u-boot/arch/mips/include/asm/sections.h

/* SPDX-License-Identifier: GPL-2.0+ */
/*
 * Copyright (c) 2012 The Chromium OS Authors.
 */

#ifndef __ASM_MIPS_SECTIONS_H
#define __ASM_MIPS_SECTIONS_H

#include <asm-generic/sections.h>

/**
 * __rel_start: Relocation data generated by the mips-relocs tool
 *
 * See arch/mips/lib/reloc.c for details on the format & use of this data.
 */
extern uint8_t __rel_start[];

#endif
SPDX: Convert all of our single license tags to Linux Kernel style When U-Boot started using SPDX tags we were among the early adopters and there weren't a lot of other examples to borrow from. So we picked the area of the file that usually had a full license text and replaced it with an appropriate SPDX-License-Identifier: entry. Since then, the Linux Kernel has adopted SPDX tags and they place it as the very first line in a file (except where shebangs are used, then it's second line) and with slightly different comment styles than us. In part due to community overlap, in part due to better tag visibility and in part for other minor reasons, switch over to that style. This commit changes all instances where we have a single declared license in the tag as both the before and after are identical in tag contents. There's also a few places where I found we did not have a tag and have introduced one. Signed-off-by: Tom Rini <trini@konsulko.com> 2018-05-06 21:58:06 +00:00			`/* SPDX-License-Identifier: GPL-2.0+ */`
Introduce generic link section.h symbol files We create a separate header file for link symbols defined by the link scripts. It is helpful to have these all in one place and try to make them common across architectures. Since Linux already has a similar file, we bring this in even though many of the symbols there are not relevant to us. Each architecture has its own asm/sections.h where symbols specifc to that architecture can be added. For now everything except AVR32 just includes the generic header. One change is needed in arch/avr32/lib/board.c to make this conversion work. Reviewed-by: Tom Rini <trini@ti.com> (version 5) Signed-off-by: Simon Glass <sjg@chromium.org> 2013-03-05 14:39:37 +00:00			`/*`
			`* Copyright (c) 2012 The Chromium OS Authors.`
			`*/`

			`#ifndef __ASM_MIPS_SECTIONS_H`
			`#define __ASM_MIPS_SECTIONS_H`

			`#include <asm-generic/sections.h>`

MIPS: Stop building position independent code U-Boot has up until now built with -fpic for the MIPS architecture, producing position independent code which uses indirection through a global offset table, making relocation fairly straightforward as it simply involves patching up GOT entries. Using -fpic does however have some downsides. The biggest of these is that generated code is bloated in various ways. For example, function calls are indirected through the GOT & the t9 register: 8f998064 lw t9,-32668(gp) 0320f809 jalr t9 Without -fpic the call is simply: 0f803f01 jal be00fc04 <puts> This is more compact & faster (due to the lack of the load & the dependency the jump has on its result). It is also easier to read & debug because the disassembly shows what function is being called, rather than just an offset from gp which would then have to be looked up in the ELF to discover the target function. Another disadvantage of -fpic is that each function begins with a sequence to calculate the value of the gp register, for example: 3c1c0004 lui gp,0x4 279c3384 addiu gp,gp,13188 0399e021 addu gp,gp,t9 Without using -fpic this sequence no longer appears at the start of each function, reducing code size considerably. This patch switches U-Boot from building with -fpic to building with -fno-pic, in order to gain the benefits described above. The cost of this is an extra step during the build process to extract relocation data from the ELF & write it into a new .rel section in a compact format, plus the added complexity of dealing with multiple types of relocation rather than the single type that applied to the GOT. The benefit is smaller, cleaner, more debuggable code. The relocate_code() function is reimplemented in C to handle the new relocation scheme, which also makes it easier to read & debug. Taking maltael_defconfig as an example the size of u-boot.bin built using the Codescape MIPS 2016.05-06 toolchain (gcc 4.9.2, binutils 2.24.90) shrinks from 254KiB to 224KiB. Signed-off-by: Paul Burton <paul.burton@imgtec.com> Cc: Daniel Schwierzeck <daniel.schwierzeck@gmail.com> Cc: u-boot@lists.denx.de Reviewed-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com> Tested-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com> 2017-06-19 18:53:47 +00:00			`/**`
			`* __rel_start: Relocation data generated by the mips-relocs tool`
			`*`
			`* See arch/mips/lib/reloc.c for details on the format & use of this data.`
			`*/`
			`extern uint8_t __rel_start[];`

Introduce generic link section.h symbol files We create a separate header file for link symbols defined by the link scripts. It is helpful to have these all in one place and try to make them common across architectures. Since Linux already has a similar file, we bring this in even though many of the symbols there are not relevant to us. Each architecture has its own asm/sections.h where symbols specifc to that architecture can be added. For now everything except AVR32 just includes the generic header. One change is needed in arch/avr32/lib/board.c to make this conversion work. Reviewed-by: Tom Rini <trini@ti.com> (version 5) Signed-off-by: Simon Glass <sjg@chromium.org> 2013-03-05 14:39:37 +00:00			`#endif`