Linux驱动修炼之道-驱动中一些常见的宏
本文档讲解一下驱动中常用的宏,下边一个一个来说,先声明我使用的内核是Linux2.6.30.4。
Linux在arch/$(ARCH)/kernel/vmlinux.lds中定义了.init段,当内核启动完毕,这个段中的内存会被释放掉供其他使用,vmlinux.lds部分内容如下:
- OUTPUT_ARCH(arm)
- ENTRY(stext)
- jiffies = jiffies_64;
- SECTIONS
- {
- . = 0xC0000000 + 0x00008000;
- .text.head : {
- _stext = .;
- _sinittext = .;
- *(.text.head)
- }
- .init : { /* Init code and data */
- *(.init.text) *(.cpuinit.text) *(.meminit.text)
- _einittext = .;
- __proc_info_begin = .;
- *(.proc.info.init)
- __proc_info_end = .;
- __arch_info_begin = .;
- *(.arch.info.init)
- __arch_info_end = .;
- __tagtable_begin = .;
- *(.taglist.init)
- __tagtable_end = .;
- . = ALIGN(16);
- __setup_start = .;
- *(.init.setup)
- __setup_end = .;
- __early_begin = .;
- *(.early_param.init)
- __early_end = .;
- __initcall_start = .;
- *(.initcallearly.init) __early_initcall_end = .; *(.initcall0.init) *(.initcall0s.init) *(.initcall1.init) *(.initcall1s.init) *(.initcall2.init) *(.initcall2s.init) *(.initcall3.init) *(.initcall3s.init) *(.initcall4.init) *(.initcall4s.init) *(.initcall5.init) *(.initcall5s.init) *(.initcallrootfs.init) *(.initcall6.init) *(.initcall6s.init) *(.initcall7.init) *(.initcall7s.init)
- __initcall_end = .;
- __con_initcall_start = .;
- *(.con_initcall.init)
- __con_initcall_end = .;
- __security_initcall_start = .;
- *(.security_initcall.init)
- __security_initcall_end = .;
- . = ALIGN(32);
- __initramfs_start = .;
- usr/built-in.o(.init.ramfs)
- __initramfs_end = .;
- . = ALIGN(4096);
- __per_cpu_load = .;
- __per_cpu_start = .;
- *(.data.percpu.page_aligned)
- *(.data.percpu)
- *(.data.percpu.shared_aligned)
- __per_cpu_end = .;
- __init_begin = _stext;
- *(.init.data) *(.cpuinit.data) *(.cpuinit.rodata) *(.meminit.data) *(.meminit.rodata)
- . = ALIGN(4096);
- __init_end = .;
- }
- /DISCARD/ : { /* Exit code and data */
- *(.exit.text) *(.cpuexit.text) *(.memexit.text)
- *(.exit.data) *(.cpuexit.data) *(.cpuexit.rodata) *(.memexit.data) *(.memexit.rodata)
- *(.exitcall.exit)
- *(.ARM.exidx.exit.text)
- *(.ARM.extab.exit.text)
- }
- .text : { /* Real text segment */
- _text = .; /* Text and read-only data */
- __exception_text_start = .;
- *(.exception.text)
- __exception_text_end = .;
- . = ALIGN(8); *(.text.hot) *(.text) *(.ref.text) *(.devinit.text) *(.devexit.text) *(.text.unlikely)
- . = ALIGN(8); __sched_text_start = .; *(.sched.text) __sched_text_end = .;
- . = ALIGN(8); __lock_text_start = .; *(.spinlock.text) __lock_text_end = .;
- . = ALIGN(8); __kprobes_text_start = .; *(.kprobes.text) __kprobes_text_end = .;
- *(.fixup)
- *(.gnu.warning)
- *(.rodata)
- *(.rodata.*)
- *(.glue_7)
- *(.glue_7t)
- *(.got) /* Global offset table */
- }
- . = ALIGN((4096)); .rodata : AT(ADDR(.rodata) - 0) { __start_rodata = .; *(.rodata) *(.rodata.*) *(__vermagic) *(__markers_strings) *(__tracepoints_strings) } .rodata1 : AT(ADDR(.rodata1) - 0) { *(.rodata1) } .pci_fixup : AT(ADDR(.pci_fixup) - 0) { __start_pci_fixups_early = .; *(.pci_fixup_early) __end_pci_fixups_early = .; __start_pci_fixups_header = .; *(.pci_fixup_header) __end_pci_fixups_header = .; __start_pci_fixups_final = .; *(.pci_fixup_final) __end_pci_fixups_final = .; __start_pci_fixups_enable = .; *(.pci_fixup_enable) __end_pci_fixups_enable = .; __start_pci_fixups_resume = .; *(.pci_fixup_resume) __end_pci_fixups_resume = .; __start_pci_fixups_resume_early = .; *(.pci_fixup_resume_early) __end_pci_fixups_resume_early = .; __start_pci_fixups_suspend = .; *(.pci_fixup_suspend) __end_pci_fixups_suspend = .; } .builtin_fw : AT(ADDR(.builtin_fw) - 0) { __start_builtin_fw = .; *(.builtin_fw) __end_builtin_fw = .; } .rio_route : AT(ADDR(.rio_route) - 0) { __start_rio_route_ops = .; *(.rio_route_ops) __end_rio_route_ops = .; } __ksymtab : AT(ADDR(__ksymtab) - 0) { __start___ksymtab = .; *(__ksymtab) __stop___ksymtab = .; } __ksymtab_gpl : AT(ADDR(__ksymtab_gpl) - 0) { __start___ksymtab_gpl = .; *(__ksymtab_gpl) __stop___ksymtab_gpl = .; } __ksymtab_unused : AT(ADDR(__ksymtab_unused) - 0) { __start___ksymtab_unused = .; *(__ksymtab_unused) __stop___ksymtab_unused = .; } __ksymtab_unused_gpl : AT(ADDR(__ksymtab_unused_gpl) - 0) { __start___ksymtab_unused_gpl = .; *(__ksymtab_unused_gpl) __stop___ksymtab_unused_gpl = .; } __ksymtab_gpl_future : AT(ADDR(__ksymtab_gpl_future) - 0) { __start___ksymtab_gpl_future = .; *(__ksymtab_gpl_future) __stop___ksymtab_gpl_future = .; } __kcrctab : AT(ADDR(__kcrctab) - 0) { __start___kcrctab = .; *(__kcrctab) __stop___kcrctab = .; } __kcrctab_gpl : AT(ADDR(__kcrctab_gpl) - 0) { __start___kcrctab_gpl = .; *(__kcrctab_gpl) __stop___kcrctab_gpl = .; } __kcrctab_unused : AT(ADDR(__kcrctab_unused) - 0) { __start___kcrctab_unused = .; *(__kcrctab_unused) __stop___kcrctab_unused = .; } __kcrctab_unused_gpl : AT(ADDR(__kcrctab_unused_gpl) - 0) { __start___kcrctab_unused_gpl = .; *(__kcrctab_unused_gpl) __stop___kcrctab_unused_gpl = .; } __kcrctab_gpl_future : AT(ADDR(__kcrctab_gpl_future) - 0) { __start___kcrctab_gpl_future = .; *(__kcrctab_gpl_future) __stop___kcrctab_gpl_future = .; } __ksymtab_strings : AT(ADDR(__ksymtab_strings) - 0) { *(__ksymtab_strings) } __init_rodata : AT(ADDR(__init_rodata) - 0) { *(.ref.rodata) *(.devinit.rodata) *(.devexit.rodata) } __param : AT(ADDR(__param) - 0) { __start___param = .; *(__param) __stop___param = .; . = ALIGN((4096)); __end_rodata = .; } . = ALIGN((4096));
- _etext = .; /* End of text and rodata section */
- /*
- * Stack unwinding tables
- */
- . = ALIGN(8);
- .ARM.unwind_idx : {
- __start_unwind_idx = .;
- *(.ARM.exidx*)
- __stop_unwind_idx = .;
- }
- .ARM.unwind_tab : {
- __start_unwind_tab = .;
- *(.ARM.extab*)
- __stop_unwind_tab = .;
- }
- . = ALIGN(8192);
- __data_loc = .;
- .data : AT(__data_loc) {
- _data = .; /* address in memory */
- /*
- * first, the init task union, aligned
- * to an 8192 byte boundary.
- */
- *(.data.init_task)
- . = ALIGN(4096);
- __nosave_begin = .;
- *(.data.nosave)
- . = ALIGN(4096);
- __nosave_end = .;
- /*
- * then the cacheline aligned data
- */
- . = ALIGN(32);
- *(.data.cacheline_aligned)
- /*
- * The exception fixup table (might need resorting at runtime)
- */
- . = ALIGN(32);
- __start___ex_table = .;
- *(__ex_table)
- __stop___ex_table = .;
- /*
- * and the usual data section
- */
- *(.data) *(.ref.data) *(.devinit.data) *(.devexit.data) . = ALIGN(8); __start___markers = .; *(__markers) __stop___markers = .; . = ALIGN(32); __start___tracepoints = .; *(__tracepoints) __stop___tracepoints = .; . = ALIGN(8); __start___verbose = .; *(__verbose) __stop___verbose = .;
- CONSTRUCTORS
- _edata = .;
- }
- _edata_loc = __data_loc + SIZEOF(.data);
- .bss : {
- __bss_start = .; /* BSS */
- *(.bss)
- *(COMMON)
- _end = .;
- }
- /* Stabs debugging sections. */
- .stab 0 : { *(.stab) }
- .stabstr 0 : { *(.stabstr) }
- .stab.excl 0 : { *(.stab.excl) }
- .stab.exclstr 0 : { *(.stab.exclstr) }
- .stab.index 0 : { *(.stab.index) }
- .stab.indexstr 0 : { *(.stab.indexstr) }
- .comment 0 : { *(.comment) }
- }
- /*
- * These must never be empty
- * If you have to comment these two assert statements out, your
- * binutils is too old (for other reasons as well)
- */
- ASSERT((__proc_info_end - __proc_info_begin), "missing CPU support")
- ASSERT((__arch_info_end - __arch_info_begin), "no machine record defined")