From b1944884fccdb9449a05ebf94c3918fa688f8503 Mon Sep 17 00:00:00 2001 From: Jiang Liu Date: Wed, 19 Jun 2013 10:06:22 +1000 Subject: [PATCH] vmlinux.lds: add comments for global variables and clean up useless declarations The original goal of this patchset is to fix the bug reported by https://bugzilla.kernel.org/show_bug.cgi?id=53501 Now it has also been expanded to reduce common code used by memory initializion. Patch 1-7: 1) add comments for global variables exported by vmlinux.lds 2) normalize global variables exported by vmlinux.lds Patch 8: Introduce helper functions mem_init_print_info() and get_num_physpages() Patch 9: Avoid using global variable num_physpages at runtime Patch 10: Don't update num_physpages in memory_hotplug.c Patch 11-40: Modify arch mm initialization code to: 1) Simplify mem_init() by using mem_init_print_info() 2) Prepare for killing global variable num_physpages Patch 41: Kill the global variable num_physpages With all patches applied, mem_init(), free_initmem(), free_initrd_mem() could be as simple as below. This patch series has reduced about 1.2K lines of code in total. #ifndef CONFIG_DISCONTIGMEM void __init mem_init(void) { max_mapnr = max_low_pfn; free_all_bootmem(); high_memory = (void *) __va(max_low_pfn * PAGE_SIZE); mem_init_print_info(NULL); } #endif /* CONFIG_DISCONTIGMEM */ void free_initmem(void) { free_initmem_default(-1); } #ifdef CONFIG_BLK_DEV_INITRD void free_initrd_mem(unsigned long start, unsigned long end) { free_reserved_area(start, end, -1, "initrd"); } #endif Due to hardware resource limitations, I have only tested this on x86_64. And the messages reported on an x86_64 system are: Log message before applying patches: Memory: 7745676k/8910848k available (6934k kernel code, 836024k absent, 329148k reserved, 6343k data, 1012k init) Log message after applying patches: Memory: 7744624K/8074824K available (6969K kernel code, 1011K data, 2828K rodata, 1016K init, 9640K bss, 330200K reserved) Great thanks to Vineet Gupta for testing on ARC. This patch: Document global variables exported from vmlinux.lds. 1) Add comments about usage guidelines for global variables exported from vmlinux.lds.S. 2) Remove unused __initdata_begin[] and __initdata_end[]. Signed-off-by: Jiang Liu Acked-by: Arnd Bergmann Cc: Arnd Bergmann Cc: Vineet Gupta Signed-off-by: Andrew Morton --- include/asm-generic/sections.h | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h index c1a1216e29ce..f1a24b5c3b90 100644 --- a/include/asm-generic/sections.h +++ b/include/asm-generic/sections.h @@ -3,6 +3,26 @@ /* References to section boundaries */ +/* + * Usage guidelines: + * _text, _data: architecture specific, don't use them in arch-independent code + * [_stext, _etext]: contains .text.* sections, may also contain .rodata.* + * and/or .init.* sections + * [_sdata, _edata]: contains .data.* sections, may also contain .rodata.* + * and/or .init.* sections. + * [__start_rodata, __end_rodata]: contains .rodata.* sections + * [__init_begin, __init_end]: contains .init.* sections, but .init.text.* + * may be out of this range on some architectures. + * [_sinittext, _einittext]: contains .init.text.* sections + * [__bss_start, __bss_stop]: contains BSS sections + * + * Following global variables are optional and may be unavailable on some + * architectures and/or kernel configurations. + * _text, _data + * __kprobes_text_start, __kprobes_text_end + * __entry_text_start, __entry_text_end + * __ctors_start, __ctors_end + */ extern char _text[], _stext[], _etext[]; extern char _data[], _sdata[], _edata[]; extern char __bss_start[], __bss_stop[]; @@ -12,7 +32,6 @@ extern char _end[]; extern char __per_cpu_load[], __per_cpu_start[], __per_cpu_end[]; extern char __kprobes_text_start[], __kprobes_text_end[]; extern char __entry_text_start[], __entry_text_end[]; -extern char __initdata_begin[], __initdata_end[]; extern char __start_rodata[], __end_rodata[]; /* Start and end of .ctors section - used for constructor calls. */ -- 2.39.5