linux-kernel - [PATCH 2/2] powerpc/kprobes: Replace ppc

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Message-Id: <46998c941d0a5664daaeb92998391aace015eddf.1620829724.git.christophe.leroy@csgroup.eu>
Date:   Wed, 12 May 2021 14:29:27 +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 2/2] powerpc/kprobes: Replace ppc_optinsn by common optinsn

Commit 51c9c0843993 ("powerpc/kprobes: Implement Optprobes")
implemented a powerpc specific version of optinsn in order
to workaround the 32Mb limitation for direct branches.

Instead of implementing a dedicated powerpc version, use the
common optinsn and override the allocation and freeing functions.

This also indirectly remove the CLANG warning about
is_kprobe_ppc_optinsn_slot() not being use, and the powerpc will
now benefit from commit 5b485629ba0d ("kprobes, extable: Identify
kprobes trampolines as kernel text area")

Suggested-by: Masami Hiramatsu <mhiramat@...nel.org>
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/kernel/optprobes.c | 23 +++++------------------
 1 file changed, 5 insertions(+), 18 deletions(-)

diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
index cdf87086fa33..a370190cd02a 100644
--- a/arch/powerpc/kernel/optprobes.c
+++ b/arch/powerpc/kernel/optprobes.c
@@ -31,11 +31,9 @@
 #define TMPL_END_IDX		\
 	(optprobe_template_end - optprobe_template_entry)
 
-DEFINE_INSN_CACHE_OPS(ppc_optinsn);
-
 static bool insn_page_in_use;
 
-static void *__ppc_alloc_insn_page(void)
+void *alloc_optinsn_page(void)
 {
 	if (insn_page_in_use)
 		return NULL;
@@ -43,20 +41,11 @@ static void *__ppc_alloc_insn_page(void)
 	return &optinsn_slot;
 }
 
-static void __ppc_free_insn_page(void *page __maybe_unused)
+void free_optinsn_page(void *page)
 {
 	insn_page_in_use = false;
 }
 
-struct kprobe_insn_cache kprobe_ppc_optinsn_slots = {
-	.mutex = __MUTEX_INITIALIZER(kprobe_ppc_optinsn_slots.mutex),
-	.pages = LIST_HEAD_INIT(kprobe_ppc_optinsn_slots.pages),
-	/* insn_size initialized later */
-	.alloc = __ppc_alloc_insn_page,
-	.free = __ppc_free_insn_page,
-	.nr_garbage = 0,
-};
-
 /*
  * Check if we can optimize this probe. Returns NIP post-emulation if this can
  * be optimized and 0 otherwise.
@@ -136,7 +125,7 @@ NOKPROBE_SYMBOL(optimized_callback);
 void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
 {
 	if (op->optinsn.insn) {
-		free_ppc_optinsn_slot(op->optinsn.insn, 1);
+		free_optinsn_slot(op->optinsn.insn, 1);
 		op->optinsn.insn = NULL;
 	}
 }
@@ -203,14 +192,12 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
 	unsigned long nip, size;
 	int rc, i;
 
-	kprobe_ppc_optinsn_slots.insn_size = MAX_OPTINSN_SIZE;
-
 	nip = can_optimize(p);
 	if (!nip)
 		return -EILSEQ;
 
 	/* Allocate instruction slot for detour buffer */
-	buff = get_ppc_optinsn_slot();
+	buff = get_optinsn_slot();
 	if (!buff)
 		return -ENOMEM;
 
@@ -297,7 +284,7 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
 	return 0;
 
 error:
-	free_ppc_optinsn_slot(buff, 0);
+	free_optinsn_slot(buff, 0);
 	return -ERANGE;
 
 }
-- 
2.25.0