[PATCH 3.10 061/319] arm64: debug: avoid resetting stepping state machine when TIF_SINGLESTEP

From	Willy Tarreau <w@1wt.eu>
Newsgroups	linux.kernel
Subject	[PATCH 3.10 061/319] arm64: debug: avoid resetting stepping state machine when TIF_SINGLESTEP
Date	2017-02-05 21:40 +0100
Message-ID	<t7BLk-3Ja-13@gated-at.bofh.it> (permalink)
References	<t7AFA-32I-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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From: Will Deacon <will.deacon@arm.com>

commit 3a402a709500c5a3faca2111668c33d96555e35a upstream.

When TIF_SINGLESTEP is set for a task, the single-step state machine is
enabled and we must take care not to reset it to the active-not-pending
state if it is already in the active-pending state.

Unfortunately, that's exactly what user_enable_single_step does, by
unconditionally setting the SS bit in the SPSR for the current task.
This causes failures in the GDB testsuite, where GDB ends up missing
expected step traps if the instruction being stepped generates another
trap, e.g. PTRACE_EVENT_FORK from an SVC instruction.

This patch fixes the problem by preserving the current state of the
stepping state machine when TIF_SINGLESTEP is set on the current thread.

Cc: <stable@vger.kernel.org>
Reported-by: Yao Qi <yao.qi@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---
 arch/arm64/kernel/debug-monitors.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
index f4726dc..49e6e30 100644
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -276,8 +276,10 @@ int kernel_active_single_step(void)
 /* ptrace API */
 void user_enable_single_step(struct task_struct *task)
 {
-	set_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP);
-	set_regs_spsr_ss(task_pt_regs(task));
+	struct thread_info *ti = task_thread_info(task);
+
+	if (!test_and_set_ti_thread_flag(ti, TIF_SINGLESTEP))
+		set_regs_spsr_ss(task_pt_regs(task));
 }
 
