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authorPeter Lieven <pl@kamp.de>2016-09-27 11:58:40 +0200
committerKevin Wolf <kwolf@redhat.com>2016-09-29 14:13:39 +0200
commit8737d9e0c4017aaa5ab1fcf1356c8ee4f7caf1df (patch)
tree9598ddbb6fc8d488755f71e9b9be1ea8839a25e9 /util
parent74e1ae7c0b66d85d2b04c153ffdf6294e6a40798 (diff)
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oslib-posix: add helpers for stack alloc and free
the allocated stack will be adjusted to the minimum supported stack size by the OS and rounded up to be a multiple of the system pagesize. Additionally an architecture dependent guard page is added to the stack to catch stack overflows. Signed-off-by: Peter Lieven <pl@kamp.de> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'util')
-rw-r--r--util/oslib-posix.c42
1 files changed, 42 insertions, 0 deletions
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index f2d4e9e..d950c34 100644
--- a/util/oslib-posix.c
+++ b/util/oslib-posix.c
@@ -499,3 +499,45 @@ pid_t qemu_fork(Error **errp)
}
return pid;
}
+
+void *qemu_alloc_stack(size_t *sz)
+{
+ void *ptr, *guardpage;
+ size_t pagesz = getpagesize();
+#ifdef _SC_THREAD_STACK_MIN
+ /* avoid stacks smaller than _SC_THREAD_STACK_MIN */
+ long min_stack_sz = sysconf(_SC_THREAD_STACK_MIN);
+ *sz = MAX(MAX(min_stack_sz, 0), *sz);
+#endif
+ /* adjust stack size to a multiple of the page size */
+ *sz = ROUND_UP(*sz, pagesz);
+ /* allocate one extra page for the guard page */
+ *sz += pagesz;
+
+ ptr = mmap(NULL, *sz, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+ if (ptr == MAP_FAILED) {
+ abort();
+ }
+
+#if defined(HOST_IA64)
+ /* separate register stack */
+ guardpage = ptr + (((*sz - pagesz) / 2) & ~pagesz);
+#elif defined(HOST_HPPA)
+ /* stack grows up */
+ guardpage = ptr + *sz - pagesz;
+#else
+ /* stack grows down */
+ guardpage = ptr;
+#endif
+ if (mprotect(guardpage, pagesz, PROT_NONE) != 0) {
+ abort();
+ }
+
+ return ptr;
+}
+
+void qemu_free_stack(void *stack, size_t sz)
+{
+ munmap(stack, sz);
+}