[PATCH v2 04/10] lib: sbi: Introduce trap context
Samuel Holland
samuel.holland at sifive.com
Tue Mar 12 09:55:36 PDT 2024
On 2024-03-12 5:27 AM, Anup Patel wrote:
> Club the struct sbi_trap_regs and struct sbi_trap_info a new
> struct sbi_trap_context (aka trap context) which must be saved
> by low-level trap handler before calling sbi_trap_handler().
>
> To track nested traps, the struct sbi_scratch points to the current
> trap context and the trap context has pointer to pervious context
> of previous trap.
>
> Signed-off-by: Anup Patel <apatel at ventanamicro.com>
> ---
> firmware/fw_base.S | 62 ++++++++++++++++++++++++++++++++++--------
> include/sbi/sbi_trap.h | 29 +++++++++++++++++++-
> lib/sbi/sbi_trap.c | 58 +++++++++++++++++----------------------
> 3 files changed, 103 insertions(+), 46 deletions(-)
>
> diff --git a/firmware/fw_base.S b/firmware/fw_base.S
> index 539fd1d..967cca5 100644
> --- a/firmware/fw_base.S
> +++ b/firmware/fw_base.S
> @@ -446,14 +446,12 @@ _start_warm:
>
> /* Setup trap handler */
> lla a4, _trap_handler
> -#if __riscv_xlen == 32
> csrr a5, CSR_MISA
> srli a5, a5, ('H' - 'A')
> andi a5, a5, 0x1
> - beq a5, zero, _skip_trap_handler_rv32_hyp
> - lla a4, _trap_handler_rv32_hyp
> -_skip_trap_handler_rv32_hyp:
> -#endif
> + beq a5, zero, _skip_trap_handler_hyp
> + lla a4, _trap_handler_hyp
> +_skip_trap_handler_hyp:
> csrw CSR_MTVEC, a4
>
> /* Initialize SBI runtime */
> @@ -564,10 +562,10 @@ memcmp:
> xor t0, tp, t0
>
> /* Save original SP on exception stack */
> - REG_S sp, (SBI_TRAP_REGS_OFFSET(sp) - SBI_TRAP_REGS_SIZE)(t0)
> + REG_S sp, (SBI_TRAP_REGS_OFFSET(sp) - SBI_TRAP_CONTEXT_SIZE)(t0)
>
> - /* Set SP to exception stack and make room for trap registers */
> - add sp, t0, -(SBI_TRAP_REGS_SIZE)
> + /* Set SP to exception stack and make room for trap context */
> + add sp, t0, -(SBI_TRAP_CONTEXT_SIZE)
The ABI requires that the stack is aligned to 16 bytes. We already weren't doing
this, so maybe it doesn't matter.
>
> /* Restore T0 from scratch space */
> REG_L t0, SBI_SCRATCH_TMP0_OFFSET(tp)
> @@ -627,6 +625,32 @@ memcmp:
> REG_S t6, SBI_TRAP_REGS_OFFSET(t6)(sp)
> .endm
>
> +.macro TRAP_SAVE_INFO have_mstatush have_h_extension
> + csrr t0, CSR_MCAUSE
> + REG_S t0, (SBI_TRAP_REGS_SIZE + SBI_TRAP_INFO_OFFSET(cause))(sp)
> + csrr t0, CSR_MTVAL
> + REG_S t0, (SBI_TRAP_REGS_SIZE + SBI_TRAP_INFO_OFFSET(tval))(sp)
> +.if \have_h_extension
> + csrr t0, CSR_MTVAL2
> + REG_S t0, (SBI_TRAP_REGS_SIZE + SBI_TRAP_INFO_OFFSET(tval2))(sp)
> + csrr t0, CSR_MTINST
> + REG_S t0, (SBI_TRAP_REGS_SIZE + SBI_TRAP_INFO_OFFSET(tinst))(sp)
> + .if \have_mstatush
> + csrr t0, CSR_MSTATUSH
> + srli t0, t0, MSTATUSH_GVA_SHIFT
> + .else
> + csrr t0, CSR_MSTATUS
> + srli t0, t0, MSTATUS_GVA_SHIFT
> + .endif
> + and t0, t0, 0x1
> +.else
> + REG_S zero, (SBI_TRAP_REGS_SIZE + SBI_TRAP_INFO_OFFSET(tval2))(sp)
> + REG_S zero, (SBI_TRAP_REGS_SIZE + SBI_TRAP_INFO_OFFSET(tinst))(sp)
> + add t0, zero, zero
Why not use `li` here?
