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qemu/target/arm/pauth_helper.c
Richard Henderson 283fc52ade target/arm: Implement an IMPDEF pauth algorithm 
Without hardware acceleration, a cryptographically strong
algorithm is too expensive for pauth_computepac.

Even with hardware accel, we are not currently expecting
to link the linux-user binaries to any crypto libraries,
and doing so would generally make the --static build fail.

So choose XXH64 as a reasonably quick and decent hash.

Tested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210111235740.462469-2-richard.henderson@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
2021-01-19 14:38:51 +00:00

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/*
* ARM v8.3-PAuth Operations
*
* Copyright (c) 2019 Linaro, Ltd.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/
#include "qemu/osdep.h"
#include "cpu.h"
#include "internals.h"
#include "exec/exec-all.h"
#include "exec/cpu_ldst.h"
#include "exec/helper-proto.h"
#include "tcg/tcg-gvec-desc.h"
#include "qemu/xxhash.h"
static uint64_t pac_cell_shuffle(uint64_t i)
{
uint64_t o = 0;
o |= extract64(i, 52, 4);
o |= extract64(i, 24, 4) << 4;
o |= extract64(i, 44, 4) << 8;
o |= extract64(i, 0, 4) << 12;
o |= extract64(i, 28, 4) << 16;
o |= extract64(i, 48, 4) << 20;
o |= extract64(i, 4, 4) << 24;
o |= extract64(i, 40, 4) << 28;
o |= extract64(i, 32, 4) << 32;
o |= extract64(i, 12, 4) << 36;
o |= extract64(i, 56, 4) << 40;
o |= extract64(i, 20, 4) << 44;
o |= extract64(i, 8, 4) << 48;
o |= extract64(i, 36, 4) << 52;
o |= extract64(i, 16, 4) << 56;
o |= extract64(i, 60, 4) << 60;
return o;
}
static uint64_t pac_cell_inv_shuffle(uint64_t i)
{
uint64_t o = 0;
o |= extract64(i, 12, 4);
o |= extract64(i, 24, 4) << 4;
o |= extract64(i, 48, 4) << 8;
o |= extract64(i, 36, 4) << 12;
o |= extract64(i, 56, 4) << 16;
o |= extract64(i, 44, 4) << 20;
o |= extract64(i, 4, 4) << 24;
o |= extract64(i, 16, 4) << 28;
o |= i & MAKE_64BIT_MASK(32, 4);
o |= extract64(i, 52, 4) << 36;
o |= extract64(i, 28, 4) << 40;
o |= extract64(i, 8, 4) << 44;
o |= extract64(i, 20, 4) << 48;
o |= extract64(i, 0, 4) << 52;
o |= extract64(i, 40, 4) << 56;
o |= i & MAKE_64BIT_MASK(60, 4);
return o;
}
static uint64_t pac_sub(uint64_t i)
{
static const uint8_t sub[16] = {
0xb, 0x6, 0x8, 0xf, 0xc, 0x0, 0x9, 0xe,
0x3, 0x7, 0x4, 0x5, 0xd, 0x2, 0x1, 0xa,
};
uint64_t o = 0;
int b;
for (b = 0; b < 64; b += 4) {
o |= (uint64_t)sub[(i >> b) & 0xf] << b;
}
return o;
}
static uint64_t pac_inv_sub(uint64_t i)
{
static const uint8_t inv_sub[16] = {
0x5, 0xe, 0xd, 0x8, 0xa, 0xb, 0x1, 0x9,
0x2, 0x6, 0xf, 0x0, 0x4, 0xc, 0x7, 0x3,
};
uint64_t o = 0;
int b;
for (b = 0; b < 64; b += 4) {
o |= (uint64_t)inv_sub[(i >> b) & 0xf] << b;
}
return o;
}
