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parisc: Reduce kernel size by packing alternative tables

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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: Helge Deller <deller@gmx.de>
This commit is contained in:
Helge Deller
2022-09-28 23:31:20 +02:00
parent 4fe89d07dc
commit b148766e2b
2 changed files with 16 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

21
arch/parisc/include/asm/alternative.h
View File

@@ -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__ */

7
arch/parisc/kernel/alternative.c
View File

@@ -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;