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qemu/target/riscv/pmp.c
Himanshu Chauhan a574b27af4 target/riscv: Smepmp: Return error when access permission not allowed in PMP 
On an address match, skip checking for default permissions and return error
based on access defined in PMP configuration.

v3 Changes:
o Removed explicit return of boolean value from comparision
  of priv/allowed_priv

v2 Changes:
o Removed goto to return in place when address matches
o Call pmp_hart_has_privs_default at the end of the loop

Fixes: 90b1fafce0 ("target/riscv: Smepmp: Skip applying default rules when address matches")
Signed-off-by: Himanshu Chauhan <hchauhan@ventanamicro.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
Message-Id: <20230605164548.715336-1-hchauhan@ventanamicro.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
2023-06-13 17:45:30 +10:00

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/*
* QEMU RISC-V PMP (Physical Memory Protection)
*
* Author: Daire McNamara, daire.mcnamara@emdalo.com
* Ivan Griffin, ivan.griffin@emdalo.com
*
* This provides a RISC-V Physical Memory Protection implementation
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2 or later, as published by the Free Software Foundation.
*
* This program is distributed in the hope it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License along with
* this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "qemu/osdep.h"
#include "qemu/log.h"
#include "qapi/error.h"
#include "cpu.h"
#include "trace.h"
#include "exec/exec-all.h"
static bool pmp_write_cfg(CPURISCVState *env, uint32_t addr_index,
uint8_t val);
static uint8_t pmp_read_cfg(CPURISCVState *env, uint32_t addr_index);
/*
* Accessor method to extract address matching type 'a field' from cfg reg
*/
static inline uint8_t pmp_get_a_field(uint8_t cfg)
{
uint8_t a = cfg >> 3;
return a & 0x3;
}
/*
* Check whether a PMP is locked or not.
*/
static inline int pmp_is_locked(CPURISCVState *env, uint32_t pmp_index)
{
if (env->pmp_state.pmp[pmp_index].cfg_reg & PMP_LOCK) {
return 1;
}
/* Top PMP has no 'next' to check */
if ((pmp_index + 1u) >= MAX_RISCV_PMPS) {
return 0;
}
return 0;
}
/*
* Count the number of active rules.
*/
uint32_t pmp_get_num_rules(CPURISCVState *env)
{
return env->pmp_state.num_rules;
}
/*
* Accessor to get the cfg reg for a specific PMP/HART
*/
static inline uint8_t pmp_read_cfg(CPURISCVState *env, uint32_t pmp_index)
{
if (pmp_index < MAX_RISCV_PMPS) {
return env->pmp_state.pmp[pmp_index].cfg_reg;
}
return 0;
}
/*
* Accessor to set the cfg reg for a specific PMP/HART
* Bounds checks and relevant lock bit.
*/
static bool pmp_write_cfg(CPURISCVState *env, uint32_t pmp_index, uint8_t val)
{
if (pmp_index < MAX_RISCV_PMPS) {
bool locked = true;
if (riscv_cpu_cfg(env)->epmp) {
/* mseccfg.RLB is set */
if (MSECCFG_RLB_ISSET(env)) {
locked = false;
}
/* mseccfg.MML is not set */
if (!MSECCFG_MML_ISSET(env) && !pmp_is_locked(env, pmp_index)) {
locked = false;
}
/* mseccfg.MML is set */
if (MSECCFG_MML_ISSET(env)) {
/* not adding execute bit */
if ((val & PMP_LOCK) != 0 && (val & PMP_EXEC) != PMP_EXEC) {
locked = false;
}
/* shared region and not adding X bit */
if ((val & PMP_LOCK) != PMP_LOCK &&
(val & 0x7) != (PMP_WRITE | PMP_EXEC)) {
locked = false;
}
}
} else {
if (!pmp_is_locked(env, pmp_index)) {
locked = false;
}
}
if (locked) {
qemu_log_mask(LOG_GUEST_ERROR, "ignoring pmpcfg write - locked\n");
} else if (env->pmp_state.pmp[pmp_index].cfg_reg != val) {
env->pmp_state.pmp[pmp_index].cfg_reg = val;
pmp_update_rule_addr(env, pmp_index);
return true;
}
} else {
qemu_log_mask(LOG_GUEST_ERROR,
"ignoring pmpcfg write - out of bounds\n");
}
return false;
}
static void pmp_decode_napot(target_ulong a, target_ulong *sa,
target_ulong *ea)
{
/*
* aaaa...aaa0 8-byte NAPOT range
* aaaa...aa01 16-byte NAPOT range
* aaaa...a011 32-byte NAPOT range
* ...