In any case, the changes LGTM, so:
Reviewed-by: Samuel Holland <samuel.holland at sifive.com>
> +.endif
> + REG_S t0, (SBI_TRAP_REGS_SIZE + SBI_TRAP_INFO_OFFSET(gva))(sp)
> +.endm
> +
> .macro TRAP_CALL_C_ROUTINE
> /* Call C routine */
> add a0, sp, zero
> @@ -696,6 +720,8 @@ _trap_handler:
>
> TRAP_SAVE_GENERAL_REGS_EXCEPT_SP_T0
>
> + TRAP_SAVE_INFO 0 0
> +
> TRAP_CALL_C_ROUTINE
>
> TRAP_RESTORE_GENERAL_REGS_EXCEPT_A0_T0
> @@ -706,27 +732,39 @@ _trap_handler:
>
> mret
>
> -#if __riscv_xlen == 32
> .section .entry, "ax", %progbits
> .align 3
> - .globl _trap_handler_rv32_hyp
> -_trap_handler_rv32_hyp:
> + .globl _trap_handler_hyp
> +_trap_handler_hyp:
> TRAP_SAVE_AND_SETUP_SP_T0
>
> +#if __riscv_xlen == 32
> TRAP_SAVE_MEPC_MSTATUS 1
> +#else
> + TRAP_SAVE_MEPC_MSTATUS 0
> +#endif
>
> TRAP_SAVE_GENERAL_REGS_EXCEPT_SP_T0
>
> +#if __riscv_xlen == 32
> + TRAP_SAVE_INFO 1 1
> +#else
> + TRAP_SAVE_INFO 0 1
> +#endif
> +
> TRAP_CALL_C_ROUTINE
>
> TRAP_RESTORE_GENERAL_REGS_EXCEPT_A0_T0
>
> +#if __riscv_xlen == 32
> TRAP_RESTORE_MEPC_MSTATUS 1
> +#else
> + TRAP_RESTORE_MEPC_MSTATUS 0
> +#endif
>
> TRAP_RESTORE_A0_T0
>
> mret
> -#endif
>
> .section .entry, "ax", %progbits
> .align 3
> diff --git a/include/sbi/sbi_trap.h b/include/sbi/sbi_trap.h
> index a6032ab..f7c170e 100644
> --- a/include/sbi/sbi_trap.h
> +++ b/include/sbi/sbi_trap.h
> @@ -112,9 +112,15 @@
> /** Size (in bytes) of sbi_trap_info */
> #define SBI_TRAP_INFO_SIZE SBI_TRAP_INFO_OFFSET(last)
>
> +/** Size (in bytes) of sbi_trap_context */
> +#define SBI_TRAP_CONTEXT_SIZE (SBI_TRAP_REGS_SIZE + \
> + SBI_TRAP_INFO_SIZE + \
> + __SIZEOF_POINTER__)
> +
> #ifndef __ASSEMBLER__
>
> #include <sbi/sbi_types.h>
> +#include <sbi/sbi_scratch.h>
>
> /** Representation of register state at time of trap/interrupt */
> struct sbi_trap_regs {
> @@ -204,6 +210,16 @@ struct sbi_trap_info {
> unsigned long gva;
> };
>
> +/** Representation of trap context saved on stack */
> +struct sbi_trap_context {
> + /** Register state */
> + struct sbi_trap_regs regs;
> + /** Trap details */
> + struct sbi_trap_info trap;
> + /** Pointer to previous trap context */
> + struct sbi_trap_context *prev_context;
> +};
> +
> static inline unsigned long sbi_regs_gva(const struct sbi_trap_regs *regs)
> {
> /*
> @@ -223,7 +239,18 @@ static inline unsigned long sbi_regs_gva(const struct sbi_trap_regs *regs)
> int sbi_trap_redirect(struct sbi_trap_regs *regs,
> const struct sbi_trap_info *trap);
>
> -struct sbi_trap_regs *sbi_trap_handler(struct sbi_trap_regs *regs);
> +static inline struct sbi_trap_context *sbi_trap_get_context(struct sbi_scratch *scratch)
> +{
> + return (scratch) ? (void *)scratch->trap_context : NULL;
> +}
> +
> +static inline void sbi_trap_set_context(struct sbi_scratch *scratch,
> + struct sbi_trap_context *tcntx)
> +{
> + scratch->trap_context = (unsigned long)tcntx;
> +}
> +
> +struct sbi_trap_context *sbi_trap_handler(struct sbi_trap_context *tcntx);
>
> #endif
>
> diff --git a/lib/sbi/sbi_trap.c b/lib/sbi/sbi_trap.c
> index b059c4b..4dbda06 100644
> --- a/lib/sbi/sbi_trap.c
> +++ b/lib/sbi/sbi_trap.c
> @@ -24,18 +24,18 @@
> #include <sbi/sbi_trap.h>
>
> static void __noreturn sbi_trap_error(const char *msg, int rc,
> - ulong mcause, ulong mtval, ulong mtval2,
> - ulong mtinst, struct sbi_trap_regs *regs)
> + const struct sbi_trap_info *trap,
> + const struct sbi_trap_regs *regs)
> {
> u32 hartid = current_hartid();
>
> sbi_printf("%s: hart%d: %s (error %d)\n", __func__, hartid, msg, rc);
> sbi_printf("%s: hart%d: mcause=0x%" PRILX " mtval=0x%" PRILX "\n",
> - __func__, hartid, mcause, mtval);
> + __func__, hartid, trap->cause, trap->tval);
> if (misa_extension('H')) {
