Re: [Qemu-devel] [ARM/FDPIC 2/4] linux-user: ARM-FDPIC: Add support of FDPIC for ARM.

[Christophe Lyon]

On 13/04/2018 17:07, Peter Maydell wrote:
> On 6 April 2018 at 16:17, 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 7ba3795..363da67 100644
> > --- a/linux-user/elfload.c
> > +++ b/linux-user/elfload.c
> > @@ -287,6 +287,23 @@ 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;
> > +#ifdef CONFIG_USE_FDPIC
> > +    /* Support ARM FDPIC.  */
> > +    /* 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
> > +     * r9 points to the main program PT_DYNAMIC info.  */
> > +    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;
> > +    }
>
> Is it really correct to set these registers always, and not only if
> this is an FDPIC ELF ?
I need to check, but I used my FDPIC-enabled QEMU to run non-FDPIC
binaries and saw no problem.

> > +#endif
> >   }
>
> >   int load_elf_binary(struct linux_binprm *bprm, struct image_info *info);
> > diff --git a/target/arm/cpu.h b/target/arm/cpu.h
> > index 19a0c03..90c8ee1 100644
> > --- a/target/arm/cpu.h
> > +++ b/target/arm/cpu.h
> > @@ -629,6 +629,12 @@ typedef struct CPUARMState {
> >       const struct arm_boot_info *boot_info;
> >       /* Store GICv3CPUState to access from this struct */
> >       void *gicv3state;
> > +
> > +#if defined(CONFIG_USER_ONLY) && defined(CONFIG_USE_FDPIC)
> > +    /* We need to know if we have an FDPIC binary to adapt signal
> > +     * syscalls.  */
> > +    int is_fdpic;
>
> linux-user specific information shouldn't live in CPUARMState;
> put it in the TaskState struct instead, perhaps.
OK, I'll have a look at that.

> > +#endif
> >   } CPUARMState;
> >
> >   /**
>
> thanks
> -- PMM
> .