powerpc/code-patching: Remove protection against patching init addresses after init

Once init section is freed, attempting to patch init code
ends up in the weed.

Commit 51c3c62 ("powerpc: Avoid code patching freed init sections")
protected patch_instruction() against that, but it is the responsibility
of the caller to ensure that the patched memory is valid.

All callers have now been verified and fixed so the check
can be removed.

This improves ftrace activation by about 2% on 8xx.

Signed-off-by: Christophe Leroy <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Link: https://lore.kernel.org/r/504310828f473d424e2ed229eff57bf075f52796.1669969781.git.christophe.leroy@csgroup.eu

Author: chleroy

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

@@ -22,8 +22,6 @@
 #define BRANCH_SET_LINK	0x1
 #define BRANCH_ABSOLUTE	0x2
 
-DECLARE_STATIC_KEY_FALSE(init_mem_is_free);
-
 /*
  * Powerpc branch instruction is :
  *

arch/powerpc/lib/code-patching.c

@@ -349,7 +349,7 @@ static int __do_patch_instruction(u32 *addr, ppc_inst_t instr)
 	return err;
 }
 
-static int do_patch_instruction(u32 *addr, ppc_inst_t instr)
+int patch_instruction(u32 *addr, ppc_inst_t instr)
 {
 	int err;
 	unsigned long flags;
@@ -372,17 +372,6 @@ static int do_patch_instruction(u32 *addr, ppc_inst_t instr)
 
 	return err;
 }
-
-__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 (static_branch_likely(&init_mem_is_free) && init_section_contains(addr, 4))
-		return 0;
-
-	return do_patch_instruction(addr, instr);
-}
 NOKPROBE_SYMBOL(patch_instruction);
 
 int patch_branch(u32 *addr, unsigned long target, int flags)

arch/powerpc/mm/mem.c

@@ -344,7 +344,6 @@ void free_initmem(void)
 {
 	ppc_md.progress = ppc_printk_progress;
 	mark_initmem_nx();
-	static_branch_enable(&init_mem_is_free);
 	free_initmem_default(POISON_FREE_INITMEM);
 	ftrace_free_init_tramp();
 }