x86_64 Auxillary vector reports platform as i686 which doesn't match the linux kernel
Host environment
- Operating system: Debian GNU/Linux 11 (bullseye)
- OS/kernel version: 5.10.0-13-amd64
- Architecture: x86-64
- QEMU flavor: qemu-x86_64-static
- QEMU version: qemu-x86_64 version 5.2.0 (Debian 1:5.2+dfsg-11+deb11u1)
- QEMU command line:
qemu-x86_64-static print-platform
Emulated/Virtualized environment
- Operating system: Linux
- OS/kernel version: 5.10.0-13-amd64
- Architecture: x86-64
Description of problem
Based on the kernel source in the auxiliary vector AT_PLATFORM should be x86_64
(confirmed by running outside qemu). However qemu sets it to i686
.
This was originally reported with docker-for-mac, but was reduced on x86_64
which is why it is pointless
Steps to reproduce
- Compile the following for x86_64 (statically if you don't want have an x86_64 dynamic linker) (code originally from https://stackoverflow.com/questions/26520163/accessing-auxiliary-vectors-c)
#include <stdio.h>
#include <elf.h>
int main(int argc, char** argv, char* envp[]) {
Elf64_auxv_t *auxv;
while(*envp++ != NULL);
/*from stack diagram above: *envp = NULL marks end of envp*/
int i = 0 ;
for (auxv = (Elf64_auxv_t *)envp; auxv->a_type != AT_NULL; auxv++)
/* auxv->a_type = AT_NULL marks the end of auxv */
{
if( auxv->a_type == AT_PLATFORM)
printf("AT_PLATFORM is: %s\n", ((char*)auxv->a_un.a_val));
}
}
- Run with
qemu-x86_64-static
- See
AT_PLATFORM is: i686
- Compare to "real" x86_64 bit system which gives
AT_PLATFORM is: x86_64
Additional information
I think that adding #define ELF_PLATFORM "x86_64"
here should work (but I don't fully understand the code). Otherwise we just end up getting the 32-bit case.