* aa01...1111 2^XLEN-byte NAPOT range
* a011...1111 2^(XLEN+1)-byte NAPOT range
* 0111...1111 2^(XLEN+2)-byte NAPOT range
* 1111...1111 Reserved
*/
a = (a << 2) | 0x3;
*sa = a & (a + 1);
*ea = a | (a + 1);
}
void pmp_update_rule_addr(CPURISCVState *env, uint32_t pmp_index)
{
uint8_t this_cfg = env->pmp_state.pmp[pmp_index].cfg_reg;
target_ulong this_addr = env->pmp_state.pmp[pmp_index].addr_reg;
target_ulong prev_addr = 0u;
target_ulong sa = 0u;
target_ulong ea = 0u;
if (pmp_index >= 1u) {
prev_addr = env->pmp_state.pmp[pmp_index - 1].addr_reg;
}
switch (pmp_get_a_field(this_cfg)) {
case PMP_AMATCH_OFF:
sa = 0u;
ea = -1;
break;
case PMP_AMATCH_TOR:
sa = prev_addr << 2; /* shift up from [xx:0] to [xx+2:2] */
ea = (this_addr << 2) - 1u;
if (sa > ea) {
sa = ea = 0u;
}
break;
case PMP_AMATCH_NA4:
sa = this_addr << 2; /* shift up from [xx:0] to [xx+2:2] */
ea = (sa + 4u) - 1u;
break;
case PMP_AMATCH_NAPOT:
pmp_decode_napot(this_addr, &sa, &ea);
break;
default:
sa = 0u;
ea = 0u;
break;
}
env->pmp_state.addr[pmp_index].sa = sa;
env->pmp_state.addr[pmp_index].ea = ea;
}
void pmp_update_rule_nums(CPURISCVState *env)
{
int i;
env->pmp_state.num_rules = 0;
for (i = 0; i < MAX_RISCV_PMPS; i++) {
const uint8_t a_field =
pmp_get_a_field(env->pmp_state.pmp[i].cfg_reg);
if (PMP_AMATCH_OFF != a_field) {
env->pmp_state.num_rules++;
}
}
}
static int pmp_is_in_range(CPURISCVState *env, int pmp_index,
target_ulong addr)
{
int result = 0;
if ((addr >= env->pmp_state.addr[pmp_index].sa) &&
(addr <= env->pmp_state.addr[pmp_index].ea)) {
result = 1;
} else {
result = 0;
}
return result;
}
/*
* Check if the address has required RWX privs when no PMP entry is matched.
*/
static bool pmp_hart_has_privs_default(CPURISCVState *env, pmp_priv_t privs,
pmp_priv_t *allowed_privs,
target_ulong mode)
{
bool ret;
if (MSECCFG_MMWP_ISSET(env)) {
/*
* The Machine Mode Whitelist Policy (mseccfg.MMWP) is set
* so we default to deny all, even for M-mode.
*/
*allowed_privs = 0;
return false;
} else if (MSECCFG_MML_ISSET(env)) {
/*
* The Machine Mode Lockdown (mseccfg.MML) bit is set
* so we can only execute code in M-mode with an applicable
* rule. Other modes are disabled.
*/
if (mode == PRV_M && !(privs & PMP_EXEC)) {
ret = true;
*allowed_privs = PMP_READ | PMP_WRITE;
} else {
ret = false;
*allowed_privs = 0;
}
return ret;
}
if (!riscv_cpu_cfg(env)->pmp || (mode == PRV_M)) {
/*
* Privileged spec v1.10 states if HW doesn't implement any PMP entry
* or no PMP entry matches an M-Mode access, the access succeeds.
