lkml.org 
[lkml]   [2017]   [Nov]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 10/24] x86/mm/kaiser: Map the entry stack variables
    Date
    From: Dave Hansen <dave.hansen@linux.intel.com>

    There are times where the kernel is entered but there is not a
    safe stack, like at SYSCALL entry. To obtain a safe stack, the
    per-CPU variables 'rsp_scratch' and 'cpu_current_top_of_stack'
    are used to save the old %rsp value and to find where the kernel
    stack should start.

    You can not directly manipulate the CR3 register. You can only
    'MOV' to it from another register, which means a register must be
    clobbered in order to do any CR3 manipulation. User-mapping
    these variables allows us to obtain a safe stack and use it for
    temporary storage *before* CR3 is switched.

    Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Cc: Andy Lutomirski <luto@kernel.org>
    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: Josh Poimboeuf <jpoimboe@redhat.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Rik van Riel <riel@redhat.com>
    Cc: daniel.gruss@iaik.tugraz.at
    Cc: hughd@google.com
    Cc: keescook@google.com
    Cc: linux-mm@kvack.org
    Cc: michael.schwarz@iaik.tugraz.at
    Cc: moritz.lipp@iaik.tugraz.at
    Cc: richard.fellner@student.tugraz.at
    Link: https://lkml.kernel.org/r/20171123003459.C0FF167A@viggo.jf.intel.com
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    ---
    arch/x86/kernel/cpu/common.c | 2 +-
    arch/x86/kernel/process_64.c | 2 +-
    2 files changed, 2 insertions(+), 2 deletions(-)

    diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
    index 7b348cc33e2d..f4f4ab8525bd 100644
    --- a/arch/x86/kernel/cpu/common.c
    +++ b/arch/x86/kernel/cpu/common.c
    @@ -1515,7 +1515,7 @@ EXPORT_PER_CPU_SYMBOL(__preempt_count);
    * the top of the kernel stack. Use an extra percpu variable to track the
    * top of the kernel stack directly.
    */
    -DEFINE_PER_CPU(unsigned long, cpu_current_top_of_stack) =
    +DEFINE_PER_CPU_USER_MAPPED(unsigned long, cpu_current_top_of_stack) =
    (unsigned long)&init_thread_union + THREAD_SIZE;
    EXPORT_PER_CPU_SYMBOL(cpu_current_top_of_stack);

    diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
    index 157f81816915..631e229ab428 100644
    --- a/arch/x86/kernel/process_64.c
    +++ b/arch/x86/kernel/process_64.c
    @@ -59,7 +59,7 @@
    #include <asm/unistd_32_ia32.h>
    #endif

    -__visible DEFINE_PER_CPU(unsigned long, rsp_scratch);
    +__visible DEFINE_PER_CPU_USER_MAPPED(unsigned long, rsp_scratch);

    /* Prints also some state that isn't saved in the pt_regs */
    void __show_regs(struct pt_regs *regs, int all)
    --
    2.14.1
    \
     
     \ /
      Last update: 2017-11-27 11:57    [W:3.435 / U:0.004 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site