diff options
Diffstat (limited to 'arch/arm64/kernel/entry.S')
| -rw-r--r-- | arch/arm64/kernel/entry.S | 70 |
1 files changed, 70 insertions, 0 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 52348869f82f..3ef6e2297fb4 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -72,6 +72,48 @@ .macro kernel_ventry label .align 7 sub sp, sp, #S_FRAME_SIZE +#ifdef CONFIG_VMAP_STACK + /* + * Test whether the SP has overflowed, without corrupting a GPR. + * Task and IRQ stacks are aligned to (1 << THREAD_SHIFT). + */ + add sp, sp, x0 // sp' = sp + x0 + sub x0, sp, x0 // x0' = sp' - x0 = (sp + x0) - x0 = sp + tbnz x0, #THREAD_SHIFT, 0f + sub x0, sp, x0 // x0'' = sp' - x0' = (sp + x0) - sp = x0 + sub sp, sp, x0 // sp'' = sp' - x0 = (sp + x0) - x0 = sp + b \label + +0: + /* + * Either we've just detected an overflow, or we've taken an exception + * while on the overflow stack. Either way, we won't return to + * userspace, and can clobber EL0 registers to free up GPRs. + */ + + /* Stash the original SP (minus S_FRAME_SIZE) in tpidr_el0. */ + msr tpidr_el0, x0 + + /* Recover the original x0 value and stash it in tpidrro_el0 */ + sub x0, sp, x0 + msr tpidrro_el0, x0 + + /* Switch to the overflow stack */ + adr_this_cpu sp, overflow_stack + OVERFLOW_STACK_SIZE, x0 + + /* + * Check whether we were already on the overflow stack. This may happen + * after panic() re-enables interrupts. + */ + mrs x0, tpidr_el0 // sp of interrupted context + sub x0, sp, x0 // delta with top of overflow stack + tst x0, #~(OVERFLOW_STACK_SIZE - 1) // within range? + b.ne __bad_stack // no? -> bad stack pointer + + /* We were already on the overflow stack. Restore sp/x0 and carry on. */ + sub sp, sp, x0 + mrs x0, tpidrro_el0 +#endif b \label .endm @@ -352,6 +394,34 @@ ENTRY(vectors) #endif END(vectors) +#ifdef CONFIG_VMAP_STACK + /* + * We detected an overflow in kernel_ventry, which switched to the + * overflow stack. Stash the exception regs, and head to our overflow + * handler. + */ +__bad_stack: + /* Restore the original x0 value */ + mrs x0, tpidrro_el0 + + /* + * Store the original GPRs to the new stack. The orginal SP (minus + * S_FRAME_SIZE) was stashed in tpidr_el0 by kernel_ventry. + */ + sub sp, sp, #S_FRAME_SIZE + kernel_entry 1 + mrs x0, tpidr_el0 + add x0, x0, #S_FRAME_SIZE + str x0, [sp, #S_SP] + + /* Stash the regs for handle_bad_stack */ + mov x0, sp + + /* Time to die */ + bl handle_bad_stack + ASM_BUG() +#endif /* CONFIG_VMAP_STACK */ + /* * Invalid mode handlers */ |