From 916f676f8dc016103f983c7ec54c18ecdbb6e349 Mon Sep 17 00:00:00 2001 From: Matthew Garrett Date: Wed, 25 May 2011 09:53:13 -0400 Subject: [PATCH] x86, efi: Retain boot service code until after switching to virtual mode UEFI stands for "Unified Extensible Firmware Interface", where "Firmware" is an ancient African word meaning "Why do something right when you can do it so wrong that children will weep and brave adults will cower before you", and "UEI" is Celtic for "We missed DOS so we burned it into your ROMs". The UEFI specification provides for runtime services (ie, another way for the operating system to be forced to depend on the firmware) and we rely on these for certain trivial tasks such as setting up the bootloader. But some hardware fails to work if we attempt to use these runtime services from physical mode, and so we have to switch into virtual mode. So far so dreadful. The specification makes it clear that the operating system is free to do whatever it wants with boot services code after ExitBootServices() has been called. SetVirtualAddressMap() can't be called until ExitBootServices() has been. So, obviously, a whole bunch of EFI implementations call into boot services code when we do that. Since we've been charmingly naive and trusted that the specification may be somehow relevant to the real world, we've already stuffed a picture of a penguin or something in that address space. And just to make things more entertaining, we've also marked it non-executable. This patch allocates the boot services regions during EFI init and makes sure that they're executable. Then, after SetVirtualAddressMap(), it discards them and everyone lives happily ever after. Except for the ones who have to work on EFI, who live sad lives haunted by the knowledge that someone's eventually going to write yet another firmware specification. [ hpa: adding this to urgent with a stable tag since it fixes currently-broken hardware. However, I do not know what the dependencies are and so I do not know which -stable versions this may be a candidate for. ] Signed-off-by: Matthew Garrett Link: http://lkml.kernel.org/r/1306331593-28715-1-git-send-email-mjg@redhat.com Signed-off-by: H. Peter Anvin Cc: Tony Luck Cc: --- arch/x86/kernel/setup.c | 7 ++++++ arch/x86/platform/efi/efi.c | 45 +++++++++++++++++++++++++++++++++- arch/x86/platform/efi/efi_64.c | 5 ++-- include/linux/efi.h | 1 + 4 files changed, 55 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index 605e5ae19c7f..b9ca498f5602 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -910,6 +910,13 @@ void __init setup_arch(char **cmdline_p) memblock.current_limit = get_max_mapped(); memblock_x86_fill(); + /* + * The EFI specification says that boot service code won't be called + * after ExitBootServices(). This is, in fact, a lie. + */ + if (efi_enabled) + efi_reserve_boot_services(); + /* preallocate 4k for mptable mpc */ early_reserve_e820_mpc_new(); diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c index b30aa26a8df2..0d3a4fa34560 100644 --- a/arch/x86/platform/efi/efi.c +++ b/arch/x86/platform/efi/efi.c @@ -304,6 +304,40 @@ static void __init print_efi_memmap(void) } #endif /* EFI_DEBUG */ +void __init efi_reserve_boot_services(void) +{ + void *p; + + for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) { + efi_memory_desc_t *md = p; + unsigned long long start = md->phys_addr; + unsigned long long size = md->num_pages << EFI_PAGE_SHIFT; + + if (md->type != EFI_BOOT_SERVICES_CODE && + md->type != EFI_BOOT_SERVICES_DATA) + continue; + + memblock_x86_reserve_range(start, start + size, "EFI Boot"); + } +} + +static void __init efi_free_boot_services(void) +{ + void *p; + + for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) { + efi_memory_desc_t *md = p; + unsigned long long start = md->phys_addr; + unsigned long long size = md->num_pages << EFI_PAGE_SHIFT; + + if (md->type != EFI_BOOT_SERVICES_CODE && + md->type != EFI_BOOT_SERVICES_DATA) + continue; + + free_bootmem_late(start, size); + } +} + void __init efi_init(void) { efi_config_table_t *config_tables; @@ -536,7 +570,9 @@ void __init efi_enter_virtual_mode(void) for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) { md = p; - if (!(md->attribute & EFI_MEMORY_RUNTIME)) + if (!(md->attribute & EFI_MEMORY_RUNTIME) && + md->type != EFI_BOOT_SERVICES_CODE && + md->type != EFI_BOOT_SERVICES_DATA) continue; size = md->num_pages << EFI_PAGE_SHIFT; @@ -592,6 +628,13 @@ void __init efi_enter_virtual_mode(void) panic("EFI call to SetVirtualAddressMap() failed!"); } + /* + * Thankfully, it does seem that no runtime services other than + * SetVirtualAddressMap() will touch boot services code, so we can + * get rid of it all at this point + */ + efi_free_boot_services(); + /* * Now that EFI is in virtual mode, update the function * pointers in the runtime service table to the new virtual addresses. diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c index 2649426a7905..ac3aa54e2654 100644 --- a/arch/x86/platform/efi/efi_64.c +++ b/arch/x86/platform/efi/efi_64.c @@ -49,10 +49,11 @@ static void __init early_code_mapping_set_exec(int executable) if (!(__supported_pte_mask & _PAGE_NX)) return; - /* Make EFI runtime service code area executable */ + /* Make EFI service code area executable */ for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) { md = p; - if (md->type == EFI_RUNTIME_SERVICES_CODE) + if (md->type == EFI_RUNTIME_SERVICES_CODE || + md->type == EFI_BOOT_SERVICES_CODE) efi_set_executable(md, executable); } } diff --git a/include/linux/efi.h b/include/linux/efi.h index 33fa1203024e..e376270cd26e 100644 --- a/include/linux/efi.h +++ b/include/linux/efi.h @@ -299,6 +299,7 @@ extern void efi_initialize_iomem_resources(struct resource *code_resource, struct resource *data_resource, struct resource *bss_resource); extern unsigned long efi_get_time(void); extern int efi_set_rtc_mmss(unsigned long nowtime); +extern void efi_reserve_boot_services(void); extern struct efi_memory_map memmap; /** -- 2.39.5