Commit b148766e authored by Helge Deller's avatar Helge Deller
Browse files

parisc: Reduce kernel size by packing alternative tables 



The values stored in the length and condition fields of the alternative
tables fit into 16 bits, so we can save 4 bytes per alternative table
entry.
Since a typical 32-bit kernel has more than 3000 entries this
saves > 12k of storage on disc.

bloat-o-meter shows a reduction of -0.01% by this change:
Total: Before=10196505, After=10195529, chg -0.01%

$ ls -la vmlinux vmlinux.before
-rwxr-xr-x  14437324 vmlinux
-rwxr-xr-x  14449512 vmlinux.before

Signed-off-by: default avatarHelge Deller <deller@gmx.de>
parent 4fe89d07

arch/parisc/include/asm/alternative.h

+12 −9
Original line number Diff line number Diff line
@@ -22,10 +22,10 @@ 


struct alt_instr {

	s32 orig_offset;	/* offset to original instructions */

	s32 len;		/* end of original instructions */

	u32 cond;		/* see ALT_COND_XXX */

	s16 len;		/* end of original instructions */

	u16 cond;		/* see ALT_COND_XXX */

	u32 replacement;	/* replacement instruction or code */

};

} __packed;



void set_kernel_text_rw(int enable_read_write);

void apply_alternatives_all(void);
@@ -35,8 +35,9 @@ void apply_alternatives(struct alt_instr *start, struct alt_instr *end, 
/* Alternative SMP implementation. */

#define ALTERNATIVE(cond, replacement)		"!0:"	\

	".section .altinstructions, \"aw\"	!"	\

	".word (0b-4-.), 1, " __stringify(cond) ","	\

		__stringify(replacement) "	!"	\

	".word (0b-4-.)				!"	\

	".hword 1, " __stringify(cond) "	!"	\

	".word " __stringify(replacement) "	!"	\

	".previous"



#else
@@ -44,15 +45,17 @@ void apply_alternatives(struct alt_instr *start, struct alt_instr *end, 
/* to replace one single instructions by a new instruction */

#define ALTERNATIVE(from, to, cond, replacement)\

	.section .altinstructions, "aw"	!	\

	.word (from - .), (to - from)/4	!	\

	.word cond, replacement		!	\

	.word (from - .)		!	\

	.hword (to - from)/4, cond	!	\

	.word replacement		!	\

	.previous



/* to replace multiple instructions by new code */

#define ALTERNATIVE_CODE(from, num_instructions, cond, new_instr_ptr)\

	.section .altinstructions, "aw"	!	\

	.word (from - .), -num_instructions !	\

	.word cond, (new_instr_ptr - .)	!	\

	.word (from - .)		!	\

	.hword -num_instructions, cond	!	\

	.word (new_instr_ptr - .)	!	\

	.previous



#endif  /*  __ASSEMBLY__  */

arch/parisc/kernel/alternative.c

+4 −3
Original line number Diff line number Diff line
@@ -26,7 +26,7 @@ void __init_or_module apply_alternatives(struct alt_instr *start, 
	struct alt_instr *entry;

	int index = 0, applied = 0;

	int num_cpus = num_online_cpus();

	u32 cond_check;

	u16 cond_check;



	cond_check = ALT_COND_ALWAYS |

		((num_cpus == 1) ? ALT_COND_NO_SMP : 0) |
@@ -45,8 +45,9 @@ void __init_or_module apply_alternatives(struct alt_instr *start, 


	for (entry = start; entry < end; entry++, index++) {



		u32 *from, cond, replacement;

		s32 len;

		u32 *from, replacement;

		u16 cond;

		s16 len;



		from = (u32 *)((ulong)&entry->orig_offset + entry->orig_offset);

		len = entry->len;