stippi]:
> I may have been looking at the wrong ioctl(), but how can a driver copy
something to a pointer that points to memory in the user land process? The
same address will point to completely unrelated kernel memory from the
driver's point of view, no?
No, the virtual address space is split. One part (on x86 currently the
upper half) is used for the kernel, the other one for userland teams. The
kernel part is fixed and always visible, the userland part switches with
the running thread. When a userland thread enters the kernel, the userland
address space for the respective team is visible and can be accessed as
usual. It *should* be accessed via user_memcpy() and friends only, though,
because those functions can deal with invalid addresses (e.g. null
pointers) passed from userland. They will simply return an error instead
of crashing the kernel.
--
Ticket URL: <http://dev.haiku-os.org/ticket/5118#comment:6>
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