- 04 4月, 2015 1 次提交
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由 Borislav Petkov 提交于
Quentin caught a corner case with the generation of instruction padding in the ALTERNATIVE_2 macro: if len(orig_insn) < len(alt1) < len(alt2), then not enough padding gets added and that is not good(tm) as we could overwrite the beginning of the next instruction. Luckily, at the time of this writing, we don't have ALTERNATIVE_2() invocations which have that problem and even if we did, a simple fix would be to prepend the instructions with enough prefixes so that that corner case doesn't happen. However, best it would be if we fixed it properly. See below for a simple, abstracted example of what we're doing. So what we ended up doing is, we compute the max(len(alt1), len(alt2)) - len(orig_insn) and feed that value to the .skip gas directive. The max() cannot have conditionals due to gas limitations, thus the fancy integer math. With this patch, all ALTERNATIVE_2 sites get padded correctly; generating obscure test cases pass too: #define alt_max_short(a, b) ((a) ^ (((a) ^ (b)) & -(-((a) < (b))))) #define gen_skip(orig, alt1, alt2, marker) \ .skip -((alt_max_short(alt1, alt2) - (orig)) > 0) * \ (alt_max_short(alt1, alt2) - (orig)),marker .pushsection .text, "ax" .globl main main: gen_skip(1, 2, 4, 0x09) gen_skip(4, 1, 2, 0x10) ... .popsection Thanks to Quentin for catching it and double-checking the fix! Reported-by: NQuentin Casasnovas <quentin.casasnovas@oracle.com> Signed-off-by: NBorislav Petkov <bp@suse.de> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20150404133443.GE21152@pd.tnicSigned-off-by: NIngo Molnar <mingo@kernel.org>
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- 23 2月, 2015 1 次提交
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由 Borislav Petkov 提交于
Up until now we have always paid attention to make sure the length of the new instruction replacing the old one is at least less or equal to the length of the old instruction. If the new instruction is longer, at the time it replaces the old instruction it will overwrite the beginning of the next instruction in the kernel image and cause your pants to catch fire. So instead of having to pay attention, teach the alternatives framework to pad shorter old instructions with NOPs at buildtime - but only in the case when len(old instruction(s)) < len(new instruction(s)) and add nothing in the >= case. (In that case we do add_nops() when patching). This way the alternatives user shouldn't have to care about instruction sizes and simply use the macros. Add asm ALTERNATIVE* flavor macros too, while at it. Also, we need to save the pad length in a separate struct alt_instr member for NOP optimization and the way to do that reliably is to carry the pad length instead of trying to detect whether we're looking at single-byte NOPs or at pathological instruction offsets like e9 90 90 90 90, for example, which is a valid instruction. Thanks to Michael Matz for the great help with toolchain questions. Signed-off-by: NBorislav Petkov <bp@suse.de>
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- 22 9月, 2012 2 次提交
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由 H. Peter Anvin 提交于
Add header guards to protect <asm/alternative-asm.h> against multiple inclusion. Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com> Link: http://lkml.kernel.org/r/1348256595-29119-6-git-send-email-hpa@linux.intel.com
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由 H. Peter Anvin 提交于
.section/.previous doesn't nest. Use .pushsection/.popsection in <asm/alternative.h> so that they can be properly nested. Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com> Link: http://lkml.kernel.org/r/1348256595-29119-5-git-send-email-hpa@linux.intel.com
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- 04 1月, 2012 1 次提交
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由 Eric Dumazet 提交于
It appears about all functions in arch/x86/lib/atomic64_cx8_32.S are wrong in case cmpxchg8b must be restarted, because LOCK_PREFIX macro defines a label "1" clashing with other local labels : 1: some_instructions LOCK_PREFIX cmpxchg8b (%ebp) jne 1b / jumps to beginning of LOCK_PREFIX ! A possible fix is to use a magic label "672" in LOCK_PREFIX asm definition, similar to the "671" one we defined in LOCK_PREFIX_HERE. Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com> Acked-by: NJan Beulich <JBeulich@suse.com> Cc: Christoph Lameter <cl@linux.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Link: http://lkml.kernel.org/r/1325608540.2320.103.camel@edumazet-HP-Compaq-6005-Pro-SFF-PCSigned-off-by: NIngo Molnar <mingo@elte.hu>
