kprobes: remove duplicated strong free_insn_page in x86 and s390

free_insn_page() in x86 and s390 is same with the common weak function in
kernel/kprobes.c.  Plus, the comment "Recover page to RW mode before
releasing it" in x86 seems insensible to be there since resetting mapping
is done by common code in vfree() of module_memfree().  So drop these two
duplicated strong functions and related comment, then mark the common one
in kernel/kprobes.c strong.

Link: https://lkml.kernel.org/r/20210608065736.32656-1-song.bao.hua@hisilicon.comSigned-off-by: Barry Song <song.bao.hua@hisilicon.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Qi Liu <liuqi115@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/s390/kernel/kprobes.c

@@ -44,11 +44,6 @@ void *alloc_insn_page(void)
 	return page;
 }
 
-void free_insn_page(void *page)
-{
-	module_memfree(page);
-}
-
 static void *alloc_s390_insn_page(void)
 {
 	if (xchg(&insn_page_in_use, 1) == 1)

arch/x86/kernel/kprobes/core.c

@@ -422,12 +422,6 @@ void *alloc_insn_page(void)
 	return page;
 }
 
-/* Recover page to RW mode before releasing it */
-void free_insn_page(void *page)
-{
-	module_memfree(page);
-}
-
 /* Kprobe x86 instruction emulation - only regs->ip or IF flag modifiers */
 
 static void kprobe_emulate_ifmodifiers(struct kprobe *p, struct pt_regs *regs)

include/linux/kprobes.h

@@ -407,7 +407,6 @@ int enable_kprobe(struct kprobe *kp);
 void dump_kprobe(struct kprobe *kp);
 
 void *alloc_insn_page(void);
-void free_insn_page(void *page);
 
 int kprobe_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
 		       char *sym);

kernel/kprobes.c

@@ -106,7 +106,7 @@ void __weak *alloc_insn_page(void)
 	return module_alloc(PAGE_SIZE);
 }
 
-void __weak free_insn_page(void *page)
+static void free_insn_page(void *page)
 {
 	module_memfree(page);
 }