On Wed, 8 Jan 2025 at 23:00, Usama Arif <usamaarif642@xxxxxxxxx> wrote: > > When this area is not reserved, it comes up as usable in > /sys/firmware/memmap. This means that kexec, which uses that memmap > to find usable memory regions, can select the region where > efi_mem_attr_table is and overwrite it and relocate_kernel. > > Since the patch in [1] was merged, all boots after kexec > are producing the warning that it introduced. > > Having a fix in firmware can be difficult to get through. I don't follow. I don't think there is anything wrong with the firmware here. Could you elaborate? > The next ideal place would be in libstub. However, it looks like > InstallMemoryAttributesTable [2] is not available as a boot service > call option [3], [4], and install_configuration_table does not > seem to work as a valid substitute. > To do what, exactly? > As a last option for a fix, this patch marks that region as reserved in > e820_table_firmware if it is currently E820_TYPE_RAM so that kexec doesn't > use it for kernel segments. > > [1] https://lore.kernel.org/all/20241031175822.2952471-2-ardb+git@xxxxxxxxxx/ > [2] https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Core/Dxe/Misc/MemoryAttributesTable.c#L100 > [3] https://github.com/tianocore/edk2/blob/42a141800c0c26a09d2344e84a89ce4097a263ae/MdeModulePkg/Core/Dxe/DxeMain/DxeMain.c#L41 > [4] https://elixir.bootlin.com/linux/v6.12.6/source/drivers/firmware/efi/libstub/efistub.h#L327 > > Reported-by: Breno Leitao <leitao@xxxxxxxxxx> > Signed-off-by: Usama Arif <usamaarif642@xxxxxxxxx> > --- > arch/x86/include/asm/e820/api.h | 2 ++ > arch/x86/kernel/e820.c | 6 ++++++ > arch/x86/platform/efi/efi.c | 9 +++++++++ > drivers/firmware/efi/memattr.c | 1 + > include/linux/efi.h | 7 +++++++ > 5 files changed, 25 insertions(+) > > diff --git a/arch/x86/include/asm/e820/api.h b/arch/x86/include/asm/e820/api.h > index 2e74a7f0e935..4e9aa24f03bd 100644 > --- a/arch/x86/include/asm/e820/api.h > +++ b/arch/x86/include/asm/e820/api.h > @@ -16,6 +16,8 @@ extern bool e820__mapped_all(u64 start, u64 end, enum e820_type type); > > extern void e820__range_add (u64 start, u64 size, enum e820_type type); > extern u64 e820__range_update(u64 start, u64 size, enum e820_type old_type, enum e820_type new_type); > +extern u64 e820__range_update_firmware(u64 start, u64 size, enum e820_type old_type, > + enum e820_type new_type); > extern u64 e820__range_remove(u64 start, u64 size, enum e820_type old_type, bool check_type); > extern u64 e820__range_update_table(struct e820_table *t, u64 start, u64 size, enum e820_type old_type, enum e820_type new_type); > > diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c > index 82b96ed9890a..01d7d3c0d299 100644 > --- a/arch/x86/kernel/e820.c > +++ b/arch/x86/kernel/e820.c > @@ -538,6 +538,12 @@ u64 __init e820__range_update_table(struct e820_table *t, u64 start, u64 size, > return __e820__range_update(t, start, size, old_type, new_type); > } > > +u64 __init e820__range_update_firmware(u64 start, u64 size, enum e820_type old_type, > + enum e820_type new_type) > +{ > + return __e820__range_update(e820_table_firmware, start, size, old_type, new_type); > +} > + > /* Remove a range of memory from the E820 table: */ > u64 __init e820__range_remove(u64 start, u64 size, enum e820_type old_type, bool check_type) > { > diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c > index a7ff189421c3..13684c5d7c05 100644 > --- a/arch/x86/platform/efi/efi.c > +++ b/arch/x86/platform/efi/efi.c > @@ -168,6 +168,15 @@ static void __init do_add_efi_memmap(void) > e820__update_table(e820_table); > } > > +/* Reserve firmware area if it was marked as RAM */ > +void arch_update_firmware_area(u64 addr, u64 size) > +{ > + if (e820__get_entry_type(addr, addr + size) == E820_TYPE_RAM) { > + e820__range_update_firmware(addr, size, E820_TYPE_RAM, E820_TYPE_RESERVED); > + e820__update_table(e820_table_firmware); > + } > +} > + > /* > * Given add_efi_memmap defaults to 0 and there is no alternative > * e820 mechanism for soft-reserved memory, import the full EFI memory > diff --git a/drivers/firmware/efi/memattr.c b/drivers/firmware/efi/memattr.c > index d3bc161361fb..d131781e2d7b 100644 > --- a/drivers/firmware/efi/memattr.c > +++ b/drivers/firmware/efi/memattr.c > @@ -53,6 +53,7 @@ int __init efi_memattr_init(void) > size = tbl->num_entries * tbl->desc_size; > tbl_size = sizeof(*tbl) + size; > memblock_reserve(efi_mem_attr_table, tbl_size); > + arch_update_firmware_area(efi_mem_attr_table, tbl_size); > set_bit(EFI_MEM_ATTR, &efi.flags); > > unmap: > diff --git a/include/linux/efi.h b/include/linux/efi.h > index e5815867aba9..8eb9698bd6a4 100644 > --- a/include/linux/efi.h > +++ b/include/linux/efi.h > @@ -1358,4 +1358,11 @@ extern struct blocking_notifier_head efivar_ops_nh; > void efivars_generic_ops_register(void); > void efivars_generic_ops_unregister(void); > > +#ifdef CONFIG_X86_64 > +void __init arch_update_firmware_area(u64 addr, u64 size); > +#else > +static inline void __init arch_update_firmware_area(u64 addr, u64 size) > +{ > +} > +#endif > #endif /* _LINUX_EFI_H */ > -- > 2.43.5 >
