Re: [Qemu-devel] [ARM/FDPIC v2 3/4] linux-user: ARM-FDPIC: Add support of FDPIC for ARM.

[Peter Maydell]

On 23 April 2018 at 08:51, Christophe Lyon <address@hidden> wrote:
> Add FDPIC info into image_info structure since interpreter info is on
> stack and needs to be saved to be accessed later on.
>
> Co-Authored-By:  Mickaël Guêné <address@hidden>
> Signed-off-by: Christophe Lyon <address@hidden>
>
> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index 76d7718..1ee1e38 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -78,6 +78,11 @@ enum {
>   */
>  #define personality(pers)       (pers & PER_MASK)
>
> +int info_is_fdpic(struct image_info *info)
> +{
> +    return (info->personality == PER_LINUX_FDPIC);
> +}
> +
>  /* this flag is uneffective under linux too, should be deleted */
>  #ifndef MAP_DENYWRITE
>  #define MAP_DENYWRITE 0
> @@ -287,6 +292,24 @@ static inline void init_thread(struct target_pt_regs 
> *regs,
>      /* For uClinux PIC binaries.  */
>      /* XXX: Linux does this only on ARM with no MMU (do we care ?) */
>      regs->uregs[10] = infop->start_data;
> +
> +    /* Support ARM FDPIC.  */
> +    if (info_is_fdpic(infop)) {
> +            /* As described in the ABI document, r7 points to the loadmap 
> info
> +             * prepared by the kernel. If an interpreter is needed, r8 points
> +             * to the interpreter loadmap and r9 points to the interpreter
> +             * PT_DYNAMIC info. If no interpreter is needed, r8 is zer0, and

"zero"

> +             * r9 points to the main program PT_DYNAMIC info.  */

Something odd seems to have happened to the indentation here.

Nit: */ should be on a line of its own.

> +            regs->uregs[7] = infop->loadmap_addr;
> +            if (infop->interpreter_loadmap_addr) {
> +                /* Executable is dynamically loaded.  */
> +                regs->uregs[8] = infop->interpreter_loadmap_addr;
> +                regs->uregs[9] = infop->interpreter_pt_dynamic_addr;
> +            } else {
> +                regs->uregs[8] = 0;
> +                regs->uregs[9] = infop->pt_dynamic_addr;
> +            }
> +        }
>  }
>
>  #define ELF_NREG    18
> @@ -1745,6 +1768,11 @@ static abi_ulong create_elf_tables(abi_ulong p, int 
> argc, int envc,
>          if (interp_info) {
>              interp_info->other_info = info;
>              sp = loader_build_fdpic_loadmap(interp_info, sp);
> +            info->interpreter_loadmap_addr = interp_info->loadmap_addr;
> +            info->interpreter_pt_dynamic_addr = interp_info->pt_dynamic_addr;
> +        } else {
> +            info->interpreter_loadmap_addr = 0;
> +            info->interpreter_pt_dynamic_addr = 0;
>          }
>      }
>
> diff --git a/linux-user/main.c b/linux-user/main.c
> index 2acac36..3579f0e 100644
> --- a/linux-user/main.c
> +++ b/linux-user/main.c
> @@ -4893,6 +4893,9 @@ int main(int argc, char **argv, char **envp)
>              env->cp15.sctlr_el[1] |= SCTLR_B;
>          }
>  #endif
> +
> +        /* Are we running an FDPIC binary?  */
> +        ((TaskState *)thread_cpu->opaque)->is_fdpic = info_is_fdpic(info);
>      }
>  #elif defined(TARGET_SPARC)
>      {
> diff --git a/linux-user/qemu.h b/linux-user/qemu.h
> index da3b517..a2ed148 100644
> --- a/linux-user/qemu.h
> +++ b/linux-user/qemu.h
> @@ -57,6 +57,8 @@ struct image_info {
>          uint16_t        nsegs;
>          void           *loadsegs;
>          abi_ulong       pt_dynamic_addr;
> +        abi_ulong       interpreter_loadmap_addr;
> +        abi_ulong       interpreter_pt_dynamic_addr;
>          struct image_info *other_info;
>  };
>
> @@ -145,6 +147,9 @@ typedef struct TaskState {
>       */
>      int signal_pending;
>
> +    /* We need to know if we have an FDPIC binary to adapt signal
> +     * syscalls.  */
> +    int is_fdpic;

Looking at the TaskState struct it already has a pointer
to the image_info struct. So we could just have something like
    bool task_is_fdpic(TaskState *ts)
    {
        return ts->info->personality == PER_LINUX_FDPIC;
    }

and save the need to set up and test a separate flag, I think.

Otherwise looks good.

thanks
-- PMM