Messages in this thread | | | Date | Sun, 10 Jul 2011 11:26:10 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] x86: kill handle_signal()->set_fs() |
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On 07/10/2011 09:44 AM, Oleg Nesterov wrote: > handle_signal()->set_fs() has a nice comment which explains what > set_fs() is, but it doesn't explain why it is needed and why it > depends on CONFIG_X86_64. > > Afaics, the history of this confusion is: > > 1. I guess today nobody can explain why it was needed > in arch/i386/kernel/signal.c, perhaps it was always > wrong. This predates 2.4.0 kernel. > > 2. then it was copy-and-past'ed to the new x86_64 arch. > > 3. then it was removed from i386 (but not from x86_64) > by b93b6ca3 "i386: remove unnecessary code". > > 4. then it was reintroduced under CONFIG_X86_64 when x86 > unified i386 and x86_64, because the patch above didn't > touch x86_64. > > Remove it. ->addr_limit should be correct. Even if it was possible > that it is wrong, it is too late to fix it after setup_rt_frame(). >
The main reason I could think of why this would be necessary is if we take an event while we have fs == KERNEL_DS inside the kernel which is then promoted to a signal. Are you absolutely sure that can't happen?
In particular, there should be a setting upstream of this, as you're correctly pointing out that it's too late. If not, we might actually have a problem.
-hpa
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