From: Ben Hutchings <ben@decadent.org.uk>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: akpm@linux-foundation.org,
"Peter Zijlstra" <peterz@infradead.org>,
"David Woodhouse" <dwmw@amazon.co.uk>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Kyle Huey" <khuey@kylehuey.com>,
"Andy Lutomirski" <luto@kernel.org>,
"Kyle Huey" <me@kylehuey.com>
Subject: [PATCH 3.16 59/63] x86/process: Correct and optimize TIF_BLOCKSTEP switch
Date: Sat, 22 Sep 2018 01:15:42 +0100 [thread overview]
Message-ID: <lsq.1537575342.558857038@decadent.org.uk> (raw)
In-Reply-To: <lsq.1537575341.194909669@decadent.org.uk>
3.16.58-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Kyle Huey <me@kylehuey.com>
commit b9894a2f5bd18b1691cb6872c9afe32b148d0132 upstream.
The debug control MSR is "highly magical" as the blockstep bit can be
cleared by hardware under not well documented circumstances.
So a task switch relying on the bit set by the previous task (according to
the previous tasks thread flags) can trip over this and not update the flag
for the next task.
To fix this its required to handle DEBUGCTLMSR_BTF when either the previous
or the next or both tasks have the TIF_BLOCKSTEP flag set.
While at it avoid branching within the TIF_BLOCKSTEP case and evaluating
boot_cpu_data twice in kernels without CONFIG_X86_DEBUGCTLMSR.
x86_64: arch/x86/kernel/process.o
text data bss dec hex
3024 8577 16 11617 2d61 Before
3008 8577 16 11601 2d51 After
i386: No change
[ tglx: Made the shift value explicit, use a local variable to make the
code readable and massaged changelog]
Originally-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Kyle Huey <khuey@kylehuey.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Link: http://lkml.kernel.org/r/20170214081104.9244-3-khuey@kylehuey.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
arch/x86/include/uapi/asm/msr-index.h | 1 +
arch/x86/kernel/process.c | 12 +++++++-----
2 files changed, 8 insertions(+), 5 deletions(-)
--- a/arch/x86/include/uapi/asm/msr-index.h
+++ b/arch/x86/include/uapi/asm/msr-index.h
@@ -109,6 +109,7 @@
/* DEBUGCTLMSR bits (others vary by model): */
#define DEBUGCTLMSR_LBR (1UL << 0) /* last branch recording */
+#define DEBUGCTLMSR_BTF_SHIFT 1
#define DEBUGCTLMSR_BTF (1UL << 1) /* single-step on branches */
#define DEBUGCTLMSR_TR (1UL << 6)
#define DEBUGCTLMSR_BTS (1UL << 7)
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -231,13 +231,15 @@ void __switch_to_xtra(struct task_struct
propagate_user_return_notify(prev_p, next_p);
- if ((tifp ^ tifn) & _TIF_BLOCKSTEP) {
- unsigned long debugctl = get_debugctlmsr();
+ if ((tifp & _TIF_BLOCKSTEP || tifn & _TIF_BLOCKSTEP) &&
+ arch_has_block_step()) {
+ unsigned long debugctl, msk;
+ rdmsrl(MSR_IA32_DEBUGCTLMSR, debugctl);
debugctl &= ~DEBUGCTLMSR_BTF;
- if (tifn & _TIF_BLOCKSTEP)
- debugctl |= DEBUGCTLMSR_BTF;
- update_debugctlmsr(debugctl);
+ msk = tifn & _TIF_BLOCKSTEP;
+ debugctl |= (msk >> TIF_BLOCKSTEP) << DEBUGCTLMSR_BTF_SHIFT;
+ wrmsrl(MSR_IA32_DEBUGCTLMSR, debugctl);
}
if ((tifp ^ tifn) & _TIF_NOTSC) {
next prev parent reply other threads:[~2018-09-22 0:24 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-22 0:15 [PATCH 3.16 00/63] 3.16.58-rc1 review Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 51/63] xfs: catch inode allocation state mismatch corruption Ben Hutchings
2018-09-22 5:25 ` Dave Chinner
2018-09-22 20:57 ` Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 07/63] usbip: usbip_host: refine probe and disconnect debug msgs to be useful Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 41/63] USB: yurex: fix out-of-bounds uaccess in read handler Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 54/63] seccomp: create internal mode-setting function Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 45/63] x86/paravirt: Fix spectre-v2 mitigations for paravirt guests Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 36/63] jbd2: don't mark block as modified if the handle is out of credits Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 18/63] sr: pass down correctly sized SCSI sense buffer Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 06/63] usbip: usbip_host: fix to hold parent lock for device_attach() calls Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 29/63] ext4: make sure bitmaps and the inode table don't overlap with bg descriptors Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 63/63] mm: get rid of vmacache_flush_all() entirely Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 26/63] ext4: verify the depth of extent tree in ext4_find_extent() Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 38/63] Fix up non-directory creation in SGID directories Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 56/63] seccomp: split mode setting routines Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 13/63] futex: Remove unnecessary warning from get_futex_key Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 21/63] Bluetooth: hidp: buffer overflow in hidp_process_report Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 32/63] ext4: always verify the magic number in xattr blocks Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 23/63] xfs: set format back to extents if xfs_bmap_extents_to_btree Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 08/63] usbip: usbip_host: delete device from busid_table after rebind Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 60/63] x86/cpu/AMD: Fix erratum 1076 (CPB bit) Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 57/63] seccomp: add "seccomp" syscall Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 20/63] scsi: sg: allocate with __GFP_ZERO in sg_build_indirect() Ben Hutchings
