linux輸出信息重定向.doc

重定向linux輸出信息（linux2.6）在運(yùn)行l(wèi)inux的時(shí)候有所有的調(diào)試信息可以分為三個(gè)部分1、 bootloader輸出信息U-Boot (Nov 19 2016 - 22:02:08)DRAM: 64 MBFlash: 512 kBNAND: 64 MiBIn: serialOut: serialErr: serialHit any key to stop autoboot: 0 yqliu2410 # tftpFound DM9000 ID:46 at address 10000000 !DM9000 work in 16 bus widthbd-bi_entaddr: 08:00:3e:26:5beth_initMAC:8:0:3e:26:a:5b:TFTP from server 52; our IP address is 55Filename uImage.Load address: 0x30008000Loading: T T T T # #doneBytes transferred = 1617316 (18ada4 hex)up-tech2410 # bootm# Booting image at 30008000 . Image Name: Linux-.4 Created: 2016-11-19 14:05:29 UTC Image Type: ARM Linux Kernel Image (uncompressed) Data Size: 1617252 Bytes = 1.5 MB Load Address: 30008000 Entry Point: 30008040 Verifying Checksum . OKStarting kernel .2、 linux低級(jí)調(diào)試信息輸出Uncompressing Linux. done, booting the kernel.3、 linux調(diào)試信息輸出Linux version .4 (rootvm-dev) (gcc version 3.4.6) #100 Sat Nov 19 07:47:35 CST 2016CPU: ARM920T 41129200 revision 0 (ARMv4T), cr=00007177Machine: SMDK2410Memory policy: ECC disabled, Data cache writebackCPU S (id 0x32410002)S2410: core 202.800 MHz, memory 101.400 MHz, peripheral 50.700 MHzS24XX Clocks, (c) 2004 Simtec ElectronicsCLOCK: Slow mode (1.500 MHz), fast, MPLL on, UPLL onCPU0: D VIVT write-back cacheCPU0: I cache: 16384 bytes, associativity 64, 32 byte lines, 8 setsCPU0: D cache: 16384 bytes, associativity 64, 32 byte lines, 8 setsBuilt 1 zonelists in Zone order, mobility grouping on. Total pages: 16256Kernel command line: root=/dev/mtdblock2 noinitrd console=ttySAC1,115200irq: clearing subpending status 00000010PID hash table entries: 256 (order: 8, 1024 bytes)timer tcon=00500000, tcnt a509, tcfg 00000200,00000000, usec 00001eConsole: colour dummy device 80x30console ttySAC1 enabledDentry cache hash table entries: 8192 (order: 3, 32768 bytes)Inode-cache hash table entries: 4096 (order: 2, 16384 bytes)Memory: 64MB = 64MB totalMemory: 61488KB available (2936K code, 305K data, 132K init)Mount-cache hash table entries: 512CPU: Testing write buffer coherency: ok.現(xiàn)在要將所有的調(diào)試信息輸出到別的串口。以com1為例(從com0開(kāi)始計(jì)算)！一、將bootloader的輸出信息輸出到com1這里以u(píng)-boot為例：很簡(jiǎn)單只需要修改一個(gè)宏定義就okVi inlcude/configs/xxxconfig.h(xxx為你定義的開(kāi)發(fā)板的名字)更改原有的宏/* select serial console configuration*/#define CONFIG_SERIAL1 1 /* we use SERIAL 1 on SMDK2410 */modify for xxx2410/by lyj_uptech#define CONFIG_SERIAL2 1 /* we use SERIAL 2 on SMDK2410 */更改完之后就可以看到u-boot的調(diào)試信息輸出到com1，這一步很簡(jiǎn)單。二、將low_level 的調(diào)試信息輸出到com1在改之前我們先分析一下在linux啟動(dòng)之前它是如何使用串口的。1、 在arch/arm/boot/compressed/misc.c文件中有定義static void putstr(const char *ptr) char c; while (c = *ptr+) != 0) if (c = n) putc(r); putc(c); flush();2、 arch/arm/boot/compressed/misc.中的函數(shù)decompress_kernel就是使用的putstr來(lái)打印的如下輸出信息：Uncompressing Linux. done, booting the kernel.3、 追根溯源，putstr函數(shù)最終調(diào)用的是putc（請(qǐng)注意這里的putc不是在misc.c函數(shù)中定義的icedcc_putc，因?yàn)闆](méi)有CONFIG_CPU_V6宏定義），真正的底層操作在文件include/asm-arm/plat-s3c/uncompress.h4、 解析該文件/* we can deal with the case the UARTs are being run* in FIFO mode, so that we dont hold up our execution* waiting for tx to happen.*/static void putc(int ch) if (uart_rd(S2410_UFCON) & S2410_UFCON_FIFOMODE) int level; while (1) level = uart_rd(S2410_UFSTAT); level &= fifo_mask; if (level fifo_max) break; else /* not using fifos */ while (uart_rd(S2410_UTRSTAT) & S2410_UTRSTAT_TXE) != S2410_UTRSTAT_TXE) barrier(); /* write byte to transmission register */ uart_wr(S2410_UTXH, ch);該函數(shù)中調(diào)用的兩個(gè)函數(shù)，uart_rd uart_wr在同一個(gè)文件中定義#define uart_base S24XX_PA_UART + (0x4000*CONFIG_S_LOWLEVEL_UART_PORT)static _inline_ voiduart_wr(unsigned int reg, unsigned int val) volatile unsigned int *ptr; ptr = (volatile unsigned int *)(reg + uart_base); *ptr = val;static _inline_ unsigned intuart_rd(unsigned int reg) volatile unsigned int *ptr; ptr = (volatile unsigned int *)(reg + uart_base); return *ptr;從宏定義uart_base中就可以清楚的看到，當(dāng)CONFIG_S3C_LOWLEVEL_UART_PORT為0時(shí),uart_base的值為0x50000000,也就是uart0的控制寄存器基地址。如果要使用uart1的話就把CONFIG_S3C_LOWLEVEL_UART_PORT賦值為1就可以了。5、 正真更改的地方只有一個(gè)下級(jí)目錄修改為1就ok！6、 需要注意的地方（你使用的串口初始化了么）我在整個(gè)內(nèi)核中找遍了解壓內(nèi)核之前運(yùn)行的代碼，都找不到關(guān)于串口初始化的代碼。所以說(shuō)，linux在啟動(dòng)之前的串口初始化是依賴bootloader的，要想正常的輸出，就必須使用你的bootloader使用的串口，因?yàn)樵赽ootloader中進(jìn)行了對(duì)要使用的串口進(jìn)行了初始化。要保證你的bootloader兼容性很好，那就在bootloader中把所有的串口都初始化一遍。如果你沒(méi)有初始化串口，一旦調(diào)用putstr，程序就死掉了！三、將linux的信息輸出到com1將linux運(yùn)行的信息輸出到com1就太簡(jiǎn)單了，直接到bootloader里面改linux的傳遞參數(shù)就可以了。setenv bootargs root=/dev/mtdblock2 noinitrd console=ttySAC1,115200saveenv現(xiàn)在啟動(dòng)一切ok！感謝yqliu的支持，沒(méi)有他的調(diào)試程序，我始終的無(wú)法知道linux的內(nèi)核是否正確調(diào)用