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Merge tag 'efi-arm-no-relocate-for-rmk' of git://git.kernel.org/pub/s…
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…cm/linux/kernel/git/ardb/linux into misc

Simplify EFI handover to decompressor

The EFI stub in the ARM kernel runs in the context of the firmware, which
means it usually runs with the caches and MMU on. Currently, we relocate
the zImage so it appears in the first 128 MiB, disable the MMU and caches
and invoke the decompressor via its ordinary entry point. However, since we
can pass the base of DRAM directly, there is no need to relocate the zImage,
which also means there is no need to disable and re-enable the caches and
create new page tables etc.

This also allows systems whose DRAM start address is not a round multiple
of 128 MB to decompress the kernel proper to the base of memory, ensuring
that all memory is usable at runtime.
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Russell King committed May 26, 2020
2 parents 2318976 + d0f9ca9 commit fce2bc2
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Showing 3 changed files with 43 additions and 86 deletions.
79 changes: 32 additions & 47 deletions arch/arm/boot/compressed/head.S
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Original file line number Diff line number Diff line change
Expand Up @@ -287,28 +287,22 @@ not_angel:
*/
mov r0, pc
cmp r0, r4
ldrcc r0, LC0+28
ldrcc r0, .Lheadroom
addcc r0, r0, pc
cmpcc r4, r0
orrcc r4, r4, #1 @ remember we skipped cache_on
blcs cache_on

restart: adr r0, LC0
ldmia r0, {r1, r2, r3, r6, r11, r12}
ldr sp, [r0, #24]

/*
* We might be running at a different address. We need
* to fix up various pointers.
*/
sub r0, r0, r1 @ calculate the delta offset
add r6, r6, r0 @ _edata
restart: adr r0, LC1
ldr sp, [r0]
ldr r6, [r0, #4]
add sp, sp, r0
add r6, r6, r0

get_inflated_image_size r9, r10, lr

#ifndef CONFIG_ZBOOT_ROM
/* malloc space is above the relocated stack (64k max) */
add sp, sp, r0
add r10, sp, #0x10000
#else
/*
Expand All @@ -322,18 +316,13 @@ restart: adr r0, LC0
mov r5, #0 @ init dtb size to 0
#ifdef CONFIG_ARM_APPENDED_DTB
/*
* r0 = delta
* r2 = BSS start
* r3 = BSS end
* r4 = final kernel address (possibly with LSB set)
* r5 = appended dtb size (still unknown)
* r6 = _edata
* r7 = architecture ID
* r8 = atags/device tree pointer
* r9 = size of decompressed image
* r10 = end of this image, including bss/stack/malloc space if non XIP
* r11 = GOT start
* r12 = GOT end
* sp = stack pointer
*
* if there are device trees (dtb) appended to zImage, advance r10 so that the
Expand Down Expand Up @@ -381,7 +370,6 @@ restart: adr r0, LC0
/* temporarily relocate the stack past the DTB work space */
add sp, sp, r5

stmfd sp!, {r0-r3, ip, lr}
mov r0, r8
mov r1, r6
mov r2, r5
Expand All @@ -400,7 +388,6 @@ restart: adr r0, LC0
mov r2, r5
bleq atags_to_fdt

ldmfd sp!, {r0-r3, ip, lr}
sub sp, sp, r5
#endif

Expand Down Expand Up @@ -537,6 +524,10 @@ dtb_check_done:
mov pc, r0

wont_overwrite:
adr r0, LC0
ldmia r0, {r1, r2, r3, r11, r12}
sub r0, r0, r1 @ calculate the delta offset

/*
* If delta is zero, we are running at the address we were linked at.
* r0 = delta
Expand Down Expand Up @@ -660,13 +651,18 @@ not_relocated: mov r0, #0
LC0: .word LC0 @ r1
.word __bss_start @ r2
.word _end @ r3
.word _edata @ r6
.word _got_start @ r11
.word _got_end @ ip
.word .L_user_stack_end @ sp
.word _end - restart + 16384 + 1024*1024
.size LC0, . - LC0

.type LC1, #object
LC1: .word .L_user_stack_end - LC1 @ sp
.word _edata - LC1 @ r6
.size LC1, . - LC1

.Lheadroom:
.word _end - restart + 16384 + 1024*1024

.Linflated_image_size_offset:
.long (input_data_end - 4) - .

