This series adds support for the extended processor state (XSTATE) for
x86_64 UML, especially the YMM registers used by AVX/AVX2 instructions.
Modern userspace programs built with AVX can now run inside x86_64 UML
without YMM registers getting corrupted.
Tested with a tiny selftest program below, which of course requires the
following patch I sent earlier today to run correctly.
um: fix FPU register double-restore after sigreturn
Also tested with a latest Arch Linux image on a CPU with AVX2 support.
Without YMM support in UML, a lot of programs crash unexpectedly,
or result in bad results (e.g., calculating SHA256 in OpenSSL).
Changes since v1:
- Refactor functions with oversized stack frame
- Add a tiny selftest program to the cover letter
Eli Cooper (3):
um: extend _fpstate to _xstate
um: add extended processor state save/restore support
um: fix ptrace PTRACE_GETFPREGS and PTRACE_SETFPREG support
arch/um/include/shared/registers.h | 2 ++
arch/um/kernel/process.c | 2 +-
arch/um/os-Linux/signal.c | 28 ++++++++++++-----
arch/x86/um/os-Linux/registers.c | 49 ++++++++++++++++++++++++++++--
arch/x86/um/ptrace_32.c | 5 +--
arch/x86/um/ptrace_64.c | 16 +++++-----
arch/x86/um/shared/sysdep/ptrace_64.h | 4 +--
arch/x86/um/signal.c | 57 +++++++++++++++++++++++------------
arch/x86/um/user-offsets.c | 2 +-
9 files changed, 121 insertions(+), 44 deletions(-)
---
/* test if context switches preserve YMM registers, should exit with code 0 */
#include <stdint.h>
#include <unistd.h>
#include <signal.h>
#include <immintrin.h>
int flag;
void sighandler(int signum)
{
if (flag)
exit(0);
alarm(1);
flag = 1;
__m256i m0 = _mm256_set_epi64x(0, 0, 0, 0);
}
int main()
{
register uint32_t a asm("eax") = 0;
signal(SIGALRM, sighandler);
alarm(1);
__m256i m0 = _mm256_set_epi64x(1L << 32, 0, 0, 0);
do {
asm("vextracti128 $1,%ymm0,%xmm1");
asm("vpextrd $3,%xmm1,%eax");
} while (a == 1);
return 1;
}
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