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2008-01-30x86: avoid build warningIngo Molnar
fix this build warning: include/asm/topology_32.h: In function 'node_to_first_cpu': include/asm/topology_32.h:66: warning: unused variable 'mask' Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: kill mk_pte_hugeJeremy Fitzhardinge
It only has a single use, which can be trivially replaced. Signed-off-by: Jeremy Fitzhardinge <Jeremy.Fitzhardinge@citrix.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x64/page.h: convert some macros to inlinesRandy Dunlap
Convert clear_page/copy_page macros to inline functions for type-checking. Andrew wants to extirpate these ugly macros. (Ingo too. Thomas as well. Please send us more "kill ugly macros" patches! :-) Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: remove arch specific segment headersGlauber de Oliveira Costa
This file puts the remainder of the arch specificic segment headers in segment.h. Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: unify common parts of segment.hGlauber de Oliveira Costa
Although segment handling in i386 and x86_64 are very different, there's a common part. Put them in segment.h instead of arch specific headers Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: put get_kernel_rpl in a common locationGlauber de Oliveira Costa
This macro is useful for both i386 and x86_64, so put it in a common location, where both arches can grab it. Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86, ptrace: support for branch trace store(BTS)Markus Metzger
Resend using different mail client Changes to the last version: - split implementation into two layers: ds/bts and ptrace - renamed TIF's - save/restore ds save area msr in __switch_to_xtra() - make block-stepping only look at BTF bit Signed-off-by: Markus Metzger <markus.t.metzger@intel.com> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: unify system.hGlauber de Oliveira Costa
This patch finishes the unification of system.h file. i386 needs a constant to be defined, and it is defined inside an ifdef. Other than that, pretty much nothing but includes are left in the arch specific headers, and they are deleted. [ mingo@elte.hu: 64-bit needs the cr8 access inlines. ] Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: move switch_to macro to system.hGlauber de Oliveira Costa
This patch moves the switch_to() macro to system.h As those macros are fundamentally different between i386 and x86_64, they are enclosed around an ifdef. Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: unify smp parts of system.hGlauber de Oliveira Costa
The memory barrier parts of system.h are not very different between i386 and x86_64, the main difference being the availability of instructions, which we handle with the use of ifdefs. They are consolidated in system.h file, and then removed from the arch-specific headers. Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: remove unused macroGlauber de Oliveira Costa
Mr. Grep says warn_if_not_ulong() is not used anymore anywhere in the code. So, we remove it. Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: unify paravirt parts of system.hGlauber de Oliveira Costa
This patch moves the i386 control registers manipulation functions, wbinvd, and clts functions to system.h. They are essentially the same as in x86_64. With this, system.h paravirt comes for free in x86_64. [ mingo@elte.hu: reintroduced the cr8 bits - needed for resume images ] Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: unify load_segment macroGlauber de Oliveira Costa
This patch unifies the load_segment() macro, making them equal in both x86_64 and i386 architectures. The common version goes to system.h, and the old are deleted. Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: put together equal pieces of system.hGlauber de Oliveira Costa
This patch puts together pieces of system_{32,64}.h that looks like the same. It's the first step towards integration of this file. Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: remove volatile keyword from clflush.Glauber de Oliveira Costa
the p parameter is an explicit memory reference, and is enough to prevent gcc to being nasty here. The volatile seems completely not needed. Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: some whitespace cleanups in paging codeJoerg Roedel
This patch does some whitespace cleanups in the paging code to fix some checkpatch.pl warnings of my formerly merged cleanup patches. Signed-off-by: Joerg Roedel <joerg.roedel@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: PIE executable randomizationJiri Kosina
main executable of (specially compiled/linked -pie/-fpie) ET_DYN binaries onto a random address (in cases in which mmap() is allowed to perform a randomization). The code has been extraced from Ingo's exec-shield patch http://people.redhat.com/mingo/exec-shield/ [akpm@linux-foundation.org: fix used-uninitialsied warning] [kamezawa.hiroyu@jp.fujitsu.com: fixed ia32 ELF on x86_64 handling] Signed-off-by: Jiri Kosina <jkosina@suse.cz> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Arjan van de Ven <arjan@infradead.org> Cc: Roland McGrath <roland@redhat.com> Cc: Jakub Jelinek <jakub@redhat.com> Cc: "Luck, Tony" <tony.luck@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: unify include/asm-x86/linkage_[32|64].hHarvey Harrison
