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opensbi/lib/sbi/sbi_trap.c
Georg Kotheimer 9d56961b23 lib: sbi_trap: Fix hstatus.SPVP update in sbi_trap_redirect() 
When redirecting from VS/VU-mode to HS-mode, hstatus.SPVP was set
to the value of mstatus.SPP, as according to the specification both
flags should be set to the same value.
However, the assignment of SPVP takes place before SPP itself is
updated, which results in SPVP having an outdated value.

Signed-off-by: Georg Kotheimer <georg.kotheimer@tu-dresden.de>
Reviewed-by: Anup Patel <anup.patel@wdc.com>
2020-08-17 18:17:42 +05:30

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/*
* SPDX-License-Identifier: BSD-2-Clause
*
* Copyright (c) 2019 Western Digital Corporation or its affiliates.
*
* Authors:
* Anup Patel <anup.patel@wdc.com>
*/
#include <sbi/riscv_asm.h>
#include <sbi/riscv_encoding.h>
#include <sbi/sbi_console.h>
#include <sbi/sbi_ecall.h>
#include <sbi/sbi_error.h>
#include <sbi/sbi_hart.h>
#include <sbi/sbi_illegal_insn.h>
#include <sbi/sbi_ipi.h>
#include <sbi/sbi_misaligned_ldst.h>
#include <sbi/sbi_timer.h>
#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)
{
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);
if (misa_extension('H')) {
sbi_printf("%s: hart%d: mtval2=0x%" PRILX
" mtinst=0x%" PRILX "\n",
__func__, hartid, mtval2, mtinst);
}
sbi_printf("%s: hart%d: mepc=0x%" PRILX " mstatus=0x%" PRILX "\n",
__func__, hartid, regs->mepc, regs->mstatus);
sbi_printf("%s: hart%d: %s=0x%" PRILX " %s=0x%" PRILX "\n", __func__,
hartid, "ra", regs->ra, "sp", regs->sp);
sbi_printf("%s: hart%d: %s=0x%" PRILX " %s=0x%" PRILX "\n", __func__,
hartid, "gp", regs->gp, "tp", regs->tp);
sbi_printf("%s: hart%d: %s=0x%" PRILX " %s=0x%" PRILX "\n", __func__,
hartid, "s0", regs->s0, "s1", regs->s1);
sbi_printf("%s: hart%d: %s=0x%" PRILX " %s=0x%" PRILX "\n", __func__,
hartid, "a0", regs->a0, "a1", regs->a1);
sbi_printf("%s: hart%d: %s=0x%" PRILX " %s=0x%" PRILX "\n", __func__,
hartid, "a2", regs->a2, "a3", regs->a3);
sbi_printf("%s: hart%d: %s=0x%" PRILX " %s=0x%" PRILX "\n", __func__,
hartid, "a4", regs->a4, "a5", regs->a5);
sbi_printf("%s: hart%d: %s=0x%" PRILX " %s=0x%" PRILX "\n", __func__,
hartid, "a6", regs->a6, "a7", regs->a7);
sbi_printf("%s: hart%d: %s=0x%" PRILX " %s=0x%" PRILX "\n", __func__,
hartid, "s2", regs->s2, "s3", regs->s3);
sbi_printf("%s: hart%d: %s=0x%" PRILX " %s=0x%" PRILX "\n", __func__,
hartid, "s4", regs->s4, "s5", regs->s5);
sbi_printf("%s: hart%d: %s=0x%" PRILX " %s=0x%" PRILX "\n", __func__,
hartid, "s6", regs->s6, "s7", regs->s7);
sbi_printf("%s: hart%d: %s=0x%" PRILX " %s=0x%" PRILX "\n", __func__,
hartid, "s8", regs->s8, "s9", regs->s9);
sbi_printf("%s: hart%d: %s=0x%" PRILX " %s=0x%" PRILX "\n", __func__,
