linux-kernel - [PATCH v2 1/2] kprobes: Allow architectures to override optinsn page allocation

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Message-Id: <40a43d6df1fdf41ade36e9a46e60a4df774ca9f6.1620896780.git.christophe.leroy@csgroup.eu>
Date:   Thu, 13 May 2021 09:07:51 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        naveen.n.rao@...ux.ibm.com, anil.s.keshavamurthy@...el.com,
        davem@...emloft.net, mhiramat@...nel.org
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        clang-built-linux@...glegroups.com
Subject: [PATCH v2 1/2] 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
overriden by the architecture.

Suggested-by: Masami Hiramatsu <mhiramat@...nel.org>
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
Acked-by: Masami Hiramatsu <mhiramat@...nel.org>
---
v2: Added missing prototypes in linux/kprobes.h
---
 include/linux/kprobes.h |  3 +++
 kernel/kprobes.c        | 14 ++++++++++++--
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 1883a4a9f16a..02d4020615a7 100644
--- 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 745f08fdd7a6..8c0a6fdef771 100644
--- 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 */
-- 
2.25.0