kernel.git/arch/x86/lib, branch linux-2.6.28.y

x86: use early clobbers in usercopy*.c

2009-02-06T21:47:17Z

commit e0a96129db574d6365e3439d16d88517c437ab33 upstream. Impact: fix rare (but currently harmless) miscompile with certain configs and gcc versions Hugh Dickins noticed that strncpy_from_user() was miscompiled in some circumstances with gcc 4.3. Thanks to Hugh's excellent analysis it was easy to track down. Hugh writes: > Try building an x86_64 defconfig 2.6.29-rc1 kernel tree, > except not quite defconfig, switch CONFIG_PREEMPT_NONE=y > and CONFIG_PREEMPT_VOLUNTARY off (because it expands a > might_fault() there, which hides the issue): using a > gcc 4.3.2 (I've checked both openSUSE 11.1 and Fedora 10). > > It generates the following: > > 0000000000000000 <__strncpy_from_user>: > 0: 48 89 d1 mov %rdx,%rcx > 3: 48 85 c9 test %rcx,%rcx > 6: 74 0e je 16 <__strncpy_from_user+0x16> > 8: ac lods %ds:(%rsi),%al > 9: aa stos %al,%es:(%rdi) > a: 84 c0 test %al,%al > c: 74 05 je 13 <__strncpy_from_user+0x13> > e: 48 ff c9 dec %rcx > 11: 75 f5 jne 8 <__strncpy_from_user+0x8> > 13: 48 29 c9 sub %rcx,%rcx > 16: 48 89 c8 mov %rcx,%rax > 19: c3 retq > > Observe that "sub %rcx,%rcx; mov %rcx,%rax", whereas gcc 4.2.1 > (and many other configs) say "sub %rcx,%rdx; mov %rdx,%rax". > Isn't it returning 0 when it ought to be returning strlen? The asm constraints for the strncpy_from_user() result were missing an early clobber, which tells gcc that the last output arguments are written before all input arguments are read. Also add more early clobbers in the rest of the file and fix 32-bit usercopy.c in the same way. Signed-off-by: Andi Kleen Signed-off-by: H. Peter Anvin [ since this API is rarely used and no in-kernel user relies on a 'len' return value (they only rely on negative return values) this miscompile was never noticed in the field. But it's worth fixing it nevertheless. ] Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

Merge branch 'x86/unify-cpu-detect' into x86-v28-for-linus-phase4-D

2008-10-11T18:23:20Z

Conflicts: arch/x86/kernel/cpu/common.c arch/x86/kernel/signal_64.c include/asm-x86/cpufeature.h

x86: drop -funroll-loops for csum_partial_64.c

2008-09-04T15:42:06Z

Impact: performance optimization I did some rebenchmarking with modern compilers and dropping -funroll-loops makes the function consistently go faster by a few percent. So drop that flag. Thanks to Richard Guenther for a hint. Signed-off-by: Andi Kleen Signed-off-by: H. Peter Anvin

Merge branch 'x86/urgent' into x86/cpu

2008-08-28T02:17:07Z

Conflicts: arch/x86/kernel/cpu/cyrix.c

x86: msr-on-cpu: remove unnecessary level of abstraction

2008-08-26T05:45:50Z

Remove an unnecessary level of abstraction in the msr-on-cpu library. Although this duplicates some code, the duplicated code is less than the additional code, and this way should be faster. Additionally, change the order of the functions to make the regular structure of this file more obvious. Signed-off-by: H. Peter Anvin

Merge branch 'x86/urgent' into x86/cleanups

2008-08-26T05:45:37Z

x86: msr: propagate errors from smp_call_function_single()

2008-08-26T00:45:48Z

Propagate error (-ENXIO) from smp_call_function_single(). These errors can happen when a CPU is unplugged while the MSR driver is open. Signed-off-by: H. Peter Anvin

x86: make movsl_mask definition non-CPU specific

2008-08-18T14:05:45Z

movsl_mask is currently defined in arch/x86/kernel/cpu/intel.c, which contains code specific to Intel CPUs. However, movsl_mask is used in the non-CPU specific code in arch/x86/lib/usercopy_32.c, which breaks the compilation when support for Intel CPUs is compiled out. This patch solves this problem by moving movsl_mask's definition close to its users in arch/x86/lib/usercopy_32.c. Signed-off-by: Thomas Petazzoni Cc: michael@free-electrons.com Signed-off-by: Ingo Molnar

x86: coding style fixes to arch/x86/lib/string_32.c

2008-08-15T14:53:25Z

Before: total: 21 errors, 0 warnings, 237 lines checked After: total: 0 errors, 0 warnings, 237 lines checked paolo@paolo-desktop:~/linux.trees.git$ md5sum /tmp/string_32.o.* c55d059ef1612b32a8bb2771a72ae0d5 /tmp/string_32.o.after c55d059ef1612b32a8bb2771a72ae0d5 /tmp/string_32.o.before Signed-off-by: Paolo Ciarrocchi Signed-off-by: Ingo Molnar

x86: coding style fixes to arch/x86/lib/strstr_32.c

2008-08-15T14:53:24Z

Before: total: 3 errors, 0 warnings, 31 lines checked After: total: 0 errors, 0 warnings, 31 lines checked paolo@paolo-desktop:~/linux.trees.git$ md5sum /tmp/strstr_32.o.* c96006ec3387862e5bacb139207a3098 /tmp/strstr_32.o.after c96006ec3387862e5bacb139207a3098 /tmp/strstr_32.o.before Signed-off-by: Paolo Ciarrocchi Signed-off-by: Ingo Molnar