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lib: sbi: Introduce sbi_trap_exit() API

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We introduce sbi_trap_exit() API which can help non-firmware
(i.e. generic or platform) code to force exit trap/interrupt
handling and resume execution at context pointed by parameter
"const struct sbi_trap_regs *regs".

This new sbi_trap_exit() API will help Keystone Enclave project
to resume execution of enclave from custom SBI call handler.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
This commit is contained in:
Anup Patel
2020-12-29 11:39:22 +05:30
committed by Anup Patel
parent 80bc5065bb
commit b7df5e4392
4 changed files with 72 additions and 3 deletions
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43
firmware/fw_base.S
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@@ -261,6 +261,9 @@ _scratch_init:
/* Store hartid-to-scratch function address in scratch space */
la a4, _hartid_to_scratch
REG_S a4, SBI_SCRATCH_HARTID_TO_SCRATCH_OFFSET(tp)
/* Store trap-exit function address in scratch space */
la a4, _trap_exit
REG_S a4, SBI_SCRATCH_TRAP_EXIT_OFFSET(tp)
/* Clear tmp0 in scratch space */
REG_S zero, SBI_SCRATCH_TMP0_OFFSET(tp)
/* Store firmware options in scratch space */
@@ -423,6 +426,18 @@ _skip_trap_handler_rv32_hyp:
#endif
csrw CSR_MTVEC, a4
#if __riscv_xlen == 32
/* Override trap exit for H-extension */
csrr a5, CSR_MISA
srli a5, a5, ('H' - 'A')
andi a5, a5, 0x1
beq a5, zero, _skip_trap_exit_rv32_hyp
la a4, _trap_exit_rv32_hyp
csrr a5, CSR_MSCRATCH
REG_S a4, SBI_SCRATCH_TRAP_EXIT_OFFSET(a5)
_skip_trap_exit_rv32_hyp:
#endif
/* Initialize SBI runtime */
csrr a0, CSR_MSCRATCH
call sbi_init
@@ -653,6 +668,20 @@ _trap_handler:
mret
.section .entry, "ax", %progbits
.align 3
.globl _trap_exit
_trap_exit:
add sp, a0, zero
TRAP_RESTORE_GENERAL_REGS_EXCEPT_SP_T0
TRAP_RESTORE_MEPC_MSTATUS 0
TRAP_RESTORE_SP_T0
mret
#if __riscv_xlen == 32
.section .entry, "ax", %progbits
.align 3
@@ -673,6 +702,20 @@ _trap_handler_rv32_hyp:
TRAP_RESTORE_SP_T0
mret
.section .entry, "ax", %progbits
.align 3
.globl _trap_exit_rv32_hyp
_trap_exit_rv32_hyp:
add sp, a0, zero
TRAP_RESTORE_GENERAL_REGS_EXCEPT_SP_T0
TRAP_RESTORE_MEPC_MSTATUS 1
TRAP_RESTORE_SP_T0
mret
#endif
.section .entry, "ax", %progbits