On Wed, 9 Oct 2019 at 15:59, Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > > Hi, > > On 09-10-2019 15:35, Ard Biesheuvel wrote: > > On Wed, 9 Oct 2019 at 15:18, Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > >> > >> Hi, > >> > >> On 09-10-2019 15:07, Ard Biesheuvel wrote: > >>> On Fri, 4 Oct 2019 at 16:51, Hans de Goede <hdegoede@xxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxx> > >>>> Acked-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> > >>>> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> > >>>> --- > >>>> Changes in v5: > >>>> -Rename the EFI_BOOT_SERVICES flag to EFI_PRESERVE_BS_REGIONS > >>>> > >>>> 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 c202e1b07e29..847730f7e74b 100644 > >>>> --- a/arch/x86/platform/efi/efi.c > >>>> +++ b/arch/x86/platform/efi/efi.c > >>>> @@ -232,6 +232,7 @@ 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_PRESERVE_BS_REGIONS, &efi.flags); > >>> > >>> Should we add a Kconfig symbol to opt into this behavior [set by the > >>> driver in question], instead of always preserving all boot services > >>> regions on all x86 systems? > >> > >> This bit does not control anything, it merely signals that the arch early > >> boot EFI code keeps the boot-services code around, which is something > >> which the x86 code already does. Where as e.g. on arm / aarch64 this is > >> freed early on, this ties in with the other bits: > >> > >>> > >>>> > >>>> return 0; > >>>> } > >>>> diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c > >>>> index 3b9fd679cea9..fab12ebf0ada 100644 > >>>> --- a/arch/x86/platform/efi/quirks.c > >>>> +++ b/arch/x86/platform/efi/quirks.c > >>>> @@ -411,6 +411,10 @@ 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; > >>>> + > >> > >> This is the point where normally on x86 we do actually free the boot-services > >> code which is a lot later then on other arches. And this new code actually > >> does change things to keep the boot-services code *forever* but only > >> if EFI debugging is enabled on the kernel commandline. > >> > > > > I get this part. But at some point, your driver is going to expect > > this memory to be preserved even if EFI_DBG is not set, right? My > > question was whether we should only opt into that if such a driver is > > enabled in the first place. > > Ah, I see. No even with CONFIG_EFI_EMBEDDED_FIRMWARE selected, the > boot-services code still gets free-ed. The efi_get_embedded_fw() > function from drivers/firmware/efi/embedded-firmware.c runs before > efi_free_boot_services() and it memdup-s any found firmwares, so it > does not cause the EFI boot-services code to stick around longer > then usual. > > The only thing which does cause it to stick around is enabling > EFI debugging with efi=debug, so that the various efi segments > (not only the code-services ones) can be inspected as debugfs > blobs. > > Basically this first patch of the series is independent of the > rest. It is part of the series, because adding new > efi_embedded_fw_desc structs to the table of firmwares to check > for becomes a lot easier when we can easily inspect the efi > segments and see if they contain the firmware we want. > > > As for Kconfig options, the compiling of > drivers/firmware/efi/embedded-firmware.c is controlled by > CONFIG_EFI_EMBEDDED_FIRMWARE which is a hidden option, which > can be selected by code which needs this. currently this is > only selected by CONFIG_TOUCHSCREEN_DMI which is defined > in drivers/platform/x86/Kconfig. > OK, thanks for clearing that up.
