1. 15 Aug, 2018 1 commit
    • Peter Zijlstra's avatar
      x86/paravirt: Fix spectre-v2 mitigations for paravirt guests · f7a0871d
      Peter Zijlstra authored
      commit 5800dc5c upstream.
      
      Nadav reported that on guests we're failing to rewrite the indirect
      calls to CALLEE_SAVE paravirt functions. In particular the
      pv_queued_spin_unlock() call is left unpatched and that is all over the
      place. This obviously wrecks Spectre-v2 mitigation (for paravirt
      guests) which relies on not actually having indirect calls around.
      
      The reason is an incorrect clobber test in paravirt_patch_call(); this
      function rewrites an indirect call with a direct call to the _SAME_
      function, there is no possible way the clobbers can be different
      because of this.
      
      Therefore remove this clobber check. Also put WARNs on the other patch
      failure case (not enough room for the instruction) which I've not seen
      trigger in my (limited) testing.
      
      Three live kernel image disassemblies for lock_sock_nested (as a small
      function that illustrates the problem nicely). PRE is the current
      situation for guests, POST is with this patch applied and NATIVE is with
      or without the patch for !guests.
      
      PRE:
      
      (gdb) disassemble lock_sock_nested
      Dump of assembler code for function lock_sock_nested:
         0xffffffff817be970 <+0>:     push   %rbp
         0xffffffff817be971 <+1>:     mov    %rdi,%rbp
         0xffffffff817be974 <+4>:     push   %rbx
         0xffffffff817be975 <+5>:     lea    0x88(%rbp),%rbx
         0xffffffff817be97c <+12>:    callq  0xffffffff819f7160 <_cond_resched>
         0xffffffff817be981 <+17>:    mov    %rbx,%rdi
         0xffffffff817be984 <+20>:    callq  0xffffffff819fbb00 <_raw_spin_lock_bh>
         0xffffffff817be989 <+25>:    mov    0x8c(%rbp),%eax
         0xffffffff817be98f <+31>:    test   %eax,%eax
         0xffffffff817be991 <+33>:    jne    0xffffffff817be9ba <lock_sock_nested+74>
         0xffffffff817be993 <+35>:    movl   $0x1,0x8c(%rbp)
         0xffffffff817be99d <+45>:    mov    %rbx,%rdi
         0xffffffff817be9a0 <+48>:    callq  *0xffffffff822299e8
         0xffffffff817be9a7 <+55>:    pop    %rbx
         0xffffffff817be9a8 <+56>:    pop    %rbp
         0xffffffff817be9a9 <+57>:    mov    $0x200,%esi
         0xffffffff817be9ae <+62>:    mov    $0xffffffff817be993,%rdi
         0xffffffff817be9b5 <+69>:    jmpq   0xffffffff81063ae0 <__local_bh_enable_ip>
         0xffffffff817be9ba <+74>:    mov    %rbp,%rdi
         0xffffffff817be9bd <+77>:    callq  0xffffffff817be8c0 <__lock_sock>
         0xffffffff817be9c2 <+82>:    jmp    0xffffffff817be993 <lock_sock_nested+35>
      End of assembler dump.
      
      POST:
      
