kprobes: Allow architectures to override optinsn page allocation

Some architectures like powerpc require a non standard
allocation of optinsn page, because module pages are
too far from the kernel for direct branches.

Define weak alloc_optinsn_page() and free_optinsn_page(), that
fall back on alloc_insn_page() and free_insn_page() when not
overridden by the architecture.

Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/40a43d6df1fdf41ade36e9a46e60a4df774ca9f6.1620896780.git.christophe.leroy@csgroup.eu

diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 1883a4a9f16a7fc70bf533cd2206d046c6722b14..02d4020615a7243e3cf2016df33f3a051c60efb2 100644 (file)
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -409,6 +409,9 @@ void dump_kprobe(struct kprobe *kp);
 void *alloc_insn_page(void);
 void free_insn_page(void *page);
 
+void *alloc_optinsn_page(void);
+void free_optinsn_page(void *page);
+
 int kprobe_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
                       char *sym);
 

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 745f08fdd7a698ebd6f3a40da3cffedaa35497c6..8c0a6fdef771ddd91bd366d41ead0cb74a200b0b 100644 (file)
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -321,11 +321,21 @@ int kprobe_cache_get_kallsym(struct kprobe_insn_cache *c, unsigned int *symnum,
 }
 
 #ifdef CONFIG_OPTPROBES
+void __weak *alloc_optinsn_page(void)
+{
+       return alloc_insn_page();
+}
+
+void __weak free_optinsn_page(void *page)
+{
+       free_insn_page(page);
+}
+
 /* For optimized_kprobe buffer */
 struct kprobe_insn_cache kprobe_optinsn_slots = {
        .mutex = __MUTEX_INITIALIZER(kprobe_optinsn_slots.mutex),
-       .alloc = alloc_insn_page,
-       .free = free_insn_page,
+       .alloc = alloc_optinsn_page,
+       .free = free_optinsn_page,
        .sym = KPROBE_OPTINSN_PAGE_SYM,
        .pages = LIST_HEAD_INIT(kprobe_optinsn_slots.pages),
        /* .insn_size is initialized later */