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 c296146c058c ("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

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 316ab0b..048e2b2 100644 (file)
--- 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
index 09297ec..2d5c6be 100644 (file)
--- 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 @@ 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
 

diff --git a/arch/powerpc/kernel/jump_label.c b/arch/powerpc/kernel/jump_label.c
index 1448580..ce87dc5 100644 (file)
--- 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));
 }