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powerpc: Switch to relative jump labels

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Convert powerpc to relative jump labels.

Before the patch, pseries_defconfig vmlinux.o has:
9074 __jump_table  0003f2a0  0000000000000000  0000000000000000  01321fa8  2**0

With the patch, the same config gets:
9074 __jump_table  0002a0e0  0000000000000000  0000000000000000  01321fb4  2**0

Size is 258720 without the patch, 172256 with the patch.
That's a 33% size reduction.

Largely copied from commit c296146c05 ("arm64/kernel: jump_label:
Switch to relative references")

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/828348da7868eda953ce023994404dfc49603b64.1616514473.git.christophe.leroy@csgroup.eu
This commit is contained in:
Christophe Leroy 2021-03-23 15:47:59 +00:00 committed by Michael Ellerman
parent 40272035e1
commit b0b3b2c78e
3 changed files with 9 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
arch/powerpc/Kconfig
View File

@ -184,6 +184,7 @@ config PPC
select HAVE_ARCH_AUDITSYSCALL
select HAVE_ARCH_HUGE_VMAP if PPC_BOOK3S_64 && PPC_RADIX_MMU
select HAVE_ARCH_JUMP_LABEL
select HAVE_ARCH_JUMP_LABEL_RELATIVE
select HAVE_ARCH_KASAN if PPC32 && PPC_PAGE_SHIFT <= 14
select HAVE_ARCH_KASAN_VMALLOC if PPC32 && PPC_PAGE_SHIFT <= 14
select HAVE_ARCH_KGDB

21
arch/powerpc/include/asm/jump_label.h
View File

@ -20,7 +20,8 @@ static __always_inline bool arch_static_branch(struct static_key *key, bool bran
asm_volatile_goto("1:\n\t"
"nop # arch_static_branch\n\t"
".pushsection __jump_table, \"aw\"\n\t"
JUMP_ENTRY_TYPE "1b, %l[l_yes], %c0\n\t"
".long 1b - ., %l[l_yes] - .\n\t"
JUMP_ENTRY_TYPE "%c0 - .\n\t"
".popsection \n\t"
: : "i" (&((char *)key)[branch]) : : l_yes);
@ -34,7 +35,8 @@ static __always_inline bool arch_static_branch_jump(struct static_key *key, bool
asm_volatile_goto("1:\n\t"
"b %l[l_yes] # arch_static_branch_jump\n\t"
".pushsection __jump_table, \"aw\"\n\t"
JUMP_ENTRY_TYPE "1b, %l[l_yes], %c0\n\t"
".long 1b - ., %l[l_yes] - .\n\t"
JUMP_ENTRY_TYPE "%c0 - .\n\t"
".popsection \n\t"
: : "i" (&((char *)key)[branch]) : : l_yes);
@ -43,23 +45,12 @@ l_yes:
return true;
}
#ifdef CONFIG_PPC64
typedef u64 jump_label_t;
#else
typedef u32 jump_label_t;
#endif
struct jump_entry {
jump_label_t code;
jump_label_t target;
jump_label_t key;
};
#else
#define ARCH_STATIC_BRANCH(LABEL, KEY) \
1098: nop; \
.pushsection __jump_table, "aw"; \
FTR_ENTRY_LONG 1098b, LABEL, KEY; \
.long 1098b - ., LABEL - .; \
FTR_ENTRY_LONG KEY; \
.popsection
#endif

4
arch/powerpc/kernel/jump_label.c
View File

@ -11,10 +11,10 @@
void arch_jump_label_transform(struct jump_entry *entry,
enum jump_label_type type)
{
struct ppc_inst *addr = (struct ppc_inst *)(unsigned long)entry->code;
struct ppc_inst *addr = (struct ppc_inst *)jump_entry_code(entry);
if (type == JUMP_LABEL_JMP)
patch_branch(addr, entry->target, 0);
patch_branch(addr, jump_entry_target(entry), 0);
else
patch_instruction(addr, ppc_inst(PPC_INST_NOP));
}