static int rot_cell(int cell, int n)
{
/* 4-bit rotate left by n. */
cell |= cell << 4;
return extract32(cell, 4 - n, 4);
}
static uint64_t pac_mult(uint64_t i)
{
uint64_t o = 0;
int b;
for (b = 0; b < 4 * 4; b += 4) {
int i0, i4, i8, ic, t0, t1, t2, t3;
i0 = extract64(i, b, 4);
i4 = extract64(i, b + 4 * 4, 4);
i8 = extract64(i, b + 8 * 4, 4);
ic = extract64(i, b + 12 * 4, 4);
t0 = rot_cell(i8, 1) ^ rot_cell(i4, 2) ^ rot_cell(i0, 1);
t1 = rot_cell(ic, 1) ^ rot_cell(i4, 1) ^ rot_cell(i0, 2);
t2 = rot_cell(ic, 2) ^ rot_cell(i8, 1) ^ rot_cell(i0, 1);
t3 = rot_cell(ic, 1) ^ rot_cell(i8, 2) ^ rot_cell(i4, 1);
o |= (uint64_t)t3 << b;
o |= (uint64_t)t2 << (b + 4 * 4);
o |= (uint64_t)t1 << (b + 8 * 4);
o |= (uint64_t)t0 << (b + 12 * 4);
}
return o;
}
static uint64_t tweak_cell_rot(uint64_t cell)
{
return (cell >> 1) | (((cell ^ (cell >> 1)) & 1) << 3);
}
static uint64_t tweak_shuffle(uint64_t i)
{
uint64_t o = 0;
o |= extract64(i, 16, 4) << 0;
o |= extract64(i, 20, 4) << 4;
o |= tweak_cell_rot(extract64(i, 24, 4)) << 8;
o |= extract64(i, 28, 4) << 12;
o |= tweak_cell_rot(extract64(i, 44, 4)) << 16;
o |= extract64(i, 8, 4) << 20;
o |= extract64(i, 12, 4) << 24;
o |= tweak_cell_rot(extract64(i, 32, 4)) << 28;
o |= extract64(i, 48, 4) << 32;
o |= extract64(i, 52, 4) << 36;
o |= extract64(i, 56, 4) << 40;
o |= tweak_cell_rot(extract64(i, 60, 4)) << 44;
o |= tweak_cell_rot(extract64(i, 0, 4)) << 48;
o |= extract64(i, 4, 4) << 52;
o |= tweak_cell_rot(extract64(i, 40, 4)) << 56;
o |= tweak_cell_rot(extract64(i, 36, 4)) << 60;
return o;
}
static uint64_t tweak_cell_inv_rot(uint64_t cell)
{
return ((cell << 1) & 0xf) | ((cell & 1) ^ (cell >> 3));
}
static uint64_t tweak_inv_shuffle(uint64_t i)
{
uint64_t o = 0;
o |= tweak_cell_inv_rot(extract64(i, 48, 4));
o |= extract64(i, 52, 4) << 4;
o |= extract64(i, 20, 4) << 8;
o |= extract64(i, 24, 4) << 12;
o |= extract64(i, 0, 4) << 16;
o |= extract64(i, 4, 4) << 20;
o |= tweak_cell_inv_rot(extract64(i, 8, 4)) << 24;
o |= extract64(i, 12, 4) << 28;
o |= tweak_cell_inv_rot(extract64(i, 28, 4)) << 32;
o |= tweak_cell_inv_rot(extract64(i, 60, 4)) << 36;
o |= tweak_cell_inv_rot(extract64(i, 56, 4)) << 40;
o |= tweak_cell_inv_rot(extract64(i, 16, 4)) << 44;
o |= extract64(i, 32, 4) << 48;
o |= extract64(i, 36, 4) << 52;
o |= extract64(i, 40, 4) << 56;
o |= tweak_cell_inv_rot(extract64(i, 44, 4)) << 60;
return o;
}
static uint64_t pauth_computepac_architected(uint64_t data, uint64_t modifier,
ARMPACKey key)
{
static const uint64_t RC[5] = {
0x0000000000000000ull,
0x13198A2E03707344ull,
0xA4093822299F31D0ull,
0x082EFA98EC4E6C89ull,
0x452821E638D01377ull,
};
const uint64_t alpha = 0xC0AC29B7C97C50DDull;
/*
* Note that in the ARM pseudocode, key0 contains bits <127:64>
* and key1 contains bits <63:0> of the 128-bit key.
