lib: sbi: abstract out insn decoding to unify mem fault handlers
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>
diff --git a/include/sbi/sbi_trap_ldst.h b/include/sbi/sbi_trap_ldst.h
index 5f0ed92..9cab4e4 100644
--- a/include/sbi/sbi_trap_ldst.h
+++ b/include/sbi/sbi_trap_ldst.h
@@ -13,7 +13,12 @@
#include <sbi/sbi_types.h>
#include <sbi/sbi_trap.h>
-struct sbi_trap_regs;
+union sbi_ldst_data {
+ u64 data_u64;
+ u32 data_u32;
+ u8 data_bytes[8];
+ ulong data_ulong;
+};
int sbi_misaligned_load_handler(struct sbi_trap_regs *regs,
const struct sbi_trap_info *orig_trap);
@@ -21,4 +26,10 @@
int sbi_misaligned_store_handler(struct sbi_trap_regs *regs,
const struct sbi_trap_info *orig_trap);
+int sbi_load_access_handler(struct sbi_trap_regs *regs,
+ const struct sbi_trap_info *orig_trap);
+
+int sbi_store_access_handler(struct sbi_trap_regs *regs,
+ const struct sbi_trap_info *orig_trap);
+
#endif
diff --git a/lib/sbi/sbi_trap.c b/lib/sbi/sbi_trap.c
index e379984..c665013 100644
--- a/lib/sbi/sbi_trap.c
+++ b/lib/sbi/sbi_trap.c
@@ -299,10 +299,12 @@
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 @@
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";
diff --git a/lib/sbi/sbi_trap_ldst.c b/lib/sbi/sbi_trap_ldst.c
index 5feef60..b9dc7ea 100644
--- a/lib/sbi/sbi_trap_ldst.c
+++ b/lib/sbi/sbi_trap_ldst.c
@@ -16,11 +16,23 @@
#include <sbi/sbi_trap.h>
#include <sbi/sbi_unpriv.h>
-union reg_data {
- u8 data_bytes[8];
- ulong data_ulong;
- u64 data_u64;
-};
+/**
+ * Load emulator callback:
+ *
+ * @return rlen=success, 0=success w/o regs modification, or negative error
+ */
+typedef int (*sbi_trap_ld_emulator)(int rlen, union sbi_ldst_data *out_val,
+ struct sbi_trap_regs *regs,
+ const struct sbi_trap_info *orig_trap);
+
+/**
+ * Store emulator callback:
+ *
+ * @return wlen=success, 0=success w/o regs modification, or negative error
+ */
+typedef int (*sbi_trap_st_emulator)(int wlen, union sbi_ldst_data in_val,
+ struct sbi_trap_regs *regs,
+ const struct sbi_trap_info *orig_trap);
static ulong sbi_misaligned_tinst_fixup(ulong orig_tinst, ulong new_tinst,
ulong addr_offset)
@@ -34,15 +46,14 @@
return orig_tinst | (addr_offset << SH_RS1);
}
-int sbi_misaligned_load_handler(struct sbi_trap_regs *regs,
- const struct sbi_trap_info *orig_trap)
+static int sbi_trap_emulate_load(struct sbi_trap_regs *regs,
+ const struct sbi_trap_info *orig_trap,
+ sbi_trap_ld_emulator emu)
{
ulong insn, insn_len;
- union reg_data val;
+ union sbi_ldst_data val = { 0 };
struct sbi_trap_info uptrap;
- int i, fp = 0, shift = 0, len = 0;
-
- sbi_pmu_ctr_incr_fw(SBI_PMU_FW_MISALIGNED_LOAD);
+ int rc, fp = 0, shift = 0, len = 0;
if (orig_trap->tinst & 0x1) {
/*
@@ -64,7 +75,12 @@
insn_len = INSN_LEN(insn);
}
- if ((insn & INSN_MASK_LW) == INSN_MATCH_LW) {
+ if ((insn & INSN_MASK_LB) == INSN_MATCH_LB) {
+ len = 1;
+ shift = 8 * (sizeof(ulong) - len);
+ } else if ((insn & INSN_MASK_LBU) == INSN_MATCH_LBU) {
+ len = 1;
+ } else if ((insn & INSN_MASK_LW) == INSN_MATCH_LW) {
len = 4;
shift = 8 * (sizeof(ulong) - len);
#if __riscv_xlen == 64
@@ -134,17 +150,10 @@
return sbi_trap_redirect(regs, orig_trap);
}
- val.data_u64 = 0;
- for (i = 0; i < len; i++) {