      (gdb) disassemble lock_sock_nested
      Dump of assembler code for function lock_sock_nested:
         0xffffffff817be970 <+0>:     push   %rbp
         0xffffffff817be971 <+1>:     mov    %rdi,%rbp
         0xffffffff817be974 <+4>:     push   %rbx
         0xffffffff817be975 <+5>:     lea    0x88(%rbp),%rbx
         0xffffffff817be97c <+12>:    callq  0xffffffff819f7160 <_cond_resched>
         0xffffffff817be981 <+17>:    mov    %rbx,%rdi
         0xffffffff817be984 <+20>:    callq  0xffffffff819fbb00 <_raw_spin_lock_bh>
         0xffffffff817be989 <+25>:    mov    0x8c(%rbp),%eax
         0xffffffff817be98f <+31>:    test   %eax,%eax
         0xffffffff817be991 <+33>:    jne    0xffffffff817be9ba <lock_sock_nested+74>
         0xffffffff817be993 <+35>:    movl   $0x1,0x8c(%rbp)
         0xffffffff817be99d <+45>:    mov    %rbx,%rdi
         0xffffffff817be9a0 <+48>:    callq  0xffffffff810a0c20 <__raw_callee_save___pv_queued_spin_unlock>
         0xffffffff817be9a5 <+53>:    xchg   %ax,%ax
         0xffffffff817be9a7 <+55>:    pop    %rbx
         0xffffffff817be9a8 <+56>:    pop    %rbp
         0xffffffff817be9a9 <+57>:    mov    $0x200,%esi
         0xffffffff817be9ae <+62>:    mov    $0xffffffff817be993,%rdi
         0xffffffff817be9b5 <+69>:    jmpq   0xffffffff81063aa0 <__local_bh_enable_ip>
         0xffffffff817be9ba <+74>:    mov    %rbp,%rdi
         0xffffffff817be9bd <+77>:    callq  0xffffffff817be8c0 <__lock_sock>
         0xffffffff817be9c2 <+82>:    jmp    0xffffffff817be993 <lock_sock_nested+35>
      End of assembler dump.
      
      NATIVE:
      
      (gdb) disassemble lock_sock_nested
      Dump of assembler code for function lock_sock_nested:
         0xffffffff817be970 <+0>:     push   %rbp
         0xffffffff817be971 <+1>:     mov    %rdi,%rbp
         0xffffffff817be974 <+4>:     push   %rbx
         0xffffffff817be975 <+5>:     lea    0x88(%rbp),%rbx
         0xffffffff817be97c <+12>:    callq  0xffffffff819f7160 <_cond_resched>
         0xffffffff817be981 <+17>:    mov    %rbx,%rdi
         0xffffffff817be984 <+20>:    callq  0xffffffff819fbb00 <_raw_spin_lock_bh>
         0xffffffff817be989 <+25>:    mov    0x8c(%rbp),%eax
         0xffffffff817be98f <+31>:    test   %eax,%eax
         0xffffffff817be991 <+33>:    jne    0xffffffff817be9ba <lock_sock_nested+74>
         0xffffffff817be993 <+35>:    movl   $0x1,0x8c(%rbp)
         0xffffffff817be99d <+45>:    mov    %rbx,%rdi
         0xffffffff817be9a0 <+48>:    movb   $0x0,(%rdi)
         0xffffffff817be9a3 <+51>:    nopl   0x0(%rax)
         0xffffffff817be9a7 <+55>:    pop    %rbx
         0xffffffff817be9a8 <+56>:    pop    %rbp
         0xffffffff817be9a9 <+57>:    mov    $0x200,%esi
         0xffffffff817be9ae <+62>:    mov    $0xffffffff817be993,%rdi
         0xffffffff817be9b5 <+69>:    jmpq   0xffffffff81063ae0 <__local_bh_enable_ip>
         0xffffffff817be9ba <+74>:    mov    %rbp,%rdi
         0xffffffff817be9bd <+77>:    callq  0xffffffff817be8c0 <__lock_sock>
         0xffffffff817be9c2 <+82>:    jmp    0xffffffff817be993 <lock_sock_nested+35>
      End of assembler dump.
      
      
      Fixes: 63f70270 ("[PATCH] i386: PARAVIRT: add common patching machinery")
      Fixes: 3010a066 ("x86/paravirt, objtool: Annotate indirect calls")
      Reported-by: default avatarNadav Amit <namit@vmware.com>
      Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: default avatarJuergen Gross <jgross@suse.com>
      Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
      Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
      Cc: David Woodhouse <dwmw2@infradead.org>
      Cc: stable@vger.kernel.org
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      f7a0871d
  2. 22 Feb, 2018 1 commit
  3. 13 Sep, 2017 1 commit
  4. 31 Aug, 2017 1 commit
  5. 13 Jun, 2017 1 commit
  6. 04 Apr, 2017 1 commit
  7. 27 Mar, 2017 1 commit
  8. 25 Feb, 2017 1 commit
  9. 01 Nov, 2016 1 commit
    • Andy Lutomirski's avatar
      x86/fpu: Remove clts() · af25ed59
      Andy Lutomirski authored
      The kernel doesn't use clts() any more.  Remove it and all of its
      paravirt infrastructure.
      
