* [PATCH v13 07/12] arm64: factor work_pending state machine to C
[not found] <1468529299-27929-1-git-send-email-cmetcalf@mellanox.com>
@ 2016-07-14 20:48 ` Chris Metcalf
2016-07-14 20:48 ` [PATCH v13 08/12] arch/arm64: enable task isolation functionality Chris Metcalf
1 sibling, 0 replies; 2+ messages in thread
From: Chris Metcalf @ 2016-07-14 20:48 UTC (permalink / raw)
To: linux-arm-kernel
Currently ret_fast_syscall, work_pending, and ret_to_user form an ad-hoc
state machine that can be difficult to reason about due to duplicated
code and a large number of branch targets.
This patch factors the common logic out into the existing
do_notify_resume function, converting the code to C in the process,
making the code more legible.
This patch tries to closely mirror the existing behaviour while using
the usual C control flow primitives. As local_irq_{disable,enable} may
be instrumented, we balance exception entry (where we will almost most
likely enable IRQs) with a call to trace_hardirqs_on just before the
return to userspace.
Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com>
---
arch/arm64/kernel/entry.S | 12 ++++--------
arch/arm64/kernel/signal.c | 36 ++++++++++++++++++++++++++----------
2 files changed, 30 insertions(+), 18 deletions(-)
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 6c3b7345a6c4..2bbf7753c674 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -689,18 +689,13 @@ ret_fast_syscall_trace:
* Ok, we need to do extra processing, enter the slow path.
*/
work_pending:
- tbnz x1, #TIF_NEED_RESCHED, work_resched
- /* TIF_SIGPENDING, TIF_NOTIFY_RESUME or TIF_FOREIGN_FPSTATE case */
mov x0, sp // 'regs'
- enable_irq // enable interrupts for do_notify_resume()
bl do_notify_resume
- b ret_to_user
-work_resched:
#ifdef CONFIG_TRACE_IRQFLAGS
- bl trace_hardirqs_off // the IRQs are off here, inform the tracing code
+ bl trace_hardirqs_on // enabled while in userspace
#endif
- bl schedule
-
+ ldr x1, [tsk, #TI_FLAGS] // re-check for single-step
+ b finish_ret_to_user
/*
* "slow" syscall return path.
*/
@@ -709,6 +704,7 @@ ret_to_user:
ldr x1, [tsk, #TI_FLAGS]
and x2, x1, #_TIF_WORK_MASK
cbnz x2, work_pending
+finish_ret_to_user:
enable_step_tsk x1, x2
kernel_exit 0
ENDPROC(ret_to_user)
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index a8eafdbc7cb8..404dd67080b9 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -402,15 +402,31 @@ static void do_signal(struct pt_regs *regs)
asmlinkage void do_notify_resume(struct pt_regs *regs,
unsigned int thread_flags)
{
- if (thread_flags & _TIF_SIGPENDING)
- do_signal(regs);
-
- if (thread_flags & _TIF_NOTIFY_RESUME) {
- clear_thread_flag(TIF_NOTIFY_RESUME);
- tracehook_notify_resume(regs);
- }
-
- if (thread_flags & _TIF_FOREIGN_FPSTATE)
- fpsimd_restore_current_state();
+ /*
+ * The assembly code enters us with IRQs off, but it hasn't
+ * informed the tracing code of that for efficiency reasons.
+ * Update the trace code with the current status.
