1. 28 Nov, 2018 1 commit
    • Thomas Gleixner's avatar
      x86/speculation: Add prctl() control for indirect branch speculation · 9137bb27
      Thomas Gleixner authored
      Add the PR_SPEC_INDIRECT_BRANCH option for the PR_GET_SPECULATION_CTRL and
      PR_SET_SPECULATION_CTRL prctls to allow fine grained per task control of
      indirect branch speculation via STIBP and IBPB.
      
      Invocations:
       Check indirect branch speculation status with
       - prctl(PR_GET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, 0, 0, 0);
      
       Enable indirect branch speculation with
       - prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_ENABLE, 0, 0);
      
       Disable indirect branch speculation with
       - prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_DISABLE, 0, 0);
      
       Force disable indirect branch speculation with
       - prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_FORCE_DISABLE, 0, 0);
      
      See Documentation/userspace-api/spec_ctrl.rst.
      Signed-off-by: default avatarTim Chen <tim.c.chen@linux.intel.com>
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: default avatarIngo Molnar <mingo@kernel.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Andy Lutomirski <luto@kernel.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Jiri Kosina <jkosina@suse.cz>
      Cc: Tom Lendacky <thomas.lendacky@amd.com>
      Cc: Josh Poimboeuf <jpoimboe@redhat.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: David Woodhouse <dwmw@amazon.co.uk>
      Cc: Andi Kleen <ak@linux.intel.com>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Casey Schaufler <casey.schaufler@intel.com>
      Cc: Asit Mallick <asit.k.mallick@intel.com>
      Cc: Arjan van de Ven <arjan@linux.intel.com>
      Cc: Jon Masters <jcm@redhat.com>
      Cc: Waiman Long <longman9394@gmail.com>
      Cc: Greg KH <gregkh@linuxfoundation.org>
      Cc: Dave Stewart <david.c.stewart@intel.com>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: stable@vger.kernel.org
      Link: https://lkml.kernel.org/r/20181125185005.866780996@linutronix.de
      9137bb27
  2. 09 May, 2018 1 commit
  3. 04 May, 2018 1 commit
    • Thomas Gleixner's avatar
      prctl: Add force disable speculation · 356e4bff
      Thomas Gleixner authored
      For certain use cases it is desired to enforce mitigations so they cannot
      be undone afterwards. That's important for loader stubs which want to
      prevent a child from disabling the mitigation again. Will also be used for
      seccomp(). The extra state preserving of the prctl state for SSB is a
      preparatory step for EBPF dymanic speculation control.
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      356e4bff
  4. 03 May, 2018 1 commit
    • Thomas Gleixner's avatar
      prctl: Add speculation control prctls · b617cfc8
      Thomas Gleixner authored
      Add two new prctls to control aspects of speculation related vulnerabilites
      and their mitigations to provide finer grained control over performance
      impacting mitigations.
      
      PR_GET_SPECULATION_CTRL returns the state of the speculation misfeature
      which is selected with arg2 of prctl(2). The return value uses bit 0-2 with
      the following meaning:
      
      Bit  Define           Description
      0    PR_SPEC_PRCTL    Mitigation can be controlled per task by
                            PR_SET_SPECULATION_CTRL
      1    PR_SPEC_ENABLE   The speculation feature is enabled, mitigation is
                            disabled
      2    PR_SPEC_DISABLE  The speculation feature is disabled, mitigation is
                            enabled
      
      If all bits are 0 the CPU is not affected by the speculation misfeature.
      
      If PR_SPEC_PRCTL is set, then the per task control of the mitigation is
      available. If not set, prctl(PR_SET_SPECULATION_CTRL) for the speculation
      misfeature will fail.
      
      PR_SET_SPECULATION_CTRL allows to control the speculation misfeature, which
      is selected by arg2 of prctl(2) per task. arg3 is used to hand in the
      control value, i.e. either PR_SPEC_ENABLE or PR_SPEC_DISABLE.
      
      The common return values are:
      
      EINVAL  prctl is not implemented by the architecture or the unused prctl()
              arguments are not 0
      ENODEV  arg2 is selecting a not supported speculation misfeature
      
      PR_SET_SPECULATION_CTRL has these additional return values:
      
      ERANGE  arg3 is incorrect, i.e. it's not either PR_SPEC_ENABLE or PR_SPEC_DISABLE
      ENXIO   prctl control of the selected speculation misfeature is disabled
      
      The first supported controlable speculation misfeature is
      PR_SPEC_STORE_BYPASS. Add the define so this can be shared between
      architectures.
      
      Based on an initial patch from Tim Chen and mostly rewritten.
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: default avatarIngo Molnar <mingo@kernel.org>
      Reviewed-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
      b617cfc8