LinuxPPC-Dev Archive on
 help / color / Atom feed
From: Christophe Leroy <>
To: Benjamin Herrenschmidt <>,
	Paul Mackerras <>,
	Michael Ellerman <>
Subject: [PATCH] powerpc/32s: Fix CPU wake-up from sleep mode
Date: Mon, 27 Jan 2020 10:42:04 +0000 (UTC)
Message-ID: <> (raw)

Commit f7354ccac844 ("powerpc/32: Remove CURRENT_THREAD_INFO and
rename TI_CPU") broke the CPU wake-up from sleep mode (i.e. when
_TLF_SLEEPING is set) by delaying the tovirt(r2, r2).

This is because r2 is not restored by fast_exception_return. It used
to work (by chance ?) because CPU wake-up interrupt never comes from
user, so r2 is expected to point to 'current' on return.

Commit e2fb9f544431 ("powerpc/32: Prepare for Kernel Userspace Access
Protection") broke it even more by clobbering r0 which is not
restored by fast_exception_return either.

Use r6 instead of r0. This is possible because r3-r6 are restored by
fast_exception_return and only r3-r5 are used for exception arguments.

For r2 it could be converted back to virtual address, but stay on the
safe side and restore it from the stack instead. It should be live
in the cache at that moment, so loading from the stack should make
no difference compared to converting it from phys to virt.

Fixes: f7354ccac844 ("powerpc/32: Remove CURRENT_THREAD_INFO and rename TI_CPU")
Fixes: e2fb9f544431 ("powerpc/32: Prepare for Kernel Userspace Access Protection")
Signed-off-by: Christophe Leroy <>
 arch/powerpc/kernel/entry_32.S | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 73b80143ffac..27e2afce8b78 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -180,7 +180,7 @@ transfer_to_handler:
 2:	/* if from kernel, check interrupted DOZE/NAP mode and
          * check for stack overflow
-	kuap_save_and_lock r11, r12, r9, r2, r0
+	kuap_save_and_lock r11, r12, r9, r2, r6
 	addi	r2, r12, -THREAD
 	lwz	r9,KSP_LIMIT(r12)
@@ -288,6 +288,7 @@ reenable_mmu:
 	rlwinm	r9,r9,0,~MSR_EE
 	lwz	r12,_LINK(r11)		/* and return to address in LR */
 	kuap_restore r11, r2, r3, r4, r5
+	lwz	r2, GPR2(r11)
 	b	fast_exception_return

             reply index

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-27 10:42 Christophe Leroy [this message]
2020-02-04 12:01 ` Michael Ellerman

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LinuxPPC-Dev Archive on

Archives are clonable:
	git clone --mirror linuxppc-dev/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linuxppc-dev linuxppc-dev/ \
	public-inbox-index linuxppc-dev

Example config snippet for mirrors

Newsgroup available over NNTP:

AGPL code for this site: git clone