runtime_exceptions.S

/*
 * Copyright (c) 2013-2016, ARM Limited and Contributors. All rights reserved.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

#include <arch.h>
#include <asm_macros.S>
#include <context.h>
#include <cpu_data.h>
#include <interrupt_mgmt.h>
#include <platform_def.h>
#include <runtime_svc.h>

	.globl	runtime_exceptions

	/* ---------------------------------------------------------------------
	 * This macro handles Synchronous exceptions.
	 * Only SMC exceptions are supported.
	 * ---------------------------------------------------------------------
	 */
	.macro	handle_sync_exception
	/* Enable the SError interrupt */
	msr	daifclr, #DAIF_ABT_BIT

	str	x30, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_LR]

#if ENABLE_RUNTIME_INSTRUMENTATION
	/*
	 * Read the timestamp value and store it in per-cpu data. The value
	 * will be extracted from per-cpu data by the C level SMC handler and
	 * saved to the PMF timestamp region.
	 */
	mrs	x30, cntpct_el0
	str	x29, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X29]
	mrs	x29, tpidr_el3
	str	x30, [x29, #CPU_DATA_PMF_TS0_OFFSET]
	ldr	x29, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X29]
#endif

	mrs	x30, esr_el3
	ubfx	x30, x30, #ESR_EC_SHIFT, #ESR_EC_LENGTH

	/* Handle SMC exceptions separately from other synchronous exceptions */
	cmp	x30, #EC_AARCH32_SMC
	b.eq	smc_handler32

	cmp	x30, #EC_AARCH64_SMC
	b.eq	smc_handler64

	/* Other kinds of synchronous exceptions are not handled */
	ldr	x30, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_LR]
	b	report_unhandled_exception
	.endm


	/* ---------------------------------------------------------------------
	 * This macro handles FIQ or IRQ interrupts i.e. EL3, S-EL1 and NS
	 * interrupts.
	 * ---------------------------------------------------------------------
	 */
	.macro	handle_interrupt_exception label
	/* Enable the SError interrupt */
	msr	daifclr, #DAIF_ABT_BIT

	str	x30, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_LR]
	bl	save_gp_registers

	/* Save the EL3 system registers needed to return from this exception */
	mrs	x0, spsr_el3
	mrs	x1, elr_el3
	stp	x0, x1, [sp, #CTX_EL3STATE_OFFSET + CTX_SPSR_EL3]

	/* Switch to the runtime stack i.e. SP_EL0 */
	ldr	x2, [sp, #CTX_EL3STATE_OFFSET + CTX_RUNTIME_SP]
	mov	x20, sp
	msr	spsel, #0
	mov	sp, x2

	/*
	 * Find out whether this is a valid interrupt type.
	 * If the interrupt controller reports a spurious interrupt then return
	 * to where we came from.
	 */
	bl	plat_ic_get_pending_interrupt_type
	cmp	x0, #INTR_TYPE_INVAL
	b.eq	interrupt_exit_\label

	/*
	 * Get the registered handler for this interrupt type.
	 * A NULL return value could be 'cause of the following conditions:
	 *
	 * a. An interrupt of a type was routed correctly but a handler for its
	 *    type was not registered.
	 *
	 * b. An interrupt of a type was not routed correctly so a handler for
	 *    its type was not registered.
	 *
	 * c. An interrupt of a type was routed correctly to EL3, but was
	 *    deasserted before its pending state could be read. Another
	 *    interrupt of a different type pended at the same time and its
	 *    type was reported as pending instead. However, a handler for this
	 *    type was not registered.
	 *
	 * a. and b. can only happen due to a programming error. The
	 * occurrence of c. could be beyond the control of Trusted Firmware.
	 * It makes sense to return from this exception instead of reporting an
	 * error.
	 */
	bl	get_interrupt_type_handler
	cbz	x0, interrupt_exit_\label
	mov	x21, x0

	mov	x0, #INTR_ID_UNAVAILABLE

	/* Set the current security state in the 'flags' parameter */
	mrs	x2, scr_el3
	ubfx	x1, x2, #0, #1

	/* Restore the reference to the 'handle' i.e. SP_EL3 */
	mov	x2, x20

	/* x3 will point to a cookie (not used now) */
	mov	x3, xzr

	/* Call the interrupt type handler */
	blr	x21

interrupt_exit_\label:
	/* Return from exception, possibly in a different security state */
	b	el3_exit

