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

[YunQiang Su]

should something like:

+    int fd, retval;
+    off_t cur_pos;
+    bool is_execfd = true;
+    char bprm_buf[BPRM_BUF_SIZE];
+
+    fd = qemu_getauxval(AT_EXECFD);
+    if (fd == 0){
+        is_execfd = false;
+        fd = open(path(filename), O_RDONLY);
+        if (fd < 0) {
+            return 0;
+        }
+    }else{
+        cur_pos = lseek(fd, 0, SEEK_CUR);
+       if ((cur_pos < 0) || (lseek(fd, 0, SEEK_SET) != 0)){
+            printf("Error while lseek in %s: %s\n", filename, strerror(errno));
+            _exit(EXIT_FAILURE);
+       }
+    }
+    retval = read(fd, bprm_buf, BPRM_BUF_SIZE);
+    if (!is_execfd)
+        close(fd);
+    else {
+       if (lseek(fd, cur_pos, SEEK_SET) != cur_pos){
+            printf("Error while lseek in %s: %s\n", filename, strerror(errno));
+            _exit(EXIT_FAILURE);
+        }
+    }
+
+    if (retval < 0) {
+        return 0;
+    }


works?

On Sun, Dec 24, 2017 at 12:34 AM, Laurent Vivier <address@hidden> wrote:
> 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);
>
> You can't do that with binfmt and credential ('C' flag) enabled (it
> implies 'O' flag, open-binary), because in this case the kernel opens
> the file and provides the file descriptor to QEMU. We need the 'C' flags
> to allow to execute binaries with the setuid flag (like "sudo") [1]
>
> See linux-user/main.c:
>
>    4446     execfd = qemu_getauxval(AT_EXECFD);
>    4447     if (execfd == 0) {
>    4448         execfd = open(filename, O_RDONLY);
>    4449         if (execfd < 0) {
>    4450             printf("Error while loading %s: %s\n", filename,
> strerror(errno));
>    4451             _exit(EXIT_FAILURE);
>    4452         }
>    4453     }
>
> Thanks,
> Laurent
> [1]
> https://github.com/torvalds/linux/blob/master/Documentation/admin-guide/binfmt-misc.rst