From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
Naresh Kamboju <naresh.kamboju@linaro.org>,
"Paul E . McKenney" <paulmck@linux.ibm.com>,
Will Deacon <will@kernel.org>, Sasha Levin <sashal@kernel.org>
Subject: [PATCH AUTOSEL 5.2 53/59] arm64: Make debug exception handlers visible from RCU
Date: Tue, 6 Aug 2019 17:33:13 -0400 [thread overview]
Message-ID: <20190806213319.19203-53-sashal@kernel.org> (raw)
In-Reply-To: <20190806213319.19203-1-sashal@kernel.org>
From: Masami Hiramatsu <mhiramat@kernel.org>
[ Upstream commit d8bb6718c4db9bcd075dde7ff55d46091ccfae15 ]
Make debug exceptions visible from RCU so that synchronize_rcu()
correctly track the debug exception handler.
This also introduces sanity checks for user-mode exceptions as same
as x86's ist_enter()/ist_exit().
The debug exception can interrupt in idle task. For example, it warns
if we put a kprobe on a function called from idle task as below.
The warning message showed that the rcu_read_lock() caused this
problem. But actually, this means the RCU is lost the context which
is already in NMI/IRQ.
/sys/kernel/debug/tracing # echo p default_idle_call >> kprobe_events
/sys/kernel/debug/tracing # echo 1 > events/kprobes/enable
/sys/kernel/debug/tracing # [ 135.122237]
[ 135.125035] =============================
[ 135.125310] WARNING: suspicious RCU usage
[ 135.125581] 5.2.0-08445-g9187c508bdc7 #20 Not tainted
[ 135.125904] -----------------------------
[ 135.126205] include/linux/rcupdate.h:594 rcu_read_lock() used illegally while idle!
[ 135.126839]
[ 135.126839] other info that might help us debug this:
[ 135.126839]
[ 135.127410]
[ 135.127410] RCU used illegally from idle CPU!
[ 135.127410] rcu_scheduler_active = 2, debug_locks = 1
[ 135.128114] RCU used illegally from extended quiescent state!
[ 135.128555] 1 lock held by swapper/0/0:
[ 135.128944] #0: (____ptrval____) (rcu_read_lock){....}, at: call_break_hook+0x0/0x178
[ 135.130499]
[ 135.130499] stack backtrace:
[ 135.131192] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.2.0-08445-g9187c508bdc7 #20
[ 135.131841] Hardware name: linux,dummy-virt (DT)
[ 135.132224] Call trace:
[ 135.132491] dump_backtrace+0x0/0x140
[ 135.132806] show_stack+0x24/0x30
[ 135.133133] dump_stack+0xc4/0x10c
[ 135.133726] lockdep_rcu_suspicious+0xf8/0x108
[ 135.134171] call_break_hook+0x170/0x178
[ 135.134486] brk_handler+0x28/0x68
[ 135.134792] do_debug_exception+0x90/0x150
[ 135.135051] el1_dbg+0x18/0x8c
[ 135.135260] default_idle_call+0x0/0x44
[ 135.135516] cpu_startup_entry+0x2c/0x30
[ 135.135815] rest_init+0x1b0/0x280
[ 135.136044] arch_call_rest_init+0x14/0x1c
[ 135.136305] start_kernel+0x4d4/0x500
[ 135.136597]
So make debug exception visible to RCU can fix this warning.
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Acked-by: Paul E. McKenney <paulmck@linux.ibm.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/arm64/mm/fault.c | 57 +++++++++++++++++++++++++++++++++++++------
1 file changed, 49 insertions(+), 8 deletions(-)
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 2d115016feb42..414b8e0f19e0e 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -800,6 +800,53 @@ void __init hook_debug_fault_code(int nr,
debug_fault_info[nr].name = name;
}
+/*
+ * In debug exception context, we explicitly disable preemption despite
+ * having interrupts disabled.
+ * This serves two purposes: it makes it much less likely that we would
+ * accidentally schedule in exception context and it will force a warning
+ * if we somehow manage to schedule by accident.
+ */
+static void debug_exception_enter(struct pt_regs *regs)
+{
+ /*
+ * Tell lockdep we disabled irqs in entry.S. Do nothing if they were
+ * already disabled to preserve the last enabled/disabled addresses.