	.endm


	.macro save_x18_to_x29_sp_el0
	stp	x18, x19, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X18]
	stp	x20, x21, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X20]
	stp	x22, x23, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X22]
	stp	x24, x25, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X24]
	stp	x26, x27, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X26]
	stp	x28, x29, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X28]
	mrs	x18, sp_el0
	str	x18, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_SP_EL0]
	.endm


vector_base runtime_exceptions

	/* ---------------------------------------------------------------------
	 * Current EL with SP_EL0 : 0x0 - 0x200
	 * ---------------------------------------------------------------------
	 */
vector_entry sync_exception_sp_el0
	/* We don't expect any synchronous exceptions from EL3 */
	b	report_unhandled_exception
	check_vector_size sync_exception_sp_el0

vector_entry irq_sp_el0
	/*
	 * EL3 code is non-reentrant. Any asynchronous exception is a serious
	 * error. Loop infinitely.
	 */
	b	report_unhandled_interrupt
	check_vector_size irq_sp_el0


vector_entry fiq_sp_el0
	b	report_unhandled_interrupt
	check_vector_size fiq_sp_el0


vector_entry serror_sp_el0
	b	report_unhandled_exception
	check_vector_size serror_sp_el0

	/* ---------------------------------------------------------------------
	 * Current EL with SP_ELx: 0x200 - 0x400
	 * ---------------------------------------------------------------------
	 */
vector_entry sync_exception_sp_elx
	/*
	 * This exception will trigger if anything went wrong during a previous
	 * exception entry or exit or while handling an earlier unexpected
	 * synchronous exception. There is a high probability that SP_EL3 is
	 * corrupted.
	 */
	b	report_unhandled_exception
	check_vector_size sync_exception_sp_elx

vector_entry irq_sp_elx
	b	report_unhandled_interrupt
	check_vector_size irq_sp_elx

vector_entry fiq_sp_elx
	b	report_unhandled_interrupt
	check_vector_size fiq_sp_elx

vector_entry serror_sp_elx
	b	report_unhandled_exception
	check_vector_size serror_sp_elx

	/* ---------------------------------------------------------------------
	 * Lower EL using AArch64 : 0x400 - 0x600
	 * ---------------------------------------------------------------------
	 */
vector_entry sync_exception_aarch64
	/*
	 * This exception vector will be the entry point for SMCs and traps
	 * that are unhandled at lower ELs most commonly. SP_EL3 should point
	 * to a valid cpu context where the general purpose and system register
	 * state can be saved.
	 */
	handle_sync_exception
	check_vector_size sync_exception_aarch64

vector_entry irq_aarch64
	handle_interrupt_exception irq_aarch64
	check_vector_size irq_aarch64

vector_entry fiq_aarch64
	handle_interrupt_exception fiq_aarch64
	check_vector_size fiq_aarch64

vector_entry serror_aarch64
	/*
	 * SError exceptions from lower ELs are not currently supported.
	 * Report their occurrence.
	 */
	b	report_unhandled_exception
	check_vector_size serror_aarch64

	/* ---------------------------------------------------------------------
	 * Lower EL using AArch32 : 0x600 - 0x800
	 * ---------------------------------------------------------------------
	 */
vector_entry sync_exception_aarch32
	/*
	 * This exception vector will be the entry point for SMCs and traps
	 * that are unhandled at lower ELs most commonly. SP_EL3 should point
	 * to a valid cpu context where the general purpose and system register
	 * state can be saved.
	 */
	handle_sync_exception
	check_vector_size sync_exception_aarch32

vector_entry irq_aarch32
	handle_interrupt_exception irq_aarch32
	check_vector_size irq_aarch32

vector_entry fiq_aarch32
	handle_interrupt_exception fiq_aarch32
	check_vector_size fiq_aarch32

vector_entry serror_aarch32
	/*
	 * SError exceptions from lower ELs are not currently supported.
	 * Report their occurrence.
	 */
	b	report_unhandled_exception
	check_vector_size serror_aarch32


	/* ---------------------------------------------------------------------
	 * The following code handles secure monitor calls.
	 * Depending upon the execution state from where the SMC has been
	 * invoked, it frees some general purpose registers to perform the
	 * remaining tasks. They involve finding the runtime service handler
	 * that is the target of the SMC & switching to runtime stacks (SP_EL0)
	 * before calling the handler.
	 *
	 * Note that x30 has been explicitly saved and can be used here
	 * ---------------------------------------------------------------------
	 */
func smc_handler
smc_handler32:
	/* Check whether aarch32 issued an SMC64 */
	tbnz	x0, #FUNCID_CC_SHIFT, smc_prohibited

