Hi Maciej, > If you can't access /proc/kcore with GDB locally, for whatever reason, > then `dd' it (or a part of it); to a regular file and copy it to another > machine. Use cross-GDB if necessary. With 16 MiB of RAM available only > it can be getting really tight; the kernel itself takes half of it too I > suppose. Both a (complete) remote copy of kcore, and one shared via v9fs, yield "Cannot access memory at address 0x80000000" with a cross-GDB, unfortunately: > > One can get a little further by sharing /proc using v9fs to obtain: > > > > # mipsel-linux-gdb -q -c /mnt/kcore > > [New process 1] > > Core was generated by `ramdisk_size=16384 crtmode=pal1 video=ps2fb:pal,640x480-32 rd_start=0x8063c000'. > > #0 0x00000000 in ?? () > > (gdb) set architecture mips:5900 > > The target architecture is assumed to be mips:5900 > > (gdb) x /32i 0x80000000 > > 0x80000000: Cannot access memory at address 0x80000000 By examining the read operations for /proc/kcore, it seems GDB reaches this "cannot access" conclusion from the ELF headers. > You need to use bus (physical) rather than virtual addresses with > /dev/mem, so: > > # xxd -s 0 -l 256 /dev/mem > > or suchlike. Ah, the value of the physical address was a misunderstanding on my part. The convoluted combination of mipsel-linux-objcopy and mipsel-linux-objdump gets the disassembly done without GDB, as shown below. :D It looks very similar to yours, with additional NOPs and SYNCs required for the R5900: # ssh ps2 head -c 128 /dev/mem >kcore && mipsel-linux-objcopy -I binary -O elf32-little kcore kcore.elf && mipsel-linux-objdump -D -m mips:5900 kcore.elf kcore.elf: file format elf32-little Disassembly of section .data: 00000000 <_binary_kcore_start>: ... 8: 3c1b8061 lui k1,0x8061 c: 0000040f sync.p 10: 401a4000 mfc0 k0,c0_badvaddr 14: 8f7b2c60 lw k1,11360(k1) 18: 001ad582 srl k0,k0,0x16 1c: 001ad080 sll k0,k0,0x2 20: 037ad821 addu k1,k1,k0 24: 0000040f sync.p 28: 401a2000 mfc0 k0,c0_context 2c: 8f7b0000 lw k1,0(k1) 30: 001ad042 srl k0,k0,0x1 34: 335a0ff8 andi k0,k0,0xff8 38: 037ad821 addu k1,k1,k0 3c: 8f7a0000 lw k0,0(k1) 40: 8f7b0004 lw k1,4(k1) 44: 001ad142 srl k0,k0,0x5 48: 409a1000 mtc0 k0,c0_entrylo0 4c: 0000040f sync.p 50: 001bd942 srl k1,k1,0x5 54: 409b1800 mtc0 k1,c0_entrylo1 58: 0000040f sync.p 5c: 42000006 tlbwr 60: 0000040f sync.p 64: 42000018 eret ... Fredrik
