[PATCH 7/8] powerpc/signal64: Rewrite handle_rt_signal64() to minimise uaccess switches
Christophe Leroy
christophe.leroy at csgroup.eu
Sat Oct 17 01:00:20 AEDT 2020
Le 15/10/2020 à 17:01, Christopher M. Riedl a écrit :
> From: Daniel Axtens <dja at axtens.net>
>
> Add uaccess blocks and use the 'unsafe' versions of functions doing user
> access where possible to reduce the number of times uaccess has to be
> opened/closed.
>
> There is no 'unsafe' version of copy_siginfo_to_user, so move it
> slightly to allow for a "longer" uaccess block.
>
> Signed-off-by: Daniel Axtens <dja at axtens.net>
> Signed-off-by: Christopher M. Riedl <cmr at codefail.de>
> ---
> arch/powerpc/kernel/signal_64.c | 54 ++++++++++++++++-----------------
> 1 file changed, 27 insertions(+), 27 deletions(-)
>
> diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
> index 6d4f7a5c4fbf..3b97e3681a8f 100644
> --- a/arch/powerpc/kernel/signal_64.c
> +++ b/arch/powerpc/kernel/signal_64.c
> @@ -843,46 +843,42 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
> /* Save the thread's msr before get_tm_stackpointer() changes it */
> unsigned long msr = regs->msr;
> #endif
> -
> frame = get_sigframe(ksig, tsk, sizeof(*frame), 0);
> - if (!access_ok(frame, sizeof(*frame)))
> + if (!user_write_access_begin(frame, sizeof(*frame)))
> goto badframe;
>
> - err |= __put_user(&frame->info, &frame->pinfo);
> - err |= __put_user(&frame->uc, &frame->puc);
> - err |= copy_siginfo_to_user(&frame->info, &ksig->info);
> - if (err)
> - goto badframe;
> + unsafe_put_user(&frame->info, &frame->pinfo, badframe_block);
> + unsafe_put_user(&frame->uc, &frame->puc, badframe_block);
>
> /* Create the ucontext. */
> - err |= __put_user(0, &frame->uc.uc_flags);
> - err |= __save_altstack(&frame->uc.uc_stack, regs->gpr[1]);
> + unsafe_put_user(0, &frame->uc.uc_flags, badframe_block);
> + unsafe_save_altstack(&frame->uc.uc_stack, regs->gpr[1], badframe_block);
> +
> #ifdef CONFIG_PPC_TRANSACTIONAL_MEM
> if (MSR_TM_ACTIVE(msr)) {
> /* The ucontext_t passed to userland points to the second
> * ucontext_t (for transactional state) with its uc_link ptr.
> */
> - err |= __put_user(&frame->uc_transact, &frame->uc.uc_link);
> + unsafe_put_user(&frame->uc_transact, &frame->uc.uc_link, badframe_block);
> + user_write_access_end();
Whaou. Doing this inside an #ifdef sequence is dirty.
Can you reorganise code to avoid that and to avoid nesting #ifdef/#endif and the if/else as I did in
signal32 ?
> err |= setup_tm_sigcontexts(&frame->uc.uc_mcontext,
> &frame->uc_transact.uc_mcontext,
> tsk, ksig->sig, NULL,
> (unsigned long)ksig->ka.sa.sa_handler,
> msr);
> + if (!user_write_access_begin(frame, sizeof(struct rt_sigframe)))
> + goto badframe;
> +
> } else
> #endif
> {
> - err |= __put_user(0, &frame->uc.uc_link);
> -
> - if (!user_write_access_begin(frame, sizeof(struct rt_sigframe)))
> - return -EFAULT;
> - err |= __unsafe_setup_sigcontext(&frame->uc.uc_mcontext, tsk,
> - ksig->sig, NULL,
> - (unsigned long)ksig->ka.sa.sa_handler, 1);
> - user_write_access_end();
> + unsafe_put_user(0, &frame->uc.uc_link, badframe_block);
> + unsafe_setup_sigcontext(&frame->uc.uc_mcontext, tsk, ksig->sig,
> + NULL, (unsigned long)ksig->ka.sa.sa_handler,
> + 1, badframe_block);
> }
> - err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
> - if (err)
> - goto badframe;
> +
> + unsafe_copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set), badframe_block);
>
> /* Make sure signal handler doesn't get spurious FP exceptions */
> tsk->thread.fp_state.fpscr = 0;
> @@ -891,15 +887,17 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
> if (vdso64_rt_sigtramp && tsk->mm->context.vdso_base) {
> regs->nip = tsk->mm->context.vdso_base + vdso64_rt_sigtramp;
> } else {
> - if (!user_write_access_begin(frame, sizeof(struct rt_sigframe)))
> - return -EFAULT;
> - err |= __unsafe_setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0]);
> - user_write_access_end();
> - if (err)
> - goto badframe;
> + unsafe_setup_trampoline(__NR_rt_sigreturn, &frame->tramp[0],
> + badframe_block);
> regs->nip = (unsigned long) &frame->tramp[0];
> }
>
> + user_write_access_end();
> +
> + /* Save the siginfo outside of the unsafe block. */
> + if (copy_siginfo_to_user(&frame->info, &ksig->info))
> + goto badframe;
> +
> /* Allocate a dummy caller frame for the signal handler. */
> newsp = ((unsigned long)frame) - __SIGNAL_FRAMESIZE;
> err |= put_user(regs->gpr[1], (unsigned long __user *)newsp);
> @@ -939,6 +937,8 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
>
> return 0;
>
> +badframe_block:
> + user_write_access_end();
> badframe:
> signal_fault(current, regs, "handle_rt_signal64", frame);
>
>
Christophe
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