The arm linker scripts had a mix of symbols and C defined variables in an effort to emit relative references instead of absolute ones e.g [0]. A linker bug prevented us from doing so [1] -- fixed since 2016. This has led to confusion over the years, ending up with mixed section definitions. Some sections are defined with overlays and different definitions between v7 and v8 architectures. For example __efi_runtime_rel_start/end is defined as a linker symbol for armv8 and a C variable in armv7.
Linker scripts nowadays can emit relative references, as long as the symbol definition is contained within the section definition. So let's switch most of the C defined variables and clean up the arm sections.c file. There's still a few symbols remaining -- __secure_start/end, __secure_stack_start/end and __end which can be cleaned up in a followup series.
For both QEMU v7/v8 bloat-o-meter shows now size difference $~ ./scripts/bloat-o-meter u-boot u-boot.new add/remove: 0/0 grow/shrink: 0/0 up/down: 0/0 (0) Function old new delta Total: Before=798861, After=798861, chg +0.00%
The symbols seem largely unchanged apart from a difference in .bss as well as the emited sections and object types of the affected variables.
On the output below the first value is from -next and the second comes from -next + this patchset. The .bss_start/end sections have disappeared from the newer binaries.
# For example on QEMU v8: efi_runtime_start 7945: 0000000000000178 0 OBJECT GLOBAL DEFAULT 2 __efi_runtime_start 7942: 0000000000000178 0 NOTYPE GLOBAL DEFAULT 2 __efi_runtime_start efi_runtime_stop 9050: 0000000000000d38 0 OBJECT GLOBAL DEFAULT 2 __efi_runtime_stop 9047: 0000000000000d38 0 NOTYPE GLOBAL DEFAULT 2 __efi_runtime_stop __efi_runtime_rel_start 7172: 00000000000dc2f0 0 OBJECT GLOBAL DEFAULT 10 __efi_runtime_rel_start 7169: 00000000000dc2f0 0 NOTYPE GLOBAL DEFAULT 10 __efi_runtime_rel_start __efi_runtime_rel_stop 7954: 00000000000dc4a0 0 OBJECT GLOBAL DEFAULT 10 __efi_runtime_rel_stop 7951: 00000000000dc4a0 0 NOTYPE GLOBAL DEFAULT 10 __efi_runtime_rel_stop __rel_dyn_start 7030: 00000000000dc4a0 0 OBJECT GLOBAL DEFAULT 11 __rel_dyn_start 7027: 00000000000dc4a0 0 NOTYPE GLOBAL DEFAULT 11 __rel_dyn_start __rel_dyn_end 8959: 0000000000102b10 0 OBJECT GLOBAL DEFAULT 12 __rel_dyn_end 8956: 0000000000102b10 0 NOTYPE GLOBAL DEFAULT 11 __rel_dyn_end image_copy_start 9051: 0000000000000000 0 OBJECT GLOBAL DEFAULT 1 __image_copy_start 9048: 0000000000000000 0 NOTYPE GLOBAL DEFAULT 1 __image_copy_start image_copy_end 7467: 00000000000dc4a0 0 OBJECT GLOBAL DEFAULT 11 __image_copy_end 7464: 00000000000dc4a0 0 NOTYPE GLOBAL DEFAULT 10 __image_copy_end bss_start 12: 0000000000102b10 0 SECTION LOCAL DEFAULT 12 .bss_start 8087: 0000000000000018 0 NOTYPE GLOBAL DEFAULT 1 _bss_start_ofs 8375: 0000000000102b10 0 OBJECT GLOBAL DEFAULT 12 __bss_start 8084: 0000000000000018 0 NOTYPE GLOBAL DEFAULT 1 _bss_start_ofs 8372: 0000000000102b80 0 NOTYPE GLOBAL DEFAULT 12 __bss_start bss_end 14: 000000000010bc30 0 SECTION LOCAL DEFAULT 14 .bss_end 7683: 000000000010bc30 0 OBJECT GLOBAL DEFAULT 14 __bss_end 8479: 0000000000000020 0 NOTYPE GLOBAL DEFAULT 1 _bss_end_ofs 7680: 000000000010bc30 0 NOTYPE GLOBAL DEFAULT 12 __bss_end 8476: 0000000000000020 0 NOTYPE GLOBAL DEFAULT 1 _bss_end_ofs
# For QEMU v7: efi_runtime_start 10703: 000003bc 0 OBJECT GLOBAL DEFAULT 2 __efi_runtime_start 10699: 000003c0 0 NOTYPE GLOBAL DEFAULT 2 __efi_runtime_start efi_runtime_stop 11796: 000012ec 0 OBJECT GLOBAL DEFAULT 2 __efi_runtime_stop 11792: 000012ec 