Re: [PATCH] binfmt_misc: pass binfmt_misc P flag to the interpreter

* YunQiang Su:

AT_* only has 32 slot and now. I was afraid that maybe we shouldn't take one.
   /* AT_* values 18 through 22 are reserved */
   27,28,29,30 are not used now.
Which should we use?

Where does this limit of 32 tags come from?  I don't see it from a
userspace perspective.

Florian Weimer [off-list ref] 于2020年3月6日周五 下午7:42写道：

* YunQiang Su:

quoted

AT_* only has 32 slot and now. I was afraid that maybe we shouldn't take one.
   /* AT_* values 18 through 22 are reserved */
   27,28,29,30 are not used now.
Which should we use?

Where does this limit of 32 tags come from?  I don't see it from a
userspace perspective.

Sorry it is my mistake: In linux/auxvec.h, I saw

#define AT_RANDOM 25    /* address of 16 random bytes */
#define AT_HWCAP2 26    /* extension of AT_HWCAP */

#define AT_EXECFN  31   /* filename of program */

The number jump to 31 from 26.

It is my fault: in x86_64-linux-gnu/bits/auxv.h, the max number is 47 now.

Le 06/03/2020 à 12:48, YunQiang Su a écrit :

Florian Weimer [off-list ref] 于2020年3月6日周五 下午7:42写道：

quoted

* YunQiang Su:

quoted

AT_* only has 32 slot and now. I was afraid that maybe we shouldn't take one.
   /* AT_* values 18 through 22 are reserved */
   27,28,29,30 are not used now.
Which should we use?

Where does this limit of 32 tags come from?  I don't see it from a
userspace perspective.

Sorry it is my mistake: In linux/auxvec.h, I saw

#define AT_RANDOM 25    /* address of 16 random bytes */
#define AT_HWCAP2 26    /* extension of AT_HWCAP */

#define AT_EXECFN  31   /* filename of program */

The number jump to 31 from 26.

It is my fault: in x86_64-linux-gnu/bits/auxv.h, the max number is 47 now.

Numbers starting from 32 are arch specific.
18 to 22 are also reserved (and used by some archs).
(linux/arch/*/include/uapi/asm/auxvec.h)

So there is only 4 entries available (27 to 30)
(linux/include/uapi/linux/auxvec.h)
Do we want to waste one more entry whereas we can use an unused one?

Thanks,
Laurent