 void user_disable_single_step(struct task_struct *task)
-- 
2.8.0.rc2.1.gbe9624a

Thread

[PATCH 3.10 030/319] PM / devfreq: Fix incorrect type issue. Willy Tarreau <w@1wt.eu> - 2017-02-05 20:30 +0100
  [PATCH 3.10 067/319] powerpc/64: Fix incorrect return value from __copy_tofrom_user Willy Tarreau <w@1wt.eu> - 2017-02-05 20:30 +0100
  [PATCH 3.10 040/319] xen/pciback: Do not install an IRQ handler for MSI interrupts. Willy Tarreau <w@1wt.eu> - 2017-02-05 20:30 +0100
  [PATCH 3.10 079/319] score: fix __get_user/get_user Willy Tarreau <w@1wt.eu> - 2017-02-05 20:30 +0100
  [PATCH 3.10 095/319] openrisc: fix the fix of copy_from_user() Willy Tarreau <w@1wt.eu> - 2017-02-05 20:30 +0100
  [PATCH 3.10 086/319] score: fix copy_from_user() and friends Willy Tarreau <w@1wt.eu> - 2017-02-05 20:30 +0100
  [PATCH 3.10 072/319] s390/dasd: fix hanging device after clear subchannel Willy Tarreau <w@1wt.eu> - 2017-02-05 20:30 +0100
  [PATCH 3.10 060/319] arm64: spinlocks: implement smp_mb__before_spinlock() as smp_mb() Willy Tarreau <w@1wt.eu> - 2017-02-05 20:40 +0100
  [PATCH 3.10 093/319] parisc: fix copy_from_user() Willy Tarreau <w@1wt.eu> - 2017-02-05 20:40 +0100
  [PATCH 3.10 087/319] sh: fix copy_from_user() Willy Tarreau <w@1wt.eu> - 2017-02-05 20:40 +0100
  [PATCH 3.10 094/319] openrisc: fix copy_from_user() Willy Tarreau <w@1wt.eu> - 2017-02-05 20:40 +0100
  [PATCH 3.10 063/319] MIPS: ptrace: Fix regs_return_value for kernel context Willy Tarreau <w@1wt.eu> - 2017-02-05 20:50 +0100
  [PATCH 3.10 059/319] arm64: Define AT_VECTOR_SIZE_ARCH for ARCH_DLINFO Willy Tarreau <w@1wt.eu> - 2017-02-05 20:50 +0100
  [PATCH 3.10 055/319] ARM: 8618/1: decompressor: reset ttbcr fields to use TTBR0 on ARMv7 Willy Tarreau <w@1wt.eu> - 2017-02-05 20:50 +0100
  [PATCH 3.10 034/319] xen-netback: don't use last request to determine minimum Tx credit Willy Tarreau <w@1wt.eu> - 2017-02-05 21:00 +0100
  [PATCH 3.10 091/319] alpha: fix copy_from_user() Willy Tarreau <w@1wt.eu> - 2017-02-05 21:00 +0100
  [PATCH 3.10 076/319] mn10300: failing __get_user() and get_user() should zero Willy Tarreau <w@1wt.eu> - 2017-02-05 21:10 +0100
  [PATCH 3.10 070/319] avr32: fix 'undefined reference to `___copy_from_user' Willy Tarreau <w@1wt.eu> - 2017-02-05 21:10 +0100
  [PATCH 3.10 049/319] x86/paravirt: Do not trace _paravirt_ident_*() functions Willy Tarreau <w@1wt.eu> - 2017-02-05 21:10 +0100
  [PATCH 3.10 068/319] powerpc/nvram: Fix an incorrect partition merge Willy Tarreau <w@1wt.eu> - 2017-02-05 21:10 +0100
  [PATCH 3.10 075/319] microblaze: fix copy_from_user() Willy Tarreau <w@1wt.eu> - 2017-02-05 21:10 +0100
  [PATCH 3.10 041/319] xen/pciback: For XEN_PCI_OP_disable_msi[|x] only disable if device has MSI(X) enabled. Willy Tarreau <w@1wt.eu> - 2017-02-05 21:20 +0100
  [PATCH 3.10 085/319] blackfin: fix copy_from_user() Willy Tarreau <w@1wt.eu> - 2017-02-05 21:20 +0100
  [PATCH 3.10 046/319] x86/mm: Disable preemption during CR3 read+write Willy Tarreau <w@1wt.eu> - 2017-02-05 21:20 +0100
  [PATCH 3.10 048/319] x86/mm/pat, /dev/mem: Remove superfluous error message Willy Tarreau <w@1wt.eu> - 2017-02-05 21:20 +0100
  [PATCH 3.10 081/319] ARC: uaccess: get_user to zero out dest in cause of fault Willy Tarreau <w@1wt.eu> - 2017-02-05 21:20 +0100
  [PATCH 3.10 037/319] xen/pciback: Save xen_pci_op commands before processing it Willy Tarreau <w@1wt.eu> - 2017-02-05 21:20 +0100
    Re: [PATCH 3.10 037/319] xen/pciback: Save xen_pci_op commands  before processing it Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> - 2017-02-06 15:40 +0100
      Re: [PATCH 3.10 037/319] xen/pciback: Save xen_pci_op commands  before processing it Willy Tarreau <w@1wt.eu> - 2017-02-06 23:40 +0100
  [PATCH 3.10 050/319] x86/build: Build compressed x86 kernels as PIE Willy Tarreau <w@1wt.eu> - 2017-02-05 21:20 +0100
  [PATCH 3.10 057/319] ARM: sa1111: fix pcmcia suspend/resume Willy Tarreau <w@1wt.eu> - 2017-02-05 21:20 +0100
  [PATCH 3.10 032/319] x86/mm/xen: Suppress hugetlbfs in PV guests Willy Tarreau <w@1wt.eu> - 2017-02-05 21:20 +0100
  [PATCH 3.10 098/319] ppc32: fix copy_from_user() Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 053/319] iommu/amd: Free domain id when free a domain of struct dma_ops_domain Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 099/319] ia64: copy_from_user() should zero the destination on access_ok() failure Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 092/319] metag: copy_from_user() should zero the destination on access_ok() failure Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 047/319] x86/apic: Do not init irq remapping if ioapic is disabled Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 066/319] powerpc/powernv: Use CPU-endian PEST in pnv_pci_dump_p7ioc_diag_data() Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 058/319] arm64: avoid returning from bad_mode Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 065/319] powerpc/vdso64: Use double word compare on pointers Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 031/319] ppp: defer netns reference release for ppp channel Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 064/319] powerpc/mm: Don't alias user region to other regions below PAGE_OFFSET Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 035/319] xen-netback: use RING_COPY_REQUEST() throughout Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 062/319] MIPS: Malta: Fix IOCU disable switch read for MIPS64 Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 033/319] xen: Add RING_COPY_REQUEST() Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 078/319] sh64: failing __get_user() should zero Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 089/319] mips: copy_from_user() must zero the destination on access_ok() failure Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 036/319] xen-blkback: only read request operation from shared ring once Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 083/319] frv: fix clear_user() Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 080/319] s390: get_user() should zero on failure Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 073/319] parisc: Ensure consistent state when switching to kernel stack at syscall entry Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 038/319] xen/pciback: Return error on XEN_PCI_OP_enable_msi when device has MSI or MSI-X enabled Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 054/319] ARM: 8616/1: dt: Respect property size when parsing CPUs Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 088/319] hexagon: fix strncpy_from_user() error return Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 052/319] iommu/amd: Update Alias-DTE in update_device_table() Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 039/319] xen/pciback: Return error on XEN_PCI_OP_enable_msix when device has MSI or MSI-X enabled Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 090/319] asm-generic: make copy_from_user() zero the destination properly Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 044/319] x86/xen: fix upper bound of pmd loop in xen_cleanhighmap() Willy Tarreau <w@1wt.eu> - 2017-02-05 21:30 +0100
  [PATCH 3.10 045/319] x86/traps: Ignore high word of regs->cs in early_idt_handler_common Willy Tarreau <w@1wt.eu> - 2017-02-05 21:40 +0100
  [PATCH 3.10 042/319] xen/pciback: Don't allow MSI-X ops if PCI_COMMAND_MEMORY is not set. Willy Tarreau <w@1wt.eu> - 2017-02-05 21:40 +0100
  [PATCH 3.10 061/319] arm64: debug: avoid resetting stepping state machine when TIF_SINGLESTEP Willy Tarreau <w@1wt.eu> - 2017-02-05 21:40 +0100
  [PATCH 3.10 097/319] sparc32: fix copy_from_user() Willy Tarreau <w@1wt.eu> - 2017-02-05 21:40 +0100
  [PATCH 3.10 051/319] x86/um: reuse asm-generic/barrier.h Willy Tarreau <w@1wt.eu> - 2017-02-05 21:40 +0100
  [PATCH 3.10 043/319] xen-pciback: Add name prefix to global 'permissive' variable Willy Tarreau <w@1wt.eu> - 2017-02-05 21:40 +0100

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