This series first fixes a bug that results in corrupted FPU state after
invoking signal handlers. It also adds support for the extended processor
state (XSTATE) for x86_64 UML, especially the YMM registers used by AVX(2)
instructions.
Tested with a minimal multi-threaded FPU-intensive test program (see below).
This series supersedes the previous sigreturn fix as that one is incorrect
when the process is multi-threaded.
Changes since v2:
- Add an improved sigreturn fix to this series
- Merge the ptrace changes into the last commit
- Make the selftest program multi-threaded
Changes since v1:
- Refactor functions with oversized stack frame
- Add a tiny selftest program to the cover letter
Eli Cooper (3):
um: fix FPU state preservation around signal handlers
um: extend fpstate to _xstate to support YMM registers
um: add extended processor state save/restore 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 | 37 +++++++++-----------------
arch/x86/um/user-offsets.c | 2 +-
9 files changed, 95 insertions(+), 50 deletions(-)
--
/* Test if context switches preserve YMM registers, multi-threaded version
* The main function, threads and the signal handler all have their unique
* ymm0 value, and constantly detect if someone steps on their toes.
* Should loop forever.
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <signal.h>
#include <unistd.h>
#include <pthread.h>
#include <sys/time.h>
#include <immintrin.h>
#define N 10
void sighandler(int signum)
{
int n = 0xffff;
register uint32_t eax asm("eax");
__m256i m0 = _mm256_set_epi64x(0x1234L << 32, 0, 0, 0);
while (n--) {
asm("vextracti128 $1,%ymm0,%xmm1");
asm("vpextrd $3,%xmm1,%eax");
if (eax != 0x1234)
exit(3);
}
}
void thread(void *arg)
{
long n = (long)arg;
register uint32_t eax asm("eax");
__m256i m0 = _mm256_set_epi64x(n << 32, 0, 0, 0);
do {
asm("vextracti128 $1,%ymm0,%xmm1");
asm("vpextrd $3,%xmm1,%eax");
} while (eax == n);
exit(2);
}
int main()
{
register uint32_t eax asm("eax");
pthread_t threads[N];
struct itimerval itv;
struct timeval tv;
struct sigaction act;
tv.tv_sec = 0;
tv.tv_usec = 100000;
itv.it_interval = tv;
itv.it_value = tv;
act.sa_handler = sighandler;
act.sa_flags = 0;
sigemptyset(&act.sa_mask);
sigaction(SIGALRM, &act, NULL);
setitimer(ITIMER_REAL, &itv, NULL);
for (long i = 0; i < N; i++)
pthread_create(threads + i, NULL, (void *)thread, (void *)i);
__m256i m0 = _mm256_set_epi64x(0xabcdL << 32, 0, 0, 0);
do {
asm("vextracti128 $1,%ymm0,%xmm1");
asm("vpextrd $3,%xmm1,%eax");
} while (eax == 0xabcd);
printf("%lx\n", eax);
return 1;
}
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