From: "Nicholas Piggin" <npiggin@gmail.com>
To: "Christophe Leroy" <christophe.leroy@csgroup.eu>,
"Michael Ellerman" <mpe@ellerman.id.au>
Cc: <linux-kernel@vger.kernel.org>, <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH] powerpc/signal32: Force inlining of __unsafe_save_user_regs() and save_tm_user_regs_unsafe()
Date: Tue, 06 Jun 2023 18:58:46 +1000 [thread overview]
Message-ID: <CT5FZBY14ZM4.OYXBJNXQU9A2@wheely> (raw)
In-Reply-To: <7e469c8f01860a69c1ada3ca6a5e2aa65f0f74b2.1685955220.git.christophe.leroy@csgroup.eu>
On Mon Jun 5, 2023 at 6:58 PM AEST, Christophe Leroy wrote:
> Looking at generated code for handle_signal32() shows calls to a
> function called __unsafe_save_user_regs.constprop.0 while user access
> is open.
>
> And that __unsafe_save_user_regs.constprop.0 function has two nops at
> the begining, allowing it to be traced, which is unexpected during
> user access open window.
>
> The solution could be to mark __unsafe_save_user_regs() no trace, but
> to be on the safe side the most efficient is to flag it __always_inline
> as already done for function __unsafe_restore_general_regs(). The
> function is relatively small and only called twice, so the size
> increase will remain in the noise.
>
> Do the same with save_tm_user_regs_unsafe() as it may suffer the
> same issue.
Could you put a comment so someone doesn't uninline it later? Marking
it notrace as well would be sufficient for a comment, if that works.
Thanks,
Nick
>
> Fixes: ef75e7318294 ("powerpc/signal32: Transform save_user_regs() and save_tm_user_regs() in 'unsafe' version")
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
> arch/powerpc/kernel/signal_32.c | 15 +++++++++------
> 1 file changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
> index c114c7f25645..7a718ed32b27 100644
> --- a/arch/powerpc/kernel/signal_32.c
> +++ b/arch/powerpc/kernel/signal_32.c
> @@ -264,8 +264,9 @@ static void prepare_save_user_regs(int ctx_has_vsx_region)
> #endif
> }
>
> -static int __unsafe_save_user_regs(struct pt_regs *regs, struct mcontext __user *frame,
> - struct mcontext __user *tm_frame, int ctx_has_vsx_region)
> +static __always_inline int
> +__unsafe_save_user_regs(struct pt_regs *regs, struct mcontext __user *frame,
> + struct mcontext __user *tm_frame, int ctx_has_vsx_region)
> {
> unsigned long msr = regs->msr;
>
> @@ -364,8 +365,9 @@ static void prepare_save_tm_user_regs(void)
> current->thread.ckvrsave = mfspr(SPRN_VRSAVE);
> }
>
> -static int save_tm_user_regs_unsafe(struct pt_regs *regs, struct mcontext __user *frame,
> - struct mcontext __user *tm_frame, unsigned long msr)
> +static __always_inline int
> +save_tm_user_regs_unsafe(struct pt_regs *regs, struct mcontext __user *frame,
> + struct mcontext __user *tm_frame, unsigned long msr)
> {
> /* Save both sets of general registers */
> unsafe_save_general_regs(¤t->thread.ckpt_regs, frame, failed);
> @@ -444,8 +446,9 @@ static int save_tm_user_regs_unsafe(struct pt_regs *regs, struct mcontext __user
> #else
> static void prepare_save_tm_user_regs(void) { }
>
> -static int save_tm_user_regs_unsafe(struct pt_regs *regs, struct mcontext __user *frame,
> - struct mcontext __user *tm_frame, unsigned long msr)
> +static __always_inline int
> +save_tm_user_regs_unsafe(struct pt_regs *regs, struct mcontext __user *frame,
> + struct mcontext __user *tm_frame, unsigned long msr)
> {
> return 0;
> }
> --
> 2.40.1
WARNING: multiple messages have this Message-ID (diff)
From: "Nicholas Piggin" <npiggin@gmail.com>
To: "Christophe Leroy" <christophe.leroy@csgroup.eu>,
"Michael Ellerman" <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] powerpc/signal32: Force inlining of __unsafe_save_user_regs() and save_tm_user_regs_unsafe()
Date: Tue, 06 Jun 2023 18:58:46 +1000 [thread overview]
Message-ID: <CT5FZBY14ZM4.OYXBJNXQU9A2@wheely> (raw)
In-Reply-To: <7e469c8f01860a69c1ada3ca6a5e2aa65f0f74b2.1685955220.git.christophe.leroy@csgroup.eu>
On Mon Jun 5, 2023 at 6:58 PM AEST, Christophe Leroy wrote:
> Looking at generated code for handle_signal32() shows calls to a
> function called __unsafe_save_user_regs.constprop.0 while user access
> is open.