      A careful reader may notice that xen_clts() appears to have been
      buggy -- it didn't update xen_cr0_value.
      Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Brian Gerst <brgerst@gmail.com>
      Cc: Dave Hansen <dave.hansen@linux.intel.com>
      Cc: Denys Vlasenko <dvlasenk@redhat.com>
      Cc: Fenghua Yu <fenghua.yu@intel.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Josh Poimboeuf <jpoimboe@redhat.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Paolo Bonzini <pbonzini@redhat.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Rusty Russell <rusty@rustcorp.com.au>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: kvm list <kvm@vger.kernel.org>
      Link: http://lkml.kernel.org/r/3d3c8ca62f17579b9849a013d71e59a4d5d1b079.1477951965.git.luto@kernel.orgSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
      af25ed59
  10. 30 Sep, 2016 1 commit
  11. 02 Sep, 2016 1 commit
    • Steven Rostedt's avatar
      x86/paravirt: Do not trace _paravirt_ident_*() functions · 15301a57
      Steven Rostedt authored
      Łukasz Daniluk reported that on a RHEL kernel that his machine would lock up
      after enabling function tracer. I asked him to bisect the functions within
      available_filter_functions, which he did and it came down to three:
      
        _paravirt_nop(), _paravirt_ident_32() and _paravirt_ident_64()
      
      It was found that this is only an issue when noreplace-paravirt is added
      to the kernel command line.
      
      This means that those functions are most likely called within critical
      sections of the funtion tracer, and must not be traced.
      
      In newer kenels _paravirt_nop() is defined within gcc asm(), and is no
      longer an issue.  But both _paravirt_ident_{32,64}() causes the
      following splat when they are traced:
      
