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2010-10-29jump label: Add work around to i386 gcc asm goto bugSteven Rostedt
On i386 (not x86_64) early implementations of gcc would have a bug with asm goto causing it to produce code like the following: (This was noticed by Peter Zijlstra) 56 pushl 0 67 nopl jmp 0x6f popl jmp 0x8c 6f mov test je 0x8c 8c mov call *(%esp) The jump added in the asm goto skipped over the popl that matched the pushl 0, which lead up to a quick crash of the system when the jump was enabled. The nopl is defined in the asm goto () statement and when tracepoints are enabled, the nop changes to a jump to the label that was specified by the asm goto. asm goto is suppose to tell gcc that the code in the asm might jump to an external label. Here gcc obviously fails to make that work. The bug report for gcc is here: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46226 The bug only appears on x86 when not compiled with -maccumulate-outgoing-args. This option is always set on x86_64 and it is also the work around for a function graph tracer i386 bug. (See commit: 746357d6a526d6da9d89a2ec645b28406e959c2e) This explains why the bug only showed up on i386 when function graph tracer was not enabled. This patch now adds a CONFIG_JUMP_LABEL option that is default off instead of using jump labels by default. When jump labels are enabled, the -maccumulate-outgoing-args will be used (causing a slightly larger kernel image on i386). This option will exist until we have a way to detect if the gcc compiler in use is safe to use on all configurations without the work around. Note, there exists such a test, but for now we will keep the enabling of jump label as a manual option. Archs that know the compiler is safe with asm goto, may choose to select JUMP_LABEL and enable it by default. Reported-by: Ingo Molnar <mingo@elte.hu> Cause-discovered-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Jason Baron <jbaron@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: David Daney <ddaney@caviumnetworks.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: David Miller <davem@davemloft.net> Cc: Richard Henderson <rth@redhat.com> LKML-Reference: <1288028746.3673.11.camel@laptop> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2009-12-08Merge branch 'x86-fixes-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip * 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: x86, mce: don't restart timer if disabled x86: Use -maccumulate-outgoing-args for sane mcount prologues x86: Prevent GCC 4.4.x (pentium-mmx et al) function prologue wreckage x86: AMD Northbridge: Verify NB's node is online x86 VSDO: Fix Kconfig help x86: Fix typo in Intel CPU cache size descriptor x86: Add new Intel CPU cache size descriptors
2009-11-28x86: Use -maccumulate-outgoing-args for sane mcount prologuesThomas Gleixner
commit 746357d (x86: Prevent GCC 4.4.x (pentium-mmx et al) function prologue wreckage) uses -mtune=generic to work around the function prologue problem with mcount on -march=pentium-mmx and others. Jakub pointed out that we can use -maccumulate-outgoing-args instead which is selected by -mtune=generic and prevents the problem without losing the -march specific optimizations. Pointed-out-by: Jakub Jelinek <jakub@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: stable@kernel.org
2009-11-20x86: Prevent GCC 4.4.x (pentium-mmx et al) function prologue wreckageThomas Gleixner
When the kernel is compiled with -pg for tracing GCC 4.4.x inserts stack alignment of a function _before_ the mcount prologue if the -march=pentium-mmx is set and -mtune=generic is not set. This breaks the assumption of the function graph tracer which expects that the mcount prologue push %ebp mov %esp, %ebp is the first stack operation in a function because it needs to modify the function return address on the stack to trap into the tracer before returning to the real caller. The generated code is: push %edi lea 0x8(%esp),%edi and $0xfffffff0,%esp pushl -0x4(%edi) push %ebp mov %esp,%ebp so the tracer modifies the copy of the return address which is stored after the stack alignment and therefor does not trap the return which in turn breaks the call chain logic of the tracer and leads to a kernel panic. Aside of the fact that the generated code is horrible for no good reason other -march -mtune options generate the expected: push %ebp mov %esp,%ebp and $0xfffffff0,%esp which does the same and keeps everything intact. After some experimenting we found out that this problem is restricted to gcc4.4.x and to the following -march settings: i586, pentium, pentium-mmx, k6, k6-2, k6-3, winchip-c6, winchip2, c3, geode By adding -mtune=generic the code generator produces always the expected code. So forcing -mtune=generic when CONFIG_FUNCTION_GRAPH_TRACER=y is not pretty, but at the moment the only way to prevent that the kernel trips over gcc-shrooms induced code madness. Most distro kernels have CONFIG_X86_GENERIC=y anyway which forces -mtune=generic as well so it will not impact those. References: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42109 http://lkml.org/lkml/2009/11/19/17 Signed-off-by: Thomas Gleixner <tglx@linutronix.de> LKML-Reference: <alpine.LFD.2.00.0911200206570.24119@localhost.localdomain> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <peterz@infradead.org> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com>, Cc: Jeff Law <law@redhat.com> Cc: gcc@gcc.gnu.org Cc: David Daney <ddaney@caviumnetworks.com> Cc: Andrew Haley <aph@redhat.com> Cc: Richard Guenther <richard.guenther@gmail.com> Cc: stable@kernel.org
2009-10-02x86: AMD Geode LX optimizationsMatteo Croce
Add CPU optimizations for AMD Geode LX. Signed-off-by: Matteo Croce <technoboy85@gmail.com> LKML-Reference: <40101cc30910010811v5d15ff4cx9dd57c9cc9b4b045@mail.gmail.com> Signed-off-by: H. Peter Anvin <hpa@zytor.com>
2009-08-23x86: add specific support for Intel Atom architectureTobias Doerffel
Add another option when selecting CPU family so the kernel can be optimized for Intel Atom CPUs. If GCC supports tuning options for Intel Atom they will be used. Signed-off-by: Tobias Doerffel <tobias.doerffel@gmail.com> Signed-off-by: H. Peter Anvin <hpa@zytor.com> LKML-Reference: <1251018457-19157-1-git-send-email-tobias.doerffel@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-10-13x86: merge winchip-2 and winchip-2a cpu choicesKrzysztof Helt
The Winchip-2 and Winchip-2A cpu choices select the same options for kernel and compiler. Merge them to save few bytes and reduce confusion. Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl> Acked-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-09-09x86: prevent binutils from being "smart" and generating NOPLs for usH. Peter Anvin
binutils, contrary to documented behaviour, will generate long NOPs (a P6-or-higher instruction which is broken on at least some VIA chips, Virtual PC/Virtual Server, and some versions of Qemu) depending on the -mtune= option, which is not supposed to change architectural behaviour. Pass an explicit override to the assembler, in case ends up passing the -mtune= parameter to gas (gcc 4.3.0 does not appear to.) Signed-off-by: H. Peter Anvin <hpa@zytor.com>
2007-10-25x86: move i386 and x86_64 Makefiles to arch/x86Sam Ravnborg
Moving the ARCH specific Makefiles for i386 and x86_64 required a litle bit tweaking in the top-lvel Makefile. SRCARCH is now set in the top-level Makefile because we need this info to include the correct arch Makefile. Signed-off-by: Sam Ravnborg <sam@ravnborg.org>