Commit d9e84fb1 authored by Alexander Lobakin's avatar Alexander Lobakin Committed by Thomas Bogendoerfer
Browse files

MIPS: relocatable: optimize the relocation process 



For now, vmlinux relocation functions for relocatable kernel are
implemented as an array of handlers of a particular type.

Convert that array into a single switch-case function to:
 - remove unused arguments;
 - change the return type of simple handlers to void;
 - remove the array and don't use any data at all;
 - avoid using indirect calls;
 - allow the compiler to inline and greatly optimize
   the relocation function[s];

and also mark do_relocations() and show_kernel_relocation() static
as they aren't used anywhere else.

The result on MIPS32 R2 with GCC 10.2 -O2 is:

scripts/bloat-o-meter -c arch/mips/kernel/__relocate.o arch/mips/kernel/relocate.o
add/remove: 0/6 grow/shrink: 1/0 up/down: 356/-640 (-284)
Function                                     old     new   delta
relocate_kernel                              852    1208    +356
apply_r_mips_32_rel                           20       -     -20
apply_r_mips_hi16_rel                         40       -     -40
apply_r_mips_64_rel                           44       -     -44
apply_r_mips_26_rel                          144       -    -144
show_kernel_relocation                       164       -    -164
do_relocations                               228       -    -228
Total: Before=1780, After=1496, chg -15.96%
add/remove: 0/1 grow/shrink: 0/0 up/down: 0/-76 (-76)
Data                                         old     new   delta
reloc_handlers_rel                            76       -     -76
Total: Before=92, After=16, chg -82.61%
add/remove: 0/0 grow/shrink: 0/0 up/down: 0/0 (0)
RO Data                                      old     new   delta
Total: Before=0, After=0, chg +0.00%

All functions were collapsed into the main one, relocate_kernel().

Signed-off-by: default avatarAlexander Lobakin <alobakin@pm.me>
Signed-off-by: default avatarThomas Bogendoerfer <tsbogend@alpha.franken.de>
parent 049a68ef

arch/mips/kernel/relocate.c

+30 −24
Original line number Diff line number Diff line
@@ -70,18 +70,14 @@ static void __init sync_icache(void *kbase, unsigned long kernel_length) 
	__sync();

}



static int __init apply_r_mips_64_rel(u32 *loc_orig, u32 *loc_new, long offset)

static void __init apply_r_mips_64_rel(u32 *loc_new, long offset)

{

	*(u64 *)loc_new += offset;



	return 0;

}



static int __init apply_r_mips_32_rel(u32 *loc_orig, u32 *loc_new, long offset)

static void __init apply_r_mips_32_rel(u32 *loc_new, long offset)

{

	*loc_new += offset;



	return 0;

}



static int __init apply_r_mips_26_rel(u32 *loc_orig, u32 *loc_new, long offset)
@@ -114,7 +110,8 @@ static int __init apply_r_mips_26_rel(u32 *loc_orig, u32 *loc_new, long offset) 
}





static int __init apply_r_mips_hi16_rel(u32 *loc_orig, u32 *loc_new, long offset)

static void __init apply_r_mips_hi16_rel(u32 *loc_orig, u32 *loc_new,

					 long offset)

{

	unsigned long insn = *loc_orig;

	unsigned long target = (insn & 0xffff) << 16; /* high 16bits of target */
@@ -122,17 +119,33 @@ static int __init apply_r_mips_hi16_rel(u32 *loc_orig, u32 *loc_new, long offset 
	target += offset;



	*loc_new = (insn & ~0xffff) | ((target >> 16) & 0xffff);

	return 0;

}



static int (*reloc_handlers_rel[]) (u32 *, u32 *, long) __initdata = {

	[R_MIPS_64]		= apply_r_mips_64_rel,

	[R_MIPS_32]		= apply_r_mips_32_rel,

	[R_MIPS_26]		= apply_r_mips_26_rel,

	[R_MIPS_HI16]		= apply_r_mips_hi16_rel,

};

static int __init reloc_handler(u32 type, u32 *loc_orig, u32 *loc_new,

				long offset)

{

	switch (type) {

	case R_MIPS_64:

		apply_r_mips_64_rel(loc_new, offset);

		break;

	case R_MIPS_32:

		apply_r_mips_32_rel(loc_new, offset);

		break;

	case R_MIPS_26:

		return apply_r_mips_26_rel(loc_orig, loc_new, offset);

	case R_MIPS_HI16:

		apply_r_mips_hi16_rel(loc_orig, loc_new, offset);

		break;

	default:

		pr_err("Unhandled relocation type %d at 0x%pK\n", type,

		       loc_orig);

		return -ENOEXEC;

	}



int __init do_relocations(void *kbase_old, void *kbase_new, long offset)

	return 0;

}



static int __init do_relocations(void *kbase_old, void *kbase_new, long offset)

{

	u32 *r;

	u32 *loc_orig;
@@ -149,14 +162,7 @@ int __init do_relocations(void *kbase_old, void *kbase_new, long offset) 
		loc_orig = kbase_old + ((*r & 0x00ffffff) << 2);

		loc_new = RELOCATED(loc_orig);



		if (reloc_handlers_rel[type] == NULL) {

			/* Unsupported relocation */

			pr_err("Unhandled relocation type %d at 0x%pK\n",

			       type, loc_orig);

			return -ENOEXEC;

		}



		res = reloc_handlers_rel[type](loc_orig, loc_new, offset);

		res = reloc_handler(type, loc_orig, loc_new, offset);

		if (res)

			return res;

	}
@@ -412,7 +418,7 @@ void *__init relocate_kernel(void) 
/*

 * Show relocation information on panic.

 */

void show_kernel_relocation(const char *level)

static void show_kernel_relocation(const char *level)

{

	unsigned long offset;