*/
ret = true;
*allowed_privs = PMP_READ | PMP_WRITE | PMP_EXEC;
} else {
/*
* Other modes are not allowed to succeed if they don't * match a rule,
* but there are rules. We've checked for no rule earlier in this
* function.
*/
ret = false;
*allowed_privs = 0;
}
return ret;
}
/*
* Public Interface
*/
/*
* Check if the address has required RWX privs to complete desired operation
* Return true if a pmp rule match or default match
* Return false if no match
*/
bool pmp_hart_has_privs(CPURISCVState *env, target_ulong addr,
target_ulong size, pmp_priv_t privs,
pmp_priv_t *allowed_privs, target_ulong mode)
{
int i = 0;
int pmp_size = 0;
target_ulong s = 0;
target_ulong e = 0;
/* Short cut if no rules */
if (0 == pmp_get_num_rules(env)) {
return pmp_hart_has_privs_default(env, privs, allowed_privs, mode);
}
if (size == 0) {
if (riscv_cpu_cfg(env)->mmu) {
/*
* If size is unknown (0), assume that all bytes
* from addr to the end of the page will be accessed.
*/
pmp_size = -(addr | TARGET_PAGE_MASK);
} else {
pmp_size = sizeof(target_ulong);
}
} else {
pmp_size = size;
}
/*
* 1.10 draft priv spec states there is an implicit order
* from low to high
*/
for (i = 0; i < MAX_RISCV_PMPS; i++) {
s = pmp_is_in_range(env, i, addr);
e = pmp_is_in_range(env, i, addr + pmp_size - 1);
/* partially inside */
if ((s + e) == 1) {
qemu_log_mask(LOG_GUEST_ERROR,
"pmp violation - access is partially inside\n");
*allowed_privs = 0;
return false;
}
/* fully inside */
const uint8_t a_field =
pmp_get_a_field(env->pmp_state.pmp[i].cfg_reg);
/*
* Convert the PMP permissions to match the truth table in the
* ePMP spec.
*/
const uint8_t epmp_operation =
((env->pmp_state.pmp[i].cfg_reg & PMP_LOCK) >> 4) |
((env->pmp_state.pmp[i].cfg_reg & PMP_READ) << 2) |
(env->pmp_state.pmp[i].cfg_reg & PMP_WRITE) |
((env->pmp_state.pmp[i].cfg_reg & PMP_EXEC) >> 2);
if (((s + e) == 2) && (PMP_AMATCH_OFF != a_field)) {
/*
* If the PMP entry is not off and the address is in range,
* do the priv check
*/
if (!MSECCFG_MML_ISSET(env)) {
/*
* If mseccfg.MML Bit is not set, do pmp priv check
* This will always apply to regular PMP.
*/
*allowed_privs = PMP_READ | PMP_WRITE | PMP_EXEC;
if ((mode != PRV_M) || pmp_is_locked(env, i)) {
*allowed_privs &= env->pmp_state.pmp[i].cfg_reg;
}
} else {
/*
* If mseccfg.MML Bit set, do the enhanced pmp priv check
*/
if (mode == PRV_M) {
switch (epmp_operation) {
case 0:
case 1:
case 4:
case 5:
case 6:
case 7:
case 8:
*allowed_privs = 0;
break;
case 2:
case 3:
case 14:
*allowed_privs = PMP_READ | PMP_WRITE;
break;
case 9:
case 10:
*allowed_privs = PMP_EXEC;
break;
case 11:
case 13:
*allowed_privs = PMP_READ | PMP_EXEC;
break;
case 12:
case 15:
*allowed_privs = PMP_READ;
break;
default:
g_assert_not_reached();
}
} else {
switch (epmp_operation) {
case 0:
case 8:
case 9:
case 12:
case 13:
case 14:
*allowed_privs = 0;
break;
case 1:
case 10:
case 11:
*allowed_privs = PMP_EXEC;
break;
case 2:
case 4:
case 15:
*allowed_privs = PMP_READ;
break;
case 3:
case 6:
*allowed_privs = PMP_READ | PMP_WRITE;
break;
case 5:
*allowed_privs = PMP_READ | PMP_EXEC;
break;
case 7:
*allowed_privs = PMP_READ | PMP_WRITE | PMP_EXEC;
break;
default:
g_assert_not_reached();
}
}
}
/*
* If matching address range was found, the protection bits
* defined with PMP must be used. We shouldn't fallback on
* finding default privileges.