       mm/pgtable-generic.c:33: bad pmd ffff8800d2435150(0000000001d00054)
       mm/pgtable-generic.c:33: bad pmd ffff8800d3624190(0000000001d00070)
       mm/pgtable-generic.c:33: bad pmd ffff8800d36a5110(0000000001d00054)
       mm/pgtable-generic.c:33: bad pmd ffff880118eb1450(0000000001d00054)
       NMI watchdog: BUG: soft lockup - CPU#2 stuck for 22s! [systemd-journal:469]
       Modules linked in: e1000e
       CPU: 2 PID: 469 Comm: systemd-journal Not tainted 4.6.0-rc4-test+ #513
       Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v02.05 05/07/2012
       task: ffff880118f740c0 ti: ffff8800d4aec000 task.ti: ffff8800d4aec000
       RIP: 0010:[<ffffffff81134148>]  [<ffffffff81134148>] queued_spin_lock_slowpath+0x118/0x1a0
       RSP: 0018:ffff8800d4aefb90  EFLAGS: 00000246
       RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff88011eb16d40
       RDX: ffffffff82485760 RSI: 000000001f288820 RDI: ffffea0000008030
       RBP: ffff8800d4aefb90 R08: 00000000000c0000 R09: 0000000000000000
       R10: ffffffff821c8e0e R11: 0000000000000000 R12: ffff880000200fb8
       R13: 00007f7a4e3f7000 R14: ffffea000303f600 R15: ffff8800d4b562e0
       FS:  00007f7a4e3d7840(0000) GS:ffff88011eb00000(0000) knlGS:0000000000000000
       CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
       CR2: 00007f7a4e3f7000 CR3: 00000000d3e71000 CR4: 00000000001406e0
       Call Trace:
         _raw_spin_lock+0x27/0x30
         handle_pte_fault+0x13db/0x16b0
         handle_mm_fault+0x312/0x670
         __do_page_fault+0x1b1/0x4e0
         do_page_fault+0x22/0x30
         page_fault+0x28/0x30
         __vfs_read+0x28/0xe0
         vfs_read+0x86/0x130
         SyS_read+0x46/0xa0
         entry_SYSCALL_64_fastpath+0x1e/0xa8
       Code: 12 48 c1 ea 0c 83 e8 01 83 e2 30 48 98 48 81 c2 40 6d 01 00 48 03 14 c5 80 6a 5d 82 48 89 0a 8b 41 08 85 c0 75 09 f3 90 8b 41 08 <85> c0 74 f7 4c 8b 09 4d 85 c9 74 08 41 0f 18 09 eb 02 f3 90 8b
      Reported-by: default avatarŁukasz Daniluk <lukasz.daniluk@intel.com>
      Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      Cc: stable@vger.kernel.org
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      15301a57
  12. 10 Aug, 2016 1 commit
    • Kees Cook's avatar
      x86: Apply more __ro_after_init and const · 404f6aac
      Kees Cook authored
      Guided by grsecurity's analogous __read_only markings in arch/x86,
      this applies several uses of __ro_after_init to structures that are
      only updated during __init, and const for some structures that are
      never updated.  Additionally extends __init markings to some functions
      that are only used during __init, and cleans up some missing C99 style
      static initializers.
      Signed-off-by: default avatarKees Cook <keescook@chromium.org>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Andy Lutomirski <luto@kernel.org>
      Cc: Arnd Bergmann <arnd@arndb.de>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Brad Spengler <spender@grsecurity.net>
      Cc: Brian Gerst <brgerst@gmail.com>
      Cc: David Brown <david.brown@linaro.org>
      Cc: Denys Vlasenko <dvlasenk@redhat.com>
      Cc: Emese Revfy <re.emese@gmail.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Josh Poimboeuf <jpoimboe@redhat.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Mathias Krause <minipli@googlemail.com>
      Cc: Michael Ellerman <mpe@ellerman.id.au>
      Cc: PaX Team <pageexec@freemail.hu>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: kernel-hardening@lists.openwall.com
      Link: http://lkml.kernel.org/r/20160808232906.GA29731@www.outflux.netSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
      404f6aac
  13. 14 Jul, 2016 1 commit
    • Paul Gortmaker's avatar
      x86/kernel: Audit and remove any unnecessary uses of module.h · 186f4360
      Paul Gortmaker authored
      Historically a lot of these existed because we did not have
      a distinction between what was modular code and what was providing
      support to modules via EXPORT_SYMBOL and friends.  That changed
      when we forked out support for the latter into the export.h file.
      
      This means we should be able to reduce the usage of module.h
      in code that is obj-y Makefile or bool Kconfig.  The advantage
      in doing so is that module.h itself sources about 15 other headers;
      adding significantly to what we feed cpp, and it can obscure what
      headers we are effectively using.
      
      Since module.h was the source for init.h (for __init) and for
      export.h (for EXPORT_SYMBOL) we consider each obj-y/bool instance
      for the presence of either and replace as needed.  Build testing
      revealed some implicit header usage that was fixed up accordingly.
      
