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 c296146 ("arm64/kernel: jump_label: Switch to relative references") Signed-off-by: Christophe Leroy <[email protected]> Signed-off-by: Michael Ellerman <[email protected]> Link: https://lore.kernel.org/r/828348da7868eda953ce023994404dfc49603b64.1616514473.git.christophe.leroy@csgroup.eu
tadfisher · Apr 3, 2021 · b0b3b2c · b0b3b2c
1 parent 4027203
commit b0b3b2c
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Showing 3 changed files with 9 additions and 17 deletions.
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
@@ -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

diff --git a/arch/powerpc/include/asm/jump_label.h b/arch/powerpc/include/asm/jump_label.h
@@ -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
 

diff --git a/arch/powerpc/kernel/jump_label.c b/arch/powerpc/kernel/jump_label.c
@@ -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));
 }