Hi all, First off Hello! My first post on the list so *wave*. I've got something going on where I'm not sure if I'm missing a subtlety (likely) or if something bizarre is going on. I'm building a hacked variant of kernel 2.6.29.6 that's come from somone who's ported it to the particular board I'm using. I've built a working kernel but I'm not sure what's going on when I try to boot it as it seems like the objcopy to make a binary image from vmlinux is a bit odd... To walk through what I'm doing : This kernel is compiled with a load address of 0x80500000. Looking at vmlinux to find kernel_entry : $ mipsel-percello-linux-gnu-nm ../../../vmlinux | grep kernel_entry 80504590 T kernel_entry Checking via GDB to see what the code looks like : (gdb) disassemble kernel_entry Dump of assembler code for function kernel_entry: 0x80504590 <kernel_entry+0>: add %ah,0x8(%eax) 0x80504593 <kernel_entry+3>: inc %eax 0x80504594 <kernel_entry+4>: add %dl,(%eax) 0x80504596 <kernel_entry+6>: add %edi,(%edi,%ebx,1) 0x80504599 <kernel_entry+9>: add %ah,(%ecx) 0x8050459b <kernel_entry+11>: xor $0x25,%al So it's where we expected it to be from the output of nm... : (gdb) x/90xw 0x80504590 0x80504590 <kernel_entry>: 0x40086000 0x3c011000 0x3421001f 0x01014025 0x805045a0 <kernel_entry+16>: 0x3908001f 0x40886000 0x000000c0 0x3c088050 I then convert this vmlinux file to a binary image : $ mipsel-percello-linux-gnu-objcopy -O binary ./vmlinux ./vmlinux.bin.test and then hexdump to see what's at the kernel_entry offset : $ xxd -g xxd -g 4 -s 0x4550 -l 0x80 ./vmlinux.bin.test 0004550: 00600840 0010013c 1f002134 25400101 .`.@...<..!4%@.. 0004560: 1f000839 00608840 c0000000 5080083c ...9.`.@....P..< 0004570: bc450825 08000001 00000000 9c80083c .E.%...........< 0004580: 00700825 000000ad a180093c dcb22925 .p.%.......<..)% 0004590: 04000825 feff0915 000000ad 9c80013c ...%...........< 00045a0: 647624ac 9c80013c 687625ac 9c80013c dv$....<hv%....< 00045b0: 6c7626ac 9c80013c 707627ac 00208040 lv&....<pv'.. .@ 00045c0: 96801c3c 00609c27 e01f1d24 21e8bc03 ...<.`.'...$!... The code for kernel_entry seems to be at an offset of 0x0004550. This is -0x40 bytes below where I'd expected! Am I missing something? I can confirm this by using my bootloader to load vmlinux.bin a (load_address + 0x40) and it runs just fine. The toolchain we have is : binutils 2.16.1 gcc 4.2.0 Any insight would be appreciated! Cheers! ~Pev
