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// SPDX-License-Identifier: GPL-2.0
/*
* Early cpufeature override framework
*
* Copyright (C) 2020 Google LLC
* Author: Marc Zyngier <maz@kernel.org>
*/
#include <linux/ctype.h>
#include <linux/kernel.h>
#include <linux/libfdt.h>
#include <asm/cacheflush.h>
#include <asm/cpufeature.h>
#include <asm/setup.h>
#define FTR_DESC_NAME_LEN 20
#define FTR_DESC_FIELD_LEN 10
#define FTR_ALIAS_NAME_LEN 30
#define FTR_ALIAS_OPTION_LEN 80
struct ftr_set_desc {
char name[FTR_DESC_NAME_LEN];
struct arm64_ftr_override *override;
struct {
char name[FTR_DESC_FIELD_LEN];
u8 shift;
bool (*filter)(u64 val);
} fields[];
};
static bool __init mmfr1_vh_filter(u64 val)
{
/*
* If we ever reach this point while running VHE, we're
* guaranteed to be on one of these funky, VHE-stuck CPUs. If
* the user was trying to force nVHE on us, proceed with
* attitude adjustment.
*/
return !(is_kernel_in_hyp_mode() && val == 0);
}
static const struct ftr_set_desc mmfr1 __initconst = {
.name = "id_aa64mmfr1",
.override = &id_aa64mmfr1_override,
.fields = {
{ "vh", ID_AA64MMFR1_VHE_SHIFT, mmfr1_vh_filter },
{}
},
};
static const struct ftr_set_desc pfr1 __initconst = {
.name = "id_aa64pfr1",
.override = &id_aa64pfr1_override,
.fields = {
{ "bt", ID_AA64PFR1_BT_SHIFT },
{ "mte", ID_AA64PFR1_MTE_SHIFT},
{}
},
};
static const struct ftr_set_desc isar1 __initconst = {
.name = "id_aa64isar1",
.override = &id_aa64isar1_override,
.fields = {
{ "gpi", ID_AA64ISAR1_GPI_SHIFT },
{ "gpa", ID_AA64ISAR1_GPA_SHIFT },
{ "api", ID_AA64ISAR1_API_SHIFT },
{ "apa", ID_AA64ISAR1_APA_SHIFT },
{}
},
};
extern struct arm64_ftr_override kaslr_feature_override;
static const struct ftr_set_desc kaslr __initconst = {
.name = "kaslr",
#ifdef CONFIG_RANDOMIZE_BASE
.override = &kaslr_feature_override,
#endif
.fields = {
{ "disabled", 0 },
{}
},
};
static const struct ftr_set_desc * const regs[] __initconst = {
&mmfr1,
&pfr1,
&isar1,
&kaslr,
};
static const struct {
char alias[FTR_ALIAS_NAME_LEN];
char feature[FTR_ALIAS_OPTION_LEN];
} aliases[] __initconst = {
{ "kvm-arm.mode=nvhe", "id_aa64mmfr1.vh=0" },
{ "kvm-arm.mode=protected", "id_aa64mmfr1.vh=0" },
{ "arm64.nobti", "id_aa64pfr1.bt=0" },
{ "arm64.nopauth",
"id_aa64isar1.gpi=0 id_aa64isar1.gpa=0 "
"id_aa64isar1.api=0 id_aa64isar1.apa=0" },
{ "arm64.nomte", "id_aa64pfr1.mte=0" },
{ "nokaslr", "kaslr.disabled=1" },
};
static int __init find_field(const char *cmdline,
const struct ftr_set_desc *reg, int f, u64 *v)
{
char opt[FTR_DESC_NAME_LEN + FTR_DESC_FIELD_LEN + 2];
int len;
len = snprintf(opt, ARRAY_SIZE(opt), "%s.%s=",
reg->name, reg->fields[f].name);
if (!parameqn(cmdline, opt, len))
return -1;
return kstrtou64(cmdline + len, 0, v);
}
static void __init match_options(const char *cmdline)
{
int i;
for (i = 0; i < ARRAY_SIZE(regs); i++) {
int f;
if (!regs[i]->override)
continue;
for (f = 0; strlen(regs[i]->fields[f].name); f++) {
u64 shift = regs[i]->fields[f].shift;
u64 mask = 0xfUL << shift;
u64 v;
if (find_field(cmdline, regs[i], f, &v))
continue;
/*
* If an override gets filtered out, advertise
* it by setting the value to 0xf, but
* clearing the mask... Yes, this is fragile.
*/
if (regs[i]->fields[f].filter &&
!regs[i]->fields[f].filter(v)) {
regs[i]->override->val |= mask;
regs[i]->override->mask &= ~mask;
continue;
}
regs[i]->override->val &= ~mask;
regs[i]->override->val |= (v << shift) & mask;
regs[i]->override->mask |= mask;
return;
}
}
}
static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
{
do {
char buf[256];
size_t len;
int i;
cmdline = skip_spaces(cmdline);
for (len = 0; cmdline[len] && !isspace(cmdline[len]); len++);
if (!len)
return;
len = min(len, ARRAY_SIZE(buf) - 1);
strncpy(buf, cmdline, len);
buf[len] = 0;
if (strcmp(buf, "--") == 0)
return;
cmdline += len;
match_options(buf);
for (i = 0; parse_aliases && i < ARRAY_SIZE(aliases); i++)
if (parameq(buf, aliases[i].alias))
__parse_cmdline(aliases[i].feature, false);
} while (1);
}
static __init const u8 *get_bootargs_cmdline(void)
{
const u8 *prop;
void *fdt;
int node;
fdt = get_early_fdt_ptr();
if (!fdt)
return NULL;
node = fdt_path_offset(fdt, "/chosen");
if (node < 0)
return NULL;
prop = fdt_getprop(fdt, node, "bootargs", NULL);
if (!prop)
return NULL;
return strlen(prop) ? prop : NULL;
}
static __init void parse_cmdline(void)
{
const u8 *prop = get_bootargs_cmdline();
if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !prop)
__parse_cmdline(CONFIG_CMDLINE, true);
if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && prop)
__parse_cmdline(prop, true);
}
/* Keep checkers quiet */
void init_feature_override(void);
asmlinkage void __init init_feature_override(void)
{
int i;
for (i = 0; i < ARRAY_SIZE(regs); i++) {
if (regs[i]->override) {
regs[i]->override->val = 0;
regs[i]->override->mask = 0;
}
}
parse_cmdline();
for (i = 0; i < ARRAY_SIZE(regs); i++) {
if (regs[i]->override)
dcache_clean_inval_poc((unsigned long)regs[i]->override,
(unsigned long)regs[i]->override +
sizeof(*regs[i]->override));
}
}
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