Re: [PATCH gnumach] Align the user stack correctly for 64 bit programs.

[Samuel Thibault]

Applied, thanks!

Flavio Cruz, le dim. 02 avril 2023 23:56:31 -0400, a ecrit:
> * i386/i386/thread.h: Define USER_STACK_ALIGN which is 16-byte for 64 bit
>   programs as recommended by the System V AMD64 guidelines. Also define
>   KERNEL_STACK_ALIGN which can differ from user land.
> * i386/i386/pcb.c: Use USER_STACK_ALIGN to align the bootstrap arguments and
>   ultimately the stack where the program starts on.
> * kern/bootstrap.c: Do not align arg_len here since it will be aligned
>   in set_user_regs.
> ---
>  i386/i386/pcb.c    | 13 +++++--------
>  i386/i386/thread.h | 13 +++++++++++++
>  kern/bootstrap.c   |  3 +--
>  3 files changed, 19 insertions(+), 10 deletions(-)
> 
> diff --git a/i386/i386/pcb.c b/i386/i386/pcb.c
> index 9210656b..61125fe8 100644
> --- a/i386/i386/pcb.c
> +++ b/i386/i386/pcb.c
> @@ -379,12 +379,7 @@ thread_t switch_context(
>  void pcb_module_init(void)
>  {
>       kmem_cache_init(&pcb_cache, "pcb", sizeof(struct pcb),
> -#ifdef __x86_64__
> -                     16,
> -#else
> -                     0,
> -#endif
> -                     NULL, 0);
> +                     KERNEL_STACK_ALIGN, NULL, 0);
>  
>       fpu_module_init();
>  }
> @@ -893,11 +888,13 @@ set_user_regs(vm_offset_t stack_base, /* low address */
>       vm_offset_t     arg_addr;
>       struct i386_saved_state *saved_state;
>  
> -     arg_size = (arg_size + sizeof(int) - 1) & ~(sizeof(int)-1);
> +     assert(P2ALIGNED(stack_size, USER_STACK_ALIGN));
> +     assert(P2ALIGNED(stack_base, USER_STACK_ALIGN));
> +     arg_size = P2ROUND(arg_size, USER_STACK_ALIGN);
>       arg_addr = stack_base + stack_size - arg_size;
>  
>       saved_state = USER_REGS(current_thread());
> -     saved_state->uesp = (long)arg_addr;
> +     saved_state->uesp = (rpc_vm_offset_t)arg_addr;
>       saved_state->eip = exec_info->entry;
>  
>       return (arg_addr);
> diff --git a/i386/i386/thread.h b/i386/i386/thread.h
> index cb317bee..933b43d8 100644
> --- a/i386/i386/thread.h
> +++ b/i386/i386/thread.h
> @@ -225,6 +225,19 @@ typedef struct pcb {
>  #define STACK_IEL(stack)     \
>       ((struct i386_exception_link *)STACK_IKS(stack) - 1)
>  
> +#ifdef __x86_64__
> +#define KERNEL_STACK_ALIGN 16
> +#else
> +#define KERNEL_STACK_ALIGN 4
> +#endif
> +
> +#if defined(__x86_64__) && !defined(USER32)
> +/* Follow System V AMD64 ABI guidelines. */
> +#define USER_STACK_ALIGN 16
> +#else
> +#define USER_STACK_ALIGN 4
> +#endif
> +
>  #define USER_REGS(thread)    (&(thread)->pcb->iss)
>  
>  
> diff --git a/kern/bootstrap.c b/kern/bootstrap.c
> index 8f66a4b5..49358ac6 100644
> --- a/kern/bootstrap.c
> +++ b/kern/bootstrap.c
> @@ -610,17 +610,16 @@ build_args_and_stack(struct exec_info *boot_exec_info,
>        *      trailing 0 pointer
>        *      pointers to environment variables
>        *      trailing 0 pointer
> -      *      and align to integer boundary
>        */
>       arg_len += (sizeof(rpc_vm_offset_t)
>                   + (arg_count + 1 + envc + 1) * sizeof(rpc_vm_offset_t));
> -     arg_len = (arg_len + sizeof(integer_t) - 1) & ~(sizeof(integer_t)-1);
>  
>       /*
>        * Allocate the stack.
>        */
>       stack_size = round_page(STACK_SIZE);
>       stack_base = user_stack_low(stack_size);
> +
>       (void) vm_allocate(current_task()->map,
>                       &stack_base,
>                       stack_size,
> -- 
> 2.39.2
> 
> 

-- 
Samuel
---
Pour une évaluation indépendante, transparente et rigoureuse !
Je soutiens la Commission d'Évaluation de l'Inria.