Re: [Qemu-devel] [PATCH 1/3] linux-user: Handle ELFv2 PPC64 binaries in user mode.

[Alexander Graf <agraf@suse.de>]

On 05/08/2014 10:26 AM, Doug Kwan wrote:
> Look at ELF header to determin ABI version on PPC64.  This is required
> for executing the first instruction correctly.
>
> Signed-off-by: Doug Kwan <dougkwan@google.com>
> ---
>   include/elf.h        |  5 +++++
>   linux-user/elfload.c | 17 +++++++++++++++--
>   2 files changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/include/elf.h b/include/elf.h
> index 1599ab2..b39f5db 100644
> --- a/include/elf.h
> +++ b/include/elf.h
> @@ -561,6 +561,11 @@ typedef struct {
>   #define SHF_ALPHA_GPREL		0x10000000
>   
>   
> +/* PowerPC specific definitions.  */
> +
> +/* Processor specific flags for the ELF header e_flags field.  */
> +#define EF_PPC64_ABI		3

Please write bitmasks in hex.

> +
>   /* PowerPC relocations defined by the ABIs */
>   #define R_PPC_NONE		0
>   #define R_PPC_ADDR32		1	/* 32bit absolute address */
> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index 995f999..b96d64a 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -777,12 +777,18 @@ static uint32_t get_elf_hwcap(void)
>           NEW_AUX_ENT(AT_IGNOREPPC, AT_IGNOREPPC);        \
>       } while (0)
>   
> +static inline uint32_t get_ppc64_abi(struct image_info *infop);
> +
>   static inline void init_thread(struct target_pt_regs *_regs, struct image_info *infop)
>   {
>       _regs->gpr[1] = infop->start_stack;
>   #if defined(TARGET_PPC64) && !defined(TARGET_ABI32)
> -    _regs->gpr[2] = ldq_raw(infop->entry + 8) + infop->load_bias;
> -    infop->entry = ldq_raw(infop->entry) + infop->load_bias;
> +    if (get_ppc64_abi(infop) < 2) {
> +      _regs->gpr[2] = ldq_raw(infop->entry + 8) + infop->load_bias;
> +      infop->entry = ldq_raw(infop->entry) + infop->load_bias;
> +    } else {
> +      _regs->gpr[12] = infop->entry;  /* r12 set to global entry address */

Uli, is this correct? Also, why don't w need to adjust for the load_bias 
with ELFv2 anymore?

> +    }
>   #endif
>       _regs->nip = infop->entry;
>   }
> @@ -1152,6 +1158,13 @@ static inline void init_thread(struct target_pt_regs *regs, struct image_info *i
>   
>   #include "elf.h"
>   
> +#ifdef TARGET_PPC
> +static inline uint32_t get_ppc64_abi(struct image_info *infop)
> +{
> +  return infop->elf_flags & EF_PPC64_ABI;
> +}
> +#endif

I'm not sure this is more readable than doing it inline ... :).


Alex