hartid, "s10", regs->s10, "s11", regs->s11);
sbi_printf("%s: hart%d: %s=0x%" PRILX " %s=0x%" PRILX "\n", __func__,
hartid, "t0", regs->t0, "t1", regs->t1);
sbi_printf("%s: hart%d: %s=0x%" PRILX " %s=0x%" PRILX "\n", __func__,
hartid, "t2", regs->t2, "t3", regs->t3);
sbi_printf("%s: hart%d: %s=0x%" PRILX " %s=0x%" PRILX "\n", __func__,
hartid, "t4", regs->t4, "t5", regs->t5);
sbi_printf("%s: hart%d: %s=0x%" PRILX "\n", __func__, hartid, "t6",
regs->t6);
sbi_hart_hang();
}
/**
* Redirect trap to lower privledge mode (S-mode or U-mode)
*
* @param regs pointer to register state
* @param trap pointer to trap details
*
* @return 0 on success and negative error code on failure
*/
int sbi_trap_redirect(struct sbi_trap_regs *regs,
struct sbi_trap_info *trap)
{
ulong hstatus, vsstatus, prev_mode;
#if __riscv_xlen == 32
bool prev_virt = (regs->mstatusH & MSTATUSH_MPV) ? TRUE : FALSE;
#else
bool prev_virt = (regs->mstatus & MSTATUS_MPV) ? TRUE : FALSE;
#endif
/* By default, we redirect to HS-mode */
bool next_virt = FALSE;
/* Sanity check on previous mode */
prev_mode = (regs->mstatus & MSTATUS_MPP) >> MSTATUS_MPP_SHIFT;
if (prev_mode != PRV_S && prev_mode != PRV_U)
return SBI_ENOTSUPP;
/* For certain exceptions from VS/VU-mode we redirect to VS-mode */
if (misa_extension('H') && prev_virt) {
switch (trap->cause) {
case CAUSE_FETCH_PAGE_FAULT:
case CAUSE_LOAD_PAGE_FAULT:
case CAUSE_STORE_PAGE_FAULT:
next_virt = TRUE;
break;
default:
break;
};
}
/* Update MSTATUS MPV bits */
#if __riscv_xlen == 32
regs->mstatusH &= ~MSTATUSH_MPV;
regs->mstatusH |= (next_virt) ? MSTATUSH_MPV : 0UL;
#else
regs->mstatus &= ~MSTATUS_MPV;
regs->mstatus |= (next_virt) ? MSTATUS_MPV : 0UL;
#endif
/* Update HSTATUS for VS/VU-mode to HS-mode transition */
if (misa_extension('H') && prev_virt && !next_virt) {
/* Update HSTATUS SPVP and SPV bits */
hstatus = csr_read(CSR_HSTATUS);
hstatus &= ~HSTATUS_SPVP;
hstatus |= (prev_mode == PRV_S) ? HSTATUS_SPVP : 0;
hstatus &= ~HSTATUS_SPV;
hstatus |= (prev_virt) ? HSTATUS_SPV : 0;
csr_write(CSR_HSTATUS, hstatus);
csr_write(CSR_HTVAL, trap->tval2);
csr_write(CSR_HTINST, trap->tinst);
}
/* Update exception related CSRs */
if (next_virt) {
/* Update VS-mode exception info */
csr_write(CSR_VSTVAL, trap->tval);
csr_write(CSR_VSEPC, trap->epc);
csr_write(CSR_VSCAUSE, trap->cause);
/* Set MEPC to VS-mode exception vector base */
regs->mepc = csr_read(CSR_VSTVEC);
/* Set MPP to VS-mode */
regs->mstatus &= ~MSTATUS_MPP;
regs->mstatus |= (PRV_S << MSTATUS_MPP_SHIFT);
/* Get VS-mode SSTATUS CSR */
vsstatus = csr_read(CSR_VSSTATUS);
/* Set SPP for VS-mode */
vsstatus &= ~SSTATUS_SPP;
if (prev_mode == PRV_S)
vsstatus |= (1UL << SSTATUS_SPP_SHIFT);
/* Set SPIE for VS-mode */
vsstatus &= ~SSTATUS_SPIE;
if (vsstatus & SSTATUS_SIE)
