[PATCH 2/3] lib: sbi: Introduce sbi_trap_exit() API
Anup Patel
Anup.Patel at wdc.com
Wed Jan 6 23:32:45 EST 2021
> -----Original Message-----
> From: Atish Patra <atishp at atishpatra.org>
> Sent: 06 January 2021 08:27
> To: Anup Patel <Anup.Patel at wdc.com>
> Cc: Atish Patra <Atish.Patra at wdc.com>; Alistair Francis
> <Alistair.Francis at wdc.com>; Anup Patel <anup at brainfault.org>; OpenSBI
> <opensbi at lists.infradead.org>
> Subject: Re: [PATCH 2/3] lib: sbi: Introduce sbi_trap_exit() API
>
> 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
Applied this patch to riscv/opensbi repo.
Regards,
Anup
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