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Message-Id: <20210513000649.23ac7bc69e30d8b9421a6ff6@kernel.org>
Date: Thu, 13 May 2021 00:06:49 +0900
From: Masami Hiramatsu <mhiramat@...nel.org>
To: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
Nathan Chancellor <nathan@...nel.org>,
kernel test robot <lkp@...el.com>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Masahiro Yamada <masahiroy@...nel.org>,
kbuild-all@...ts.01.org, clang-built-linux@...glegroups.com,
linux-kernel@...r.kernel.org, Michael Ellerman <mpe@...erman.id.au>
Subject: Re: arch/powerpc/kernel/optprobes.c:34:1: error: unused function
'is_kprobe_ppc_optinsn_slot'
On Wed, 12 May 2021 21:50:57 +0900
Masami Hiramatsu <mhiramat@...nel.org> wrote:
> On Wed, 12 May 2021 11:52:30 +0200
> Christophe Leroy <christophe.leroy@...roup.eu> wrote:
> >
> > Le 12/05/2021 à 11:36, Christophe Leroy a écrit :
> > >
> > >
> > > Le 11/05/2021 à 20:46, Nathan Chancellor a écrit :
> > >> On 5/11/2021 9:47 AM, Christophe Leroy wrote:
> > >>> Hi All,
> > >>>
> > >>> Le 11/05/2021 à 18:30, kernel test robot a écrit :
> > >>>> Hi Christophe,
> > >>>>
> > >>>> First bad commit (maybe != root cause):
> > >>>>
> > >>>> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > >>>> head: 1140ab592e2ebf8153d2b322604031a8868ce7a5
> > >>>> commit: eacf4c0202654adfa94bbb17b5c5c77c0be14af8 powerpc: Enable OPTPROBES on PPC32
> > >
> > > Ok, the problem appears on PPC32 with that patch, but it must have been there on PPC64 since the
> > > implementation of optprobes with commit 51c9c0843993 ("powerpc/kprobes: Implement Optprobes")
> > >
> > >
> > >>>> date: 3 weeks ago
> > >>>> config: powerpc-randconfig-r033-20210511 (attached as .config)
> > >>>> compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project
> > >>>> a0fed635fe1701470062495a6ffee1c608f3f1bc)
> > >>>
> > >>> A clang issue ?
> > >>>
> > >>>
> > >>>> reproduce (this is a W=1 build):
> > >>>> wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O
> > >>>> ~/bin/make.cross
> > >>>> chmod +x ~/bin/make.cross
> > >>>> # install powerpc cross compiling tool for clang build
> > >>>> # apt-get install binutils-powerpc-linux-gnu
> > >>>> #
> > >>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=eacf4c0202654adfa94bbb17b5c5c77c0be14af8
> > >>>>
> > >>>> git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> > >>>> git fetch --no-tags linus master
> > >>>> git checkout eacf4c0202654adfa94bbb17b5c5c77c0be14af8
> > >>>> # save the attached .config to linux build tree
> > >>>> COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 ARCH=powerpc
> > >>>>
> > >>>> If you fix the issue, kindly add following tag as appropriate
> > >>>> Reported-by: kernel test robot <lkp@...el.com>
> > >>>>
> > >>>> All errors (new ones prefixed by >>):
> > >>>>
> > >>>>>> arch/powerpc/kernel/optprobes.c:34:1: error: unused function 'is_kprobe_ppc_optinsn_slot'
> > >>>>>> [-Werror,-Wunused-function]
> > >>>> DEFINE_INSN_CACHE_OPS(ppc_optinsn);
> > >>>> ^
> > >>>> include/linux/kprobes.h:306:20: note: expanded from macro 'DEFINE_INSN_CACHE_OPS'
> > >>>> static inline bool is_kprobe_##__name##_slot(unsigned long addr) \
> > >>>
> > >>> That's a 'static inline', shouldn't generate an 'unused function' warning.
> > >> This is a W=1 build, which means that "inline" does not silence unused function warnings with
> > >> clang because of commit 6863f5643dd7 ("kbuild: allow Clang to find unused static inline functions
> > >> for W=1 build").
> > >
> > > Ok, I didn't know that.
> >
> > After looking at it in more details, I don't really know what should be done to avoid that.
>
> Ah, thanks for reporting!
>
> >
> > This unused function is defined as part of DEFINE_INSN_CACHE_OPS(ppc_optinsn).
> >
> > The code uses other items defined by macro DEFINE_INSN_CACHE_OPS, so it cannot be removed.
> >
> > Solution could be to hide that in a .h, but is that worth it ?
>
> The best solution is to remove ppc_optinsn, but that is defined in kernel/kprobes.c
> just because page allocation is different.
> I think the easiest fix is to add weak alloc_optinsn_page() and override it
> in arch/powerpc/kernel/optprobe.c.
Please try this patch.
Thank you,
>From 7782fa154349923ed52baa8843cc1d5eed26e82d Mon Sep 17 00:00:00 2001
From: Masami Hiramatsu <mhiramat@...nel.org>
Date: Wed, 12 May 2021 23:33:10 +0900
Subject: [PATCH] powerpc/kprobes: Define arch specific optinsn memory
allocation
Define arch specific optinsn memory allocate functions
instead of using arch specific ppc_optinsn_slot.
This fixes the unused function warning on is_kprobe_ppc_optinsn_slot()
when building with W=1 and also this makes kernel_text_address()
works correctly on optinsn page.
Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
---
arch/powerpc/kernel/optprobes.c | 24 +++++++-----------------
kernel/kprobes.c | 15 +++++++++++++--
2 files changed, 20 insertions(+), 19 deletions(-)
diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
index cdf87086fa33..aa017ccbd66e 100644
--- a/arch/powerpc/kernel/optprobes.c
+++ b/arch/powerpc/kernel/optprobes.c
@@ -31,11 +31,10 @@
#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)
+/* Override optinsn page allocation */
+void *alloc_optinsn_page(void)
{
if (insn_page_in_use)
return NULL;
@@ -43,20 +42,11 @@ 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 __maybe_unused)
{
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 +126,7 @@ 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 +193,14 @@ 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;
+ kprobe_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 +287,7 @@ 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;
}
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 745f08fdd7a6..251fcb9d6c4c 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -321,11 +321,22 @@ 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 */
--
2.25.1
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