Commit 96d7a4e0 authored by Daniel Axtens's avatar Daniel Axtens Committed by Michael Ellerman
Browse files

powerpc/signal64: Rewrite handle_rt_signal64() to minimise uaccess switches 



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.

Co-developed-by: default avatarChristopher M. Riedl <cmr@codefail.de>
Signed-off-by: default avatarDaniel Axtens <dja@axtens.net>
Signed-off-by: default avatarChristopher M. Riedl <cmr@codefail.de>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210227011259.11992-9-cmr@codefail.de
parent 193323e1

arch/powerpc/kernel/signal_64.c

+36 −21
Original line number Diff line number Diff line
@@ -854,45 +854,53 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set, 
	unsigned long msr = regs->msr;



	frame = get_sigframe(ksig, tsk, sizeof(*frame), 0);

	if (!access_ok(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)

	/*

	 * This only applies when calling unsafe_setup_sigcontext() and must be

	 * called before opening the uaccess window.

	 */

	if (!MSR_TM_ACTIVE(msr))

		prepare_setup_sigcontext(tsk);



	if (!user_write_access_begin(frame, sizeof(*frame)))

		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);



	if (MSR_TM_ACTIVE(msr)) {

#ifdef CONFIG_PPC_TRANSACTIONAL_MEM

		/* 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();



		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->uc.uc_sigmask,

					     sizeof(frame->uc.uc_sigmask)))

			goto badframe;



#endif

	} else {

		err |= __put_user(0, &frame->uc.uc_link);

		prepare_setup_sigcontext(tsk);

		if (!user_write_access_begin(&frame->uc.uc_mcontext,

					     sizeof(frame->uc.uc_mcontext)))

			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);

	user_write_access_end();



	/* Make sure signal handler doesn't get spurious FP exceptions */

	tsk->thread.fp_state.fpscr = 0;
@@ -907,6 +915,11 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set, 
		regs->nip = (unsigned long) &frame->tramp[0];

	}





	/* 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);
@@ -946,6 +959,8 @@ 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);