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- 18 Jun, 2008 1 commit
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Linus Torvalds authored
Most users by far do not care about the exact return value (they only really care about whether the copy succeeded in its entirety or not), but a few special core routines actually care deeply about exactly how many bytes were copied from user space. And the unrolled versions of the x86-64 user copy routines would sometimes report that it had copied more bytes than it actually had. Very few uses actually have partial copies to begin with, but to make this bug even harder to trigger, most x86 CPU's use the "rep string" instructions for normal user copies, and that version didn't have this issue. To make it even harder to hit, the one user of this that really cared about the return value (and used the uncached version of the copy that doesn't use the "rep string" instructions) was the generic write routine, which pre-populated its source, once more hiding the problem by avoiding the exception case that triggers the bug. In other words, very special thanks to Bron Gondwana who not only triggered this, but created a test-program to show it, and bisected the behavior down to commit 08291429 ("mm: fix pagecache write deadlocks") which changed the access pattern just enough that you can now trigger it with 'writev()' with multiple iovec's. That commit itself was not the cause of the bug, it just allowed all the stars to align just right that you could trigger the problem. [ Side note: this is just the minimal fix to make the copy routines (with __copy_from_user_inatomic_nocache as the particular version that was involved in showing this) have the right return values. We really should improve on the exceptional case further - to make the copy do a byte-accurate copy up to the exact page limit that causes it to fail. As it is, the callers have to do extra work to handle the limit case gracefully. ] Reported-by:
Bron Gondwana <brong@fastmail.fm> Cc: Nick Piggin <npiggin@suse.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andi Kleen <andi@firstfloor.org> Cc: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org> (which didn't have this problem), and since most users that do the carethis was very hard to trigger, but
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- 11 Oct, 2007 2 commits
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Thomas Gleixner authored
Signed-off-by:
Thomas Gleixner <tglx@linutronix.de> Signed-off-by:
Ingo Molnar <mingo@elte.hu>
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Thomas Gleixner authored
Signed-off-by:
Thomas Gleixner <tglx@linutronix.de> Signed-off-by:
Ingo Molnar <mingo@elte.hu>
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- 26 Sep, 2006 2 commits
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Andi Kleen authored
- Don't zero for __copy_from_user_inatomic following i386. This will prevent spurious zeros for parallel file system writers when one does a exception - The string instruction version didn't zero the output on exception. Oops. Also I cleaned up the code a bit while I was at it and added a minor optimization to the string instruction path. Signed-off-by:
Andi Kleen <ak@suse.de>
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Jan Beulich authored
Add unwind annotations to arch/x86_64/lib/*.S, and also use the macros provided by linux/linkage.h where-ever possible. Some of the alternative instructions handling needed to be adjusted so that the replacement code would also have valid unwind information. Signed-off-by:
Jan Beulich <jbeulich@novell.com> Signed-off-by:
Andi Kleen <ak@suse.de>
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- 05 Feb, 2006 1 commit
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Andi Kleen authored
They cause quite bad performance regressions on Netburst This is temporary until we can get new optimized functions for these CPUs. This undoes changes that were done in 2.6.15 and in 2.6.16-rc1, essentially bringing the code back to 2.6.14 level. Only change is I renamed the X86_FEATURE_K8_C flag to X86_FEATURE_REP_GOOD and fixed the check for the flag and also fixed some comments. Signed-off-by:
Andi Kleen <ak@suse.de> Signed-off-by:
Linus Torvalds <torvalds@osdl.org>
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- 12 Jan, 2006 1 commit
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Andi Kleen authored
- Remove optimization for old B stepping Opteron - Make the fast path for copies with a multiple of eight length faster. - Minor instruction rearrangement to hopefully avoid a pipeline stall or two. - Add comment about errata to consider. Signed-off-by:
Andi Kleen <ak@suse.de> Signed-off-by:
Linus Torvalds <torvalds@osdl.org>
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- 09 Sep, 2005 1 commit
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Sam Ravnborg authored
Delete obsolete stuff from arch makefiles Rename .h file to asm-offsets.h Signed-off-by:
Sam Ravnborg <sam@ravnborg.org>
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- 16 Apr, 2005 1 commit
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Linus Torvalds authored
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
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