Expand Down Expand Up @@ -1434,37 +1430,26 @@ reloc_code_end:

#ifdef CONFIG_EFI_STUB
ENTRY(efi_enter_kernel)
mov r7, r0 @ preserve image base
mov r4, r1 @ preserve DT pointer
mov r4, r0 @ preserve image base
mov r8, r1 @ preserve DT pointer

mov r0, r4 @ DT start
add r1, r4, r2 @ DT end
bl cache_clean_flush
mrc p15, 0, r0, c1, c0, 0 @ read SCTLR
tst r0, #0x1 @ MMU enabled?
orreq r4, r4, #1 @ set LSB if not

mov r0, r7 @ relocated zImage
ldr r1, =_edata @ size of zImage
add r1, r1, r0 @ end of zImage
mov r0, r8 @ DT start
add r1, r8, r2 @ DT end
bl cache_clean_flush

@ The PE/COFF loader might not have cleaned the code we are
@ running beyond the PoU, and so calling cache_off below from
@ inside the PE/COFF loader allocated region is unsafe unless
@ we explicitly clean it to the PoC.
adr r0, call_cache_fn @ region of code we will
adr r1, 0f @ run with MMU off
bl cache_clean_flush
bl cache_off
adr r0, 0f @ switch to our stack
ldr sp, [r0]
add sp, sp, r0

@ Set parameters for booting zImage according to boot protocol
@ put FDT address in r2, it was returned by efi_entry()
@ r1 is the machine type, and r0 needs to be 0
mov r0, #0
mov r1, #0xFFFFFFFF
mov r2, r4
add r7, r7, #(__efi_start - start)
mov pc, r7 @ no mode switch
mov r5, #0 @ appended DTB size
mov r7, #0xFFFFFFFF @ machine ID
b wont_overwrite
ENDPROC(efi_enter_kernel)
0:
0: .long .L_user_stack_end - .
#endif

.align
Expand Down
5 changes: 5 additions & 0 deletions arch/arm/boot/compressed/vmlinux.lds.S
View file
Original file line number Diff line number Diff line change
Expand Up @@ -63,9 +63,11 @@ SECTIONS
_etext = .;

.got.plt : { *(.got.plt) }
#ifndef CONFIG_EFI_STUB
_got_start = .;
.got : { *(.got) }
_got_end = .;
#endif

/* ensure the zImage file size is always a multiple of 64 bits */
/* (without a dummy byte, ld just ignores the empty section) */
Expand All @@ -74,6 +76,9 @@ SECTIONS
#ifdef CONFIG_EFI_STUB
.data : ALIGN(4096) {
__pecoff_data_start = .;
_got_start = .;
*(.got)
_got_end = .;
/*
* The EFI stub always executes from RAM, and runs strictly before the
* decompressor, so we can make an exception for its r/w data, and keep it
Expand Down
45 changes: 6 additions & 39 deletions drivers/firmware/efi/libstub/arm32-stub.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -199,14 +199,8 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,
unsigned long kernel_base;
efi_status_t status;

/*
* Verify that the DRAM base address is compatible with the ARM
* boot protocol, which determines the base of DRAM by masking
* off the low 27 bits of the address at which the zImage is
* loaded. These assumptions are made by the decompressor,
* before any memory map is available.
*/
kernel_base = round_up(dram_base, SZ_128M);
/* use a 16 MiB aligned base for the decompressed kernel */
kernel_base = round_up(dram_base, SZ_16M) + TEXT_OFFSET;

/*
* Note that some platforms (notably, the Raspberry Pi 2) put
Expand All @@ -215,41 +209,14 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,
* base of the kernel image is only partially used at the moment.
* (Up to 5 pages are used for the swapper page tables)
*/
kernel_base += TEXT_OFFSET - 5 * PAGE_SIZE;

status = reserve_kernel_base(kernel_base, reserve_addr, reserve_size);
status = reserve_kernel_base(kernel_base - 5 * PAGE_SIZE, reserve_addr,
reserve_size);
if (status != EFI_SUCCESS) {
pr_efi_err("Unable to allocate memory for uncompressed kernel.\n");
return status;
}

/*
* Relocate the zImage, so that it appears in the lowest 128 MB
* memory window.
*/
*image_addr = (unsigned long)image->image_base;
*image_size = image->image_size;
status = efi_relocate_kernel(image_addr, *image_size, *image_size,
kernel_base + MAX_UNCOMP_KERNEL_SIZE, 0, 0);
if (status != EFI_SUCCESS) {
pr_efi_err("Failed to relocate kernel.\n");
efi_free(*reserve_size, *reserve_addr);
*reserve_size = 0;
return status;
}

/*
* Check to see if we were able to allocate memory low enough
* in memory. The kernel determines the base of DRAM from the
* address at which the zImage is loaded.
*/
if (*image_addr + *image_size > dram_base + ZIMAGE_OFFSET_LIMIT) {
pr_efi_err("Failed to relocate kernel, no low memory available.\n");
efi_free(*reserve_size, *reserve_addr);
*reserve_size = 0;
efi_free(*image_size, *image_addr);
*image_size = 0;
return EFI_LOAD_ERROR;
}
*image_addr = kernel_base;
*image_size = 0;
return EFI_SUCCESS;
}

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