Re: [U-Boot] [PATCH] futile c relocation attempt

Dear Albert ARIBAUD,

...

include/configs/top9000_9xe.h | 1 +

That's my board. Not in mainstream yet. Just sets the define there.

...

+#ifdef CONFIG_USE_C_RELOCATION

• /* TODO: check for identical source and destination */
• /* TODO: check for overlapping */
• /* copy image, including initialized data */
• debug ("memcpy(%08lx,%08lx,%ld)\n",

• addr, _TEXT_BASE, _bss_start_ofs);
  

• memcpy ((void *)addr, (void *)_TEXT_BASE, _bss_start_ofs);
• /* now fix the code */
• debug ("_dynsym_start_ofs=%08lx _rel_dyn_start_ofs=%08lx _rel_dyn_end_ofs=%08lx\n",

• _dynsym_start_ofs, _rel_dyn_start_ofs, _rel_dyn_end_ofs);
  

• for (rel_dyn_ptr = (Elf32_Rel *)(_TEXT_BASE + _rel_dyn_start_ofs);

• 	rel_dyn_ptr<   (Elf32_Rel *)(_TEXT_BASE + _rel_dyn_end_ofs);
  

• 	rel_dyn_ptr++) {
  

• ulong *patchaddr = (ulong *) (rel_dyn_ptr->r_offset + gd->reloc_off);
  

• debug ("patch %08lx : %08lx\n",
  

• 	(ulong)patchaddr, (ulong)rel_dyn_ptr->r_info);
  

• switch (ELF32_R_TYPE(rel_dyn_ptr->r_info)) {
  

• case 23: /* rel fixup */
  

• 	*patchaddr += gd->reloc_off;
  

• 	break;
  

• case 2: /* abs fixup */
  

• 	{
  

• 		Elf32_Sym *sym = (Elf32_Sym *)(_TEXT_BASE + _dynsym_start_ofs);
  

• 		sym += ELF32_R_SYM(rel_dyn_ptr->r_info);
  

• 		*patchaddr = gd->reloc_off + sym->st_value;
  

• 	}
  

• 	break;
  

• default: /* unhandled fixup */
  

• 	break;
  

• }
  

• }
• /* clear BSS */

+# ifndef CONFIG_PRELOADER

• debug ("clearing BSS %08lx..%08lx\n",

• addr + _bss_start_ofs, addr + _bss_end_ofs);
  

• for (p = (ulong *)(addr + _bss_start_ofs);

• 	p<   (ulong *)(addr + _bss_end_ofs);
  

• 	*p++ = 0)
  

• ;
  

+# endif +#endif

All of _bss_start_ofs, _rel_dyn_start_ofs, _rel_dyn_end_ofs, _dynsym_start_ofs and _bss_end_ofs are going to be modified by the relocation fixup loop. The compiler *might* preload them into registers... or not; which could cause issues with ..._end_ofs ones, because it could cause the loops to overflow/underflow.

They are not going to be modified, they are in the unrelocated location!

...

• debug ("calling relocate_code\n"); relocate_code (addr_sp, id, addr);

Have you not just relocated and fixed up in the C code? If so, relocate_code (which would then become a misnomer) should have its own relocate and fixup code removed (your patch does not), and only perform the C environment (stack, etc) switch.

Incorrect. I removed the relocation (#ifndef) in start.S leaving only setting of the SP and calling of board_init_r active. True for the misnomer... It was supposed to be a quick hack, beauty comes later ;)

Side note: if board_init_f handles relocation and fixup and relocate_code just does stack switch between board_init_f and board_init_r, then I'd rather board_init_f *return* to start.S rather than *call* it if that's possible. That would make the control flow less circuitous: begin in start.S, set a minimal stack, call board_init_f, returns to start.S, switch to final stack, calls (branches to) board_init_r.

I agree here. I would have board_init_f return the desired SP value, for example, or let it return the gd pointer - something along that line.

Or one completely skips returning back to asm and sets the sp with an asm() statement in "C", obtains a function pointer to board_init_r, adjusts that and calls that function.

Amicalement,

Reinhard