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[Qemu-devel] [PATCH V9 1/7] oslib-posix: add helpers for stack alloc and
From: |
Peter Lieven |
Subject: |
[Qemu-devel] [PATCH V9 1/7] oslib-posix: add helpers for stack alloc and free |
Date: |
Tue, 27 Sep 2016 11:58:40 +0200 |
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 <address@hidden>
---
include/sysemu/os-posix.h | 27 +++++++++++++++++++++++++++
util/oslib-posix.c | 42 ++++++++++++++++++++++++++++++++++++++++++
2 files changed, 69 insertions(+)
diff --git a/include/sysemu/os-posix.h b/include/sysemu/os-posix.h
index 9c7dfdf..3cfedbc 100644
--- a/include/sysemu/os-posix.h
+++ b/include/sysemu/os-posix.h
@@ -60,4 +60,31 @@ int qemu_utimens(const char *path, const qemu_timespec
*times);
bool is_daemonized(void);
+/**
+ * qemu_alloc_stack:
+ * @sz: pointer to a size_t holding the requested usable stack size
+ *
+ * Allocate memory that can be used as a stack, for instance for
+ * coroutines. If the memory cannot be allocated, this function
+ * will abort (like g_malloc()). This function also inserts an
+ * additional guard page to catch a potential stack overflow.
+ * Note that the memory required for the guard page and alignment
+ * and minimal stack size restrictions will increase the value of sz.
+ *
+ * The allocated stack must be freed with qemu_free_stack().
+ *
+ * Returns: pointer to (the lowest address of) the stack memory.
+ */
+void *qemu_alloc_stack(size_t *sz);
+
+/**
+ * qemu_free_stack:
+ * @stack: stack to free
+ * @sz: size of stack in bytes
+ *
+ * Free a stack allocated via qemu_alloc_stack(). Note that sz must
+ * be exactly the adjusted stack size returned by qemu_alloc_stack.
+ */
+void qemu_free_stack(void *stack, size_t sz);
+
#endif
diff --git a/util/oslib-posix.c b/util/oslib-posix.c
index f2d4e9e..5745229 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);
+}
--
1.9.1
- [Qemu-devel] [PATCH V9 0/7] coroutine: mmap stack memory and stack size, Peter Lieven, 2016/09/27
- [Qemu-devel] [PATCH V9 3/7] coroutine: add a macro for the coroutine stack size, Peter Lieven, 2016/09/27
- [Qemu-devel] [PATCH V9 1/7] oslib-posix: add helpers for stack alloc and free,
Peter Lieven <=
- [Qemu-devel] [PATCH V9 6/7] oslib-posix: add a configure switch to debug stack usage, Peter Lieven, 2016/09/27
- [Qemu-devel] [PATCH V9 5/7] coroutine-sigaltstack: use helper for allocating stack memory, Peter Lieven, 2016/09/27
- [Qemu-devel] [PATCH V9 7/7] coroutine: reduce stack size to 60kB, Peter Lieven, 2016/09/27
- [Qemu-devel] [PATCH V9 2/7] coroutine-sigaltstack: rename coroutine struct appropriately, Peter Lieven, 2016/09/27