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author | James Morse <james.morse@arm.com> | 2018-01-08 15:38:12 +0000 |
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committer | Catalin Marinas <catalin.marinas@arm.com> | 2018-01-13 10:45:17 +0000 |
commit | f5df26961853d6809d704cedcaf082c57f635a64 (patch) | |
tree | d5e3d710633bfad8e761daeeffe13f3b9ef23c71 /arch/arm64/kernel/entry.S | |
parent | e1281f56f114f3a945bf9ec30698bd3caa59d322 (diff) | |
download | linux-stable-f5df26961853d6809d704cedcaf082c57f635a64.tar.gz linux-stable-f5df26961853d6809d704cedcaf082c57f635a64.tar.bz2 linux-stable-f5df26961853d6809d704cedcaf082c57f635a64.zip |
arm64: kernel: Add arch-specific SDEI entry code and CPU masking
The Software Delegated Exception Interface (SDEI) is an ARM standard
for registering callbacks from the platform firmware into the OS.
This is typically used to implement RAS notifications.
Such notifications enter the kernel at the registered entry-point
with the register values of the interrupted CPU context. Because this
is not a CPU exception, it cannot reuse the existing entry code.
(crucially we don't implicitly know which exception level we interrupted),
Add the entry point to entry.S to set us up for calling into C code. If
the event interrupted code that had interrupts masked, we always return
to that location. Otherwise we pretend this was an IRQ, and use SDEI's
complete_and_resume call to return to vbar_el1 + offset.
This allows the kernel to deliver signals to user space processes. For
KVM this triggers the world switch, a quick spin round vcpu_run, then
back into the guest, unless there are pending signals.
Add sdei_mask_local_cpu() calls to the smp_send_stop() code, this covers
the panic() code-path, which doesn't invoke cpuhotplug notifiers.
Because we can interrupt entry-from/exit-to another EL, we can't trust the
value in sp_el0 or x29, even if we interrupted the kernel, in this case
the code in entry.S will save/restore sp_el0 and use the value in
__entry_task.
When we have VMAP stacks we can interrupt the stack-overflow test, which
stirs x0 into sp, meaning we have to have our own VMAP stacks. For now
these are allocated when we probe the interface. Future patches will add
refcounting hooks to allow the arch code to allocate them lazily.
Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/kernel/entry.S')
-rw-r--r-- | arch/arm64/kernel/entry.S | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 07a7d4db8ec4..40bf5083d182 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -1153,3 +1153,104 @@ ENTRY(ret_from_fork) b ret_to_user ENDPROC(ret_from_fork) NOKPROBE(ret_from_fork) + +#ifdef CONFIG_ARM_SDE_INTERFACE + +#include <asm/sdei.h> +#include <uapi/linux/arm_sdei.h> + +/* + * Software Delegated Exception entry point. + * + * x0: Event number + * x1: struct sdei_registered_event argument from registration time. + * x2: interrupted PC + * x3: interrupted PSTATE + * + * Firmware has preserved x0->x17 for us, we must save/restore the rest to + * follow SMC-CC. We save (or retrieve) all the registers as the handler may + * want them. + */ +ENTRY(__sdei_asm_handler) + stp x2, x3, [x1, #SDEI_EVENT_INTREGS + S_PC] + stp x4, x5, [x1, #SDEI_EVENT_INTREGS + 16 * 2] + stp x6, x7, [x1, #SDEI_EVENT_INTREGS + 16 * 3] + stp x8, x9, [x1, #SDEI_EVENT_INTREGS + 16 * 4] + stp x10, x11, [x1, #SDEI_EVENT_INTREGS + 16 * 5] + stp x12, x13, [x1, #SDEI_EVENT_INTREGS + 16 * 6] + stp x14, x15, [x1, #SDEI_EVENT_INTREGS + 16 * 7] + stp x16, x17, [x1, #SDEI_EVENT_INTREGS + 16 * 8] + stp x18, x19, [x1, #SDEI_EVENT_INTREGS + 16 * 9] + stp x20, x21, [x1, #SDEI_EVENT_INTREGS + 16 * 10] + stp x22, x23, [x1, #SDEI_EVENT_INTREGS + 16 * 11] + stp x24, x25, [x1, #SDEI_EVENT_INTREGS + 16 * 12] + stp x26, x27, [x1, #SDEI_EVENT_INTREGS + 16 * 13] + stp x28, x29, [x1, #SDEI_EVENT_INTREGS + 16 * 14] + mov x4, sp + stp lr, x4, [x1, #SDEI_EVENT_INTREGS + S_LR] + + mov x19, x1 + +#ifdef CONFIG_VMAP_STACK + /* + * entry.S may have been using sp as a scratch register, find whether + * this is a normal or critical event and switch to the appropriate + * stack for this CPU. + */ + ldrb w4, [x19, #SDEI_EVENT_PRIORITY] + cbnz w4, 1f + ldr_this_cpu dst=x5, sym=sdei_stack_normal_ptr, tmp=x6 + b 2f +1: ldr_this_cpu dst=x5, sym=sdei_stack_critical_ptr, tmp=x6 +2: mov x6, #SDEI_STACK_SIZE + add x5, x5, x6 + mov sp, x5 +#endif + + /* + * We may have interrupted userspace, or a guest, or exit-from or + * return-to either of these. We can't trust sp_el0, restore it. + */ + mrs x28, sp_el0 + ldr_this_cpu dst=x0, sym=__entry_task, tmp=x1 + msr sp_el0, x0 + + /* If we interrupted the kernel point to the previous stack/frame. */ + and x0, x3, #0xc + mrs x1, CurrentEL + cmp x0, x1 + csel x29, x29, xzr, eq // fp, or zero + csel x4, x2, xzr, eq // elr, or zero + + stp x29, x4, [sp, #-16]! + mov x29, sp + + add x0, x19, #SDEI_EVENT_INTREGS + mov x1, x19 + bl __sdei_handler + + msr sp_el0, x28 + /* restore regs >x17 that we clobbered */ + ldp x28, x29, [x19, #SDEI_EVENT_INTREGS + 16 * 14] + ldp lr, x4, [x19, #SDEI_EVENT_INTREGS + S_LR] + mov sp, x4 + ldp x18, x19, [x19, #SDEI_EVENT_INTREGS + 16 * 9] + + mov x1, x0 // address to complete_and_resume + /* x0 = (x0 <= 1) ? EVENT_COMPLETE:EVENT_COMPLETE_AND_RESUME */ + cmp x0, #1 + mov_q x2, SDEI_1_0_FN_SDEI_EVENT_COMPLETE + mov_q x3, SDEI_1_0_FN_SDEI_EVENT_COMPLETE_AND_RESUME + csel x0, x2, x3, ls + + /* On success, this call never returns... */ + ldr_l x2, sdei_exit_mode + cmp x2, #SDEI_EXIT_SMC + b.ne 1f + smc #0 + b . +1: hvc #0 + b . +ENDPROC(__sdei_asm_handler) +NOKPROBE(__sdei_asm_handler) +#endif /* CONFIG_ARM_SDE_INTERFACE */ |