From: Ard Biesheuvel ard.biesheuvel@linaro.org
[ Upstream commit 4e46c2a956215482418d7b315749fb1b6c6bc224 ]
The UEFI spec revision 2.7 errata A section 8.4 has the following to say about the virtual memory runtime services:
"This section contains function definitions for the virtual memory support that may be optionally used by an operating system at runtime. If an operating system chooses to make EFI runtime service calls in a virtual addressing mode instead of the flat physical mode, then the operating system must use the services in this section to switch the EFI runtime services from flat physical addressing to virtual addressing."
So it is pretty clear that calling SetVirtualAddressMap() is entirely optional, and so there is no point in doing so unless it achieves anything useful for us.
This is not the case for 64-bit ARM. The identity mapping used by the firmware is arbitrarily converted into another permutation of userland addresses (i.e., bits [63:48] cleared), and the runtime code could easily deal with the original layout in exactly the same way as it deals with the converted layout. However, due to constraints related to page size differences if the OS is not running with 4k pages, and related to systems that may expose the individual sections of PE/COFF runtime modules as different memory regions, creating the virtual layout is a bit fiddly, and requires us to sort the memory map and reason about adjacent regions with identical memory types etc etc.
So the obvious fix is to stop calling SetVirtualAddressMap() altogether on arm64 systems. However, to avoid surprises, which are notoriously hard to diagnose when it comes to OS<->firmware interactions, let's start by making it an opt-out feature, and implement support for the 'efi=novamap' kernel command line parameter on ARM and arm64 systems.
( Note that 32-bit ARM generally does require SetVirtualAddressMap() to be used, given that the physical memory map and the kernel virtual address map are not guaranteed to be non-overlapping like on arm64. However, having support for efi=novamap,noruntime on 32-bit ARM, combined with the recently proposed support for earlycon=efifb, is likely to be useful to diagnose boot issues on such systems if they have no accessible serial port. )
Tested-by: Jeffrey Hugo jhugo@codeaurora.org Tested-by: Bjorn Andersson bjorn.andersson@linaro.org Tested-by: Lee Jones lee.jones@linaro.org Signed-off-by: Ard Biesheuvel ard.biesheuvel@linaro.org Cc: AKASHI Takahiro takahiro.akashi@linaro.org Cc: Alexander Graf agraf@suse.de Cc: Borislav Petkov bp@alien8.de Cc: Heinrich Schuchardt xypron.glpk@gmx.de Cc: Leif Lindholm leif.lindholm@linaro.org Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Matt Fleming matt@codeblueprint.co.uk Cc: Peter Jones pjones@redhat.com Cc: Peter Zijlstra peterz@infradead.org Cc: Sai Praneeth Prakhya sai.praneeth.prakhya@intel.com Cc: Thomas Gleixner tglx@linutronix.de Cc: linux-efi@vger.kernel.org Link: http://lkml.kernel.org/r/20190202094119.13230-8-ard.biesheuvel@linaro.org Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/firmware/efi/libstub/arm-stub.c | 5 +++++ drivers/firmware/efi/libstub/efi-stub-helper.c | 10 ++++++++++ drivers/firmware/efi/libstub/efistub.h | 1 + drivers/firmware/efi/libstub/fdt.c | 3 +++ 4 files changed, 19 insertions(+)
diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c index 6920033de6d4..6c09644d620e 100644 --- a/drivers/firmware/efi/libstub/arm-stub.c +++ b/drivers/firmware/efi/libstub/arm-stub.c @@ -340,6 +340,11 @@ void efi_get_virtmap(efi_memory_desc_t *memory_map, unsigned long map_size, paddr = in->phys_addr; size = in->num_pages * EFI_PAGE_SIZE;
+ if (novamap()) { + in->virt_addr = in->phys_addr; + continue; + } + /* * Make the mapping compatible with 64k pages: this allows * a 4k page size kernel to kexec a 64k page size kernel and diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c index e94975f4655b..442f51c2a53d 100644 --- a/drivers/firmware/efi/libstub/efi-stub-helper.c +++ b/drivers/firmware/efi/libstub/efi-stub-helper.c @@ -34,6 +34,7 @@ static unsigned long __chunk_size = EFI_READ_CHUNK_SIZE;
static int __section(.data) __nokaslr; static int __section(.data) __quiet; +static int __section(.data) __novamap;
int __pure nokaslr(void) { @@ -43,6 +44,10 @@ int __pure is_quiet(void) { return __quiet; } +int __pure novamap(void) +{ + return __novamap; +}
#define EFI_MMAP_NR_SLACK_SLOTS 8
@@ -482,6 +487,11 @@ efi_status_t efi_parse_options(char const *cmdline) __chunk_size = -1UL; }
+ if (!strncmp(str, "novamap", 7)) { + str += strlen("novamap"); + __novamap = 1; + } + /* Group words together, delimited by "," */ while (*str && *str != ' ' && *str != ',') str++; diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h index 32799cf039ef..337b52c4702c 100644 --- a/drivers/firmware/efi/libstub/efistub.h +++ b/drivers/firmware/efi/libstub/efistub.h @@ -27,6 +27,7 @@
extern int __pure nokaslr(void); extern int __pure is_quiet(void); +extern int __pure novamap(void);
#define pr_efi(sys_table, msg) do { \ if (!is_quiet()) efi_printk(sys_table, "EFI stub: "msg); \ diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c index 0c0d2312f4a8..dba296a44f4e 100644 --- a/drivers/firmware/efi/libstub/fdt.c +++ b/drivers/firmware/efi/libstub/fdt.c @@ -327,6 +327,9 @@ efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table, if (status == EFI_SUCCESS) { efi_set_virtual_address_map_t *svam;
+ if (novamap()) + return EFI_SUCCESS; + /* Install the new virtual address map */ svam = sys_table->runtime->set_virtual_address_map; status = svam(runtime_entry_count * desc_size, desc_size,