nproc: prepare for arbitrarily large CPU masks

function                                             old     new   delta
get_malloc_cpu_affinity                                -      76     +76
nproc_main                                           216     206     -10
process_pid_str                                      250     206     -44
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 0/2 up/down: 76/-54)             Total: 22 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 30 insertions, 0 deletions

diff --git a/libbb/Kbuild.src b/libbb/Kbuild.src
index c3b30003f..a0e2a6da7 100644
--- a/libbb/Kbuild.src
+++ b/libbb/Kbuild.src
@@ -10,6 +10,7 @@ lib-y:=
 
 INSERT
 
+lib-y += alloc_affinity.o
 lib-y += appletlib.o
 lib-y += ask_confirmation.o
 lib-y += bb_askpass.o
diff --git a/libbb/alloc_affinity.c b/libbb/alloc_affinity.c
new file mode 100644
index 000000000..b6d9f649a
--- /dev/null
+++ b/libbb/alloc_affinity.c
@@ -0,0 +1,29 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Utility routines.
+ *
+ * Copyright (C) 2024 Denys Vlasenko
+ *
+ * Licensed under GPLv2, see file LICENSE in this source tree.
+ */
+#include <sched.h>
+#include "libbb.h"
+
+unsigned long* FAST_FUNC get_malloc_cpu_affinity(int pid, unsigned *sz)
+{
+        unsigned long *mask = NULL;
+        unsigned sz_in_bytes = *sz;
+
+        for (;;) {
+                mask = xrealloc(mask, sz_in_bytes);
+                if (sched_getaffinity(pid, sz_in_bytes, (void*)mask) == 0)
+                        break; /* got it */
+                sz_in_bytes *= 2;
+                if (errno == EINVAL && (int)sz_in_bytes > 0)
+                        continue;
+                bb_perror_msg_and_die("can't %cet pid %d's affinity", 'g', pid);
+        }
+        //bb_error_msg("get mask[0]:%lx sz_in_bytes:%d", mask[0], sz_in_bytes);
+        *sz = sz_in_bytes;
+        return mask;
+}