Remove definitions of FASTCALL/fastcall from linkage_32 as compiled with -regparm=3 by default since 2.6.20 and should no longer be needed. CONFIG X86_64 and CONFIG_X86_ALIGNMENT_16 are mutually exclusive as found in Kconfig.cpu so it should be fine to test them separately. Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: integrate 32-bit and 64-bit code in msr.hGlauber de Oliveira Costa
This patches proceeds with the integration of msr.h, making the code unified, instead of having a version for each architecture. We stick with the native_* functions, and then paravirt comes for free. Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: make fixups wordsize agnosticGlauber de Oliveira Costa
This patch uses the _ASM_ALIGN and _ASM_PTR macros to make the fixups in native_read/write_msr_safe look the same for x86_64 and i386. Besides using this macros, we also have to take the explicit instruction suffixes out. It's okay because all this instructions uses registers, and can be sized by them. Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: change write msr functions interfaceGlauber de Oliveira Costa
This patche changes the native_write_msr() and friends interface to explicitly take 2 32-bit registers instead of a 64-bit value. The change will ease the merge with 64-bit code. As the 64-bit value will be passed as two registers anyway in i386, the PVOP_CALL interface has to account for that and use low/high parameters It would force the x86_64 version to be different. The change does not make i386 generated code less efficient. As said above, it would get the values from two registers anyway. Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: change rdpmc interfaceGlauber de Oliveira Costa
the rdpmc instruction gets a counter argument in rcx. However, the i386 version was ignoring it. To make both x86_64 and i386 versions the same, as well as to comply with the instruction semantics, this parameter is added in the i386 version Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: introduce native_read_tscpGlauber de Oliveira Costa
Targetting paravirt, this patch introduces native_read_tscp, in place of rdtscp() macro. When in a paravirt guest, this will involve a function call, and thus, cannot be done in the vdso area. These users then have to call the native version directly Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: unify cpuid functionsGlauber de Oliveira Costa
cpuid is not very different between i386 and x86_64. We move away the x86_64 version from msr.h, and unify them at processor.h, where they belong. cpuid() paravirt then comes for free. Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: split get_cycles_syncGlauber de Oliveira Costa
This patch splits get_cycles_sync() into __get_cycles_sync(), and the rdtscll part. Paravirt guests cannot issue rdtscl directly, as it involves a function call in vdso area. So, using the __get_cycles_sync() base, we introduce vget_cycles_sync, which then calls the native version of rdtscll. Ideally, however, a guest should define its own clocksource, together with a vread function Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: unify msr smp funcsGlauber de Oliveira Costa
The functions under #ifdef CONFIG_SMP in msr.h are the same for both x86_64 and i386, and this patches removes one of them, putting them in a single location Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: define all _PAGE_* in terms of _PAGE_BIT_* on 64-bitJoerg Roedel
This patch defines the _PAGE_* paging attributes in pgtable_64.h in terms of the former defined _PAGE_BIT_* values. Signed-off-by: Joerg Roedel <joerg.roedel@amd.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: use generic register name in the thread and tss structuresH. Peter Anvin
This changes size-specific register names (eip/rip, esp/rsp, etc.) to generic names in the thread and tss structures. Signed-off-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: x86 ptrace merge completeRoland McGrath
This switches over the 64-bit build to use the shared ptrace code, instead of the old ptrace_64.c and arch/x86/ia32/ptrace32.c code. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: x86-32 thread_struct.debugregRoland McGrath
This replaces the debugreg[7] member of thread_struct with individual members debugreg0, etc. This saves two words for the dummies 4 and 5, and harmonizes the code between 32 and 64. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: eflags enumRoland McGrath
This removes the EF_* enum from <asm/ptrace.h>. It is no longer used, and duplicates the X86_EFLAGS_* constants from <asm/processor-flags.h>. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: use generic register names in struct sigcontextH. Peter Anvin
