arm64: irq: allow FIQs to be handled

On contemporary platforms we don't use FIQ, and treat any stray FIQ as a
fatal event. However, some platforms have an interrupt controller wired
to FIQ, and need to handle FIQ as part of regular operation.

So that we can support both cases dynamically, this patch updates the
FIQ exception handling code to operate the same way as the IRQ handling
code, with its own handle_arch_fiq handler. Where a root FIQ handler is
not registered, an unexpected FIQ exception will trigger the default FIQ
handler, which will panic() as today. Where a root FIQ handler is
registered, handling of the FIQ is deferred to that handler.

As el0_fiq_invalid_compat is supplanted by el0_fiq, the former is
removed. For !CONFIG_COMPAT builds we never expect to take an exception
from AArch32 EL0, so we keep the common el0_fiq_invalid handler.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Hector Martin <marcan@marcan.st>
Cc: James Morse <james.morse@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210315115629.57191-7-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/include/asm/irq.h b/arch/arm64/include/asm/irq.h
index 8391c6f6f7463ccd84ccc2b4ff069a21d631f72d..fac08e18bcd512eec9bbafe7fa79a38ccea1d48c 100644 (file)
--- a/arch/arm64/include/asm/irq.h
+++ b/arch/arm64/include/asm/irq.h
@@ -10,6 +10,7 @@ struct pt_regs;
 
 int set_handle_irq(void (*handle_irq)(struct pt_regs *));
 #define set_handle_irq set_handle_irq
+int set_handle_fiq(void (*handle_fiq)(struct pt_regs *));
 
 static inline int nr_legacy_irqs(void)
 {

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index ce8d4dc416fbd90ba5d87be09c838a593edf6a37..a86f50de2c7b891fb0a6ad1d0368e516c22c4654 100644 (file)
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -588,18 +588,18 @@ SYM_CODE_START(vectors)
 
        kernel_ventry   1, sync                         // Synchronous EL1h
        kernel_ventry   1, irq                          // IRQ EL1h
-       kernel_ventry   1, fiq_invalid                  // FIQ EL1h
+       kernel_ventry   1, fiq                          // FIQ EL1h
        kernel_ventry   1, error                        // Error EL1h
 
        kernel_ventry   0, sync                         // Synchronous 64-bit EL0
        kernel_ventry   0, irq                          // IRQ 64-bit EL0
-       kernel_ventry   0, fiq_invalid                  // FIQ 64-bit EL0
+       kernel_ventry   0, fiq                          // FIQ 64-bit EL0
        kernel_ventry   0, error                        // Error 64-bit EL0
 
 #ifdef CONFIG_COMPAT
        kernel_ventry   0, sync_compat, 32              // Synchronous 32-bit EL0
        kernel_ventry   0, irq_compat, 32               // IRQ 32-bit EL0
-       kernel_ventry   0, fiq_invalid_compat, 32       // FIQ 32-bit EL0
+       kernel_ventry   0, fiq_compat, 32               // FIQ 32-bit EL0
        kernel_ventry   0, error_compat, 32             // Error 32-bit EL0
 #else
        kernel_ventry   0, sync_invalid, 32             // Synchronous 32-bit EL0
@@ -665,12 +665,6 @@ SYM_CODE_START_LOCAL(el0_error_invalid)
        inv_entry 0, BAD_ERROR
 SYM_CODE_END(el0_error_invalid)
 
-#ifdef CONFIG_COMPAT
-SYM_CODE_START_LOCAL(el0_fiq_invalid_compat)
-       inv_entry 0, BAD_FIQ, 32
-SYM_CODE_END(el0_fiq_invalid_compat)
-#endif
-
 SYM_CODE_START_LOCAL(el1_sync_invalid)
        inv_entry 1, BAD_SYNC
 SYM_CODE_END(el1_sync_invalid)
@@ -705,6 +699,12 @@ SYM_CODE_START_LOCAL_NOALIGN(el1_irq)
        kernel_exit 1
 SYM_CODE_END(el1_irq)
 
+SYM_CODE_START_LOCAL_NOALIGN(el1_fiq)
+       kernel_entry 1
+       el1_interrupt_handler handle_arch_fiq
+       kernel_exit 1
+SYM_CODE_END(el1_fiq)
+
 /*
  * EL0 mode handlers.
  */
@@ -731,6 +731,11 @@ SYM_CODE_START_LOCAL_NOALIGN(el0_irq_compat)
        b       el0_irq_naked
 SYM_CODE_END(el0_irq_compat)
 
+SYM_CODE_START_LOCAL_NOALIGN(el0_fiq_compat)
+       kernel_entry 0, 32
+       b       el0_fiq_naked
+SYM_CODE_END(el0_fiq_compat)
+
 SYM_CODE_START_LOCAL_NOALIGN(el0_error_compat)
        kernel_entry 0, 32
        b       el0_error_naked
@@ -745,6 +750,13 @@ el0_irq_naked:
        b       ret_to_user
 SYM_CODE_END(el0_irq)
 
+SYM_CODE_START_LOCAL_NOALIGN(el0_fiq)
+       kernel_entry 0
+el0_fiq_naked:
+       el0_interrupt_handler handle_arch_fiq
+       b       ret_to_user
+SYM_CODE_END(el0_fiq)
+
 SYM_CODE_START_LOCAL(el1_error)
        kernel_entry 1
        mrs     x1, esr_el1

diff --git a/arch/arm64/kernel/irq.c b/arch/arm64/kernel/irq.c
index 2fe0b535de30c2acbadbd02550f432599f8f0e9d..bda49430c9ea3c9beb0669689e760bc6bd26c3ce 100644 (file)
--- a/arch/arm64/kernel/irq.c
+++ b/arch/arm64/kernel/irq.c
@@ -76,7 +76,13 @@ static void default_handle_irq(struct pt_regs *regs)
        panic("IRQ taken without a root IRQ handler\n");
 }
 
+static void default_handle_fiq(struct pt_regs *regs)
+{
+       panic("FIQ taken without a root FIQ handler\n");
+}
+
 void (*handle_arch_irq)(struct pt_regs *) __ro_after_init = default_handle_irq;
+void (*handle_arch_fiq)(struct pt_regs *) __ro_after_init = default_handle_fiq;
 
 int __init set_handle_irq(void (*handle_irq)(struct pt_regs *))
 {
@@ -88,6 +94,16 @@ int __init set_handle_irq(void (*handle_irq)(struct pt_regs *))
        return 0;
 }
 
+int __init set_handle_fiq(void (*handle_fiq)(struct pt_regs *))
+{
+       if (handle_arch_fiq != default_handle_fiq)
+               return -EBUSY;
+
+       handle_arch_fiq = handle_fiq;
+       pr_info("Root FIQ handler: %ps\n", handle_fiq);
+       return 0;
+}
+
 void __init init_IRQ(void)
 {
        init_irq_stacks();