>
> And that __unsafe_save_user_regs.constprop.0 function has two nops at
> the begining, allowing it to be traced, which is unexpected during
> user access open window.
>
> The solution could be to mark __unsafe_save_user_regs() no trace, but
> to be on the safe side the most efficient is to flag it __always_inline
> as already done for function __unsafe_restore_general_regs(). The
> function is relatively small and only called twice, so the size
> increase will remain in the noise.
>
> Do the same with save_tm_user_regs_unsafe() as it may suffer the
> same issue.
Could you put a comment so someone doesn't uninline it later? Marking
it notrace as well would be sufficient for a comment, if that works.
Thanks,
Nick
>
> Fixes: ef75e7318294 ("powerpc/signal32: Transform save_user_regs() and save_tm_user_regs() in 'unsafe' version")
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
> arch/powerpc/kernel/signal_32.c | 15 +++++++++------
> 1 file changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
> index c114c7f25645..7a718ed32b27 100644
> --- a/arch/powerpc/kernel/signal_32.c
> +++ b/arch/powerpc/kernel/signal_32.c
> @@ -264,8 +264,9 @@ static void prepare_save_user_regs(int ctx_has_vsx_region)
> #endif
> }
>
> -static int __unsafe_save_user_regs(struct pt_regs *regs, struct mcontext __user *frame,
> - struct mcontext __user *tm_frame, int ctx_has_vsx_region)
> +static __always_inline int
> +__unsafe_save_user_regs(struct pt_regs *regs, struct mcontext __user *frame,
> + struct mcontext __user *tm_frame, int ctx_has_vsx_region)
> {
> unsigned long msr = regs->msr;
>
> @@ -364,8 +365,9 @@ static void prepare_save_tm_user_regs(void)
> current->thread.ckvrsave = mfspr(SPRN_VRSAVE);
> }
>
> -static int save_tm_user_regs_unsafe(struct pt_regs *regs, struct mcontext __user *frame,
> - struct mcontext __user *tm_frame, unsigned long msr)
> +static __always_inline int
> +save_tm_user_regs_unsafe(struct pt_regs *regs, struct mcontext __user *frame,
> + struct mcontext __user *tm_frame, unsigned long msr)
> {
> /* Save both sets of general registers */
> unsafe_save_general_regs(¤t->thread.ckpt_regs, frame, failed);
> @@ -444,8 +446,9 @@ static int save_tm_user_regs_unsafe(struct pt_regs *regs, struct mcontext __user
> #else
> static void prepare_save_tm_user_regs(void) { }
>
> -static int save_tm_user_regs_unsafe(struct pt_regs *regs, struct mcontext __user *frame,
> - struct mcontext __user *tm_frame, unsigned long msr)
> +static __always_inline int
> +save_tm_user_regs_unsafe(struct pt_regs *regs, struct mcontext __user *frame,
> + struct mcontext __user *tm_frame, unsigned long msr)
> {
> return 0;
> }
> --
> 2.40.1
next prev parent reply other threads:[~2023-06-06 8:59 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-05 8:58 [PATCH] powerpc/signal32: Force inlining of __unsafe_save_user_regs() and save_tm_user_regs_unsafe() Christophe Leroy
2023-06-05 8:58 ` Christophe Leroy
2023-06-06 8:58 ` Nicholas Piggin [this message]
2023-06-06 8:58 ` Nicholas Piggin
2023-06-09 13:06 ` Michael Ellerman
2023-06-09 13:06 ` Michael Ellerman
2023-07-03 5:26 ` Michael Ellerman
2023-07-03 5:26 ` Michael Ellerman
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