> sbi_printf("%s: hart%d: mtval2=0x%" PRILX
> " mtinst=0x%" PRILX "\n",
> - __func__, hartid, mtval2, mtinst);
> + __func__, hartid, trap->tval2, trap->tinst);
> }
> sbi_printf("%s: hart%d: mepc=0x%" PRILX " mstatus=0x%" PRILX "\n",
> __func__, hartid, regs->mepc, regs->mstatus);
> @@ -258,20 +258,20 @@ static int sbi_trap_aia_irq(struct sbi_trap_regs *regs, ulong mcause)
> * 6. Stack pointer (SP) is setup for current HART
> * 7. Interrupts are disabled in MSTATUS CSR
> *
> - * @param regs pointer to register state
> + * @param tcntx pointer to trap context
> */
> -struct sbi_trap_regs *sbi_trap_handler(struct sbi_trap_regs *regs)
> +struct sbi_trap_context *sbi_trap_handler(struct sbi_trap_context *tcntx)
> {
> int rc = SBI_ENOTSUPP;
> const char *msg = "trap handler failed";
> - ulong mcause = csr_read(CSR_MCAUSE);
> - ulong mtval = csr_read(CSR_MTVAL), mtval2 = 0, mtinst = 0;
> - struct sbi_trap_info trap;
> + struct sbi_scratch *scratch = sbi_scratch_thishart_ptr();
> + const struct sbi_trap_info *trap = &tcntx->trap;
> + struct sbi_trap_regs *regs = &tcntx->regs;
> + ulong mcause = tcntx->trap.cause;
>
> - if (misa_extension('H')) {
> - mtval2 = csr_read(CSR_MTVAL2);
> - mtinst = csr_read(CSR_MTINST);
> - }
> + /* Update trap context pointer */
> + tcntx->prev_context = sbi_trap_get_context(scratch);
> + sbi_trap_set_context(scratch, tcntx);
>
> if (mcause & (1UL << (__riscv_xlen - 1))) {
> if (sbi_hart_has_extension(sbi_scratch_thishart_ptr(),
> @@ -279,32 +279,23 @@ struct sbi_trap_regs *sbi_trap_handler(struct sbi_trap_regs *regs)
> rc = sbi_trap_aia_irq(regs, mcause);
> else
> rc = sbi_trap_nonaia_irq(regs, mcause);
> - if (rc) {
> - msg = "unhandled local interrupt";
> - goto trap_error;
> - }
> - return regs;
> + msg = "unhandled local interrupt";
> + goto trap_done;
> }
> - /* Original trap_info */
> - trap.cause = mcause;
> - trap.tval = mtval;
> - trap.tval2 = mtval2;
> - trap.tinst = mtinst;
> - trap.gva = sbi_regs_gva(regs);
>
> switch (mcause) {
> case CAUSE_ILLEGAL_INSTRUCTION:
> - rc = sbi_illegal_insn_handler(mtval, regs);
> + rc = sbi_illegal_insn_handler(tcntx->trap.tval, regs);
> msg = "illegal instruction handler failed";
> break;
> case CAUSE_MISALIGNED_LOAD:
> sbi_pmu_ctr_incr_fw(SBI_PMU_FW_MISALIGNED_LOAD);
> - rc = sbi_misaligned_load_handler(regs, &trap);
> + rc = sbi_misaligned_load_handler(regs, trap);
> msg = "misaligned load handler failed";
> break;
> case CAUSE_MISALIGNED_STORE:
> sbi_pmu_ctr_incr_fw(SBI_PMU_FW_MISALIGNED_STORE);
> - rc = sbi_misaligned_store_handler(regs, &trap);
> + rc = sbi_misaligned_store_handler(regs, trap);
> msg = "misaligned store handler failed";
> break;
> case CAUSE_SUPERVISOR_ECALL:
> @@ -314,23 +305,24 @@ struct sbi_trap_regs *sbi_trap_handler(struct sbi_trap_regs *regs)
> break;
> case CAUSE_LOAD_ACCESS:
> sbi_pmu_ctr_incr_fw(SBI_PMU_FW_ACCESS_LOAD);
> - rc = sbi_load_access_handler(regs, &trap);
> + rc = sbi_load_access_handler(regs, trap);
> msg = "load fault handler failed";
> break;
> case CAUSE_STORE_ACCESS:
> sbi_pmu_ctr_incr_fw(SBI_PMU_FW_ACCESS_STORE);
> - rc = sbi_store_access_handler(regs, &trap);
> + rc = sbi_store_access_handler(regs, trap);
> msg = "store fault handler failed";
> break;
> default:
> /* If the trap came from S or U mode, redirect it there */
> msg = "trap redirect failed";
> - rc = sbi_trap_redirect(regs, &trap);
> + rc = sbi_trap_redirect(regs, trap);
> break;
> }
>
> -trap_error:
> +trap_done:
> if (rc)
> - sbi_trap_error(msg, rc, mcause, mtval, mtval2, mtinst, regs);
> - return regs;
> + sbi_trap_error(msg, rc, trap, regs);
> + sbi_trap_set_context(scratch, tcntx->prev_context);
> + return tcntx;
> }
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