*/
uint64_t key0 = key.hi, key1 = key.lo;
uint64_t workingval, runningmod, roundkey, modk0;
int i;
modk0 = (key0 << 63) | ((key0 >> 1) ^ (key0 >> 63));
runningmod = modifier;
workingval = data ^ key0;
for (i = 0; i <= 4; ++i) {
roundkey = key1 ^ runningmod;
workingval ^= roundkey;
workingval ^= RC[i];
if (i > 0) {
workingval = pac_cell_shuffle(workingval);
workingval = pac_mult(workingval);
}
workingval = pac_sub(workingval);
runningmod = tweak_shuffle(runningmod);
}
roundkey = modk0 ^ runningmod;
workingval ^= roundkey;
workingval = pac_cell_shuffle(workingval);
workingval = pac_mult(workingval);
workingval = pac_sub(workingval);
workingval = pac_cell_shuffle(workingval);
workingval = pac_mult(workingval);
workingval ^= key1;
workingval = pac_cell_inv_shuffle(workingval);
workingval = pac_inv_sub(workingval);
workingval = pac_mult(workingval);
workingval = pac_cell_inv_shuffle(workingval);
workingval ^= key0;
workingval ^= runningmod;
for (i = 0; i <= 4; ++i) {
workingval = pac_inv_sub(workingval);
if (i < 4) {
workingval = pac_mult(workingval);
workingval = pac_cell_inv_shuffle(workingval);
}
runningmod = tweak_inv_shuffle(runningmod);
roundkey = key1 ^ runningmod;
workingval ^= RC[4 - i];
workingval ^= roundkey;
workingval ^= alpha;
}
workingval ^= modk0;
return workingval;
}
static uint64_t pauth_computepac_impdef(uint64_t data, uint64_t modifier,
ARMPACKey key)
{
return qemu_xxhash64_4(data, modifier, key.lo, key.hi);
}
static uint64_t pauth_computepac(CPUARMState *env, uint64_t data,
uint64_t modifier, ARMPACKey key)
{
if (cpu_isar_feature(aa64_pauth_arch, env_archcpu(env))) {
return pauth_computepac_architected(data, modifier, key);
} else {
return pauth_computepac_impdef(data, modifier, key);
}
}
static uint64_t pauth_addpac(CPUARMState *env, uint64_t ptr, uint64_t modifier,
ARMPACKey *key, bool data)
{
ARMMMUIdx mmu_idx = arm_stage1_mmu_idx(env);
ARMVAParameters param = aa64_va_parameters(env, ptr, mmu_idx, data);
uint64_t pac, ext_ptr, ext, test;
int bot_bit, top_bit;
/* If tagged pointers are in use, use ptr<55>, otherwise ptr<63>. */
if (param.tbi) {
ext = sextract64(ptr, 55, 1);
} else {
ext = sextract64(ptr, 63, 1);
}
/* Build a pointer with known good extension bits. */
top_bit = 64 - 8 * param.tbi;
bot_bit = 64 - param.tsz;
ext_ptr = deposit64(ptr, bot_bit, top_bit - bot_bit, ext);
pac = pauth_computepac(env, ext_ptr, modifier, *key);
/*
* Check if the ptr has good extension bits and corrupt the
* pointer authentication code if not.
*/
test = sextract64(ptr, bot_bit, top_bit - bot_bit);
if (test != 0 && test != -1) {
/*
* Note that our top_bit is one greater than the pseudocode's
* version, hence "- 2" here.
*/
pac ^= MAKE_64BIT_MASK(top_bit - 2, 1);
}
/*
* Preserve the determination between upper and lower at bit 55,
* and insert pointer authentication code.
*/
if (param.tbi) {
ptr &= ~MAKE_64BIT_MASK(bot_bit, 55 - bot_bit + 1);
pac &= MAKE_64BIT_MASK(bot_bit, 54 - bot_bit + 1);
} else {
ptr &= MAKE_64BIT_MASK(0, bot_bit);
pac &= ~(MAKE_64BIT_MASK(55, 1) | MAKE_64BIT_MASK(0, bot_bit));
}
ext &= MAKE_64BIT_MASK(55, 1);
return pac | ext | ptr;
}
static uint64_t pauth_original_ptr(uint64_t ptr, ARMVAParameters param)
{
/* Note that bit 55 is used whether or not the regime has 2 ranges. */
uint64_t extfield = sextract64(ptr, 55, 1);
int bot_pac_bit = 64 - param.tsz;
int top_pac_bit = 64 - 8 * param.tbi;
return deposit64(ptr, bot_pac_bit, top_pac_bit - bot_pac_bit, extfield);
}
static uint64_t pauth_auth(CPUARMState *env, uint64_t ptr, uint64_t modifier,
ARMPACKey *key, bool data, int keynumber)
{
ARMMMUIdx mmu_idx = arm_stage1_mmu_idx(env);
ARMVAParameters param = aa64_va_parameters(env, ptr, mmu_idx, data);
int bot_bit, top_bit;
uint64_t pac, orig_ptr, test;
orig_ptr = pauth_original_ptr(ptr, param);
pac = pauth_computepac(env, orig_ptr, modifier, *key);
