powerpc/code-patching: Use jump_label for testing freed initmem

Once init is done, initmem is freed forever so no need to
test system_state at every call to patch_instruction().

Use jump_label.

This reduces by 2% the time needed to activate ftrace on an 8xx.

Signed-off-by: Christophe Leroy <[e-mail]>
Signed-off-by: Michael Ellerman <[e-mail]>
Link: https://lore.kernel.org/r/0aee9647[e-mail]

arch/powerpc/include/asm/code-patching.h

···
 #define BRANCH_SET_LINK	0x1
 #define BRANCH_ABSOLUTE	0x2
 
+DECLARE_STATIC_KEY_FALSE(init_mem_is_free);
+
 bool is_offset_in_branch_range(long offset);
 bool is_offset_in_cond_branch_range(long offset);
 int create_branch(ppc_inst_t *instr, const u32 *addr,

arch/powerpc/lib/code-patching.c

···
 #include <linux/init.h>
 #include <linux/cpuhotplug.h>
 #include <linux/uaccess.h>
+#include <linux/jump_label.h>
 
 #include <asm/tlbflush.h>
 #include <asm/page.h>
···
 
 #endif /* CONFIG_STRICT_KERNEL_RWX */
 
+__ro_after_init DEFINE_STATIC_KEY_FALSE(init_mem_is_free);
+
 int patch_instruction(u32 *addr, ppc_inst_t instr)
 {
 	/* Make sure we aren't patching a freed init section */
-	if (system_state >= SYSTEM_FREEING_INITMEM && init_section_contains(addr, 4))
+	if (static_branch_likely(&init_mem_is_free) && init_section_contains(addr, 4))
 		return 0;
 
 	return do_patch_instruction(addr, instr);

arch/powerpc/mm/mem.c

···
 #include <asm/kasan.h>
 #include <asm/svm.h>
 #include <asm/mmzone.h>
+#include <asm/code-patching.h>
 
 #include <mm/mmu_decl.h>
 
···
 {
 	ppc_md.progress = ppc_printk_progress;
 	mark_initmem_nx();
+	static_branch_enable(&init_mem_is_free);
 	free_initmem_default(POISON_FREE_INITMEM);
 }