On Mon, Mar 18, 2019 at 10:49:21AM +0000, Sudeep Holla wrote:
> Currently each architecture handles PTRACE_SYSEMU in very similar way.
> It's completely arch independent and can be handled in the code helping
> to consolidate PTRACE_SYSEMU handling.
>
> Let's introduce a hook 'ptrace_syscall_enter' that arch specific syscall
> entry code can call.
>
> Cc: Oleg Nesterov <o...@redhat.com>
> Signed-off-by: Sudeep Holla <sudeep.ho...@arm.com>
> ---
> include/linux/ptrace.h | 1 +
> kernel/ptrace.c | 22 ++++++++++++++++++++++
> 2 files changed, 23 insertions(+)
>
> diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
> index edb9b040c94c..e30f51e3363e 100644
> --- a/include/linux/ptrace.h
> +++ b/include/linux/ptrace.h
> @@ -407,6 +407,7 @@ static inline void user_single_step_report(struct pt_regs
> *regs)
> #define current_user_stack_pointer() user_stack_pointer(current_pt_regs())
> #endif
>
> +extern long ptrace_syscall_enter(struct pt_regs *regs);
> extern int task_current_syscall(struct task_struct *target, long *callno,
> unsigned long args[6], unsigned int maxargs,
> unsigned long *sp, unsigned long *pc);
> diff --git a/kernel/ptrace.c b/kernel/ptrace.c
> index 4fa3b7f4c3c7..c9c505c483df 100644
> --- a/kernel/ptrace.c
> +++ b/kernel/ptrace.c
> @@ -29,6 +29,7 @@
> #include <linux/hw_breakpoint.h>
> #include <linux/cn_proc.h>
> #include <linux/compat.h>
> +#include <linux/tracehook.h>
>
> /*
> * Access another process' address space via ptrace.
> @@ -557,6 +558,27 @@ static int ptrace_detach(struct task_struct *child,
> unsigned int data)
> return 0;
> }
>
> +/*
> + * Hook to check and report for PTRACE_SYSEMU, can be called from arch
> + * arch syscall entry code
> + */
> +long ptrace_syscall_enter(struct pt_regs *regs)
> +{
> +#ifdef TIF_SYSCALL_EMU
> + if (test_thread_flag(TIF_SYSCALL_EMU)) {
> + if (tracehook_report_syscall_entry(regs))
> + /*
> + * We can ignore the return code here as we need
> + * return -1 always for syscall emulation irrespective
> + * of whether the tracehook report fails or succeed.
> + */
> + ;This is problematic as it causes build errors with -Werror=empty-body, see https://lore.kernel.org/lkml/20181218205305.26647-1-ma...@debian.org/ -- ldv
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