Commit b0b3b2c7 authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

powerpc: Switch to relative jump labels 



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 c296146c ("arm64/kernel: jump_label:
Switch to relative references")

Signed-off-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/828348da7868eda953ce023994404dfc49603b64.1616514473.git.christophe.leroy@csgroup.eu
parent 40272035

arch/powerpc/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/powerpc/include/asm/jump_label.h

+6 −15
Original line number Diff line number Diff line
@@ -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 @@ static __always_inline bool arch_static_branch_jump(struct static_key *key, bool 
	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

arch/powerpc/kernel/jump_label.c

+2 −2
Original line number Diff line number Diff line
@@ -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));

}