+ */
+ if (interrupts_enabled(regs))
+ trace_hardirqs_off();
+
+ if (user_mode(regs)) {
+ RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
+ } else {
+ /*
+ * We might have interrupted pretty much anything. In
+ * fact, if we're a debug exception, we can even interrupt
+ * NMI processing. We don't want this code makes in_nmi()
+ * to return true, but we need to notify RCU.
+ */
+ rcu_nmi_enter();
+ }
+
+ preempt_disable();
+
+ /* This code is a bit fragile. Test it. */
+ RCU_LOCKDEP_WARN(!rcu_is_watching(), "exception_enter didn't work");
+}
+NOKPROBE_SYMBOL(debug_exception_enter);
+
+static void debug_exception_exit(struct pt_regs *regs)
+{
+ preempt_enable_no_resched();
+
+ if (!user_mode(regs))
+ rcu_nmi_exit();
+
+ if (interrupts_enabled(regs))
+ trace_hardirqs_on();
+}
+NOKPROBE_SYMBOL(debug_exception_exit);
+
#ifdef CONFIG_ARM64_ERRATUM_1463225
DECLARE_PER_CPU(int, __in_cortex_a76_erratum_1463225_wa);
@@ -840,12 +887,7 @@ asmlinkage void __exception do_debug_exception(unsigned long addr_if_watchpoint,
if (cortex_a76_erratum_1463225_debug_handler(regs))
return;
- /*
- * Tell lockdep we disabled irqs in entry.S. Do nothing if they were
- * already disabled to preserve the last enabled/disabled addresses.
- */
- if (interrupts_enabled(regs))
- trace_hardirqs_off();
+ debug_exception_enter(regs);
if (user_mode(regs) && !is_ttbr0_addr(pc))
arm64_apply_bp_hardening();
@@ -855,7 +897,6 @@ asmlinkage void __exception do_debug_exception(unsigned long addr_if_watchpoint,
inf->sig, inf->code, (void __user *)pc, esr);
}
- if (interrupts_enabled(regs))
- trace_hardirqs_on();
+ debug_exception_exit(regs);
}
NOKPROBE_SYMBOL(do_debug_exception);
--
2.20.1
next prev parent reply other threads:[~2019-08-06 21:35 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-06 21:32 [PATCH AUTOSEL 5.2 01/59] RDMA/hns: Fix sg offset non-zero issue Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 02/59] IB/mlx5: Replace kfree with kvfree Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 03/59] clk: at91: generated: Truncate divisor to GENERATED_MAX_DIV + 1 Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 04/59] clk: sprd: Select REGMAP_MMIO to avoid compile errors Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 05/59] clk: renesas: cpg-mssr: Fix reset control race condition Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 06/59] dma-mapping: check pfn validity in dma_common_{mmap,get_sgtable} Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 07/59] xtensa: fix build for cores with coprocessors Sasha Levin
2019-08-06 21:55 ` Max Filippov
2019-08-18 1:45 ` Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 08/59] platform/x86: pcengines-apuv2: Fix softdep statement Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 09/59] platform/x86: intel_pmc_core: Add ICL-NNPI support to PMC Core Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 10/59] mm/hmm: always return EBUSY for invalid ranges in hmm_range_{fault,snapshot} Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 11/59] xen/pciback: remove set but not used variable 'old_state' Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 12/59] irqchip/gic-v3-its: Free unused vpt_page when alloc vpe table fail Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 13/59] irqchip/irq-imx-gpcv2: Forward irq type to parent Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 14/59] f2fs: fix to read source block before invalidating it Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 15/59] tools perf beauty: Fix usbdevfs_ioctl table generator to handle _IOC() Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 16/59] perf header: Fix divide by zero error if f_header.attr_size==0 Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 17/59] perf header: Fix use of unitialized value warning Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 18/59] RDMA/qedr: Fix the hca_type and hca_rev returned in device attributes Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 19/59] ALSA: pcm: fix lost wakeup event scenarios in snd_pcm_drain Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 20/59] libata: zpodd: Fix small read overflow in zpodd_get_mech_type() Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 21/59] powerpc/nvdimm: Pick nearby online node if the device node is not online Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 