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arm64: idreg-override: Avoid kstrtou64() to parse a single hex digit

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All ID register value overrides are =0 with the exception of the nokaslr
pseudo feature which uses =1. In order to remove the dependency on
kstrtou64(), which is part of the core kernel and no longer usable once
we move idreg-override into the early mini C runtime, let's just parse a
single hex digit (with optional leading 0x) and set the output value
accordingly.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20231129111555.3594833-62-ardb@google.com
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Ard Biesheuvel
2023-11-29 12:16:15 +01:00
committed by Will Deacon
parent 060260a6be
commit ea48626f8f
1 changed files with 15 additions and 1 deletions
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16
arch/arm64/kernel/idreg-override.c
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@@ -206,6 +206,20 @@ static int __init parse_nokaslr(char *unused)
}
early_param("nokaslr", parse_nokaslr);
static int __init parse_hexdigit(const char *p, u64 *v)
{
// skip "0x" if it comes next
if (p[0] == '0' && tolower(p[1]) == 'x')
p += 2;
// check whether the RHS is a single hex digit
if (!isxdigit(p[0]) || (p[1] && !isspace(p[1])))
return -EINVAL;
*v = tolower(*p) - (isdigit(*p) ? '0' : 'a' - 10);
return 0;
}
static int __init find_field(const char *cmdline, char *opt, int len,
const struct ftr_set_desc *reg, int f, u64 *v)
{
@@ -219,7 +233,7 @@ static int __init find_field(const char *cmdline, char *opt, int len,
if (memcmp(cmdline, opt, len))
return -1;
return kstrtou64(cmdline + len, 0, v);
return parse_hexdigit(cmdline + len, v);
}
static void __init match_options(const char *cmdline)