[ATF]-ARM级别/异常/状态切回时候的寄存器保存与恢复

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1、save/restore函数的定义

(1)、el1_sysregs_context_save //保存系统寄存器
/* -----------------------------------------------------
 * The following function strictly follows the AArch64
 * PCS to use x9-x17 (temporary caller-saved registers)
 * to save EL1 system register context. It assumes that
 * 'x0' is pointing to a 'el1_sys_regs' structure where
 * the register context will be saved.
 * -----------------------------------------------------
 */
func el1_sysregs_context_save

	mrs	x9, spsr_el1
	mrs	x10, elr_el1
	stp	x9, x10, [x0, #CTX_SPSR_EL1]

	mrs	x11, spsr_abt
	mrs	x12, spsr_und
	stp	x11, x12, [x0, #CTX_SPSR_ABT]

	mrs	x13, spsr_irq
	mrs	x14, spsr_fiq
	stp	x13, x14, [x0, #CTX_SPSR_IRQ]

	mrs	x15, sctlr_el1
	mrs	x16, actlr_el1
	stp	x15, x16, [x0, #CTX_SCTLR_EL1]

	mrs	x17, cpacr_el1
	mrs	x9, csselr_el1
	stp	x17, x9, [x0, #CTX_CPACR_EL1]

	mrs	x10, sp_el1
	mrs	x11, esr_el1
	stp	x10, x11, [x0, #CTX_SP_EL1]

	mrs	x12, ttbr0_el1
	mrs	x13, ttbr1_el1
	stp	x12, x13, [x0, #CTX_TTBR0_EL1]

	mrs	x14, mair_el1
	mrs	x15, amair_el1
	stp	x14, x15, [x0, #CTX_MAIR_EL1]

	mrs	x16, tcr_el1
	mrs	x17, tpidr_el1
	stp	x16, x17, [x0, #CTX_TCR_EL1]

	mrs	x9, tpidr_el0
	mrs	x10, tpidrro_el0
	stp	x9, x10, [x0, #CTX_TPIDR_EL0]
#if !STPU
	mrs	x11, dacr32_el2
	mrs	x12, ifsr32_el2
	stp	x11, x12, [x0, #CTX_DACR32_EL2]
#endif
	mrs	x13, par_el1
	mrs	x14, far_el1
	stp	x13, x14, [x0, #CTX_PAR_EL1]

	mrs	x15, afsr0_el1
	mrs	x16, afsr1_el1
	stp	x15, x16, [x0, #CTX_AFSR0_EL1]

	mrs	x17, contextidr_el1
	mrs	x9, vbar_el1
	stp	x17, x9, [x0, #CTX_CONTEXTIDR_EL1]

	/* Save NS timer registers if the build has instructed so */
#if NS_TIMER_SWITCH
	mrs	x10, cntp_ctl_el0
	mrs	x11, cntp_cval_el0
	stp	x10, x11, [x0, #CTX_CNTP_CTL_EL0]

	mrs	x12, cntv_ctl_el0
	mrs	x13, cntv_cval_el0
	stp	x12, x13, [x0, #CTX_CNTV_CTL_EL0]

	mrs	x14, cntkctl_el1
	str	x14, [x0, #CTX_CNTKCTL_EL1]
#endif

#if !STPU
	mrs	x15, fpexc32_el2
	str	x15, [x0, #CTX_FP_FPEXC32_EL2]
#endif
	ret
endfunc el1_sysregs_context_save
(2)、el1_sysregs_context_restore //恢复系统寄存器
/* -----------------------------------------------------
 * The following function strictly follows the AArch64
 * PCS to use x9-x17 (temporary caller-saved registers)
 * to restore EL1 system register context.  It assumes
 * that 'x0' is pointing to a 'el1_sys_regs' structure
 * from where the register context will be restored
 * -----------------------------------------------------
 */
func el1_sysregs_context_restore

