From faf396aa1df4c9f97598be3ebf7dbc02ede34ad0 Mon Sep 17 00:00:00 2001 From: Ilias Apalodimas Date: Fri, 15 Mar 2024 08:43:46 +0200 Subject: [PATCH] arm: clean up v7 and v8 linker scripts for bss_start/end commit 3ebd1cbc49f0 ("arm: make __bss_start and __bss_end__ compiler-generated") and commit f84a7b8f54db ("ARM: Fix __bss_start and __bss_end in linker scripts") were moving the bss_start/end on c generated variables that were injected in their own sections. The reason was that we needed relative relocations for position independent code and linker bugs back then prevented us from doing so [0]. However, the linker documentation pages states that symbols that are defined within a section definition will create a relocatable type with the value being a fixed offset from the base of a section [1]. So let's start cleaning this up starting with the bss_start and bss_end variables. Convert them into symbols within the .bss section definition. [0] binutils commit 6b3b0ab89663 ("Make linker assigned symbol dynamic only for shared object") [1] https://sourceware.org/binutils/docs/ld/Expression-Section.html Tested-by: Caleb Connolly # Qualcomm sdm845 Tested-by: Sam Edwards # Binary output identical Signed-off-by: Ilias Apalodimas Reviewed-by: Richard Henderson --- arch/arm/cpu/armv8/u-boot-spl.lds | 18 +++++++----------- arch/arm/cpu/armv8/u-boot.lds | 16 ++++------------ arch/arm/cpu/u-boot.lds | 22 +++++++--------------- arch/arm/lib/sections.c | 2 -- arch/arm/mach-rockchip/u-boot-tpl-v8.lds | 15 ++++----------- arch/arm/mach-zynq/u-boot.lds | 22 +++++++--------------- 6 files changed, 29 insertions(+), 66 deletions(-) diff --git a/arch/arm/cpu/armv8/u-boot-spl.lds b/arch/arm/cpu/armv8/u-boot-spl.lds index 7cb9d73124..8998c4985e 100644 --- a/arch/arm/cpu/armv8/u-boot-spl.lds +++ b/arch/arm/cpu/armv8/u-boot-spl.lds @@ -63,18 +63,11 @@ SECTIONS _image_binary_end = .; - .bss_start (NOLOAD) : { - . = ALIGN(8); - KEEP(*(.__bss_start)); - } >.sdram - - .bss (NOLOAD) : { + .bss : { + __bss_start = .; *(.bss*) - . = ALIGN(8); - } >.sdram - - .bss_end (NOLOAD) : { - KEEP(*(.__bss_end)); + . = ALIGN(8); + __bss_end = .; } >.sdram /DISCARD/ : { *(.rela*) } @@ -89,3 +82,6 @@ SECTIONS #include "linux-kernel-image-header-vars.h" #endif } + +ASSERT(ADDR(.bss) % 8 == 0, \ + ".bss must be 8-byte aligned"); diff --git a/arch/arm/cpu/armv8/u-boot.lds b/arch/arm/cpu/armv8/u-boot.lds index fb6a30c922..9640cc7a04 100644 --- a/arch/arm/cpu/armv8/u-boot.lds +++ b/arch/arm/cpu/armv8/u-boot.lds @@ -149,19 +149,11 @@ SECTIONS _end = .; - . = ALIGN(8); - - .bss_start : { - KEEP(*(.__bss_start)); - } - - .bss : { + .bss ALIGN(8): { + __bss_start = .; *(.bss*) - . = ALIGN(8); - } - - .bss_end : { - KEEP(*(.__bss_end)); + . = ALIGN(8); + __bss_end = .; } /DISCARD/ : { *(.dynsym) } diff --git a/arch/arm/cpu/u-boot.lds b/arch/arm/cpu/u-boot.lds index 7724c9332c..0dfe5f633b 100644 --- a/arch/arm/cpu/u-boot.lds +++ b/arch/arm/cpu/u-boot.lds @@ -207,23 +207,15 @@ SECTIONS } /* - * Compiler-generated __bss_start and __bss_end, see arch/arm/lib/bss.c - * __bss_base and __bss_limit are for linker only (overlay ordering) + * These sections occupy the same memory, but their lifetimes do + * not overlap: U-Boot initializes .bss only after applying dynamic + * relocations and therefore after it doesn't need .rel.dyn any more. */ - - .bss_start __rel_dyn_start (OVERLAY) : { - KEEP(*(.__bss_start)); - __bss_base = .; - } - - .bss __bss_base (OVERLAY) : { + .bss ADDR(.rel.dyn) (OVERLAY): { + __bss_start = .; *(.bss*) - . = ALIGN(4); - __bss_limit = .; - } - - .bss_end __bss_limit (OVERLAY) : { - KEEP(*(.__bss_end)); + . = ALIGN(4); + __bss_end = .; } .dynsym _image_binary_end : { *(.dynsym) } diff --git a/arch/arm/lib/sections.c b/arch/arm/lib/sections.c index 857879711c..8e8bd5797e 100644 --- a/arch/arm/lib/sections.c +++ b/arch/arm/lib/sections.c @@ -19,8 +19,6 @@ * aliasing warnings. */ -char __bss_start[0] __section(".__bss_start"); -char __bss_end[0] __section(".__bss_end"); char __image_copy_start[0] __section(".__image_copy_start"); char __image_copy_end[0] __section(".__image_copy_end"); char __rel_dyn_start[0] __section(".__rel_dyn_start"); diff --git a/arch/arm/mach-rockchip/u-boot-tpl-v8.lds b/arch/arm/mach-rockchip/u-boot-tpl-v8.lds index 74618eba59..712c485d4d 100644 --- a/arch/arm/mach-rockchip/u-boot-tpl-v8.lds +++ b/arch/arm/mach-rockchip/u-boot-tpl-v8.lds @@ -56,18 +56,11 @@ SECTIONS _image_binary_end = .; - .bss_start (NOLOAD) : { - . = ALIGN(8); - KEEP(*(.__bss_start)); - } - - .bss (NOLOAD) : { + .bss ALIGN(8) : { + __bss_start = .; *(.bss*) - . = ALIGN(8); - } - - .bss_end (NOLOAD) : { - KEEP(*(.__bss_end)); + . = ALIGN(8); + __bss_end = .; } /DISCARD/ : { *(.dynsym) } diff --git a/arch/arm/mach-zynq/u-boot.lds b/arch/arm/mach-zynq/u-boot.lds index 3b7c9d515f..3c5008b573 100644 --- a/arch/arm/mach-zynq/u-boot.lds +++ b/arch/arm/mach-zynq/u-boot.lds @@ -103,23 +103,15 @@ SECTIONS _image_binary_end = .; /* - * Compiler-generated __bss_start and __bss_end, see arch/arm/lib/bss.c - * __bss_base and __bss_limit are for linker only (overlay ordering) + * These sections occupy the same memory, but their lifetimes do + * not overlap: U-Boot initializes .bss only after applying dynamic + * relocations and therefore after it doesn't need .rel.dyn any more. */ - - .bss_start __rel_dyn_start (OVERLAY) : { - KEEP(*(.__bss_start)); - __bss_base = .; - } - - .bss __bss_base (OVERLAY) : { + .bss ADDR(.rel.dyn) (OVERLAY): { + __bss_start = .; *(.bss*) - . = ALIGN(8); - __bss_limit = .; - } - - .bss_end __bss_limit (OVERLAY) : { - KEEP(*(.__bss_end)); + . = ALIGN(8); + __bss_end = .; } /* -- 2.39.5