+ */
+ trace_hardirqs_off();
+ do {
+ if (thread_flags & _TIF_NEED_RESCHED) {
+ schedule();
+ } else {
+ local_irq_enable();
+
+ if (thread_flags & _TIF_SIGPENDING)
+ do_signal(regs);
+
+ if (thread_flags & _TIF_NOTIFY_RESUME) {
+ clear_thread_flag(TIF_NOTIFY_RESUME);
+ tracehook_notify_resume(regs);
+ }
+
+ if (thread_flags & _TIF_FOREIGN_FPSTATE)
+ fpsimd_restore_current_state();
+ }
+ local_irq_disable();
+ thread_flags = READ_ONCE(current_thread_info()->flags);
+ } while (thread_flags & _TIF_WORK_MASK);
}
--
2.7.2
^ permalink raw reply related [flat|nested] 2+ messages in thread
* [PATCH v13 08/12] arch/arm64: enable task isolation functionality
[not found] <1468529299-27929-1-git-send-email-cmetcalf@mellanox.com>
2016-07-14 20:48 ` [PATCH v13 07/12] arm64: factor work_pending state machine to C Chris Metcalf
@ 2016-07-14 20:48 ` Chris Metcalf
1 sibling, 0 replies; 2+ messages in thread
From: Chris Metcalf @ 2016-07-14 20:48 UTC (permalink / raw)
To: linux-arm-kernel
In do_notify_resume(), call task_isolation_ready() for
TIF_TASK_ISOLATION tasks when we are checking the thread-info flags;
and after we've handled the other work, call task_isolation_enter()
for such tasks. To ensure we always call task_isolation_enter() when
returning to userspace, add _TIF_TASK_ISOLATION to _TIF_WORK_MASK,
while leaving the old bitmask value as _TIF_WORK_LOOP_MASK to
check while looping.
We tweak syscall_trace_enter() slightly to carry the "flags"
value from current_thread_info()->flags for each of the tests,
rather than doing a volatile read from memory for each one. This
avoids a small overhead for each test, and in particular avoids
that overhead for TIF_NOHZ when TASK_ISOLATION is not enabled.
We instrument the smp_send_reschedule() routine so that it checks for
isolated tasks and generates a suitable warning if we are about
to disturb one of them in strict or debug mode.
Finally, report on page faults in task-isolation processes in
do_page_faults().
Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com>
---
arch/arm64/Kconfig | 1 +
arch/arm64/include/asm/thread_info.h | 5 ++++-
arch/arm64/kernel/ptrace.c | 15 ++++++++++++---
arch/arm64/kernel/signal.c | 10 ++++++++++
arch/arm64/kernel/smp.c | 2 ++
arch/arm64/mm/fault.c | 8 +++++++-
6 files changed, 36 insertions(+), 5 deletions(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 5a0a691d4220..36ada13f503f 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -58,6 +58,7 @@ config ARM64
select HAVE_ARCH_MMAP_RND_BITS
select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT
select HAVE_ARCH_SECCOMP_FILTER
+ select HAVE_ARCH_TASK_ISOLATION
select HAVE_ARCH_TRACEHOOK
select HAVE_ARCH_TRANSPARENT_HUGEPAGE
select HAVE_ARM_SMCCC
diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index abd64bd1f6d9..bdc6426b9968 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -109,6 +109,7 @@ static inline struct thread_info *current_thread_info(void)
#define TIF_NEED_RESCHED 1
#define TIF_NOTIFY_RESUME 2 /* callback before returning to user */
#define TIF_FOREIGN_FPSTATE 3 /* CPU's FP state is not current's */
+#define TIF_TASK_ISOLATION 4
#define TIF_NOHZ 7
#define TIF_SYSCALL_TRACE 8
#define TIF_SYSCALL_AUDIT 9
@@ -124,6 +125,7 @@ static inline struct thread_info *current_thread_info(void)
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
#define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
#define _TIF_FOREIGN_FPSTATE (1 << TIF_FOREIGN_FPSTATE)
+#define _TIF_TASK_ISOLATION (1 << TIF_TASK_ISOLATION)
#define _TIF_NOHZ (1 << TIF_NOHZ)
#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
@@ -132,7 +134,8 @@ static inline struct thread_info *current_thread_info(void)
#define _TIF_32BIT (1 << TIF_32BIT)
#define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