*/
return (privs & *allowed_privs) == privs;
}
}
/* No rule matched */
return pmp_hart_has_privs_default(env, privs, allowed_privs, mode);
}
/*
* Handle a write to a pmpcfg CSR
*/
void pmpcfg_csr_write(CPURISCVState *env, uint32_t reg_index,
target_ulong val)
{
int i;
uint8_t cfg_val;
int pmpcfg_nums = 2 << riscv_cpu_mxl(env);
bool modified = false;
trace_pmpcfg_csr_write(env->mhartid, reg_index, val);
for (i = 0; i < pmpcfg_nums; i++) {
cfg_val = (val >> 8 * i) & 0xff;
modified |= pmp_write_cfg(env, (reg_index * 4) + i, cfg_val);
}
/* If PMP permission of any addr has been changed, flush TLB pages. */
if (modified) {
pmp_update_rule_nums(env);
tlb_flush(env_cpu(env));
}
}
/*
* Handle a read from a pmpcfg CSR
*/
target_ulong pmpcfg_csr_read(CPURISCVState *env, uint32_t reg_index)
{
int i;
target_ulong cfg_val = 0;
target_ulong val = 0;
int pmpcfg_nums = 2 << riscv_cpu_mxl(env);
for (i = 0; i < pmpcfg_nums; i++) {
val = pmp_read_cfg(env, (reg_index * 4) + i);
cfg_val |= (val << (i * 8));
}
trace_pmpcfg_csr_read(env->mhartid, reg_index, cfg_val);
return cfg_val;
}
/*
* Handle a write to a pmpaddr CSR
*/
void pmpaddr_csr_write(CPURISCVState *env, uint32_t addr_index,
target_ulong val)
{
trace_pmpaddr_csr_write(env->mhartid, addr_index, val);
bool is_next_cfg_tor = false;
if (addr_index < MAX_RISCV_PMPS) {
/*
* In TOR mode, need to check the lock bit of the next pmp
* (if there is a next).
*/
if (addr_index + 1 < MAX_RISCV_PMPS) {
uint8_t pmp_cfg = env->pmp_state.pmp[addr_index + 1].cfg_reg;
is_next_cfg_tor = PMP_AMATCH_TOR == pmp_get_a_field(pmp_cfg);
if (pmp_cfg & PMP_LOCK && is_next_cfg_tor) {
qemu_log_mask(LOG_GUEST_ERROR,
"ignoring pmpaddr write - pmpcfg + 1 locked\n");
return;
}
}
if (!pmp_is_locked(env, addr_index)) {
if (env->pmp_state.pmp[addr_index].addr_reg != val) {
env->pmp_state.pmp[addr_index].addr_reg = val;
pmp_update_rule_addr(env, addr_index);
if (is_next_cfg_tor) {
pmp_update_rule_addr(env, addr_index + 1);
}
tlb_flush(env_cpu(env));
}
} else {
qemu_log_mask(LOG_GUEST_ERROR,
"ignoring pmpaddr write - locked\n");
}
} else {
qemu_log_mask(LOG_GUEST_ERROR,
"ignoring pmpaddr write - out of bounds\n");
}
}
/*
* Handle a read from a pmpaddr CSR
*/
target_ulong pmpaddr_csr_read(CPURISCVState *env, uint32_t addr_index)
{
target_ulong val = 0;
if (addr_index < MAX_RISCV_PMPS) {
val = env->pmp_state.pmp[addr_index].addr_reg;
trace_pmpaddr_csr_read(env->mhartid, addr_index, val);
} else {
qemu_log_mask(LOG_GUEST_ERROR,
"ignoring pmpaddr read - out of bounds\n");
}
return val;
}
/*
* Handle a write to a mseccfg CSR
*/
void mseccfg_csr_write(CPURISCVState *env, target_ulong val)
{
int i;
trace_mseccfg_csr_write(env->mhartid, val);
/* RLB cannot be enabled if it's already 0 and if any regions are locked */
if (!MSECCFG_RLB_ISSET(env)) {
for (i = 0; i < MAX_RISCV_PMPS; i++) {
if (pmp_is_locked(env, i)) {
val &= ~MSECCFG_RLB;
break;
}
}
}
if (riscv_cpu_cfg(env)->epmp) {
/* Sticky bits */
val |= (env->mseccfg & (MSECCFG_MMWP | MSECCFG_MML));
if ((val ^ env->mseccfg) & (MSECCFG_MMWP | MSECCFG_MML)) {
tlb_flush(env_cpu(env));
}
} else {
val &= ~(MSECCFG_MMWP | MSECCFG_MML | MSECCFG_RLB);
}
env->mseccfg = val;
}
/*
* Handle a read from a mseccfg CSR
*/
target_ulong mseccfg_csr_read(CPURISCVState *env)
{
trace_mseccfg_csr_read(env->mhartid, env->mseccfg);
return env->mseccfg;
}
/*
* Calculate the TLB size.