	ldp	x9, x10, [x0, #CTX_SPSR_EL1]
	msr	spsr_el1, x9
	msr	elr_el1, x10

	ldp	x11, x12, [x0, #CTX_SPSR_ABT]
	msr	spsr_abt, x11
	msr	spsr_und, x12

	ldp	x13, x14, [x0, #CTX_SPSR_IRQ]
	msr	spsr_irq, x13
	msr	spsr_fiq, x14

	ldp	x15, x16, [x0, #CTX_SCTLR_EL1]
	msr	sctlr_el1, x15
	msr	actlr_el1, x16

	ldp	x17, x9, [x0, #CTX_CPACR_EL1]
	msr	cpacr_el1, x17
	msr	csselr_el1, x9

	ldp	x10, x11, [x0, #CTX_SP_EL1]
	msr	sp_el1, x10
	msr	esr_el1, x11

	ldp	x12, x13, [x0, #CTX_TTBR0_EL1]
	msr	ttbr0_el1, x12
	msr	ttbr1_el1, x13

	ldp	x14, x15, [x0, #CTX_MAIR_EL1]
	msr	mair_el1, x14
	msr	amair_el1, x15

	ldp	x16, x17, [x0, #CTX_TCR_EL1]
	msr	tcr_el1, x16
	msr	tpidr_el1, x17

	ldp	x9, x10, [x0, #CTX_TPIDR_EL0]
	msr	tpidr_el0, x9
	msr	tpidrro_el0, x10

#if !STPU
	ldp	x11, x12, [x0, #CTX_DACR32_EL2]
	msr	dacr32_el2, x11
	msr	ifsr32_el2, x12
#endif
	ldp	x13, x14, [x0, #CTX_PAR_EL1]
	msr	par_el1, x13
	msr	far_el1, x14

	ldp	x15, x16, [x0, #CTX_AFSR0_EL1]
	msr	afsr0_el1, x15
	msr	afsr1_el1, x16

	ldp	x17, x9, [x0, #CTX_CONTEXTIDR_EL1]
	msr	contextidr_el1, x17
	msr	vbar_el1, x9

	/* Restore NS timer registers if the build has instructed so */
#if NS_TIMER_SWITCH
	ldp	x10, x11, [x0, #CTX_CNTP_CTL_EL0]
	msr	cntp_ctl_el0, x10
	msr	cntp_cval_el0, x11

	ldp	x12, x13, [x0, #CTX_CNTV_CTL_EL0]
	msr	cntv_ctl_el0, x12
	msr	cntv_cval_el0, x13

	ldr	x14, [x0, #CTX_CNTKCTL_EL1]
	msr	cntkctl_el1, x14
#endif
	/* No explict ISB required here as ERET covers it */

	ret
endfunc el1_sysregs_context_restore
(3)、restore_gp_registers_eret //保存通用寄存器
func restore_gp_registers_eret
	ldp	x0, x1, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X0]
	ldp	x2, x3, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X2]
	b	restore_gp_registers_callee_eret
endfunc restore_gp_registers_eret

func restore_gp_registers_callee_eret
	ldp	x4, x5, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X4]
	ldp	x6, x7, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X6]
	ldp	x8, x9, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X8]
	ldp	x10, x11, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X10]
	ldp	x12, x13, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X12]
	ldp	x14, x15, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X14]
	ldp	x18, x19, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X18]
	ldp	x20, x21, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X20]
	ldp	x22, x23, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X22]
	ldp	x24, x25, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X24]
	ldp	x26, x27, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X26]
	ldp	x28, x29, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X28]
	ldp	 x30, x17, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_LR]
	msr	sp_el0, x17
	ldp	x16, x17, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X16]
	eret
endfunc	restore_gp_registers_callee_eret
(4)、save_gp_registers //恢复通用寄存器
/* -----------------------------------------------------
 * The following functions are used to save and restore
 * all the general purpose registers. Ideally we would
 * only save and restore the callee saved registers when
 * a world switch occurs but that type of implementation
 * is more complex. So currently we will always save and
 * restore these registers on entry and exit of EL3.
 * These are not macros to ensure their invocation fits
 * within the 32 instructions per exception vector.
 * clobbers: x18
 * -----------------------------------------------------
 */
func save_gp_registers
	stp	x0, x1, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X0]
	stp	x2, x3, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X2]
	stp	x4, x5, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X4]
	stp	x6, x7, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X6]
	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]
	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]
	ret
endfunc save_gp_registers
(5)、fpregs_context_save //保存浮点型寄存器

注意:搜索整个ATF代码,fpregs_context_save/fpregs_context_restore 并没有使用到

/* -----------------------------------------------------
 * The following function follows the aapcs_64 strictly
 * to use x9-x17 (temporary caller-saved registers
 * according to AArch64 PCS) to save floating point
 * register context. It assumes that 'x0' is pointing to
 * a 'fp_regs' structure where the register context will
 * be saved.
 *
 * Access to VFP registers will trap if CPTR_EL3.TFP is
 * set.  However currently we don't use VFP registers
 * nor set traps in Trusted Firmware, and assume it's
 * cleared
 *
 * TODO: Revisit when VFP is used in secure world
 * -----------------------------------------------------
 */
#if CTX_INCLUDE_FPREGS
func fpregs_context_save
	stp	q0, q1, [x0, #CTX_FP_Q0]
	stp	q2, q3, [x0, #CTX_FP_Q2]
	stp	q4, q5, [x0, #CTX_FP_Q4]
	stp	q6, q7, [x0, #CTX_FP_Q6]
	stp	q8, q9, [x0, #CTX_FP_Q8]
	stp	q10, q11, [x0, #CTX_FP_Q10]
	stp	q12, q13, [x0, #CTX_FP_Q12]
	stp	q14, q15, [x0, #CTX_FP_Q14]
	stp	q16, q17, [x0, #CTX_FP_Q16]
	stp	q18, q19, [x0, #CTX_FP_Q18]
	stp	q20, q21, [x0, #CTX_FP_Q20]
	stp	q22, q23, [x0, #CTX_FP_Q22]
	stp	q24, q25, [x0, #CTX_FP_Q24]
	stp	q26, q27, [x0, #CTX_FP_Q26]
	stp	q28, q29, [x0, #CTX_FP_Q28]
	stp	q30, q31, [x0, #CTX_FP_Q30]