vsstatus |= (1UL << SSTATUS_SPIE_SHIFT);
/* Clear SIE for VS-mode */
vsstatus &= ~SSTATUS_SIE;
/* Update VS-mode SSTATUS CSR */
csr_write(CSR_VSSTATUS, vsstatus);
} else {
/* Update S-mode exception info */
csr_write(CSR_STVAL, trap->tval);
csr_write(CSR_SEPC, trap->epc);
csr_write(CSR_SCAUSE, trap->cause);
/* Set MEPC to S-mode exception vector base */
regs->mepc = csr_read(CSR_STVEC);
/* Set MPP to S-mode */
regs->mstatus &= ~MSTATUS_MPP;
regs->mstatus |= (PRV_S << MSTATUS_MPP_SHIFT);
/* Set SPP for S-mode */
regs->mstatus &= ~MSTATUS_SPP;
if (prev_mode == PRV_S)
regs->mstatus |= (1UL << MSTATUS_SPP_SHIFT);
/* Set SPIE for S-mode */
regs->mstatus &= ~MSTATUS_SPIE;
if (regs->mstatus & MSTATUS_SIE)
regs->mstatus |= (1UL << MSTATUS_SPIE_SHIFT);
/* Clear SIE for S-mode */
regs->mstatus &= ~MSTATUS_SIE;
}
return 0;
}
/**
* Handle trap/interrupt
*
* This function is called by firmware linked to OpenSBI
* library for handling trap/interrupt. It expects the
* following:
* 1. The 'mscratch' CSR is pointing to sbi_scratch of current HART
* 2. The 'mcause' CSR is having exception/interrupt cause
* 3. The 'mtval' CSR is having additional trap information
* 4. The 'mtval2' CSR is having additional trap information
* 5. The 'mtinst' CSR is having decoded trap instruction
* 6. Stack pointer (SP) is setup for current HART
* 7. Interrupts are disabled in MSTATUS CSR
*
* @param regs pointer to register state
*/
void sbi_trap_handler(struct sbi_trap_regs *regs)
{
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;
if (misa_extension('H')) {
mtval2 = csr_read(CSR_MTVAL2);
mtinst = csr_read(CSR_MTINST);
}
if (mcause & (1UL << (__riscv_xlen - 1))) {
mcause &= ~(1UL << (__riscv_xlen - 1));
switch (mcause) {
case IRQ_M_TIMER:
sbi_timer_process();
break;
case IRQ_M_SOFT:
sbi_ipi_process();
break;
default:
msg = "unhandled external interrupt";
goto trap_error;
};
return;
}
switch (mcause) {
case CAUSE_ILLEGAL_INSTRUCTION:
rc = sbi_illegal_insn_handler(mtval, regs);
msg = "illegal instruction handler failed";
break;
case CAUSE_MISALIGNED_LOAD:
rc = sbi_misaligned_load_handler(mtval, mtval2, mtinst, regs);
msg = "misaligned load handler failed";
break;
case CAUSE_MISALIGNED_STORE:
rc = sbi_misaligned_store_handler(mtval, mtval2, mtinst, regs);
msg = "misaligned store handler failed";
break;
case CAUSE_SUPERVISOR_ECALL:
case CAUSE_HYPERVISOR_ECALL:
rc = sbi_ecall_handler(regs);
msg = "ecall handler failed";
break;
default:
/* If the trap came from S or U mode, redirect it there */
trap.epc = regs->mepc;
trap.cause = mcause;
trap.tval = mtval;
trap.tval2 = mtval2;
trap.tinst = mtinst;
rc = sbi_trap_redirect(regs, &trap);
break;
};
trap_error:
if (rc)
sbi_trap_error(msg, rc, mcause, mtval, mtval2, mtinst, regs);
}
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