0 NOTYPE GLOBAL DEFAULT 2 __efi_runtime_stop __efi_runtime_rel_start 9937: 000c40dc 0 OBJECT GLOBAL DEFAULT 8 __efi_runtime_rel_start 9935: 000c40dc 0 NOTYPE GLOBAL DEFAULT 9 __efi_runtime_rel_start __efi_runtime_rel_stop 10712: 000c41dc 0 OBJECT GLOBAL DEFAULT 10 __efi_runtime_rel_stop 10708: 000c41dc 0 NOTYPE GLOBAL DEFAULT 9 __efi_runtime_rel_stop __rel_dyn_start 9791: 000c41dc 0 OBJECT GLOBAL DEFAULT 10 __rel_dyn_start 9789: 000c41dc 0 NOTYPE GLOBAL DEFAULT 10 __rel_dyn_start __rel_dyn_end 11708: 000da5f4 0 OBJECT GLOBAL DEFAULT 10 __rel_dyn_end 11704: 000da5f4 0 NOTYPE GLOBAL DEFAULT 10 __rel_dyn_end image_copy_start 448: 0000177c 0 NOTYPE LOCAL DEFAULT 3 _image_copy_start_ofs 11797: 00000000 0 OBJECT GLOBAL DEFAULT 1 __image_copy_start 445: 0000177c 0 NOTYPE LOCAL DEFAULT 3 _image_copy_start_ofs 11793: 00000000 0 NOTYPE GLOBAL DEFAULT 1 __image_copy_start image_copy_end 450: 00001780 0 NOTYPE LOCAL DEFAULT 3 _image_copy_end_ofs 10225: 000c41dc 0 OBJECT GLOBAL DEFAULT 10 __image_copy_end 447: 00001780 0 NOTYPE LOCAL DEFAULT 3 _image_copy_end_ofs 10222: 000c41dc 0 NOTYPE GLOBAL DEFAULT 9 __image_copy_end bss_start 11: 000c41dc 0 SECTION LOCAL DEFAULT 11 .bss_start 11124: 000c41dc 0 OBJECT GLOBAL DEFAULT 11 __bss_start 11120: 000c41dc 0 NOTYPE GLOBAL DEFAULT 11 __bss_start bss_end 13: 000cbbf8 0 SECTION LOCAL DEFAULT 13 .bss_end 10442: 000cbbf8 0 OBJECT GLOBAL DEFAULT 13 __bss_end 10439: 000cbbf8 0 NOTYPE GLOBAL DEFAULT 11 __bss_end
It's worth noting that since the efi regions are affected by the change, booting with EFI is preferable while testing. Booting the kernel only should be enough since the efi stub and the kernel proper do request boottime and runtime services respectively. Something along the lines of
virtio scan && load virtio 0 $kernel_addr_r Image && bootefi $kernel_addr_r
will work for QEMU aarch64.
Tested platforms: - QEMU aarch64 - Xilinx kv260 kria starter kit & zynq - QEMU armv7 - STM32MP157C-DK2
[0] commit 3ebd1cbc49f0 ("arm: make __bss_start and __bss_end__ compiler-generated") [1] binutils commit 6b3b0ab89663 ("Make linker assigned symbol dynamic only for shared object")
Changes since v1: - bring back overlays for armv7 rel.dyn and bss sections and add a comment explaining why we overlay those - Remove redundant alignment from sections (new patch #7) - Added r-b tags from Sam Changes since RFC: - Rebase on top of -next and get rid of the dragonboard linker script changes. Caleb removed that file completely - Rewrite some commit messages to include the binutils bug details (thanks Sam)
Ilias Apalodimas (7): arm: baltos: remove custom linker script arm: clean up v7 and v8 linker scripts for bss_start/end arm: fix __efi_runtime_rel_start/end definitions arm: clean up v7 and v8 linker scripts for __rel_dyn_start/end arm: fix __efi_runtime_start/end definitions arm: move image_copy_start/end to linker symbols arm: remove redundant section alignments
arch/arm/cpu/armv8/u-boot-spl.lds | 21 +--- arch/arm/cpu/armv8/u-boot.lds | 38 +----- arch/arm/cpu/u-boot-spl.lds | 2 +- arch/arm/cpu/u-boot.lds | 66 +++------- arch/arm/lib/sections.c | 10 -- arch/arm/mach-aspeed/ast2600/u-boot-spl.lds | 2 +- arch/arm/mach-rockchip/u-boot-tpl-v8.lds | 21 +--- arch/arm/mach-zynq/u-boot-spl.lds | 2 +- arch/arm/mach-zynq/u-boot.lds | 67 +++------- board/vscom/baltos/u-boot.lds | 128 -------------------- include/asm-generic/sections.h | 3 + lib/efi_loader/efi_runtime.c | 1 + 12 files changed, 52 insertions(+), 309 deletions(-) delete mode 100644 board/vscom/baltos/u-boot.lds
-- 2.37.2