22/59] drm/bridge: lvds-encoder: Fix build error while CONFIG_DRM_KMS_HELPER=m Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 23/59] drm/bridge: tc358764: Fix build error Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 24/59] Btrfs: fix deadlock between fiemap and transaction commits Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 25/59] scsi: hpsa: correct scsi command status issue after reset Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 26/59] scsi: qla2xxx: Fix possible fcport null-pointer dereferences Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 27/59] exit: make setting exit_state consistent Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 28/59] tracing: Fix header include guards in trace event headers Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 29/59] drm/amdkfd: Fix byte align on VegaM Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 30/59] drm/amd/powerplay: fix null pointer dereference around dpm state relates Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 31/59] drm/amdgpu: fix error handling in amdgpu_cs_process_fence_dep Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 32/59] drm/amdgpu: fix a potential information leaking bug Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 33/59] ata: libahci: do not complain in case of deferred probe Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 34/59] kbuild: modpost: handle KBUILD_EXTRA_SYMBOLS only for external modules Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 35/59] kbuild: Check for unknown options with cc-option usage in Kconfig and clang Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 36/59] arm64/efi: fix variable 'si' set but not used Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 37/59] drm/vgem: fix cache synchronization on arm/arm64 Sasha Levin
2019-08-06 22:45 ` Rob Clark
2019-08-18 1:45 ` Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 38/59] riscv: Fix perf record without libelf support Sasha Levin
2019-08-06 21:32 ` [PATCH AUTOSEL 5.2 39/59] i2c: iproc: Fix i2c master read more than 63 bytes Sasha Levin
2019-08-06 21:33 ` [PATCH AUTOSEL 5.2 40/59] arm64: Lower priority mask for GIC_PRIO_IRQON Sasha Levin
2019-08-06 21:33 ` [PATCH AUTOSEL 5.2 41/59] arm64: unwind: Prohibit probing on return_address() Sasha Levin
2019-08-06 21:33 ` [PATCH AUTOSEL 5.2 42/59] arm64/mm: fix variable 'pud' set but not used Sasha Levin
2019-08-06 21:33 ` [PATCH AUTOSEL 5.2 43/59] arm64/mm: fix variable 'tag' " Sasha Levin
2019-08-06 21:33 ` [PATCH AUTOSEL 5.2 44/59] IB/core: Add mitigation for Spectre V1 Sasha Levin
2019-08-06 21:33 ` [PATCH AUTOSEL 5.2 45/59] IB/mlx5: Fix MR registration flow to use UMR properly Sasha Levin
2019-08-06 21:33 ` [PATCH AUTOSEL 5.2 46/59] RDMA/restrack: Track driver QP types in resource tracker Sasha Levin
2019-08-06 21:33 ` [PATCH AUTOSEL 5.2 47/59] IB/mad: Fix use-after-free in ib mad completion handling Sasha Levin
2019-08-06 21:33 ` [PATCH AUTOSEL 5.2 48/59] RDMA/mlx5: Release locks during notifier unregister Sasha Levin
2019-08-06 21:33 ` [PATCH AUTOSEL 5.2 49/59] drm: msm: Fix add_gpu_components Sasha Levin
2019-08-06 21:33 ` [PATCH AUTOSEL 5.2 50/59] RDMA/hns: Fix error return code in hns_roce_v1_rsv_lp_qp() Sasha Levin
2019-08-06 21:33 ` [PATCH AUTOSEL 5.2 51/59] drm/exynos: fix missing decrement of retry counter Sasha Levin
2019-08-07 8:49 ` David Laight
2019-08-18 1:47 ` Sasha Levin
2019-08-06 21:33 ` [PATCH AUTOSEL 5.2 52/59] arm64: kprobes: Recover pstate.D in single-step exception handler Sasha Levin
2019-08-06 21:33 ` Sasha Levin [this message]
2019-08-06 21:33 ` [PATCH AUTOSEL 5.2 54/59] Revert "kmemleak: allow to coexist with fault injection" Sasha Levin
2019-08-06 21:33 ` [PATCH AUTOSEL 5.2 55/59] ocfs2: remove set but not used variable 'last_hash' Sasha Levin
2019-08-06 21:33 ` [PATCH AUTOSEL 5.2 56/59] page flags: prioritize kasan bits over last-cpuid Sasha Levin
2019-08-06 21:33 ` [PATCH AUTOSEL 5.2 57/59] coredump: split pipe command whitespace before expanding template Sasha Levin
2019-08-07 1:41 ` Paul Wise
2019-08-18 1:48 ` Sasha Levin
2019-08-06 21:33 ` [PATCH AUTOSEL 5.2 58/59] asm-generic: fix -Wtype-limits compiler warnings Sasha Levin
2019-08-06 21:33 ` [PATCH AUTOSEL 5.2 59/59] tpm: tpm_ibm_vtpm: Fix unallocated banks Sasha Levin
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