- _TIF_NOTIFY_RESUME | _TIF_FOREIGN_FPSTATE)
+ _TIF_NOTIFY_RESUME | _TIF_FOREIGN_FPSTATE | \
+ _TIF_TASK_ISOLATION)
#define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
_TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 3f6cd5c5234f..ae336065733d 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -37,6 +37,7 @@
#include <linux/regset.h>
#include <linux/tracehook.h>
#include <linux/elf.h>
+#include <linux/isolation.h>
#include <asm/compat.h>
#include <asm/debug-monitors.h>
@@ -1246,14 +1247,22 @@ static void tracehook_report_syscall(struct pt_regs *regs,
asmlinkage int syscall_trace_enter(struct pt_regs *regs)
{
- /* Do the secure computing check first; failures should be fast. */
+ unsigned long work = ACCESS_ONCE(current_thread_info()->flags);
+
+ /* In isolation mode, we may prevent the syscall from running. */
+ if (work & _TIF_TASK_ISOLATION) {
+ if (task_isolation_syscall(regs->syscallno) == -1)
+ return -1;
+ }
+
+ /* Do the secure computing check early; failures should be fast. */
if (secure_computing() == -1)
return -1;
- if (test_thread_flag(TIF_SYSCALL_TRACE))
+ if (work & _TIF_SYSCALL_TRACE)
tracehook_report_syscall(regs, PTRACE_SYSCALL_ENTER);
- if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
+ if (work & _TIF_SYSCALL_TRACEPOINT)
trace_sys_enter(regs, regs->syscallno);
audit_syscall_entry(regs->syscallno, regs->orig_x0, regs->regs[1],
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index 404dd67080b9..f9b9b25636ca 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -25,6 +25,7 @@
#include <linux/uaccess.h>
#include <linux/tracehook.h>
#include <linux/ratelimit.h>
+#include <linux/isolation.h>
#include <asm/debug-monitors.h>
#include <asm/elf.h>
@@ -424,9 +425,18 @@ asmlinkage void do_notify_resume(struct pt_regs *regs,
if (thread_flags & _TIF_FOREIGN_FPSTATE)
fpsimd_restore_current_state();
+
+ if (thread_flags & _TIF_TASK_ISOLATION)
+ task_isolation_enter();
}
local_irq_disable();
thread_flags = READ_ONCE(current_thread_info()->flags);
+
+ /* Clear task isolation from cached_flags manually. */
+ if ((thread_flags & _TIF_TASK_ISOLATION) &&
+ task_isolation_ready())
+ thread_flags &= ~_TIF_TASK_ISOLATION;
+
} while (thread_flags & _TIF_WORK_MASK);
}
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 62ff3c0622e2..30559aebde5c 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -37,6 +37,7 @@
#include <linux/completion.h>
#include <linux/of.h>
#include <linux/irq_work.h>
+#include <linux/isolation.h>
#include <asm/alternative.h>
#include <asm/atomic.h>
@@ -866,6 +867,7 @@ void handle_IPI(int ipinr, struct pt_regs *regs)
void smp_send_reschedule(int cpu)
{
+ task_isolation_debug(cpu, "reschedule IPI");
smp_cross_call(cpumask_of(cpu), IPI_RESCHEDULE);
}
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index b1166d1e5955..9c2ba2a318b0 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -29,6 +29,7 @@
#include <linux/sched.h>
#include <linux/highmem.h>
#include <linux/perf_event.h>
+#include <linux/isolation.h>
#include <asm/cpufeature.h>
#include <asm/exception.h>
@@ -354,8 +355,13 @@ retry:
* Handle the "normal" case first - VM_FAULT_MAJOR
*/
if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP |
- VM_FAULT_BADACCESS))))
+ VM_FAULT_BADACCESS)))) {
+ /* No signal was generated, but notify task-isolation tasks. */
+ if (user_mode(regs))
+ task_isolation_quiet_exception("page fault at %#lx",
+ addr);
return 0;
+ }
/*
* If we are in kernel mode at this point, we have no context to
--
2.7.2
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2016-07-14 20:48 ` [PATCH v13 07/12] arm64: factor work_pending state machine to C Chris Metcalf
2016-07-14 20:48 ` [PATCH v13 08/12] arch/arm64: enable task isolation functionality Chris Metcalf
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