Re: [PATCH 2/7] arm64: Implement copy_thread_tls

Christian Brauner
2020-01-02T18:02:00Z

On Thu, Jan 02, 2020 at 06:24:08PM +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-arm-kernel@lists.infradead.org
> Cc: <stable@vger.kernel.org> # 5.3.x

This looks sane to me but I'd like an ack from someone who knows his arm
from his arse before taking this. :)
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>

> ---
> arch/arm64/Kconfig | 1 +
> arch/arm64/kernel/process.c | 10 +++++-----
> 2 files changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index b1b4476ddb83..e688dfad0b72 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -138,6 +138,7 @@ config ARM64
> select HAVE_CMPXCHG_DOUBLE
> select HAVE_CMPXCHG_LOCAL
> select HAVE_CONTEXT_TRACKING
> + select HAVE_COPY_THREAD_TLS
> select HAVE_DEBUG_BUGVERBOSE
> select HAVE_DEBUG_KMEMLEAK
> select HAVE_DMA_CONTIGUOUS
> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> index 71f788cd2b18..d54586d5b031 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -360,8 +360,8 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
>
> asmlinkage void ret_from_fork(void) asm("ret_from_fork");
>
> -int copy_thread(unsigned long clone_flags, unsigned long stack_start,
> - unsigned long stk_sz, struct task_struct *p)
> +int copy_thread_tls(unsigned long clone_flags, unsigned long stack_start,
> + unsigned long stk_sz, struct task_struct *p, unsigned long tls)
> {
> struct pt_regs *childregs = task_pt_regs(p);
>
> @@ -394,11 +394,11 @@ int copy_thread(unsigned long clone_flags, unsigned long stack_start,
> }
>
> /*
> - * If a TLS pointer was passed to clone (4th argument), use it
> - * for the new thread.
> + * If a TLS pointer was passed to clone, use it for the new
> + * thread.
> */
> if (clone_flags & CLONE_SETTLS)
> - p->thread.uw.tp_value = childregs->regs[3];
> + p->thread.uw.tp_value = tls;
> } else {
> memset(childregs, 0, sizeof(struct pt_regs));
> childregs->pstate = PSR_MODE_EL1h;
> --
> 2.24.1