- val.data_bytes[i] =
- sbi_load_u8((void *)(orig_trap->tval + i), &uptrap);
- if (uptrap.cause) {
- uptrap.epc = regs->mepc;
- uptrap.tinst = sbi_misaligned_tinst_fixup(
- orig_trap->tinst, uptrap.tinst, i);
- return sbi_trap_redirect(regs, &uptrap);
- }
- }
+ rc = emu(len, &val, regs, orig_trap);
+
+ if (rc <= 0)
+ return rc;
if (!fp)
SET_RD(insn, regs, ((long)(val.data_ulong << shift)) >> shift);
@@ -160,15 +169,14 @@
return 0;
}
-int sbi_misaligned_store_handler(struct sbi_trap_regs *regs,
- const struct sbi_trap_info *orig_trap)
+static int sbi_trap_emulate_store(struct sbi_trap_regs *regs,
+ const struct sbi_trap_info *orig_trap,
+ sbi_trap_st_emulator emu)
{
ulong insn, insn_len;
- union reg_data val;
+ union sbi_ldst_data val;
struct sbi_trap_info uptrap;
- int i, len = 0;
-
- sbi_pmu_ctr_incr_fw(SBI_PMU_FW_MISALIGNED_STORE);
+ int rc, len = 0;
if (orig_trap->tinst & 0x1) {
/*
@@ -192,7 +200,9 @@
val.data_ulong = GET_RS2(insn, regs);
- if ((insn & INSN_MASK_SW) == INSN_MATCH_SW) {
+ if ((insn & INSN_MASK_SB) == INSN_MATCH_SB) {
+ len = 1;
+ } else if ((insn & INSN_MASK_SW) == INSN_MATCH_SW) {
len = 4;
#if __riscv_xlen == 64
} else if ((insn & INSN_MASK_SD) == INSN_MATCH_SD) {
@@ -245,9 +255,26 @@
return sbi_trap_redirect(regs, orig_trap);
}
- for (i = 0; i < len; i++) {
- sbi_store_u8((void *)(orig_trap->tval + i), val.data_bytes[i],
- &uptrap);
+ rc = emu(len, val, regs, orig_trap);
+
+ if (rc <= 0)
+ return rc;
+
+ regs->mepc += insn_len;
+
+ return 0;
+}
+
+static int sbi_misaligned_ld_emulator(int rlen, union sbi_ldst_data *out_val,
+ struct sbi_trap_regs *regs,
+ const struct sbi_trap_info *orig_trap)
+{
+ struct sbi_trap_info uptrap;
+ int i;
+
+ for (i = 0; i < rlen; i++) {
+ out_val->data_bytes[i] =
+ sbi_load_u8((void *)(orig_trap->tval + i), &uptrap);
if (uptrap.cause) {
uptrap.epc = regs->mepc;
uptrap.tinst = sbi_misaligned_tinst_fixup(
@@ -255,8 +282,51 @@
return sbi_trap_redirect(regs, &uptrap);
}
}
+ return rlen;
+}
- regs->mepc += insn_len;
+int sbi_misaligned_load_handler(struct sbi_trap_regs *regs,
+ const struct sbi_trap_info *orig_trap)
+{
+ return sbi_trap_emulate_load(regs, orig_trap,
+ sbi_misaligned_ld_emulator);
+}
- return 0;
+static int sbi_misaligned_st_emulator(int wlen, union sbi_ldst_data in_val,
+ struct sbi_trap_regs *regs,
+ const struct sbi_trap_info *orig_trap)
+{
+ struct sbi_trap_info uptrap;
+ int i;
+
+ for (i = 0; i < wlen; i++) {
+ sbi_store_u8((void *)(orig_trap->tval + i),
+ in_val.data_bytes[i], &uptrap);
+ if (uptrap.cause) {
+ uptrap.epc = regs->mepc;
+ uptrap.tinst = sbi_misaligned_tinst_fixup(
+ orig_trap->tinst, uptrap.tinst, i);
+ return sbi_trap_redirect(regs, &uptrap);
+ }
+ }
+ return wlen;
+}
+
+int sbi_misaligned_store_handler(struct sbi_trap_regs *regs,
+ const struct sbi_trap_info *orig_trap)
+{
+ return sbi_trap_emulate_store(regs, orig_trap,
+ sbi_misaligned_st_emulator);
+}
+
+int sbi_load_access_handler(struct sbi_trap_regs *regs,
+ const struct sbi_trap_info *orig_trap)
+{
+ return sbi_trap_redirect(regs, orig_trap);
+}
+
+int sbi_store_access_handler(struct sbi_trap_regs *regs,
+ const struct sbi_trap_info *orig_trap)
+{
+ return sbi_trap_redirect(regs, orig_trap);
}
