git: d9cacbf4b010 - main - sched_get/setaffinity(): try to be more compatible with Linux

[Konstantin Belousov]

The branch main has been updated by kib:

URL: 
https://cgit.FreeBSD.org/src/commit/?id=d9cacbf4b010d96dbfe96a09259972a95c675f26

commit d9cacbf4b010d96dbfe96a09259972a95c675f26
Author:     Konstantin Belousov <k...@freebsd.org>
AuthorDate: 2022-01-02 22:11:49 +0000
Commit:     Konstantin Belousov <k...@freebsd.org>
CommitDate: 2022-01-03 02:31:40 +0000

    sched_get/setaffinity(): try to be more compatible with Linux
    
    in handling the cpuset sizes different from sizeof(cpuset_t).
    
    For both cases, cpuset size shorter than sizeof(cpuset_t) results
    in EINVAL on Linux.
    
    For sched_getaffinity(), be more permissive and accept cpuset size
    larger than our cpuset_t, by clipping the syscall argument and zeroing
    the rest of the output buffer.  For sched_setaffinity(), we should allow
    shorter cpusets than current ABI size, again zeroing the rest of the bits.
    
    With this change, python os.sched_get/setaffinity functions work.
    
    Reported by:    se
    Sponsored by:   The FreeBSD Foundation
    MFC after:      1 week
---
 lib/libc/gen/sched_getaffinity.c | 20 ++++++++++++++++++++
 lib/libc/gen/sched_setaffinity.c | 13 ++++++++++++-
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/lib/libc/gen/sched_getaffinity.c b/lib/libc/gen/sched_getaffinity.c
index 2ae8c5b763a3..7d345eb82a3b 100644
--- a/lib/libc/gen/sched_getaffinity.c
+++ b/lib/libc/gen/sched_getaffinity.c
@@ -26,11 +26,31 @@
  * SUCH DAMAGE.
  */
 
+#include <errno.h>
 #include <sched.h>
+#include <string.h>
 
 int
 sched_getaffinity(pid_t pid, size_t cpusetsz, cpuset_t *cpuset)
 {
+       /*
+        * Be more Linux-compatible:
+        * - return EINVAL in passed size is less than size of cpuset_t
+        *   in advance, instead of ERANGE from the syscall
+        * - if passed size is larger than the size of cpuset_t, be
+        *   permissive by claming it back to sizeof(cpuset_t) and
+        *   zeroing the rest.
+        */
+       if (cpusetsz < sizeof(cpuset_t)) {
+               errno = EINVAL;
+               return (-1);
+       }
+       if (cpusetsz > sizeof(cpuset_t)) {
+               memset((char *)cpuset + sizeof(cpuset_t), 0,
+                   cpusetsz - sizeof(cpuset_t));
+               cpusetsz = sizeof(cpuset_t);
+       }
+
        return (cpuset_getaffinity(CPU_LEVEL_WHICH, CPU_WHICH_PID,
            pid == 0 ? -1 : pid, cpusetsz, cpuset));
 }
diff --git a/lib/libc/gen/sched_setaffinity.c b/lib/libc/gen/sched_setaffinity.c
index 52fc6d4bc811..91ab2a401bda 100644
--- a/lib/libc/gen/sched_setaffinity.c
+++ b/lib/libc/gen/sched_setaffinity.c
@@ -26,11 +26,22 @@
  * SUCH DAMAGE.
  */
 
+#include <errno.h>
 #include <sched.h>
+#include <string.h>
 
 int
 sched_setaffinity(pid_t pid, size_t cpusetsz, const cpuset_t *cpuset)
 {
+       cpuset_t c;
+
+       if (cpusetsz > sizeof(cpuset_t)) {
+               errno = EINVAL;
+               return (-1);
+       } else {
+               memset(&c, 0, sizeof(c));
+               memcpy(&c, cpuset, cpusetsz);
+       }
        return (cpuset_setaffinity(CPU_LEVEL_WHICH, CPU_WHICH_PID,
-           pid == 0 ? -1 : pid, cpusetsz, cpuset));
+           pid == 0 ? -1 : pid, sizeof(cpuset_t), &c));
 }