Switch struct sigcontext (defined in <asm/sigcontext*.h>) to using register names withut e- or r-prefixes for both 32- and 64-bit x86. This is intended as a preliminary step in unifying this code between architectures. Signed-off-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: use generic register names in struct user_regs_structH. Peter Anvin
Switch struct user_regs_struct (defined in <asm/user.h>, which is no longer exported to userspace) to using register names without e- or r-prefixes for both 32 and 64 bit x86. This is intended as a preliminary step in unifying this code between architectures. Also, be a bit more strict in truncating 32-bit "extended" segment register values to 16 bits. Signed-off-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: rename the struct pt_regs members for 32/64-bit consistencyH. Peter Anvin
We have a lot of code which differs only by the naming of specific members of structures that contain registers. In order to enable additional unifications, this patch drops the e- or r- size prefix from the register names in struct pt_regs, and drops the x- prefixes for segment registers on the 32-bit side. This patch also performs the equivalent renames in some additional places that might be candidates for unification in the future. Signed-off-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: add set/clear_cpu_cap operationsJeremy Fitzhardinge
The patch to suppress bitops-related warnings added a pile of ugly casts. Many of these were related to the management of x86 CPU capabilities. Clean these up by adding specific set/clear_cpu_cap macros, and use them consistently. Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com> Cc: Andi Kleen <ak@suse.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: clean up bitops-related warningsJeremy Fitzhardinge
Add casts to appropriate places to silence spurious bitops warnings. Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com> Cc: Andi Kleen <ak@suse.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: partial unification of asm-x86/bitops.hJeremy Fitzhardinge
This unifies the set/clear/test bit functions of asm/bitops.h. I have not attempted to merge the bit-finding functions, since they rely on the machine word size and can't be easily restructured to work generically without a lot of #ifdefs. In particular, the 64-bit code can assume the presence of conditional move instructions, whereas 32-bit needs to be more careful. The inline assembly for the bit operations has been changed to remove explicit sizing hints on the instructions, so the assembler will pick the appropriate instruction forms depending on the architecture and the context. Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com> Cc: Andi Kleen <ak@suse.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: PTRACE_SINGLEBLOCKRoland McGrath
This adds the PTRACE_SINGLEBLOCK request on x86, matching the ia64 feature. The implementation comes from the generic ptrace code and relies on the low-level machine support provided by arch_has_block_step() et al. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: debugctlmsr arch_has_block_stepRoland McGrath
This implements user-mode step-until-branch on x86 using the BTF bit in MSR_IA32_DEBUGCTLMSR. It's just like single-step, only less so. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: debugctlmsr context switchRoland McGrath
This adds low-level support for a per-thread value of MSR_IA32_DEBUGCTLMSR. The per-thread value is switched in when TIF_DEBUGCTLMSR is set. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: debugctlmsr constantsRoland McGrath
This adds constant macros for a few of the bits in MSR_IA32_DEBUGCTLMSR. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30ptrace: generic PTRACE_SINGLEBLOCKRoland McGrath
This makes ptrace_request handle PTRACE_SINGLEBLOCK along with PTRACE_CONT et al. The new generic code makes use of the arch_has_block_step macro and generic entry points on machines that define them. [ mingo@elte.hu: bugfix ] Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30ptrace: arch_has_block_stepRoland McGrath
This defines the new macro arch_has_block_step() in linux/ptrace.h, a default for when asm/ptrace.h does not define it. This is the analog of arch_has_single_step() for step-until-branch on machines that have it. It declares the new user_enable_block_step function, which goes with the existing user_enable_single_step and user_disable_single_step. This is not used yet, but paves the way to harmonize on this interface for the arch-specific calls on all machines. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: x86-64 ptrace debugreg cleanupRoland McGrath
This cleans up the 64-bit ptrace code to separate the guts of the debug register access from the implementation of PTRACE_PEEKUSR and PTRACE_POKEUSR. The new functions ptrace_[gs]et_debugreg are made global so that the ia32 code can later be changed to call them too. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30powerpc: arch_has_single_stepRoland McGrath
