linux-stable.git/arch/arm64/kernel/debug-monitors.c, branch linux-3.10.y Linux kernel stable tree arm64: debug: avoid resetting stepping state machine when TIF_SINGLESTEP 2017-02-06T22:32:54+00:00 Will Deacon will.deacon@arm.com 2016-08-26T10:36:39+00:00 83099f397a9faaf75a8f249733b2b57d72a264eb 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> 
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>
arm64: debug: clear mdscr_el1 instead of taking the OS lock 2013-05-13T10:44:56+00:00 Will Deacon will.deacon@arm.com 2013-05-08T16:01:12+00:00 9c413e25d95fd3c0abe23eadad66191b22baa549 During boot, we take the debug OS lock before interrupts are enabled. This is required to prevent clearing of PSTATE.D on the interrupt entry path, which could result in spurious debug exceptions before we've got round to resetting things like the hardware breakpoints registers to a sane state. A problem with this approach is that taking the OS lock prevents an external JTAG debugger from debugging the system, which is especially irritating during boot, where JTAG debugging can be most useful. This patch clears mdscr_el1 rather than taking the lock, clearing the MDE and KDE bits and preventing self-hosted hardware debug exceptions from occurring. Tested-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Cc: stable@vger.kernel.org 
During boot, we take the debug OS lock before interrupts are enabled.
This is required to prevent clearing of PSTATE.D on the interrupt entry
path, which could result in spurious debug exceptions before we've got
round to resetting things like the hardware breakpoints registers to a
sane state.

A problem with this approach is that taking the OS lock prevents an
external JTAG debugger from debugging the system, which is especially
irritating during boot, where JTAG debugging can be most useful.

This patch clears mdscr_el1 rather than taking the lock, clearing the
MDE and KDE bits and preventing self-hosted hardware debug exceptions
from occurring.

Tested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: stable@vger.kernel.org
arm64: Debugging support 2012-09-17T12:42:14+00:00 Will Deacon will.deacon@arm.com 2012-03-05T11:49:33+00:00 478fcb2cdb2351dcfc3fb23f42d76f4436ee4149 This patch adds ptrace, debug monitors and hardware breakpoints support. Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Acked-by: Tony Lindgren <tony@atomide.com> Acked-by: Nicolas Pitre <nico@linaro.org> Acked-by: Olof Johansson <olof@lixom.net> Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com> Acked-by: Arnd Bergmann <arnd@arndb.de> 
This patch adds ptrace, debug monitors and hardware breakpoints support.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>