When trying to run linux with various opensource riscv core on resource limited FPGA platforms, for example, those FPGAs with less than 16MB SDRAM, I want to save mem as much as possible. One of the major technologies is kernel size optimizations, I found that riscv does not currently support HAVE_LD_DEAD_CODE_DATA_ELIMINATION, which passes -fdata-sections, -ffunction-sections to CFLAGS and passes the --gc-sections flag to the linker. This not only benefits my case on FPGA but also benefits defconfigs. Here are some notable improvements from enabling this with defconfigs: nommu_k210_defconfig: text data bss dec hex 1112009 410288 59837 1582134 182436 before 962838 376656 51285 1390779 1538bb after rv32_defconfig: text data bss dec hex 8804455 2816544 290577 11911576 b5c198 before 8692295 2779872 288977 11761144 b375f8 after defconfig: text data bss dec hex 9438267 3391332 485333 13314932 cb2b74 before 9285914 3350052 483349 13119315 c82f53 after patch1 and patch2 are clean ups. patch3 fixes a typo. patch4 finally enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION for riscv. Jisheng Zhang (4): riscv: vmlinux-xip.lds.S: remove .alternative section riscv: move HAVE_RETHOOK to keep entries sorted riscv: enable HAVE_LD_DEAD_CODE_DATA_ELIMINATION vmlinux.lds.h: use correct .init.data.* section name arch/riscv/Kconfig | 3 ++- arch/riscv/kernel/vmlinux-xip.lds.S | 6 ------ arch/riscv/kernel/vmlinux.lds.S | 6 +++--- include/asm-generic/vmlinux.lds.h | 2 +- 4 files changed, 6 insertions(+), 11 deletions(-) -- 2.40.1
