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</o:shapelayout></xml><![endif]--></head><body lang=KO link="#0563C1" vlink="#954F72"><div class=WordSection1><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>Hello all,<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'><o:p> </o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>I</span><span style='font-size:11.0pt;font-family:"맑은 고딕"'>’<span lang=EN-US>m debugging linux boot on an FPGA board (with limited RAM size, only 8MB SRAM in place of DDR3 memory).<o:p></o:p></span></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>I</span><span style='font-size:11.0pt;font-family:"맑은 고딕"'>’<span lang=EN-US>m using linux 5.4.21 for now and because the printk doesn</span>’<span lang=EN-US>t work yet, I</span>’<span lang=EN-US>m writing some info on memory to see how it</span>’<span lang=EN-US>s doing.<o:p></o:p></span></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>After it goes into start_kernel, it calls smp_setup_processor_id(); and inside it, it calls pr_info which is just printk.<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri",sans-serif'> <o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>==== init/main.c<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>uint64_t mydebug2[64] = {0,};<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>uint32_t myidx = 0;<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>uint64_t mycnt = 0; // for left shift, 64bit<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri",sans-serif'> <o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>asmlinkage __visible void __init start_kernel(void)<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>{<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> char *command_line;<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> char *after_dashes;<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> uint64_t el;<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri",sans-serif'> <o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>set_task_stack_end_magic(&init_task);<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> mydebug2[(myidx++)&63] = (mycnt++ << 32) + 0x1000;<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> smp_setup_processor_id();<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> mydebug2[(myidx++)&63] = (mycnt++ << 32) + 0x2000;<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri",sans-serif'> <o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>==== arch/arm64/kernel/setup.c<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>void __init smp_setup_processor_id(void)<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>{<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> u64 mpidr = read_cpuid_mpidr() & MPIDR_HWID_BITMASK;<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> cpu_logical_map(0) = mpidr;<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri",sans-serif'> <o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> /*<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> * clear __my_cpu_offset on boot CPU to avoid hang caused by<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> * using percpu variable early, for example, lockdep will<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> * access percpu variable inside lock_release<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> */<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> set_my_cpu_offset(0);<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>mydebug2[(myidx++)&63] = (mycnt++ << 32) + 0x1100;<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> pr_info("test message\n"); // just printk<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> mydebug2[(myidx++)&63] = (mycnt++ << 32) + 0x1200;<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> pr_info("Booting Linux on physical CPU 0x%010lx [0x%08x]\n", // printk<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> (unsigned long)mpidr, read_cpuid_id());<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>}<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri",sans-serif'> <o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>==== kernel/printk/printk.c<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>asmlinkage __visible int printk(const char *fmt, ...)<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>{<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> va_list args;<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> int r;<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri",sans-serif'> <o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> va_start(args, fmt);<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> //why.. read_pkcontext(0x32);<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> mydebug2[(myidx++)&63] = (mycnt++ << 32) + 0x1110;<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> r = vprintk_func(fmt, args);<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> mydebug2[(myidx++)&63] = (mycnt++ << 32) + 0x1120;<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> va_end(args);<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri",sans-serif'> <o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> return r; <o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>}<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri",sans-serif'> <o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>==== kernel/printk/printk_safe.c<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>__printf(1, 0) int vprintk_func(const char *fmt, va_list args)<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>{<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> /* <o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> * Try to use the main logbuf even in NMI. But avoid calling console<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> * drivers that might have their own locks.<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> */<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> mydebug2[(myidx++)&63] = (mycnt++ << 32) + 0x1111;<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> if ((this_cpu_read(printk_context) & PRINTK_NMI_DIRECT_CONTEXT_MASK) &&<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> raw_spin_trylock(&logbuf_lock)) {<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> mydebug2[(myidx++)&63] = (mycnt++ << 32) + 0x1112;<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> int len; <o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> <o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> len = vprintk_store(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> raw_spin_unlock(&logbuf_lock);<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> defer_console_output();<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> return len;<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> } <o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri",sans-serif'> <o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> mydebug2[(myidx++)&63] = (mycnt++ << 32) + 0x1113;<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> /* Use extra buffer in NMI when logbuf_lock is taken or in safe mode. */<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> if (this_cpu_read(printk_context) & PRINTK_NMI_CONTEXT_MASK) {<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> mydebug2[(myidx++)&63] = (mycnt++ << 32) + 0x1114;<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> return vprintk_nmi(fmt, args);<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> }<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri",sans-serif'> <o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> //write_pkcontext(); <o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> /* Use extra buffer to prevent a recursion deadlock in safe mode. */<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> mydebug2[(myidx++)&63] = (mycnt++ << 32) + 0x1115;<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> if (this_cpu_read(printk_context) & PRINTK_SAFE_CONTEXT_MASK) {<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> mydebug2[(myidx++)&63] = (mycnt++ << 32) + 0x1116;<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> return vprintk_safe(fmt, args);<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> }<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> <o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> /* No obstacles. */ <o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> mydebug2[(myidx++)&63] = (mycnt++ << 32) + 0x1117;<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'> return vprintk_default(fmt, args); <o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>}<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri",sans-serif'> <o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>When I examine mydebug2 data, it is like this. (the physical address of mydebug2 is 0x80622000 and I can read the value in memory using ocd,<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>The LSB 32 bits are displayed first here. The memory is set non-cacheable for this test.)<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri",sans-serif'> <o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>0x80622000: 00001000 00000000 00001100 00000001 00001110 00000002 00001111 00000003<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>0x80622020: 00001113 00000004 00001115 00000005 00001117 00000006 00001110 00000007<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>0x80622040: 00001111 00000008 00001113 00000009 00001115 0000000a 00001116 0000000b<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>0x80622060: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri",sans-serif'> <o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>As you can see, in the vprintk_safe function, it goes into vprintk_default and then without 0x1120 being written, printk is called again and this time it goes into vprintk_nmi and seems to hang (waiting for console lock I remember..).<o:p></o:p></span></p><p style='margin:0cm;margin-bottom:.0001pt'><span lang=EN-US style='font-size:11.0pt;font-family:"맑은 고딕"'>Could anyone give me some light on what</span><span style='font-size:11.0pt;font-family:"맑은 고딕"'>’<span lang=EN-US>s going on here? (Actual print to serial port is supposed to come out much later inside setup_arch).<o:p></o:p></span></span></p><p class=MsoNormal><span lang=EN-US>Any comment will be very much appreciated.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Thank you!<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>Chan Kim<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p></div></body></html>