      Note that some bool/obj-y instances remain since module.h is
      the header for some exception table entry stuff, and for things
      like __init_or_module (code that is tossed when MODULES=n).
      Signed-off-by: default avatarPaul Gortmaker <paul.gortmaker@windriver.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Link: http://lkml.kernel.org/r/20160714001901.31603-4-paul.gortmaker@windriver.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
      186f4360
  14. 22 Apr, 2016 1 commit
    • Luis R. Rodriguez's avatar
      x86/paravirt: Remove paravirt_enabled() · 867fe800
      Luis R. Rodriguez authored
      Now that all previous paravirt_enabled() uses were replaced with proper
      x86 semantics by the previous patches we can remove the unused
      paravirt_enabled() mechanism.
      Signed-off-by: default avatarLuis R. Rodriguez <mcgrof@kernel.org>
      Acked-by: default avatarJuergen Gross <jgross@suse.com>
      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: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: andrew.cooper3@citrix.com
      Cc: andriy.shevchenko@linux.intel.com
      Cc: bigeasy@linutronix.de
      Cc: boris.ostrovsky@oracle.com
      Cc: david.vrabel@citrix.com
      Cc: ffainelli@freebox.fr
      Cc: george.dunlap@citrix.com
      Cc: glin@suse.com
      Cc: jlee@suse.com
      Cc: josh@joshtriplett.org
      Cc: julien.grall@linaro.org
      Cc: konrad.wilk@oracle.com
      Cc: kozerkov@parallels.com
      Cc: lenb@kernel.org
      Cc: lguest@lists.ozlabs.org
      Cc: linux-acpi@vger.kernel.org
      Cc: lv.zheng@intel.com
      Cc: matt@codeblueprint.co.uk
      Cc: mbizon@freebox.fr
      Cc: rjw@rjwysocki.net
      Cc: robert.moore@intel.com
      Cc: rusty@rustcorp.com.au
      Cc: tiwai@suse.de
      Cc: toshi.kani@hp.com
      Cc: xen-devel@lists.xensource.com
      Link: http://lkml.kernel.org/r/1460592286-300-15-git-send-email-mcgrof@kernel.orgSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
      867fe800
  15. 13 Apr, 2016 2 commits
  16. 25 Nov, 2015 1 commit
  17. 23 Nov, 2015 2 commits
  18. 19 Nov, 2015 1 commit
  19. 07 Nov, 2015 1 commit
  20. 22 Sep, 2015 1 commit
    • Andy Lutomirski's avatar
      x86/paravirt: Replace the paravirt nop with a bona fide empty function · fc57a7c6
      Andy Lutomirski authored
      PARAVIRT_ADJUST_EXCEPTION_FRAME generates this code (using nmi as an
      example, trimmed for readability):
      
          ff 15 00 00 00 00       callq  *0x0(%rip)        # 2796 <nmi+0x6>
                    2792: R_X86_64_PC32     pv_irq_ops+0x2c
      
      That's a call through a function pointer to regular C function that
      does nothing on native boots, but that function isn't protected
      against kprobes, isn't marked notrace, and is certainly not
      guaranteed to preserve any registers if the compiler is feeling
      perverse.  This is bad news for a CLBR_NONE operation.
      
      Of course, if everything works correctly, once paravirt ops are
      patched, it gets nopped out, but what if we hit this code before
      paravirt ops are patched in?  This can potentially cause breakage
      that is very difficult to debug.
      
      A more subtle failure is possible here, too: if _paravirt_nop uses
      the stack at all (even just to push RBP), it will overwrite the "NMI
      executing" variable if it's called in the NMI prologue.
      
      The Xen case, perhaps surprisingly, is fine, because it's already
      written in asm.
      
      Fix all of the cases that default to paravirt_nop (including
      adjust_exception_frame) with a big hammer: replace paravirt_nop with
      an asm function that is just a ret instruction.
      
      The Xen case may have other problems, so document them.
      
      This is part of a fix for some random crashes that Sasha saw.
      Reported-and-tested-by: default avatarSasha Levin <sasha.levin@oracle.com>
      Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
      Cc: stable@vger.kernel.org
      Link: http://lkml.kernel.org/r/8f5d2ba295f9d73751c33d97fda03e0495d9ade0.1442791737.git.luto@kernel.orgSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      fc57a7c6
  21. 06 Jul, 2015 1 commit
    • Andy Lutomirski's avatar
      x86/asm/tsc, x86/paravirt: Remove read_tsc() and read_tscp() paravirt hooks · 9261e050
      Andy Lutomirski authored
      We've had ->read_tsc() and ->read_tscp() paravirt hooks since
      the very beginning of paravirt, i.e.,
      
        d3561b7f ("[PATCH] paravirt: header and stubs for paravirtualisation").
      
