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Commit b74406f3 authored by Mathieu Desnoyers's avatar Mathieu Desnoyers Committed by Thomas Gleixner
Browse files

arm: Add syscall detection for restartable sequences 



Syscalls are not allowed inside restartable sequences, so add a call to
rseq_syscall() at the very beginning of system call exiting path for
CONFIG_DEBUG_RSEQ=y kernel. This could help us to detect whether there
is a syscall issued inside restartable sequences.

Signed-off-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Joel Fernandes <joelaf@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Watson <davejwatson@fb.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: Chris Lameter <cl@linux.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Andrew Hunter <ahh@google.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Paul Turner <pjt@google.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Maurer <bmaurer@fb.com>
Cc: linux-api@vger.kernel.org
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lkml.kernel.org/r/20180602124408.8430-5-mathieu.desnoyers@efficios.com
parent 9800b9dc

arch/arm/kernel/entry-common.S

+19 −6
Original line number Diff line number Diff line
@@ -39,12 +39,13 @@ saved_pc .req lr 


	.section .entry.text,"ax",%progbits

	.align	5

#if !(IS_ENABLED(CONFIG_TRACE_IRQFLAGS) || IS_ENABLED(CONFIG_CONTEXT_TRACKING))

#if !(IS_ENABLED(CONFIG_TRACE_IRQFLAGS) || IS_ENABLED(CONFIG_CONTEXT_TRACKING) || \

	IS_ENABLED(CONFIG_DEBUG_RSEQ))

/*

 * This is the fast syscall return path.  We do as little as possible here,

 * such as avoiding writing r0 to the stack.  We only use this path if we

 * have tracing and context tracking disabled - the overheads from those

 * features make this path too inefficient.

 * have tracing, context tracking and rseq debug disabled - the overheads

 * from those features make this path too inefficient.

 */

ret_fast_syscall:

 UNWIND(.fnstart	)
@@ -71,14 +72,20 @@ fast_work_pending: 
	/* fall through to work_pending */

#else

/*

 * The "replacement" ret_fast_syscall for when tracing or context tracking

 * is enabled.  As we will need to call out to some C functions, we save

 * r0 first to avoid needing to save registers around each C function call.

 * The "replacement" ret_fast_syscall for when tracing, context tracking,

 * or rseq debug is enabled.  As we will need to call out to some C functions,

 * we save r0 first to avoid needing to save registers around each C function

 * call.

 */

ret_fast_syscall:

 UNWIND(.fnstart	)

 UNWIND(.cantunwind	)

	str	r0, [sp, #S_R0 + S_OFF]!	@ save returned r0

#if IS_ENABLED(CONFIG_DEBUG_RSEQ)

	/* do_rseq_syscall needs interrupts enabled. */

	mov	r0, sp				@ 'regs'

	bl	do_rseq_syscall

#endif

	disable_irq_notrace			@ disable interrupts

	ldr	r2, [tsk, #TI_ADDR_LIMIT]

	cmp	r2, #TASK_SIZE
@@ -113,6 +120,12 @@ ENDPROC(ret_fast_syscall) 
 */

ENTRY(ret_to_user)

ret_slow_syscall:

#if IS_ENABLED(CONFIG_DEBUG_RSEQ)

	/* do_rseq_syscall needs interrupts enabled. */

	enable_irq_notrace			@ enable interrupts

	mov	r0, sp				@ 'regs'

	bl	do_rseq_syscall

#endif

	disable_irq_notrace			@ disable interrupts

ENTRY(ret_to_user_from_irq)

	ldr	r2, [tsk, #TI_ADDR_LIMIT]

arch/arm/kernel/signal.c

+7 −0
Original line number Diff line number Diff line
@@ -710,3 +710,10 @@ asmlinkage void addr_limit_check_failed(void) 
{

	addr_limit_user_check();

}



#ifdef CONFIG_DEBUG_RSEQ

asmlinkage void do_rseq_syscall(struct pt_regs *regs)

{

	rseq_syscall(regs);

}

#endif