Messages in this thread | | | Subject | Re: [PATCH v4 1/5] efi: Export boot-services code and data as debugfs-blobs | From | Hans de Goede <> | Date | Thu, 26 Apr 2018 23:02:39 +0200 |
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Hi,
On 26-04-18 18:51, Ard Biesheuvel wrote: > On 26 April 2018 at 14:06, Hans de Goede <hdegoede@redhat.com> wrote: >> Sometimes it is useful to be able to dump the efi boot-services code and >> data. This commit adds these as debugfs-blobs to /sys/kernel/debug/efi, >> but only if efi=debug is passed on the kernel-commandline as this requires >> not freeing those memory-regions, which costs 20+ MB of RAM. >> >> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> >> Signed-off-by: Hans de Goede <hdegoede@redhat.com> >> --- >> Changes in v4: >> -Add new EFI_BOOT_SERVICES flag and use it to determine if the boot-services >> memory segments are available (and thus if it makes sense to register the >> debugfs bits for them) >> >> Changes in v2: >> -Do not call pr_err on debugfs call failures >> --- >> arch/x86/platform/efi/efi.c | 1 + >> arch/x86/platform/efi/quirks.c | 4 +++ >> drivers/firmware/efi/efi.c | 53 ++++++++++++++++++++++++++++++++++ >> include/linux/efi.h | 1 + >> 4 files changed, 59 insertions(+) >> >> diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c >> index 9061babfbc83..568b7ee3d323 100644 >> --- a/arch/x86/platform/efi/efi.c >> +++ b/arch/x86/platform/efi/efi.c >> @@ -208,6 +208,7 @@ int __init efi_memblock_x86_reserve_range(void) >> efi.memmap.desc_version); >> >> memblock_reserve(pmap, efi.memmap.nr_map * efi.memmap.desc_size); >> + set_bit(EFI_BOOT_SERVICES, &efi.flags); >> > > I think it would be better if the flag conveys whether boot services > regions are being preserved, because they will always exist when > EFI_BOOT is set. > The name should then reflect that as well, e.g., EFI_PRESERVE_BS_REGIONS.
Ok, I will rename the flag to EFI_PRESERVE_BS_REGIONS for v5 (I'm going to wait a bit with sending out v5 to give others a change to comment on v4).
>> return 0; >> } >> diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c >> index 36c1f8b9f7e0..16bdb9e3b343 100644 >> --- a/arch/x86/platform/efi/quirks.c >> +++ b/arch/x86/platform/efi/quirks.c >> @@ -376,6 +376,10 @@ void __init efi_free_boot_services(void) >> int num_entries = 0; >> void *new, *new_md; >> >> + /* Keep all regions for /sys/kernel/debug/efi */ >> + if (efi_enabled(EFI_DBG)) >> + return; >> + > > Why is this only necessary when EFI_DBG is enabled? How are you > ensuring that the firmware is still in memory when the subsequent > patches start relying on that?
The 2nd patch in this series makes init/main.c call efi_check_for_embedded_firmwares() before efi_free_boot_services(), efi_check_for_embedded_firmwares() then walks the dmi_system_id-s "registered" (its a static list) by drivers and if their is a dmi_match searches for the firmware described by the dmi_system_id.driver_data ptr. If a firmware gets found it gets memdup-ed, so that we do not have to keep all of the boot-services code around.
Regards,
Hans
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