      AFAICT, the only paravirt guest implementation that ever
      replaced these calls was vmware, and it's gone. Arguably even
      vmware shouldn't have hooked RDTSC -- we fully support systems
      that don't have a TSC at all, so there's no point for a paravirt
      implementation to pretend that we have a TSC but to replace it.
      
      I also doubt that these hooks actually worked. Calls to rdtscl()
      and rdtscll(), which respected the hooks, were used seemingly
      interchangeably with native_read_tsc(), which did not.
      
      Just remove them. If anyone ever needs them again, they can try
      to make a case for why they need them.
      
      Before, on a paravirt config:
        text    	data     bss     dec     hex filename
        12618257      1816384 1093632 15528273 ecf151 vmlinux
      
      After:
        text		data     bss     dec     hex filename
        12617207      1816384 1093632 15527223 eced37 vmlinux
      Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
      Signed-off-by: default avatarBorislav 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: Huang Rui <ray.huang@amd.com>
      Cc: John Stultz <john.stultz@linaro.org>
      Cc: Len Brown <lenb@kernel.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Ralf Baechle <ralf@linux-mips.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: kvm ML <kvm@vger.kernel.org>
      Cc: virtualization@lists.linux-foundation.org
      Link: http://lkml.kernel.org/r/d08a2600fb298af163681e5efd8e599d889a5b97.1434501121.git.luto@kernel.orgSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
      9261e050
  22. 22 Apr, 2015 1 commit
  23. 14 Apr, 2015 1 commit
  24. 24 Apr, 2014 2 commits
  25. 04 Sep, 2013 1 commit
  26. 06 Aug, 2013 1 commit
  27. 11 Apr, 2013 1 commit
  28. 10 Apr, 2013 1 commit
  29. 07 Jun, 2012 1 commit
  30. 14 May, 2012 1 commit
  31. 28 Mar, 2012 1 commit
  32. 29 Feb, 2012 1 commit
  33. 24 Feb, 2012 1 commit
    • Ingo Molnar's avatar
      static keys: Introduce 'struct static_key', static_key_true()/false() and... · c5905afb
      Ingo Molnar authored
      static keys: Introduce 'struct static_key', static_key_true()/false() and static_key_slow_[inc|dec]()
      
      So here's a boot tested patch on top of Jason's series that does
      all the cleanups I talked about and turns jump labels into a
      more intuitive to use facility. It should also address the
      various misconceptions and confusions that surround jump labels.
      
      Typical usage scenarios:
      
              #include <linux/static_key.h>
      
              struct static_key key = STATIC_KEY_INIT_TRUE;
      
              if (static_key_false(&key))
                      do unlikely code
              else
                      do likely code
      
      Or:
      
              if (static_key_true(&key))
                      do likely code
              else
                      do unlikely code
      
      The static key is modified via:
      
              static_key_slow_inc(&key);
              ...
              static_key_slow_dec(&key);
      
      The 'slow' prefix makes it abundantly clear that this is an
      expensive operation.
      
      I've updated all in-kernel code to use this everywhere. Note
      that I (intentionally) have not pushed through the rename
      blindly through to the lowest levels: the actual jump-label
      patching arch facility should be named like that, so we want to
      decouple jump labels from the static-key facility a bit.
      
      On non-jump-label enabled architectures static keys default to
      likely()/unlikely() branches.
      Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      Acked-by: default avatarJason Baron <jbaron@redhat.com>
      Acked-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      Cc: a.p.zijlstra@chello.nl
      Cc: mathieu.desnoyers@efficios.com
      Cc: davem@davemloft.net
      Cc: ddaney.cavm@gmail.com
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Link: http://lkml.kernel.org/r/20120222085809.GA26397@elte.huSigned-off-by: default avatarIngo Molnar <mingo@elte.hu>
      c5905afb
  34. 04 Aug, 2011 1 commit
  35. 14 Jul, 2011 1 commit
  36. 14 Jan, 2011 1 commit
  37. 24 Aug, 2010 1 commit