diff options
| author | Will Deacon <will@kernel.org> | 2020-07-02 21:16:20 +0100 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2020-07-16 11:41:07 +0100 |
| commit | ac2081cdc4d99c57f219c1a6171526e0fa0a6fff (patch) | |
| tree | e611aa9681fd5665310f37a5585feba904584f6e /arch/arm64/include | |
| parent | bdc5c744c7b6457d18a95c26769dad0e7f480a08 (diff) | |
arm64: ptrace: Consistently use pseudo-singlestep exceptions
Although the arm64 single-step state machine can be fast-forwarded in
cases where we wish to generate a SIGTRAP without actually executing an
instruction, this has two major limitations outside of simply skipping
an instruction due to emulation.
1. Stepping out of a ptrace signal stop into a signal handler where
SIGTRAP is blocked. Fast-forwarding the stepping state machine in
this case will result in a forced SIGTRAP, with the handler reset to
SIG_DFL.
2. The hardware implicitly fast-forwards the state machine when executing
an SVC instruction for issuing a system call. This can interact badly
with subsequent ptrace stops signalled during the execution of the
system call (e.g. SYSCALL_EXIT or seccomp traps), as they may corrupt
the stepping state by updating the PSTATE for the tracee.
Resolve both of these issues by injecting a pseudo-singlestep exception
on entry to a signal handler and also on return to userspace following a
system call.
Cc: <stable@vger.kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Tested-by: Luis Machado <luis.machado@linaro.org>
Reported-by: Keno Fischer <keno@juliacomputing.com>
Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'arch/arm64/include')
| -rw-r--r-- | arch/arm64/include/asm/thread_info.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h index 6ea8b6a26ae9..5e784e16ee89 100644 --- a/arch/arm64/include/asm/thread_info.h +++ b/arch/arm64/include/asm/thread_info.h @@ -93,6 +93,7 @@ void arch_release_task_struct(struct task_struct *tsk); #define _TIF_SYSCALL_EMU (1 << TIF_SYSCALL_EMU) #define _TIF_UPROBE (1 << TIF_UPROBE) #define _TIF_FSCHECK (1 << TIF_FSCHECK) +#define _TIF_SINGLESTEP (1 << TIF_SINGLESTEP) #define _TIF_32BIT (1 << TIF_32BIT) #define _TIF_SVE (1 << TIF_SVE) |