Re: [Qemu-devel] [PATCH] linux-user: MIPS set cpu to r6 CPU if binary is R6

[Laurent Vivier]

Peter, Riku,

what do you think of the idea of using the ELF header to select the CPU
to emulate?

Thanks,
Laurent

Le 19/12/2017 à 12:50, YunQiang Su a écrit :
> MIPS r6 is not just simple super set for pre-R6,
> it also drops some instruction and even changes encoding for some.
> But r6 binary has the same header for binfmt_misc.
> 
> So here we need to detect the version of binaries and set
> cpu_model for it.
> ---
>  include/elf.h        |  4 ++++
>  linux-user/elfload.c | 36 ++++++++++++++++++++++++++++++++++++
>  linux-user/main.c    | 15 +++++++++++++++
>  linux-user/qemu.h    |  1 +
>  4 files changed, 56 insertions(+)
> 
> diff --git a/include/elf.h b/include/elf.h
> index e8a515ce3d..f2104809b1 100644
> --- a/include/elf.h
> +++ b/include/elf.h
> @@ -40,6 +40,10 @@ typedef int64_t  Elf64_Sxword;
>  #define EF_MIPS_ARCH_5               0x40000000      /* -mips5 code.  */
>  #define EF_MIPS_ARCH_32              0x50000000      /* MIPS32 code.  */
>  #define EF_MIPS_ARCH_64              0x60000000      /* MIPS64 code.  */
> +#define EF_MIPS_ARCH_32R2       0x70000000      /* MIPS32r2 code.  */
> +#define EF_MIPS_ARCH_64R2       0x80000000      /* MIPS64r2 code.  */
> +#define EF_MIPS_ARCH_32R6       0x90000000      /* MIPS32r6 code.  */
> +#define EF_MIPS_ARCH_64R6       0xa0000000      /* MIPS64r6 code.  */
>  
>  /* The ABI of a file. */
>  #define EF_MIPS_ABI_O32              0x00001000      /* O32 ABI.  */
> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index 20f3d8c2c3..f9b8e028ca 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -2224,6 +2224,42 @@ static void load_elf_interp(const char *filename, 
> struct image_info *info,
>      exit(-1);
>  }
>  
> +uint32_t get_elf_eflags(const char *filename)
> +{
> +    int fd, retval;
> +    char bprm_buf[BPRM_BUF_SIZE];
> +
> +    fd = open(path(filename), O_RDONLY);
> +    if (fd < 0) {
> +        return 0;
> +    }
> +    retval = read(fd, bprm_buf, BPRM_BUF_SIZE);
> +    close(fd);
> +    if (retval < 0) {
> +        return 0;
> +    }
> +    if (retval < BPRM_BUF_SIZE) {
> +        memset(bprm_buf + retval, 0, BPRM_BUF_SIZE - retval);
> +    }
> +
> +    if (bprm_buf[0] != 0x7f
> +             || bprm_buf[1] != 'E'
> +             || bprm_buf[2] != 'L'
> +             || bprm_buf[3] != 'F') {
> +        return 0;
> +    }
> +
> +    struct elfhdr *ehdr = (struct elfhdr *)bprm_buf;
> +    if (!elf_check_ident(ehdr)) {
> +        return 0;
> +    }
> +    bswap_ehdr(ehdr);
> +    if (!elf_check_ehdr(ehdr)) {
> +        return 0;
> +    }
> +    return ehdr->e_flags;
> +}
> +
>  static int symfind(const void *s0, const void *s1)
>  {
>      target_ulong addr = *(target_ulong *)s0;
> diff --git a/linux-user/main.c b/linux-user/main.c
> index 7c0bffeff6..b4626e5aa0 100644
> --- a/linux-user/main.c
> +++ b/linux-user/main.c
> @@ -4287,6 +4287,21 @@ int main(int argc, char **argv, char **envp)
>      }
>      trace_init_file(trace_file);
>  
> +#if defined(TARGET_MIPS)
> +    if (cpu_model == NULL) {
> +        uint32_t eflags = get_elf_eflags(filename);
> +#if defined(TARGET_ABI_MIPSN32) || defined(TARGET_ABI_MIPSN64)
> +        if ((eflags & EF_MIPS_ARCH_64R6) != 0) {
> +            cpu_model = "I6400";
> +        }
> +#else
> +        if ((eflags & EF_MIPS_ARCH_32R6) != 0) {
> +            cpu_model = "mips32r6-generic";
> +        }
> +#endif
> +    }
> +#endif
> +
>      /* Zero out regs */
>      memset(regs, 0, sizeof(struct target_pt_regs));
>  
> diff --git a/linux-user/qemu.h b/linux-user/qemu.h
> index 4edd7d0c08..cf09110bf9 100644
> --- a/linux-user/qemu.h
> +++ b/linux-user/qemu.h
> @@ -190,6 +190,7 @@ int loader_exec(int fdexec, const char *filename, char 
> **argv, char **envp,
>  
>  int load_elf_binary(struct linux_binprm *bprm, struct image_info *info);
>  int load_flt_binary(struct linux_binprm *bprm, struct image_info *info);
> +uint32_t get_elf_eflags(const char *filename);
>  
>  abi_long memcpy_to_target(abi_ulong dest, const void *src,
>                            unsigned long len);
>