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lib: sbi: abstract out insn decoding to unify mem fault handlers

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This patch abstracts out the instruction decoding part of misaligned ld/st
fault handlers, so it can be reused by ld/st access fault handlers.
Also Added lb/lbu/sb decoding. (previously unreachable by misaligned fault)

sbi_trap_emulate_load/store is now the common handler which takes a `emu`
parameter that is responsible for emulating the misaligned or access fault.
The `emu` callback is expected to fixup the fault, and based on the return
code of `emu`, sbi_trap_emulate_load/store will:

  r/wlen => the fixup is successful and regs/mepc needs to be updated.
  0      => the fixup is successful, but regs/mepc should be left untouched
            (this is usually used if `emu` does `sbi_trap_redirect`)
  -err   => failed, sbi_trap_error will be called

For now, load/store access faults are blindly redirected. It will be
enhanced in the following patches.

Signed-off-by: Bo Gan <ganboing@gmail.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Bo Gan
2024-03-05 18:35:38 -08:00
committed by Anup Patel
parent 9221fe58d1
commit 4c112650bb
3 changed files with 129 additions and 41 deletions
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13
lib/sbi/sbi_trap.c
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@@ -299,10 +299,12 @@ struct sbi_trap_regs *sbi_trap_handler(struct sbi_trap_regs *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);
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);
msg = "misaligned store handler failed";
break;
@@ -312,10 +314,15 @@ struct sbi_trap_regs *sbi_trap_handler(struct sbi_trap_regs *regs)
msg = "ecall handler failed";
break;
case CAUSE_LOAD_ACCESS:
sbi_pmu_ctr_incr_fw(SBI_PMU_FW_ACCESS_LOAD);
rc = sbi_load_access_handler(regs, &trap);
msg = "load fault handler failed";
break;
case CAUSE_STORE_ACCESS:
sbi_pmu_ctr_incr_fw(mcause == CAUSE_LOAD_ACCESS ?
SBI_PMU_FW_ACCESS_LOAD : SBI_PMU_FW_ACCESS_STORE);
/* fallthrough */
sbi_pmu_ctr_incr_fw(SBI_PMU_FW_ACCESS_STORE);
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";