* It's possible that PMP regions only cover partial of the TLB page, and
* this may split the page into regions with different permissions.
* For example if PMP0 is (0x80000008~0x8000000F, R) and PMP1 is (0x80000000
* ~0x80000FFF, RWX), then region 0x80000008~0x8000000F has R permission, and
* the other regions in this page have RWX permissions.
* A write access to 0x80000000 will match PMP1. However we cannot cache the
* translation result in the TLB since this will make the write access to
* 0x80000008 bypass the check of PMP0.
* To avoid this we return a size of 1 (which means no caching) if the PMP
* region only covers partial of the TLB page.
*/
target_ulong pmp_get_tlb_size(CPURISCVState *env, target_ulong addr)
{
target_ulong pmp_sa;
target_ulong pmp_ea;
target_ulong tlb_sa = addr & ~(TARGET_PAGE_SIZE - 1);
target_ulong tlb_ea = tlb_sa + TARGET_PAGE_SIZE - 1;
int i;
/*
* If PMP is not supported or there are no PMP rules, the TLB page will not
* be split into regions with different permissions by PMP so we set the
* size to TARGET_PAGE_SIZE.
*/
if (!riscv_cpu_cfg(env)->pmp || !pmp_get_num_rules(env)) {
return TARGET_PAGE_SIZE;
}
for (i = 0; i < MAX_RISCV_PMPS; i++) {
if (pmp_get_a_field(env->pmp_state.pmp[i].cfg_reg) == PMP_AMATCH_OFF) {
continue;
}
pmp_sa = env->pmp_state.addr[i].sa;
pmp_ea = env->pmp_state.addr[i].ea;
/*
* Only the first PMP entry that covers (whole or partial of) the TLB
* page really matters:
* If it covers the whole TLB page, set the size to TARGET_PAGE_SIZE,
* since the following PMP entries have lower priority and will not
* affect the permissions of the page.
* If it only covers partial of the TLB page, set the size to 1 since
* the allowed permissions of the region may be different from other
* region of the page.
*/
if (pmp_sa <= tlb_sa && pmp_ea >= tlb_ea) {
return TARGET_PAGE_SIZE;
} else if ((pmp_sa >= tlb_sa && pmp_sa <= tlb_ea) ||
(pmp_ea >= tlb_sa && pmp_ea <= tlb_ea)) {
return 1;
}
}
/*
* If no PMP entry matches the TLB page, the TLB page will also not be
* split into regions with different permissions by PMP so we set the size
* to TARGET_PAGE_SIZE.
*/
return TARGET_PAGE_SIZE;
}
/*
* Convert PMP privilege to TLB page privilege.
*/
int pmp_priv_to_page_prot(pmp_priv_t pmp_priv)
{
int prot = 0;
if (pmp_priv & PMP_READ) {
prot |= PAGE_READ;
}
if (pmp_priv & PMP_WRITE) {
prot |= PAGE_WRITE;
}
if (pmp_priv & PMP_EXEC) {
prot |= PAGE_EXEC;
}
return prot;
}
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