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author | Ahmad Fatoum <a.fatoum@pengutronix.de> | 2022-10-24 08:57:13 +0200 |
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committer | Sascha Hauer <s.hauer@pengutronix.de> | 2022-10-26 06:21:43 +0200 |
commit | 2d68037eb90ad8dab6402da04c7fc66f798b159f (patch) | |
tree | 11cd9d85e5cde81266c21b0694427d3588a3cfbe | |
parent | eee1b8846b0788c866dabf04e85742a48662455f (diff) | |
download | barebox-2d68037eb90ad8dab6402da04c7fc66f798b159f.tar.gz barebox-2d68037eb90ad8dab6402da04c7fc66f798b159f.tar.xz |
ARM64: asm: rewrite ENTRY_FUNCTION(_WITHSTACK) fully in assembly
Recent episode with pointer authentication showed again that for
platforms without __attribute__((naked)), we are better off writing
the early header in assembly. We still want to keep the board specific
entry points in C for ease of use, so we have ENTRY_FUNCTION_WITHSTACK
generate two symbols:
- A 32-bit stack top value that's placed in .rodata
- An entry point with the normal C code, including stack-using
prologues
The new common assembly head code will access the stack pointer in a
position-independent manner and set it up, before continuing with the
C code. The barebox header is part of the common assembly head code
ensuring it's not moved around due to compiler code generation.
The common code will need access to board-specific entry point and stack
top. The former is readily available as the alias __pbl_board_entry.
The latter is a bit more complicated, as the symbol may not exist for
boards not using the common header in a multi-image build.
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Link: https://lore.barebox.org/20221024065716.1215046-6-a.fatoum@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
-rw-r--r-- | Makefile | 3 | ||||
-rw-r--r-- | arch/arm/cpu/Makefile | 2 | ||||
-rw-r--r-- | arch/arm/cpu/head_64.S | 33 | ||||
-rw-r--r-- | arch/arm/include/asm/barebox-arm.h | 28 | ||||
-rw-r--r-- | arch/arm/lib/pbl.lds.S | 9 |
5 files changed, 53 insertions, 22 deletions
@@ -660,8 +660,7 @@ KBUILD_CFLAGS += $(call cc-option,-fno-stack-check) KBUILD_CFLAGS += $(call cc-option,-fcf-protection=none) # We don't have the necessary infrastructure to benefit from ARMv8.3+ pointer -# authentication. On older CPUs, they are interpreted as NOPs and blot the -# code and break less portable code that expects a very specific code layout +# authentication. On older CPUs, they are interpreted as NOPs bloating the code KBUILD_CFLAGS += $(call cc-option,-mbranch-protection=none) KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member) diff --git a/arch/arm/cpu/Makefile b/arch/arm/cpu/Makefile index c0993c1abe..7674c1464c 100644 --- a/arch/arm/cpu/Makefile +++ b/arch/arm/cpu/Makefile @@ -13,6 +13,8 @@ AFLAGS_hyp.pbl.o :=-Wa,-march=armv7-a -Wa,-mcpu=all obj-y += start.o entry.o entry_ll$(S64).o KASAN_SANITIZE_start.o := n +pbl-$(CONFIG_CPU_64) += head_64.o + pbl-$(CONFIG_BOARD_ARM_GENERIC_DT) += board-dt-2nd.o pbl-$(CONFIG_BOARD_ARM_GENERIC_DT_AARCH64) += board-dt-2nd-aarch64.o diff --git a/arch/arm/cpu/head_64.S b/arch/arm/cpu/head_64.S new file mode 100644 index 0000000000..f934e96c6e --- /dev/null +++ b/arch/arm/cpu/head_64.S @@ -0,0 +1,33 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +#include <linux/linkage.h> +#include <asm/barebox-arm64.h> +#include <asm/image.h> + +/* Linker will point these at board-specific symbols */ +.globl __pbl_board_stack_top +.globl __pbl_board_entry + +.section .text_head_prologue_common, "x" +ENTRY(__barebox_arm64_head) + nop + adr x9, __pbl_board_stack_top + ldr w9, [x9] + cbz x9, 1f + mov sp, x9 +1: +#ifdef CONFIG_PBL_BREAK + brk #17 + nop +#else + nop + nop +#endif + b __pbl_board_entry + .org 0x20 + .asciz "barebox" + .word 0xffffffff + .word _barebox_image_size /* image size to copy */ + .rept 8 + .word 0x55555555 + .endr +END(__barebox_arm64_head) diff --git a/arch/arm/include/asm/barebox-arm.h b/arch/arm/include/asm/barebox-arm.h index 68a9610398..89b4a89755 100644 --- a/arch/arm/include/asm/barebox-arm.h +++ b/arch/arm/include/asm/barebox-arm.h @@ -136,24 +136,7 @@ static inline unsigned long arm_mem_barebox_image(unsigned long membase, } } -#ifdef CONFIG_CPU_64 - -#define ____emit_entry_prologue(name, instr, ...) do { \ - static __attribute__ ((unused,section(".text_head_prologue_" __stringify(name)))) \ - const u32 __entry_prologue[] = {(instr), ##__VA_ARGS__}; \ - __keep_symbolref(__entry_prologue); \ -} while(0) - -#define __emit_entry_prologue(name, instr1, instr2, instr3, instr4, instr5) \ - ____emit_entry_prologue(name, instr1, instr2, instr3, instr4, instr5) - -#define __ARM_SETUP_STACK(name, stack_top) \ - __emit_entry_prologue(name, 0x14000002 /* b pc+0x8 */, \ - stack_top /* 32-bit literal */, \ - 0x18ffffe9 /* ldr w9, top */, \ - 0xb4000049 /* cbz x9, pc+0x8 */, \ - 0x9100013f /* mov sp, x9 */) -#else +#ifndef CONFIG_CPU_64 #define __ARM_SETUP_STACK(name, stack_top) if (stack_top) arm_setup_stack(stack_top) #endif @@ -166,6 +149,9 @@ static inline unsigned long arm_mem_barebox_image(unsigned long membase, * code block will not be inlined and may spill to stack right away. */ #ifdef CONFIG_CPU_64 + +void __barebox_arm64_head(ulong x0, ulong x1, ulong x2); + #define ENTRY_FUNCTION_WITHSTACK(name, stack_top, arg0, arg1, arg2) \ void name(ulong r0, ulong r1, ulong r2); \ \ @@ -174,8 +160,10 @@ static inline unsigned long arm_mem_barebox_image(unsigned long membase, void __section(.text_head_entry_##name) name \ (ulong r0, ulong r1, ulong r2) \ { \ - __barebox_arm_head(); \ - __ARM_SETUP_STACK(name, stack_top); \ + static __section(.pbl_board_stack_top_##name) \ + const u32 __stack_top = (stack_top); \ + __keep_symbolref(__barebox_arm64_head); \ + __keep_symbolref(__stack_top); \ __##name(r0, r1, r2); \ } \ static void noinline __##name \ diff --git a/arch/arm/lib/pbl.lds.S b/arch/arm/lib/pbl.lds.S index ae1babdcfd..114ec7bc81 100644 --- a/arch/arm/lib/pbl.lds.S +++ b/arch/arm/lib/pbl.lds.S @@ -44,6 +44,15 @@ SECTIONS . = ALIGN(4); .rodata : { *(.rodata*) } + . = ALIGN(4); + __pbl_board_stack_top = .; + .rodata.pbl_board_stack_top : { + *(.pbl_board_stack_top_*) + /* Dummy for when BootROM sets up usable stack */ + LONG(0x00000000); + } + ASSERT(. - __pbl_board_stack_top <= 8, "Only One PBL per Image allowed") + .barebox_imd : { BAREBOX_IMD } _etext = .; /* End of text and rodata section */ |