From 22e6a2e14cb8ebcae059488cf24e778e4058c2bf Mon Sep 17 00:00:00 2001 From: Anup Patel Date: Wed, 19 Dec 2018 18:06:57 +0530 Subject: [PATCH] RISC-V: Make BSS section as the last section in vmlinux.lds.S The objcopy only emits loadable sections when creating flat kernel Image. To have minimal possible size of flat kernel Image, we should have all non-loadable sections after loadable sections. Currently, execption table section (loadable section) is after BSS section (non-loadable section) in the RISC-V vmlinux.lds.S. This is not optimal for having minimal flat kernel Image size hence this patch makes BSS section as the last section in RISC-V vmlinux.lds.S. In addition, we make BSS section aligned to 16byte instead of PAGE aligned which further reduces flat kernel Image size by few KBs. The flat kernel Image size of Linux-4.20-rc4 using GCC 8.2.0 is 8819980 bytes with current RISC-V vmlinux.lds.S and it reduces to 7991740 bytes with this patch applied. In summary, this patch reduces Linux-4.20-rc4 flat kernel Image size by 809 KB. Signed-off-by: Anup Patel Reviewed-by: Bin Meng Signed-off-by: Palmer Dabbelt --- arch/riscv/kernel/vmlinux.lds.S | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S index 65df1df..1e1395d 100644 --- a/arch/riscv/kernel/vmlinux.lds.S +++ b/arch/riscv/kernel/vmlinux.lds.S @@ -18,6 +18,8 @@ #include #include +#define MAX_BYTES_PER_LONG 0x10 + OUTPUT_ARCH(riscv) ENTRY(_start) @@ -74,8 +76,6 @@ SECTIONS *(.sbss*) } - BSS_SECTION(PAGE_SIZE, PAGE_SIZE, 0) - EXCEPTION_TABLE(0x10) NOTES @@ -83,6 +83,10 @@ SECTIONS *(.rel.dyn*) } + BSS_SECTION(MAX_BYTES_PER_LONG, + MAX_BYTES_PER_LONG, + MAX_BYTES_PER_LONG) + _end = .; STABS_DEBUG -- 2.7.4