From b7df5e4392d34d8b8d5290d5b857676e672d4c96 Mon Sep 17 00:00:00 2001
From: Anup Patel <anup.patel@wdc.com>
Date: Tue, 29 Dec 2020 11:39:22 +0530
Subject: lib: sbi: Introduce sbi_trap_exit() API
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>
---
firmware/fw_base.S | 43 +++++++++++++++++++++++++++++++++++++++++++
1 file changed, 43 insertions(+)
(limited to 'firmware')
diff --git a/firmware/fw_base.S b/firmware/fw_base.S
index fb504e8..ab33e11 100644
--- a/firmware/fw_base.S
+++ b/firmware/fw_base.S
@@ -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
--
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