Revert "arm64: Stash shadow stack pointer in the task struct on interrupt"

This reverts commit 3f225f29c69c13ce1cbdb1d607a42efeef080056 which is
commit 59b37fe52f49955791a460752c37145f1afdcad1 upstream.

The shadow call stack for irq now is stored in current task's thread info
in irq_stack_entry. There is a possibility that we have some soft irqs
pending at the end of hard irq, and when we process softirq with the irq
enabled, irq_stack_entry will enter again and overwrite the shadow call
stack whitch stored in current task's thread info, leading to the
incorrect shadow call stack restoration for the first entry of the hard
IRQ, then the system end up with a panic.

task A                               |  task A
-------------------------------------+------------------------------------
el1_irq        //irq1 enter          |
  irq_handler  //save scs_sp1        |
    gic_handle_irq                   |
    irq_exit                         |
      __do_softirq                   |
                                     | el1_irq         //irq2 enter
                                     |   irq_handler   //save scs_sp2
                                     |                 //overwrite scs_sp1
                                     |   ...
                                     |   irq_stack_exit //restore scs_sp2
  irq_stack_exit //restore wrong     |
                 //scs_sp2           |

So revert this commit to fix it.

Fixes: 3f225f29c69c ("arm64: Stash shadow stack pointer in the task struct on interrupt")
Signed-off-by: Xiang Yang <xiangyang3@huawei.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index a94acea770c7c5e6acf21a2b265584980a803bff..020a455824bed2b8a442e02fcc9b2ba509c650a2 100644 (file)
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -431,7 +431,9 @@ SYM_CODE_END(__swpan_exit_el0)
 
        .macro  irq_stack_entry
        mov     x19, sp                 // preserve the original sp
-       scs_save tsk                    // preserve the original shadow stack
+#ifdef CONFIG_SHADOW_CALL_STACK
+       mov     x24, scs_sp             // preserve the original shadow stack
+#endif
 
        /*
         * Compare sp with the base of the task stack.
@@ -465,7 +467,9 @@ SYM_CODE_END(__swpan_exit_el0)
         */
        .macro  irq_stack_exit
        mov     sp, x19
-       scs_load_current
+#ifdef CONFIG_SHADOW_CALL_STACK
+       mov     scs_sp, x24
+#endif
        .endm
 
 /* GPRs used by entry code */