	mrs	x9, fpsr
	str	x9, [x0, #CTX_FP_FPSR]

	mrs	x10, fpcr
	str	x10, [x0, #CTX_FP_FPCR]

	ret
endfunc fpregs_context_save
(6)、fpregs_context_restore //恢复浮点型寄存器

注意:搜索整个ATF代码,fpregs_context_save/fpregs_context_restore 并没有使用到

/* -----------------------------------------------------
 * The following function follows the aapcs_64 strictly
 * to use x9-x17 (temporary caller-saved registers
 * according to AArch64 PCS) to restore floating point
 * register context. It assumes that 'x0' is pointing to
 * a 'fp_regs' structure from where the register context
 * will be restored.
 *
 * Access to VFP registers will trap if CPTR_EL3.TFP is
 * set.  However currently we don't use VFP registers
 * nor set traps in Trusted Firmware, and assume it's
 * cleared
 *
 * TODO: Revisit when VFP is used in secure world
 * -----------------------------------------------------
 */
func fpregs_context_restore
	ldp	q0, q1, [x0, #CTX_FP_Q0]
	ldp	q2, q3, [x0, #CTX_FP_Q2]
	ldp	q4, q5, [x0, #CTX_FP_Q4]
	ldp	q6, q7, [x0, #CTX_FP_Q6]
	ldp	q8, q9, [x0, #CTX_FP_Q8]
	ldp	q10, q11, [x0, #CTX_FP_Q10]
	ldp	q12, q13, [x0, #CTX_FP_Q12]
	ldp	q14, q15, [x0, #CTX_FP_Q14]
	ldp	q16, q17, [x0, #CTX_FP_Q16]
	ldp	q18, q19, [x0, #CTX_FP_Q18]
	ldp	q20, q21, [x0, #CTX_FP_Q20]
	ldp	q22, q23, [x0, #CTX_FP_Q22]
	ldp	q24, q25, [x0, #CTX_FP_Q24]
	ldp	q26, q27, [x0, #CTX_FP_Q26]
	ldp	q28, q29, [x0, #CTX_FP_Q28]
	ldp	q30, q31, [x0, #CTX_FP_Q30]

	ldr	x9, [x0, #CTX_FP_FPSR]
	msr	fpsr, x9

	ldr	x10, [x0, #CTX_FP_FPCR]
	msr	fpcr, x10

	/*
	 * No explict ISB required here as ERET to
	 * switch to secure EL1 or non-secure world
	 * covers it
	 */

	ret
endfunc fpregs_context_restore
#endif /* CTX_INCLUDE_FPREGS */

2、sava/restore函数的应用场景

(1)、sync_exception_aarch64 //同步异常,调用smc指令后将进入这里

sync_exception_aarch64—>handle_sync_exception—>smc_handler64—>opteed_smc_handler

a . 先(仅仅)保存了x4-x7, x18, sp_el0

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

b. 保存一个os的系统寄存器,恢复另外一个os的系统寄存器
在opteed_smc_handler中:

如果是ATF----->TEE:

cm_el1_sysregs_context_save(NON_SECURE); 
cm_el1_sysregs_context_restore(SECURE);

如果是ATF----->REE:

cm_el1_sysregs_context_save(SECURE);
cm_el1_sysregs_context_restore(NON_SECURE);

c. 恢复通用寄存器
在opteed_smc_handler处理完毕后,再回到smc_handler64,调用el3_exit

在el3_exit中,先恢复gp寄存器,再eret恢复pc/pstate,返回到执行smc触发同步异常的地方

restore_gp_registers_eret
(2)、irq_aarch64 //atf中的同步异常

irq_aarch64 —>handle_interrupt_exception----->中断函数处理—>el3_exit

先调用save_gp_registers保存通用寄存器,然后进行中断函数处理
再在el3_exit中调用restore_gp_registers_eret恢复通用寄存器

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