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- 16 9月, 2011 1 次提交
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由 Linus Torvalds 提交于
On x86-64, they were just wasteful: with the explicitly added (now unnecessary) padding, the size of the alternatives structure was 16 bytes, and an alignment of 8 bytes didn't hurt much. However, it was still silly, since the natural size and alignment for the structure is actually just 12 bytes, 4-byte aligned since commit 59e97e4d ("x86: Make alternative instruction pointers relative"). So removing the padding, and removing the extra alignment is just a good idea. On x86-32, the alignment of 4 bytes was correct, but was incorrectly hardcoded as 8 bytes in <asm/alternative-asm.h>. That header file had used to be an x86-64 only header file, but various unification efforts have made it be used for x86-32 too (ie the unification of rwlock and rwsem). That in turn caused x86-32 boot failures, because the extra alignment would result in random zero-filled words in the altinstructions section, causing oopses early at boot when doing alternative instruction replacement. So just remove all the alignment noise entirely. It's wrong, and it's unnecessary. The section itself is already properly aligned by the linker scripts, and all additions to the section had better be of the proper 12-byte format, keeping it aligned. So if the align directive were to ever make a difference, that would be an indication of a serious bug to begin with. Reported-by: NWerner Landgraf <w.landgraf@ru.r> Acked-by: NAndrew Lutomirski <luto@mit.edu> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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- 14 7月, 2011 1 次提交
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由 Andy Lutomirski 提交于
This save a few bytes on x86-64 and means that future patches can apply alternatives to unrelocated code. Signed-off-by: NAndy Lutomirski <luto@mit.edu> Link: http://lkml.kernel.org/r/ff64a6b9a1a3860ca4a7b8b6dc7b4754f9491cd7.1310563276.git.luto@mit.eduSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>
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- 18 5月, 2011 1 次提交
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由 Fenghua Yu 提交于
Add altinstruction_entry macro to generate .altinstructions section entries from assembly code. This should be less failure-prone than open-coding. Signed-off-by: NFenghua Yu <fenghua.yu@intel.com> Link: http://lkml.kernel.org/r/1305671358-14478-5-git-send-email-fenghua.yu@intel.comSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>
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- 29 4月, 2010 1 次提交
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由 Jan Beulich 提交于
Reduce the SMP locks table size by using relative pointers instead of absolute ones, thus cutting the table size by half. Signed-off-by: NJan Beulich <jbeulich@novell.com> LKML-Reference: <4BCF30FE020000780003B3B6@vpn.id2.novell.com> Signed-off-by: NH. Peter Anvin <hpa@zytor.com>
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- 02 12月, 2009 1 次提交
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由 Jan Beulich 提交于
This at once also gets the alignment specification right for x86-64. Signed-off-by: NJan Beulich <jbeulich@novell.com> LKML-Reference: <4B0FF8F80200007800022708@vpn.id2.novell.com> Signed-off-by: NIngo Molnar <mingo@elte.hu>
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- 23 10月, 2008 1 次提交
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由 Al Viro 提交于
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk> Signed-off-by: NH. Peter Anvin <hpa@zytor.com>
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- 18 10月, 2007 1 次提交
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由 Adrian Bunk 提交于
.i is an ending used for preprocessed stuff. This patch therefore renames assembler include files to .h and guards the contents with an #ifdef __ASSEMBLY__. [ tglx: arch/x86 adaptation ] Signed-off-by: NAdrian Bunk <bunk@kernel.org> Signed-off-by: NAndi Kleen <ak@suse.de> Signed-off-by: NIngo Molnar <mingo@elte.hu> Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
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