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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/setup.h>
#define FTR_DESC_NAME_LEN 20
#define FTR_DESC_FIELD_LEN 10
struct ftr_set_desc {
char name[FTR_DESC_NAME_LEN];
struct arm64_ftr_override *override;
struct {
char name[FTR_DESC_FIELD_LEN];
u8 shift;
} fields[];
};
static const struct ftr_set_desc * const regs[] __initconst = {
};
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;
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)
{
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);
} while (1);
}
static __init void parse_cmdline(void)
{
if (!IS_ENABLED(CONFIG_CMDLINE_FORCE)) {
const u8 *prop;
void *fdt;
int node;
fdt = get_early_fdt_ptr();
if (!fdt)
goto out;
node = fdt_path_offset(fdt, "/chosen");
if (node < 0)
goto out;
prop = fdt_getprop(fdt, node, "bootargs", NULL);
if (!prop)
goto out;
__parse_cmdline(prop);
if (!IS_ENABLED(CONFIG_CMDLINE_EXTEND))
return;
}
out:
__parse_cmdline(CONFIG_CMDLINE);
}
/* 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)
__flush_dcache_area(regs[i]->override,
sizeof(*regs[i]->override));
}
}
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