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9b0b26580a
While efi-entry.S mentions that efi_entry() will have relocated the
kernel image, it actually means that efi_entry will have placed a copy
of the kernel in the appropriate location, and until this is branched to
at the end of efi_entry.S, all instructions are executed from the
original image.
Thus while the flush in efi_entry.S does ensure that the copy is visible
to noncacheable accesses, it does not guarantee that this is true for
the image instructions are being executed from. This could have
disasterous effects when the MMU and caches are disabled if the image
has not been naturally evicted to the PoC.
Additionally, due to a missing dsb following the ic ialluis, the new
kernel image is not necessarily clean in the I-cache when it is branched
to, with similar potentially disasterous effects.
This patch adds additional flushing to ensure that the currently
executing stub text is flushed to the PoC and is thus visible to
noncacheable accesses. As it is placed after the instructions cache
maintenance for the new image and __flush_dcache_area already contains a
dsb, we do not need to add a separate barrier to ensure completion of
the icache maintenance.
Comments are updated to clarify the situation with regard to the two
images and the maintenance required for both.
Fixes: 3c7f255039
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Joel Schopp <joel.schopp@amd.com>
Reviewed-by: Roy Franz <roy.franz@linaro.org>
Tested-by: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Ian Campbell <ijc@hellion.org.uk>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Mark Salter <msalter@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: stable@vger.kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
124 lines
2.9 KiB
ArmAsm
124 lines
2.9 KiB
ArmAsm
/*
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* EFI entry point.
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*
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* Copyright (C) 2013, 2014 Red Hat, Inc.
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* Author: Mark Salter <msalter@redhat.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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*/
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#include <linux/linkage.h>
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#include <linux/init.h>
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#include <asm/assembler.h>
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#define EFI_LOAD_ERROR 0x8000000000000001
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__INIT
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/*
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* We arrive here from the EFI boot manager with:
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*
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* * CPU in little-endian mode
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* * MMU on with identity-mapped RAM
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* * Icache and Dcache on
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*
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* We will most likely be running from some place other than where
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* we want to be. The kernel image wants to be placed at TEXT_OFFSET
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* from start of RAM.
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*/
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ENTRY(efi_stub_entry)
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/*
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* Create a stack frame to save FP/LR with extra space
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* for image_addr variable passed to efi_entry().
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*/
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stp x29, x30, [sp, #-32]!
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/*
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* Call efi_entry to do the real work.
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* x0 and x1 are already set up by firmware. Current runtime
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* address of image is calculated and passed via *image_addr.
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*
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* unsigned long efi_entry(void *handle,
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* efi_system_table_t *sys_table,
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* unsigned long *image_addr) ;
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*/
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adrp x8, _text
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add x8, x8, #:lo12:_text
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add x2, sp, 16
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str x8, [x2]
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bl efi_entry
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cmn x0, #1
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b.eq efi_load_fail
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/*
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* efi_entry() will have copied the kernel image if necessary and we
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* return here with device tree address in x0 and the kernel entry
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* point stored at *image_addr. Save those values in registers which
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* are callee preserved.
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*/
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mov x20, x0 // DTB address
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ldr x0, [sp, #16] // relocated _text address
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mov x21, x0
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/*
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* Calculate size of the kernel Image (same for original and copy).
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*/
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adrp x1, _text
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add x1, x1, #:lo12:_text
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adrp x2, _edata
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add x2, x2, #:lo12:_edata
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sub x1, x2, x1
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/*
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* Flush the copied Image to the PoC, and ensure it is not shadowed by
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* stale icache entries from before relocation.
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*/
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bl __flush_dcache_area
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ic ialluis
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/*
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* Ensure that the rest of this function (in the original Image) is
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* visible when the caches are disabled. The I-cache can't have stale
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* entries for the VA range of the current image, so no maintenance is
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* necessary.
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*/
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adr x0, efi_stub_entry
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adr x1, efi_stub_entry_end
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sub x1, x1, x0
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bl __flush_dcache_area
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/* Turn off Dcache and MMU */
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mrs x0, CurrentEL
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cmp x0, #CurrentEL_EL2
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b.ne 1f
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mrs x0, sctlr_el2
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bic x0, x0, #1 << 0 // clear SCTLR.M
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bic x0, x0, #1 << 2 // clear SCTLR.C
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msr sctlr_el2, x0
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isb
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b 2f
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1:
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mrs x0, sctlr_el1
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bic x0, x0, #1 << 0 // clear SCTLR.M
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bic x0, x0, #1 << 2 // clear SCTLR.C
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msr sctlr_el1, x0
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isb
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2:
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/* Jump to kernel entry point */
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mov x0, x20
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mov x1, xzr
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mov x2, xzr
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mov x3, xzr
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br x21
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efi_load_fail:
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mov x0, #EFI_LOAD_ERROR
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ldp x29, x30, [sp], #32
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ret
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efi_stub_entry_end:
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ENDPROC(efi_stub_entry)
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