This defines the new standard arch_has_single_step macro. It makes the existing set_single_step and clear_single_step entry points global, and renames them to the new standard names user_enable_single_step and user_disable_single_step, respectively. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86 single_step: TIF_FORCED_TFRoland McGrath
This changes the single-step support to use a new thread_info flag TIF_FORCED_TF instead of the PT_DTRACE flag in task_struct.ptrace. This keeps arch implementation uses out of this non-arch field. This changes the ptrace access to eflags to mask TF and maintain the TIF_FORCED_TF flag directly if userland sets TF, instead of relying on ptrace_signal_deliver. The 64-bit and 32-bit kernels are harmonized on this same behavior. The ptrace_signal_deliver approach works now, but this change makes the low-level register access code reliable when called from different contexts than a ptrace stop, which will be possible in the future. The 64-bit do_debug exception handler is also changed not to clear TF from user-mode registers. This matches the 32-bit kernel's behavior. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: arch_has_single_stepRoland McGrath
This defines the new standard arch_has_single_step macro. It makes the existing set_singlestep and clear_singlestep entry points global, and renames them to the new standard names user_enable_single_step and user_disable_single_step, respectively. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: segment selector macrosRoland McGrath
This copies into asm-x86/segment_64.h some macros from asm-x86/segment_32.h for dissecting segment selectors. This lets other code use these macros uniformly on 32/64-bit rather than duplicating the constants elsewhere. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30ptrace: arch_has_single_stepRoland McGrath
This defines the new macro arch_has_single_step() in linux/ptrace.h, a default for when asm/ptrace.h does not define it. It declares the new user_enable_single_step and user_disable_single_step functions. This is not used yet, but paves the way to harmonize on this interface for the arch-specific calls on all machines. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: fall back on interrupt disable in cmpxchg8b on 80386 and 80486Mathieu Desnoyers
Actually, on 386, cmpxchg and cmpxchg_local fall back on cmpxchg_386_u8/16/32: it disables interruptions around non atomic updates to mimic the cmpxchg behavior. The comment: /* Poor man's cmpxchg for 386. Unsuitable for SMP */ already present in cmpxchg_386_u32 tells much about how this cmpxchg implementation should not be used in a SMP context. However, the cmpxchg_local can perfectly use this fallback, since it only needs to be atomic wrt the local cpu. This patch adds a cmpxchg_486_u64 and uses it as a fallback for cmpxchg64 and cmpxchg64_local on 80386 and 80486. Q: but why is it called cmpxchg_486 when the other functions are called A: Because the standard cmpxchg is missing only on 386, but cmpxchg8b is missing both on 386 and 486. Citing Intel's Instruction set reference: cmpxchg: This instruction is not supported on Intel processors earlier than the Intel486 processors. cmpxchg8b: This instruction encoding is not supported on Intel processors earlier than the Pentium processors. Q: What's the reason to have cmpxchg64_local on 32 bit architectures? Without that need all this would just be a few simple defines. A: cmpxchg64_local on 32 bits architectures takes unsigned long long parameters, but cmpxchg_local only takes longs. Since we have cmpxchg8b to execute a 8 byte cmpxchg atomically on pentium and +, it makes sense to provide a flavor of cmpxchg and cmpxchg_local using this instruction. Also, for 32 bits architectures lacking the 64 bits atomic cmpxchg, it makes sense _not_ to define cmpxchg64 while cmpxchg could still be available. Moreover, the fallback for cmpxchg8b on i386 for 386 and 486 is a However, cmpxchg64_local will be emulated by disabling interrupts on all architectures where it is not supported atomically. Therefore, we *could* turn cmpxchg64_local into a cmpxchg_local, but it would make the 386/486 fallbacks ugly, make its design different from cmpxchg/cmpxchg64 (which really depends on atomic operations and cannot be emulated) and require the __cmpxchg_local to be expressed as a macro rather than an inline function so the parameters would not be fixed to unsigned long long in every case. So I think cmpxchg64_local makes sense there, but I am open to suggestions. Q: Are there any callers? A: I am actually using it in LTTng in my timestamping code. I use it to work around CPUs with asynchronous TSCs. I need to update 64 bits values atomically on this 32 bits architecture. Changelog: - Ran though checkpatch. Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Cc: Andi Kleen <ak@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>