[PATCH 2/3] lib: sbi: Introduce sbi_trap_exit() API
Atish Patra
atishp at atishpatra.org
Tue Jan 5 21:56:51 EST 2021
On Tue, Dec 29, 2020 at 7:33 PM Anup Patel <anup.patel at wdc.com> wrote:
>
> 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 at wdc.com>
> ---
> firmware/fw_base.S | 43 +++++++++++++++++++++++++++++++++++++++
> include/sbi/sbi_scratch.h | 10 ++++++---
> include/sbi/sbi_trap.h | 2 ++
> lib/sbi/sbi_trap.c | 20 ++++++++++++++++++
> 4 files changed, 72 insertions(+), 3 deletions(-)
>
> 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
> diff --git a/include/sbi/sbi_scratch.h b/include/sbi/sbi_scratch.h
> index 9f3453d..e7079f5 100644
> --- a/include/sbi/sbi_scratch.h
> +++ b/include/sbi/sbi_scratch.h
> @@ -30,12 +30,14 @@
> #define SBI_SCRATCH_PLATFORM_ADDR_OFFSET (6 * __SIZEOF_POINTER__)
> /** Offset of hartid_to_scratch member in sbi_scratch */
> #define SBI_SCRATCH_HARTID_TO_SCRATCH_OFFSET (7 * __SIZEOF_POINTER__)
> +/** Offset of trap_exit member in sbi_scratch */
> +#define SBI_SCRATCH_TRAP_EXIT_OFFSET (8 * __SIZEOF_POINTER__)
> /** Offset of tmp0 member in sbi_scratch */
> -#define SBI_SCRATCH_TMP0_OFFSET (8 * __SIZEOF_POINTER__)
> +#define SBI_SCRATCH_TMP0_OFFSET (9 * __SIZEOF_POINTER__)
> /** Offset of options member in sbi_scratch */
> -#define SBI_SCRATCH_OPTIONS_OFFSET (9 * __SIZEOF_POINTER__)
> +#define SBI_SCRATCH_OPTIONS_OFFSET (10 * __SIZEOF_POINTER__)
> /** Offset of extra space in sbi_scratch */
> -#define SBI_SCRATCH_EXTRA_SPACE_OFFSET (10 * __SIZEOF_POINTER__)
> +#define SBI_SCRATCH_EXTRA_SPACE_OFFSET (11 * __SIZEOF_POINTER__)
> /** Maximum size of sbi_scratch (4KB) */
> #define SBI_SCRATCH_SIZE (0x1000)
>
> @@ -63,6 +65,8 @@ struct sbi_scratch {
> unsigned long platform_addr;
> /** Address of HART ID to sbi_scratch conversion function */
> unsigned long hartid_to_scratch;
> + /** Address of trap exit function */
> + unsigned long trap_exit;
> /** Temporary storage */
> unsigned long tmp0;
> /** Options for OpenSBI library */
> diff --git a/include/sbi/sbi_trap.h b/include/sbi/sbi_trap.h
> index 5d0962f..04001df 100644
> --- a/include/sbi/sbi_trap.h
> +++ b/include/sbi/sbi_trap.h
> @@ -207,6 +207,8 @@ int sbi_trap_redirect(struct sbi_trap_regs *regs,
>
> void sbi_trap_handler(struct sbi_trap_regs *regs);
>
> +void __noreturn sbi_trap_exit(const struct sbi_trap_regs *regs);
> +
> #endif
>
> #endif
> diff --git a/lib/sbi/sbi_trap.c b/lib/sbi/sbi_trap.c
> index db5aa2f..b7349d2 100644
> --- a/lib/sbi/sbi_trap.c
> +++ b/lib/sbi/sbi_trap.c
> @@ -16,6 +16,7 @@
> #include <sbi/sbi_illegal_insn.h>
> #include <sbi/sbi_ipi.h>
> #include <sbi/sbi_misaligned_ldst.h>
> +#include <sbi/sbi_scratch.h>
> #include <sbi/sbi_timer.h>
> #include <sbi/sbi_trap.h>
>
> @@ -271,3 +272,22 @@ trap_error:
> if (rc)
> sbi_trap_error(msg, rc, mcause, mtval, mtval2, mtinst, regs);
> }
> +
> +typedef void (*trap_exit_t)(const struct sbi_trap_regs *regs);
> +
> +/**
> + * Exit trap/interrupt handling
> + *
> + * This function is called by non-firmware code to abruptly exit
> + * trap/interrupt handling and resume execution at context pointed
> + * by given register state.
> + *
> + * @param regs pointer to register state
> + */
> +void __noreturn sbi_trap_exit(const struct sbi_trap_regs *regs)
> +{
> + struct sbi_scratch *scratch = sbi_scratch_thishart_ptr();
> +
> + ((trap_exit_t)scratch->trap_exit)(regs);
> + __builtin_unreachable();
> +}
> --
> 2.25.1
>
>
> --
> opensbi mailing list
> opensbi at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/opensbi
Reviewed-by: Atish Patra <atish.patra at wdc.com>
--
Regards,
Atish
More information about the opensbi
mailing list