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    Subject[PATCH 4.14 080/159] x86/dumpstack: Add get_stack_info() support for the SYSENTER stack
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Andy Lutomirski <luto@kernel.org>

    commit 33a2f1a6c4d7c0a02d1c006fb0379cc5ca3b96bb upstream.

    get_stack_info() doesn't currently know about the SYSENTER stack, so
    unwinding will fail if we entered the kernel on the SYSENTER stack
    and haven't fully switched off. Teach get_stack_info() about the
    SYSENTER stack.

    With future patches applied that run part of the entry code on the
    SYSENTER stack and introduce an intentional BUG(), I would get:

    PANIC: double fault, error_code: 0x0
    ...
    RIP: 0010:do_error_trap+0x33/0x1c0
    ...
    Call Trace:
    Code: ...

    With this patch, I get:

    PANIC: double fault, error_code: 0x0
    ...
    Call Trace:
    <SYSENTER>
    ? async_page_fault+0x36/0x60
    ? invalid_op+0x22/0x40
    ? async_page_fault+0x36/0x60
    ? sync_regs+0x3c/0x40
    ? sync_regs+0x2e/0x40
    ? error_entry+0x6c/0xd0
    ? async_page_fault+0x36/0x60
    </SYSENTER>
    Code: ...

    which is a lot more informative.

    Signed-off-by: Andy Lutomirski <luto@kernel.org>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Reviewed-by: Borislav Petkov <bp@suse.de>
    Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Borislav Petkov <bpetkov@suse.de>
    Cc: Brian Gerst <brgerst@gmail.com>
    Cc: Dave Hansen <dave.hansen@intel.com>
    Cc: Dave Hansen <dave.hansen@linux.intel.com>
    Cc: David Laight <David.Laight@aculab.com>
    Cc: Denys Vlasenko <dvlasenk@redhat.com>
    Cc: Eduardo Valentin <eduval@amazon.com>
    Cc: Greg KH <gregkh@linuxfoundation.org>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Josh Poimboeuf <jpoimboe@redhat.com>
    Cc: Juergen Gross <jgross@suse.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Rik van Riel <riel@redhat.com>
    Cc: Will Deacon <will.deacon@arm.com>
    Cc: aliguori@amazon.com
    Cc: daniel.gruss@iaik.tugraz.at
    Cc: hughd@google.com
    Cc: keescook@google.com
    Link: https://lkml.kernel.org/r/20171204150605.392711508@linutronix.de
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    diff --git a/arch/x86/include/asm/stacktrace.h b/arch/x86/include/asm/stacktrace.h
    index 8da111b3c342..f8062bfd43a0 100644
    --- a/arch/x86/include/asm/stacktrace.h
    +++ b/arch/x86/include/asm/stacktrace.h
    @@ -16,6 +16,7 @@ enum stack_type {
    STACK_TYPE_TASK,
    STACK_TYPE_IRQ,
    STACK_TYPE_SOFTIRQ,
    + STACK_TYPE_SYSENTER,
    STACK_TYPE_EXCEPTION,
    STACK_TYPE_EXCEPTION_LAST = STACK_TYPE_EXCEPTION + N_EXCEPTION_STACKS-1,
    };
    @@ -28,6 +29,8 @@ struct stack_info {
    bool in_task_stack(unsigned long *stack, struct task_struct *task,
    struct stack_info *info);

    +bool in_sysenter_stack(unsigned long *stack, struct stack_info *info);
    +
    int get_stack_info(unsigned long *stack, struct task_struct *task,
    struct stack_info *info, unsigned long *visit_mask);

    diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
    index 0bc95be5c638..a33a1373a252 100644
    --- a/arch/x86/kernel/dumpstack.c
    +++ b/arch/x86/kernel/dumpstack.c
    @@ -43,6 +43,25 @@ bool in_task_stack(unsigned long *stack, struct task_struct *task,
    return true;
    }

    +bool in_sysenter_stack(unsigned long *stack, struct stack_info *info)
    +{
    + struct tss_struct *tss = this_cpu_ptr(&cpu_tss);
    +
    + /* Treat the canary as part of the stack for unwinding purposes. */
    + void *begin = &tss->SYSENTER_stack_canary;
    + void *end = (void *)&tss->SYSENTER_stack + sizeof(tss->SYSENTER_stack);
    +
    + if ((void *)stack < begin || (void *)stack >= end)
    + return false;
    +
    + info->type = STACK_TYPE_SYSENTER;
    + info->begin = begin;
    + info->end = end;
    + info->next_sp = NULL;
    +
    + return true;
    +}
    +
    static void printk_stack_address(unsigned long address, int reliable,
    char *log_lvl)
    {
    diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c
    index daefae83a3aa..5ff13a6b3680 100644
    --- a/arch/x86/kernel/dumpstack_32.c
    +++ b/arch/x86/kernel/dumpstack_32.c
    @@ -26,6 +26,9 @@ const char *stack_type_name(enum stack_type type)
    if (type == STACK_TYPE_SOFTIRQ)
    return "SOFTIRQ";

    + if (type == STACK_TYPE_SYSENTER)
    + return "SYSENTER";
    +
    return NULL;
    }

    @@ -93,6 +96,9 @@ int get_stack_info(unsigned long *stack, struct task_struct *task,
    if (task != current)
    goto unknown;

    + if (in_sysenter_stack(stack, info))
    + goto recursion_check;
    +
    if (in_hardirq_stack(stack, info))
    goto recursion_check;

    diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
    index 88ce2ffdb110..abc828f8c297 100644
    --- a/arch/x86/kernel/dumpstack_64.c
    +++ b/arch/x86/kernel/dumpstack_64.c
    @@ -37,6 +37,9 @@ const char *stack_type_name(enum stack_type type)
    if (type == STACK_TYPE_IRQ)
    return "IRQ";

    + if (type == STACK_TYPE_SYSENTER)
    + return "SYSENTER";
    +
    if (type >= STACK_TYPE_EXCEPTION && type <= STACK_TYPE_EXCEPTION_LAST)
    return exception_stack_names[type - STACK_TYPE_EXCEPTION];

    @@ -115,6 +118,9 @@ int get_stack_info(unsigned long *stack, struct task_struct *task,
    if (in_irq_stack(stack, info))
    goto recursion_check;

    + if (in_sysenter_stack(stack, info))
    + goto recursion_check;
    +
    goto unknown;

    recursion_check:

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