On Thu, 25 Feb 2021 12:59:20 +0000,
Will Deacon <will@xxxxxxxxxx> wrote:
>
> The built-in kernel commandline (CONFIG_CMDLINE) can be configured in
> three different ways:
>
> 1. CMDLINE_FORCE: Use CONFIG_CMDLINE instead of any bootloader args
> 2. CMDLINE_EXTEND: Append the bootloader args to CONFIG_CMDLINE
> 3. CMDLINE_FROM_BOOTLOADER: Only use CONFIG_CMDLINE if there aren't
> any bootloader args.
>
> The early cmdline parsing to detect idreg overrides gets (2) and (3)
> slightly wrong: in the case of (2) the bootloader args are parsed first
> and in the case of (3) the CMDLINE is always parsed.
>
> Fix these issues by moving the bootargs parsing out into a helper
> function and following the same logic as that used by the EFI stub.
>
> Cc: Marc Zyngier <maz@xxxxxxxxxx>
> Fixes: 33200303553d ("arm64: cpufeature: Add an early command-line cpufeature override facility")
> Signed-off-by: Will Deacon <will@xxxxxxxxxx>
> ---
> arch/arm64/kernel/idreg-override.c | 44 +++++++++++++++++-------------
> 1 file changed, 25 insertions(+), 19 deletions(-)
>
> diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
> index dffb16682330..cc071712c6f9 100644
> --- a/arch/arm64/kernel/idreg-override.c
> +++ b/arch/arm64/kernel/idreg-override.c
> @@ -163,33 +163,39 @@ static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
> } while (1);
> }
>
> -static __init void parse_cmdline(void)
> +static __init const u8 *get_bootargs_cmdline(void)
> {
> - if (!IS_ENABLED(CONFIG_CMDLINE_FORCE)) {
> - const u8 *prop;
> - void *fdt;
> - int node;
> + const u8 *prop;
> + void *fdt;
> + int node;
>
> - fdt = get_early_fdt_ptr();
> - if (!fdt)
> - goto out;
> + fdt = get_early_fdt_ptr();
> + if (!fdt)
> + return NULL;
>
> - node = fdt_path_offset(fdt, "/chosen");
> - if (node < 0)
> - goto out;
> + node = fdt_path_offset(fdt, "/chosen");
> + if (node < 0)
> + return NULL;
>
> - prop = fdt_getprop(fdt, node, "bootargs", NULL);
> - if (!prop)
> - goto out;
> + prop = fdt_getprop(fdt, node, "bootargs", NULL);
> + if (!prop)
> + return NULL;
>
> - __parse_cmdline(prop, true);
> + return strlen(prop) ? prop : NULL;
> +}
>
> - if (!IS_ENABLED(CONFIG_CMDLINE_EXTEND))
> - return;
> +static __init void parse_cmdline(void)
> +{
> + const u8 *prop = get_bootargs_cmdline();
> +
> + if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) ||
> + IS_ENABLED(CONFIG_CMDLINE_FORCE) ||
> + !prop) {
The logic hurts, but I think I grok it now. The last term is actually
a reduction of
(IS_ENABLED(CONFIG_CMDLINE_FROM_BOOTLOADER) && !prop)
and we know for sure that if none of the other two terms are true,
then CMDLINE_FROM_BOOTLOADER *must* be enabled.
> + __parse_cmdline(CONFIG_CMDLINE, true);
> }
>
> -out:
> - __parse_cmdline(CONFIG_CMDLINE, true);
> + if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && prop)
> + __parse_cmdline(prop, true);
> }
>
> /* Keep checkers quiet */
I don't think we need to backport anything to stable for the nokaslr
handling, do we?
Otherwise,
Reviewed-by: Marc Zyngier <maz@xxxxxxxxxx>
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