2018-09-22 0:19 ` syzbot
2018-09-22 0:15 ` [PATCH 3.16 04/63] net: Set sk_prot_creator when cloning sockets to the right proto Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 33/63] ext4: never move the system.data xattr out of the inode body Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 55/63] seccomp: extract check/assign mode helpers Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 16/63] KVM: x86: pass kvm_vcpu to kvm_read_guest_virt and kvm_write_guest_virt_system Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 35/63] ext4: add more inode number paranoia checks Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 42/63] ALSA: rawmidi: Change resized buffers atomically Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 27/63] ext4: always check block group bounds in ext4_init_block_bitmap() Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 25/63] ext4: fix check to prevent initializing reserved inodes Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 14/63] KVM: x86: Emulator ignores LDTR/TR extended base on LLDT/LTR Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 15/63] KVM: x86: introduce linear_{read,write}_system Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 61/63] x86/cpu/intel: Add Knights Mill to Intel family Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 40/63] infiniband: fix a possible use-after-free bug Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 09/63] usbip: usbip_host: run rebind from exit when module is removed Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 11/63] usbip: usbip_host: fix bad unlock balance during stub_probe() Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 12/63] futex: Remove requirement for lock_page() in get_futex_key() Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 30/63] ext4: fix false negatives *and* false positives in ext4_check_descriptors() Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 37/63] ext4: avoid running out of journal credits when appending to an inline file Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 47/63] uas: replace WARN_ON_ONCE() with lockdep_assert_held() Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 44/63] x86/speculation: Protect against userspace-userspace spectreRSB Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 49/63] btrfs: relocation: Only remove reloc rb_trees if reloc control has been initialized Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 24/63] ext4: only look at the bg_flags field if it is valid Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 53/63] xfs: don't call xfs_da_shrink_inode with NULL bp Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 17/63] kvm: x86: use correct privilege level for sgdt/sidt/fxsave/fxrstor access Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 43/63] x86/speculation: Clean up various Spectre related details Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 52/63] xfs: validate cached inodes are free when allocated Ben Hutchings
2018-09-22 5:26 ` Dave Chinner
2018-09-22 20:57 ` Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 48/63] video: uvesafb: Fix integer overflow in allocation Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 19/63] jfs: Fix inconsistency between memory allocation and ea_buf->max_size Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 22/63] scsi: libsas: defer ata device eh commands to libata Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 05/63] usbip: fix error handling in stub_probe() Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 10/63] usbip: usbip_host: fix NULL-ptr deref and use-after-free errors Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 46/63] cdrom: Fix info leak/OOB read in cdrom_ioctl_drive_status Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 28/63] ext4: don't allow r/w mounts if metadata blocks overlap the superblock Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 03/63] Revert "vti4: Don't override MTU passed on link creation via IFLA_MTU" Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 34/63] ext4: clear i_data in ext4_inode_info when removing inline data Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 01/63] x86/fpu: Fix the 'nofxsr' boot parameter to also clear X86_FEATURE_FXSR_OPT Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 02/63] x86/fpu: Default eagerfpu if FPU and FXSR are enabled Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 58/63] x86/process: Optimize TIF checks in __switch_to_xtra() Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 31/63] ext4: add corruption check in ext4_xattr_set_entry() Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 39/63] x86/entry/64: Remove %ebx handling from error_entry/exit Ben Hutchings
2018-09-22 0:15 ` Ben Hutchings [this message]
2018-09-22 0:15 ` [PATCH 3.16 50/63] hfsplus: fix NULL dereference in hfsplus_lookup() Ben Hutchings
2018-09-22 0:15 ` [PATCH 3.16 62/63] KVM: x86: introduce num_emulated_msrs Ben Hutchings
2018-09-22 12:28 ` [PATCH 3.16 00/63] 3.16.58-rc1 review Guenter Roeck
2018-09-22 21:03 ` Ben Hutchings
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