ZTEXTADDR和ZRELADDR
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例子:*** 30008000 zImage 是zImage内存中的地址 ==ZRELADDR 解压后的内核运行地址 30800000 ramdisk 在内存中地址 ZTEXTADDR following symbol definitions rely on you knowing the translation that __virt_to_phys() does for your machine.?? This macro converts the passed virtual address to a physical address.?? Normally,it is simply: phys = virt - PAGE_OFFSET + PHYS_OFFSET Decompressor Symbols -------------------- ZTEXTADDR Start address of decompressor.?? There's no point in talking about virtual or physical addresses here,since the MMU will be off at the time when you call the decompressor code.?? You normally call the kernel at this address to start it booting.?? This doesn't have to be located in RAM,it can be in flash or other read-only or read-write addressable medium. ZBSSADDR Start address of zero-initialised work area for the decompressor. This must be pointing at RAM.?? The decompressor will zero initialise this for you.?? Again,the MMU will be off. ZRELADDR This is the address where the decompressed kernel will be written, and eventually executed.?? The following constraint must be valid: __virt_to_phys(TEXTADDR) == ZRELADDR The initial part of the kernel is carefully coded to be position independent. INITRD_PHYS Physical address to place the initial RAM disk.?? Only relevant if you are using the bootpImage stuff (which only works on the old struct param_struct). INITRD_VIRT Virtual address of the initial RAM disk.?? The following?? constraint must be valid: __virt_to_phys(INITRD_VIRT) == INITRD_PHYS PARAMS_PHYS Physical address of the struct param_struct or tag list,giving the kernel various parameters about its execution environment. Kernel Symbols -------------- PHYS_OFFSET Physical start address of the first bank of RAM. PAGE_OFFSET Virtual start address of the first bank of RAM.?? During the kernel boot phase,virtual address PAGE_OFFSET will be mapped to physical address PHYS_OFFSET,along with any other mappings you supply. This should be the same value as TASK_SIZE. TASK_SIZE The maximum size of a user process in bytes.?? Since user space always starts at zero,this is the maximum address that a user process can access+1.?? The user space stack grows down from this address. Any virtual address below TASK_SIZE is deemed to be user process area,and therefore managed dynamically on a process by process basis by the kernel.?? I'll call this the user segment. Anything above TASK_SIZE is common to all processes.?? I'll call this the kernel segment. (In other words,you can't put IO mappings below TASK_SIZE,and hence PAGE_OFFSET). TEXTADDR Virtual start address of kernel,normally PAGE_OFFSET + 0x8000. This is where the kernel image ends up.?? With the latest kernels, it must be located at 32768 bytes into a 128MB region.?? Previous kernels placed a restriction of 256MB here. DATAADDR Virtual address for the kernel data segment.?? Must not be defined when using the decompressor. VMALLOC_START VMALLOC_END Virtual addresses bounding the vmalloc() area.?? There must not be any static mappings in this area; vmalloc will overwrite them. The addresses must also be in the kernel segment (see above). Normally,the vmalloc() area starts VMALLOC_OFFSET bytes above the last virtual RAM address (found using variable high_memory). VMALLOC_OFFSET Offset normally incorporated into VMALLOC_START to provide a hole between virtual RAM and the vmalloc area.?? We do this to allow out of bounds memory accesses (eg,something writing off the end of the mapped memory map) to be caught.?? Normally set to 8MB. Architecture Specific Macros ---------------------------- BOOT_MEM(pram,pio,vio) `pram' specifies the physical start address of RAM.?? Must always be present,and should be the same as PHYS_OFFSET. `pio' is the physical address of an 8MB region containing IO for use with the debugging macros in arch/arm/kernel/debug-armv.S. `vio' is the virtual address of the 8MB debugging region. It is expected that the debugging region will be re-initialised by the architecture specific code later in the code (via the MAPIO function). BOOT_PARAMS Same as,and see PARAMS_PHYS. FIXUP(func) Machine specific fixups,run before memory subsystems have been initialised. MAPIO(func) Machine specific function to map IO areas (including the debug region above). INITIRQ(func) Machine specific function to initialise interrupts. zImage是位置无关的,解压之后的内核的物理启动地址是ZRELADDR, 而如果是在flash中运行,也就是运行解压操作的话 # We now have a PIC decompressor implementation.?? Decompressors running 可以这样理解,如果bootloader是在flash运行之后,分nand和nor两种,nand的话,需要把bootloader的后半部分以及kernel都拷到ram里运行,这样bootloader执行完了之后会跳到压缩内核,然后执行zImage里的解压部分,zImage是位置无关的,解压之后的内核要放到指定位置ZRELADDR.如果是nor flash的话,则既可以在flash上运行完bootloader,然后把压缩内核拷到ram,这样不需要指定ZTEXTADDR,也可以一直运行到执行解压缩操作,然后把内核解压到ZRELADDR,这样需要指定ZTEXTADDR. em86xx的bootloader是在nor执行,而且在bootloader里将内核解压到指定的地址,也就是下面的0x90090000 OUTPUT_ARCH(arm) 一般的是这样 OUTPUT_ARCH(arm) ENTRY(_start) SECTIONS { ??? . = LOAD_ADDR; ??? _load_addr = .; ??? . = TEXT_START; ??? _text = .; ??? .text : { ????? _start = .; 在kernel/arch/arm/boot/compressed/Makefile文件有一行脚本： SEDFLAGS???? = s/TEXT_START/$(ZTEXTADDR)/;s/LOAD_ADDR/$(ZRELADDR)/;s/BSS_START/$(ZBSSADDR)/ 使得TEXT_START = ZTEXTADDR，LOAD_ADDR = ZRELADDR。 （编辑：李大同） 【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容! |