On Wed, Sep 2, 2009 at 2:32 AM, Geoff Levand <geoffrey.lev...@am.sony.com>wrote:
> On 09/01/2009 03:58 AM, Lee HongWoo wrote: > > __start (in head_64.S) > > ---> __start_initialization_multiplatform (in head_64.S) > > ---> __boot_from_prom (in head_64.S) > > ---> prom_init ( in prom_init.c) > > ---> __start ??? > > > > And I don't understand where __start is called, because I can find > __start > > only in head_64.S. > > If it calls __start in head_64.S, it's a recursive call. > > > > Can anybody explain about this precedure ? > > In the general case, __start is the entry point of the kernel. > It is where the bootloader or boot wrapper program jumps to > when it transfers control to the kernel. > > -Geoff > > Thanks Geoff, I believe __start is the entry point of the kernel in this case. And the entry point is __GLOBAL(__start) in the head_64.S. What I asked is where or what __start is called in the prom_init.c __start(hdr, KERNELBASE + offset, 0); Below is the simple function call flow of linux kernel boot procedure. file : head_64.S _GLOBAL(__start) /* NOP this out unconditionally */ BEGIN_FTR_SECTION b .__start_initialization_multiplatform END_FTR_SECTION(0, 1) .... _GLOBAL(__start_initialization_multiplatform) /* * Are we booted from a PROM Of-type client-interface ? */ cmpldi cr0,r5,0 bne .__boot_from_prom /* yes -> prom */ .... _STATIC(__boot_from_prom) /* Save parameters */ mr r31,r3 mr r30,r4 mr r29,r5 mr r28,r6 mr r27,r7 /* * Align the stack to 16-byte boundary * Depending on the size and layout of the ELF sections in the initial * boot binary, the stack pointer will be unalignet on PowerMac */ rldicr r1,r1,0,59 /* Make sure we are running in 64 bits mode */ bl .enable_64b_mode /* put a relocation offset into r3 */ bl .reloc_offset LOAD_REG_IMMEDIATE(r2,__toc_start) addi r2,r2,0x4000 addi r2,r2,0x4000 /* Relocate the TOC from a virt addr to a real addr */ add r2,r2,r3 /* Restore parameters */ mr r3,r31 mr r4,r30 mr r5,r29 mr r6,r28 mr r7,r27 /* Do all of the interaction with OF client interface */ bl .prom_init /* We never return */ trap file : prom_init.c unsigned long __init prom_init(unsigned long r3, unsigned long r4, unsigned long pp, unsigned long r6, unsigned long r7) { ... ... __start(hdr, KERNELBASE + offset, 0); return 0; } HongWoo.
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