bot_bit = 64 - param.tsz;
top_bit = 64 - 8 * param.tbi;
test = (pac ^ ptr) & ~MAKE_64BIT_MASK(55, 1);
if (unlikely(extract64(test, bot_bit, top_bit - bot_bit))) {
int error_code = (keynumber << 1) | (keynumber ^ 1);
if (param.tbi) {
return deposit64(orig_ptr, 53, 2, error_code);
} else {
return deposit64(orig_ptr, 61, 2, error_code);
}
}
return orig_ptr;
}
static uint64_t pauth_strip(CPUARMState *env, uint64_t ptr, bool data)
{
ARMMMUIdx mmu_idx = arm_stage1_mmu_idx(env);
ARMVAParameters param = aa64_va_parameters(env, ptr, mmu_idx, data);
return pauth_original_ptr(ptr, param);
}
static void QEMU_NORETURN pauth_trap(CPUARMState *env, int target_el,
uintptr_t ra)
{
raise_exception_ra(env, EXCP_UDEF, syn_pactrap(), target_el, ra);
}
static void pauth_check_trap(CPUARMState *env, int el, uintptr_t ra)
{
if (el < 2 && arm_feature(env, ARM_FEATURE_EL2)) {
uint64_t hcr = arm_hcr_el2_eff(env);
bool trap = !(hcr & HCR_API);
if (el == 0) {
/* Trap only applies to EL1&0 regime. */
trap &= (hcr & (HCR_E2H | HCR_TGE)) != (HCR_E2H | HCR_TGE);
}
/* FIXME: ARMv8.3-NV: HCR_NV trap takes precedence for ERETA[AB]. */
if (trap) {
pauth_trap(env, 2, ra);
}
}
if (el < 3 && arm_feature(env, ARM_FEATURE_EL3)) {
if (!(env->cp15.scr_el3 & SCR_API)) {
pauth_trap(env, 3, ra);
}
}
}
static bool pauth_key_enabled(CPUARMState *env, int el, uint32_t bit)
{
return (arm_sctlr(env, el) & bit) != 0;
}
uint64_t HELPER(pacia)(CPUARMState *env, uint64_t x, uint64_t y)
{
int el = arm_current_el(env);
if (!pauth_key_enabled(env, el, SCTLR_EnIA)) {
return x;
}
pauth_check_trap(env, el, GETPC());
return pauth_addpac(env, x, y, &env->keys.apia, false);
}
uint64_t HELPER(pacib)(CPUARMState *env, uint64_t x, uint64_t y)
{
int el = arm_current_el(env);
if (!pauth_key_enabled(env, el, SCTLR_EnIB)) {
return x;
}
pauth_check_trap(env, el, GETPC());
return pauth_addpac(env, x, y, &env->keys.apib, false);
}
uint64_t HELPER(pacda)(CPUARMState *env, uint64_t x, uint64_t y)
{
int el = arm_current_el(env);
if (!pauth_key_enabled(env, el, SCTLR_EnDA)) {
return x;
}
pauth_check_trap(env, el, GETPC());
return pauth_addpac(env, x, y, &env->keys.apda, true);
}
uint64_t HELPER(pacdb)(CPUARMState *env, uint64_t x, uint64_t y)
{
int el = arm_current_el(env);
if (!pauth_key_enabled(env, el, SCTLR_EnDB)) {
return x;
}
pauth_check_trap(env, el, GETPC());
return pauth_addpac(env, x, y, &env->keys.apdb, true);
}
uint64_t HELPER(pacga)(CPUARMState *env, uint64_t x, uint64_t y)
{
uint64_t pac;
pauth_check_trap(env, arm_current_el(env), GETPC());
pac = pauth_computepac(env, x, y, env->keys.apga);
return pac & 0xffffffff00000000ull;
}
uint64_t HELPER(autia)(CPUARMState *env, uint64_t x, uint64_t y)
{
int el = arm_current_el(env);
if (!pauth_key_enabled(env, el, SCTLR_EnIA)) {
return x;
}
pauth_check_trap(env, el, GETPC());
return pauth_auth(env, x, y, &env->keys.apia, false, 0);
}
uint64_t HELPER(autib)(CPUARMState *env, uint64_t x, uint64_t y)
{
int el = arm_current_el(env);
if (!pauth_key_enabled(env, el, SCTLR_EnIB)) {
return x;
}
pauth_check_trap(env, el, GETPC());
return pauth_auth(env, x, y, &env->keys.apib, false, 1);
}
uint64_t HELPER(autda)(CPUARMState *env, uint64_t x, uint64_t y)
{
int el = arm_current_el(env);
if (!pauth_key_enabled(env, el, SCTLR_EnDA)) {
return x;
}
pauth_check_trap(env, el, GETPC());
return pauth_auth(env, x, y, &env->keys.apda, true, 0);
}
uint64_t HELPER(autdb)(CPUARMState *env, uint64_t x, uint64_t y)
{
int el = arm_current_el(env);
if (!pauth_key_enabled(env, el, SCTLR_EnDB)) {
return x;
}
pauth_check_trap(env, el, GETPC());
return pauth_auth(env, x, y, &env->keys.apdb, true, 1);
}
uint64_t HELPER(xpaci)(CPUARMState *env, uint64_t a)
{
return pauth_strip(env, a, false);
}
uint64_t HELPER(xpacd)(CPUARMState *env, uint64_t a)
{
return pauth_strip(env, a, true);
}
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