Re: [PATCH v2 1/2] arm64: cpufeatures: Fix handling of CONFIG_CMDLINE for idreg overrides
From: Will Deacon <will@kernel.org>
Date: 2021-03-04 09:34:55
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On Wed, Mar 03, 2021 at 04:30:21PM -0600, Rob Herring wrote:
On Wed, Mar 3, 2021 at 7:50 AM Will Deacon [off-list ref] wrote:quoted
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. Reviewed-by: Marc Zyngier <maz@kernel.org> Fixes: 33200303553d ("arm64: cpufeature: Add an early command-line cpufeature override facility") Signed-off-by: Will Deacon <will@kernel.org> --- arch/arm64/kernel/idreg-override.c | 44 +++++++++++++++++------------- 1 file changed, 25 insertions(+), 19 deletions(-)It bothers me a bit having command line handling here. It means how the command line is assembled in 2 places.
It's more than 2 places, it's also done in the EFI stub; see efi_pe_entry() in drivers/firmware/efi/libstub/efi-stub.c. That's why I'm pushing on this, because at the moment the command-line reported by /proc/cmdline doesn't match the command-line that was parsed there because they stitch it together in opposite orders when CMDLINE_EXTEND is used.
I guess if we get rid of ambiguous 'extend' then it's better, but perhaps a better implementation would be an api get a specific command line parameter. The main downside would be searching the DT again for each parameter if we can't store any data in between calls, but there's ways around that. PowerPC also needs similar functionality in disabled_on_cmdline().
Christophe's patches at least aim to put the assembling all in one place, although we'll have to see whether or not it can be used in the EFI stub environment. Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel