Re: [Minios-devel] [UNIKRAFT PATCH v3 3/7] plat/kvm: Add preinit_array and init_array sections (x86)

[Yuri Volchkov <yuri.volchkov@xxxxxxxxx>]

Reviewed-by: Yuri Volchkov <yuri.volchkov@xxxxxxxxx>

Simon Kuenzer <simon.kuenzer@xxxxxxxxx> writes:

> Adds preinit_array and init_array sections with the linker script.
> Those sections are populated by the compiler/linker with function
> pointer arrays. Such functions are typically part of initializing
> the language runtime (e.g., C++) and have to be called early during
> bootstrapping. However, they can also be used by Unikraft libraries
> for early initializations (functions with constructor attribute).
>
> Signed-off-by: Simon Kuenzer <simon.kuenzer@xxxxxxxxx>
> ---
>  plat/kvm/memory.c      | 22 ++++++++++++++++------
>  plat/kvm/x86/link64.ld | 18 ++++++++++++++++++
>  2 files changed, 34 insertions(+), 6 deletions(-)
>
> diff --git a/plat/kvm/memory.c b/plat/kvm/memory.c
> index 705c6df..d2fd235 100644
> --- a/plat/kvm/memory.c
> +++ b/plat/kvm/memory.c
> @@ -32,13 +32,13 @@ extern void *_libkvmplat_mem_end;
>  
>  int ukplat_memregion_count(void)
>  {
> -     return 6;
> +     return 7;
>  }
>  
>  int ukplat_memregion_get(int i, struct ukplat_memregion_desc *m)
>  {
>       extern char _text, _etext, _data, _edata, _rodata, _erodata,
> -                 __bss_start, _end;
> +                 _ctors, _ectors, __bss_start, _end;
>       int ret;
>  
>       UK_ASSERT(m);
> @@ -64,7 +64,17 @@ int ukplat_memregion_get(int i, struct 
> ukplat_memregion_desc *m)
>  #endif
>               ret = 0;
>               break;
> -     case 2: /* data */
> +     case 2: /* ctors */
> +             m->base  = &_ctors;
> +             m->len   = (size_t) &_ectors - (size_t) &_ctors;
> +             m->flags = (UKPLAT_MEMRF_RESERVED
> +                         | UKPLAT_MEMRF_READABLE);
> +#if UKPLAT_MEMRNAME
> +             m->name  = "ctors";
> +#endif
> +             ret = 0;
> +             break;
> +     case 3: /* data */
>               m->base  = &_data;
>               m->len   = (size_t) &_edata - (size_t) &_data;
>               m->flags = (UKPLAT_MEMRF_RESERVED
> @@ -75,7 +85,7 @@ int ukplat_memregion_get(int i, struct 
> ukplat_memregion_desc *m)
>  #endif
>               ret = 0;
>               break;
> -     case 3: /* bss */
> +     case 4: /* bss */
>               m->base  = &__bss_start;
>               m->len   = (size_t) &_end - (size_t) &__bss_start;
>               m->flags = (UKPLAT_MEMRF_RESERVED
> @@ -86,7 +96,7 @@ int ukplat_memregion_get(int i, struct 
> ukplat_memregion_desc *m)
>  #endif
>               ret = 0;
>               break;
> -     case 4: /* heap */
> +     case 5: /* heap */
>               m->base  = _libkvmplat_heap_start;
>               m->len   = (size_t) _libkvmplat_stack_top
>                          - (size_t) _libkvmplat_heap_start;
> @@ -96,7 +106,7 @@ int ukplat_memregion_get(int i, struct 
> ukplat_memregion_desc *m)
>  #endif
>               ret = 0;
>               break;
> -     case 5: /* stack */
> +     case 6: /* stack */
>               m->base  = _libkvmplat_stack_top;
>               m->len   = (size_t) _libkvmplat_mem_end
>                          - (size_t) _libkvmplat_stack_top;
> diff --git a/plat/kvm/x86/link64.ld b/plat/kvm/x86/link64.ld
> index a9f3ac3..d1bfa73 100644
> --- a/plat/kvm/x86/link64.ld
> +++ b/plat/kvm/x86/link64.ld
> @@ -50,6 +50,24 @@ SECTIONS
>       }
>       _erodata = .;
>  
> +     /* Constructor tables (read-only) */
> +     _ctors = .;
> +     .preinit_array : {
> +             . = ALIGN(0x8);
> +             PROVIDE_HIDDEN (__preinit_array_start = .);
> +             KEEP (*(.preinit_array))
> +             PROVIDE_HIDDEN (__preinit_array_end = .);
> +     }
> +
> +     .init_array : {
> +             . = ALIGN(0x8);
> +             PROVIDE_HIDDEN (__init_array_start = .);
> +             KEEP (*(SORT_BY_INIT_PRIORITY(.init_array.*) 
> SORT_BY_INIT_PRIORITY(.ctors.*)))
> +             KEEP (*(.init_array .ctors))
> +             PROVIDE_HIDDEN (__init_array_end = .);
> +     }
> +     _ectors = .;
> +
>       /* Read-write data (initialized) */
>       . = ALIGN(0x1000);
>       _data = .;
> -- 
> 2.7.4
>
>
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-- 
Yuri Volchkov
Software Specialist

NEC Europe Ltd
Kurfürsten-Anlage 36
D-69115 Heidelberg

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