Re: [PATCH] um: Implement copy_thread_tls

[Christian Brauner <christian.brauner@ubuntu.com>]

On Sat, Jan 04, 2020 at 01:39:30PM +0100, Amanieu d'Antras wrote:
> This is required for clone3 which passes the TLS value through a
> struct rather than a register.
> 
> Signed-off-by: Amanieu d'Antras <amanieu@gmail.com>
> Cc: linux-um@lists.infradead.org
> Cc: <stable@vger.kernel.org> # 5.3.x

Thanks. I'm picking this up as part of the copy_thread_tls() series.
(Leaving the patch in tact so people can Ack right here if they want to.)
If I could get an Ack from one of the maintainers that would be great;
see
https://lore.kernel.org/lkml/20200102172413.654385-1-amanieu@gmail.com
for more context.

Acked-by: Christian Brauner <christian.brauner@ubuntu.com>

> ---
>  arch/um/Kconfig                      | 1 +
>  arch/um/include/asm/ptrace-generic.h | 2 +-
>  arch/um/kernel/process.c             | 6 +++---
>  arch/x86/um/tls_32.c                 | 6 ++----
>  arch/x86/um/tls_64.c                 | 7 +++----
>  5 files changed, 10 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/um/Kconfig b/arch/um/Kconfig
> index 2a6d04fcb3e9..6f0edd0c0220 100644
> --- a/arch/um/Kconfig
> +++ b/arch/um/Kconfig
> @@ -14,6 +14,7 @@ config UML
>  	select HAVE_FUTEX_CMPXCHG if FUTEX
>  	select HAVE_DEBUG_KMEMLEAK
>  	select HAVE_DEBUG_BUGVERBOSE
> +	select HAVE_COPY_THREAD_TLS
>  	select GENERIC_IRQ_SHOW
>  	select GENERIC_CPU_DEVICES
>  	select GENERIC_CLOCKEVENTS
> diff --git a/arch/um/include/asm/ptrace-generic.h b/arch/um/include/asm/ptrace-generic.h
> index 81c647ef9c6c..adf91ef553ae 100644
> --- a/arch/um/include/asm/ptrace-generic.h
> +++ b/arch/um/include/asm/ptrace-generic.h
> @@ -36,7 +36,7 @@ extern long subarch_ptrace(struct task_struct *child, long request,
>  extern unsigned long getreg(struct task_struct *child, int regno);
>  extern int putreg(struct task_struct *child, int regno, unsigned long value);
>  
> -extern int arch_copy_tls(struct task_struct *new);
> +extern int arch_set_tls(struct task_struct *new, unsigned long tls);
>  extern void clear_flushed_tls(struct task_struct *task);
>  extern int syscall_trace_enter(struct pt_regs *regs);
>  extern void syscall_trace_leave(struct pt_regs *regs);
> diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
> index 263a8f069133..17045e7211bf 100644
> --- a/arch/um/kernel/process.c
> +++ b/arch/um/kernel/process.c
> @@ -153,8 +153,8 @@ void fork_handler(void)
>  	userspace(&current->thread.regs.regs, current_thread_info()->aux_fp_regs);
>  }
>  
> -int copy_thread(unsigned long clone_flags, unsigned long sp,
> -		unsigned long arg, struct task_struct * p)
> +int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
> +		unsigned long arg, struct task_struct * p, unsigned long tls)
>  {
>  	void (*handler)(void);
>  	int kthread = current->flags & PF_KTHREAD;
> @@ -188,7 +188,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
>  		 * Set a new TLS for the child thread?
>  		 */
>  		if (clone_flags & CLONE_SETTLS)
> -			ret = arch_copy_tls(p);
> +			ret = arch_set_tls(p, tls);
>  	}
>  
>  	return ret;
> diff --git a/arch/x86/um/tls_32.c b/arch/x86/um/tls_32.c
> index 5bd949da7a4a..ac8eee093f9c 100644
> --- a/arch/x86/um/tls_32.c
> +++ b/arch/x86/um/tls_32.c
> @@ -215,14 +215,12 @@ static int set_tls_entry(struct task_struct* task, struct user_desc *info,
>  	return 0;
>  }
>  
> -int arch_copy_tls(struct task_struct *new)
> +int arch_set_tls(struct task_struct *new, unsigned long tls)
>  {
>  	struct user_desc info;
>  	int idx, ret = -EFAULT;
>  
> -	if (copy_from_user(&info,
> -			   (void __user *) UPT_SI(&new->thread.regs.regs),
> -			   sizeof(info)))
> +	if (copy_from_user(&info, (void __user *) tls, sizeof(info)))
>  		goto out;
>  
>  	ret = -EINVAL;
> diff --git a/arch/x86/um/tls_64.c b/arch/x86/um/tls_64.c
> index 3a621e0d3925..ebd3855d9b13 100644
> --- a/arch/x86/um/tls_64.c
> +++ b/arch/x86/um/tls_64.c
> @@ -6,14 +6,13 @@ void clear_flushed_tls(struct task_struct *task)
>  {
>  }
>  
> -int arch_copy_tls(struct task_struct *t)
> +int arch_set_tls(struct task_struct *t, unsigned long tls)
>  {
>  	/*
>  	 * If CLONE_SETTLS is set, we need to save the thread id
> -	 * (which is argument 5, child_tid, of clone) so it can be set
> -	 * during context switches.
> +	 * so it can be set during context switches.
>  	 */
> -	t->thread.arch.fs = t->thread.regs.regs.gp[R8 / sizeof(long)];
> +	t->thread.arch.fs = tls;
>  
>  	return 0;
>  }
> -- 
> 2.24.1
>