	/*
	 * Since we're are coming from aarch32, x8-x18 need to be saved as per
	 * SMC32 calling convention. If a lower EL in aarch64 is making an
	 * SMC32 call then it must have saved x8-x17 already therein.
	 */
	stp	x8, x9, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X8]
	stp	x10, x11, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X10]
	stp	x12, x13, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X12]
	stp	x14, x15, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X14]
	stp	x16, x17, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X16]

	/* x4-x7, x18, sp_el0 are saved below */

smc_handler64:
	/*
	 * Populate the parameters for the SMC handler.
	 * We already have x0-x4 in place. x5 will point to a cookie (not used
	 * now). x6 will point to the context structure (SP_EL3) and x7 will
	 * contain flags we need to pass to the handler Hence save x5-x7.
	 *
	 * Note: x4 only needs to be preserved for AArch32 callers but we do it
	 *       for AArch64 callers as well for convenience
	 */
	stp	x4, x5, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X4]
	stp	x6, x7, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X6]

	/* Save rest of the gpregs and sp_el0*/
	save_x18_to_x29_sp_el0

	mov	x5, xzr
	mov	x6, sp

	/* Get the unique owning entity number */
	ubfx	x16, x0, #FUNCID_OEN_SHIFT, #FUNCID_OEN_WIDTH
	ubfx	x15, x0, #FUNCID_TYPE_SHIFT, #FUNCID_TYPE_WIDTH
	orr	x16, x16, x15, lsl #FUNCID_OEN_WIDTH

	adr	x11, (__RT_SVC_DESCS_START__ + RT_SVC_DESC_HANDLE)

	/* Load descriptor index from array of indices */
	adr	x14, rt_svc_descs_indices
	ldrb	w15, [x14, x16]

	/*
	 * Restore the saved C runtime stack value which will become the new
	 * SP_EL0 i.e. EL3 runtime stack. It was saved in the 'cpu_context'
	 * structure prior to the last ERET from EL3.
	 */
	ldr	x12, [x6, #CTX_EL3STATE_OFFSET + CTX_RUNTIME_SP]

	/*
	 * Any index greater than 127 is invalid. Check bit 7 for
	 * a valid index
	 */
	tbnz	w15, 7, smc_unknown

	/* Switch to SP_EL0 */
	msr	spsel, #0

	/*
	 * Get the descriptor using the index
	 * x11 = (base + off), x15 = index
	 *
	 * handler = (base + off) + (index << log2(size))
	 */
	lsl	w10, w15, #RT_SVC_SIZE_LOG2
	ldr	x15, [x11, w10, uxtw]

	/*
	 * Save the SPSR_EL3, ELR_EL3, & SCR_EL3 in case there is a world
	 * switch during SMC handling.
	 * TODO: Revisit if all system registers can be saved later.
	 */
	mrs	x16, spsr_el3
	mrs	x17, elr_el3
	mrs	x18, scr_el3
	stp	x16, x17, [x6, #CTX_EL3STATE_OFFSET + CTX_SPSR_EL3]
	str	x18, [x6, #CTX_EL3STATE_OFFSET + CTX_SCR_EL3]

	/* Copy SCR_EL3.NS bit to the flag to indicate caller's security */
	bfi	x7, x18, #0, #1

	mov	sp, x12

	/*
	 * Call the Secure Monitor Call handler and then drop directly into
	 * el3_exit() which will program any remaining architectural state
	 * prior to issuing the ERET to the desired lower EL.
	 */
#if DEBUG
	cbz	x15, rt_svc_fw_critical_error
#endif
	blr	x15

	b	el3_exit

smc_unknown:
	/*
	 * Here we restore x4-x18 regardless of where we came from. AArch32
	 * callers will find the registers contents unchanged, but AArch64
	 * callers will find the registers modified (with stale earlier NS
	 * content). Either way, we aren't leaking any secure information
	 * through them.
	 */
	mov	w0, #SMC_UNK
	b	restore_gp_registers_callee_eret

smc_prohibited:
	ldr	x30, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_LR]
	mov	w0, #SMC_UNK
	eret

rt_svc_fw_critical_error:
	/* Switch to SP_ELx */
	msr	spsel, #1
	no_ret	report_unhandled_exception
endfunc smc_handler