Re: [PATCH v5 16/38] kmsan: x86/asm: softirq: add KMSAN IRQ entry hooks

[Andrey Konovalov <andreyknvl@google.com>]

On Wed, Mar 25, 2020 at 5:13 PM <glider@google.com> wrote:
>
> Add assembly helpers to entry_64.S that invoke hooks from kmsan_entry.c and
> notify KMSAN about interrupts.
> Also call these hooks from kernel/softirq.c
> This is needed to switch between several KMSAN contexts holding function
> parameter metadata.
>
> Signed-off-by: Alexander Potapenko <glider@google.com>
> To: Alexander Potapenko <glider@google.com>
> Cc: Jens Axboe <axboe@kernel.dk>
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Vegard Nossum <vegard.nossum@oracle.com>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Cc: Marco Elver <elver@google.com>
> Cc: Andrey Konovalov <andreyknvl@google.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: linux-mm@kvack.org

Acked-by: Andrey Konovalov <andreyknvl@google.com>

> ---
>
> v4:
>  - moved softirq changes to this patch
>
> Change-Id: I3037d51672fe69d09e588b27adb2d9fdc6ad3a7d
> ---
>  arch/x86/entry/entry_64.S | 16 ++++++++++++++++
>  kernel/softirq.c          |  5 +++++
>  2 files changed, 21 insertions(+)
>
> diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
> index 0e9504fabe526..03f5a32b0af4d 100644
> --- a/arch/x86/entry/entry_64.S
> +++ b/arch/x86/entry/entry_64.S
> @@ -35,6 +35,7 @@
>  #include <asm/asm.h>
>  #include <asm/smap.h>
>  #include <asm/pgtable_types.h>
> +#include <asm/kmsan.h>
>  #include <asm/export.h>
>  #include <asm/frame.h>
>  #include <asm/nospec-branch.h>
> @@ -575,6 +576,7 @@ SYM_CODE_START(interrupt_entry)
>
>  1:
>         ENTER_IRQ_STACK old_rsp=%rdi save_ret=1
> +       KMSAN_INTERRUPT_ENTER
>         /* We entered an interrupt context - irqs are off: */
>         TRACE_IRQS_OFF
>
> @@ -604,12 +606,14 @@ SYM_CODE_START_LOCAL(common_interrupt)
>         addq    $-0x80, (%rsp)                  /* Adjust vector to [-256, -1] range */
>         call    interrupt_entry
>         UNWIND_HINT_REGS indirect=1
> +       KMSAN_UNPOISON_PT_REGS
>         call    do_IRQ  /* rdi points to pt_regs */
>         /* 0(%rsp): old RSP */
>  ret_from_intr:
>         DISABLE_INTERRUPTS(CLBR_ANY)
>         TRACE_IRQS_OFF
>
> +       KMSAN_INTERRUPT_EXIT
>         LEAVE_IRQ_STACK
>
>         testb   $3, CS(%rsp)
> @@ -801,6 +805,7 @@ SYM_CODE_START(\sym)
>  .Lcommon_\sym:
>         call    interrupt_entry
>         UNWIND_HINT_REGS indirect=1
> +       KMSAN_UNPOISON_PT_REGS
>         call    \do_sym /* rdi points to pt_regs */
>         jmp     ret_from_intr
>  SYM_CODE_END(\sym)
> @@ -908,15 +913,18 @@ apicinterrupt IRQ_WORK_VECTOR                     irq_work_interrupt              smp_irq_work_interrupt
>
>         .if \shift_ist != -1
>         subq    $\ist_offset, CPU_TSS_IST(\shift_ist)
> +       KMSAN_IST_ENTER(\shift_ist)
>         .endif
>
>         .if \read_cr2
>         movq    %r12, %rdx                      /* Move CR2 into 3rd argument */
>         .endif
>
> +       KMSAN_UNPOISON_PT_REGS
>         call    \do_sym
>
>         .if \shift_ist != -1
> +       KMSAN_IST_EXIT(\shift_ist)
>         addq    $\ist_offset, CPU_TSS_IST(\shift_ist)
>         .endif
>
> @@ -1079,7 +1087,9 @@ SYM_FUNC_START(do_softirq_own_stack)
>         pushq   %rbp
>         mov     %rsp, %rbp
>         ENTER_IRQ_STACK regs=0 old_rsp=%r11
> +       KMSAN_SOFTIRQ_ENTER
>         call    __do_softirq
> +       KMSAN_SOFTIRQ_EXIT
>         LEAVE_IRQ_STACK regs=0
>         leaveq
>         ret
> @@ -1466,9 +1476,12 @@ SYM_CODE_START(nmi)
>          * done with the NMI stack.
>          */
>
> +       KMSAN_NMI_ENTER
>         movq    %rsp, %rdi
>         movq    $-1, %rsi
> +       KMSAN_UNPOISON_PT_REGS
>         call    do_nmi
> +       KMSAN_NMI_EXIT
>
>         /*
>          * Return back to user mode.  We must *not* do the normal exit
> @@ -1678,10 +1691,13 @@ end_repeat_nmi:
>         call    paranoid_entry
>         UNWIND_HINT_REGS
>
> +       KMSAN_NMI_ENTER
>         /* paranoidentry do_nmi, 0; without TRACE_IRQS_OFF */
>         movq    %rsp, %rdi
>         movq    $-1, %rsi
> +       KMSAN_UNPOISON_PT_REGS
>         call    do_nmi
> +       KMSAN_NMI_EXIT
>
>         /* Always restore stashed CR3 value (see paranoid_entry) */
>         RESTORE_CR3 scratch_reg=%r15 save_reg=%r14
> diff --git a/kernel/softirq.c b/kernel/softirq.c
> index 0427a86743a46..98c5f4062cbfe 100644
> --- a/kernel/softirq.c
> +++ b/kernel/softirq.c
> @@ -11,6 +11,7 @@
>
>  #include <linux/export.h>
>  #include <linux/kernel_stat.h>
> +#include <linux/kmsan.h>
>  #include <linux/interrupt.h>
>  #include <linux/init.h>
>  #include <linux/mm.h>
> @@ -370,7 +371,9 @@ static inline void invoke_softirq(void)
>                  * it is the irq stack, because it should be near empty
>                  * at this stage.
>                  */
> +               kmsan_context_enter();
>                 __do_softirq();
> +               kmsan_context_exit();
>  #else
>                 /*
>                  * Otherwise, irq_exit() is called on the task stack that can
> @@ -600,7 +603,9 @@ static void run_ksoftirqd(unsigned int cpu)
>                  * We can safely run softirq on inline stack, as we are not deep
>                  * in the task stack here.
>                  */
> +               kmsan_context_enter();
>                 __do_softirq();
> +               kmsan_context_exit();
>                 local_irq_enable();
>                 cond_resched();
>                 return;
> --
> 2.25.1.696.g5e7596f4ac-goog
>