From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37379) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bosqB-0001S7-Eh for qemu-devel@nongnu.org; Tue, 27 Sep 2016 09:54:39 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bosq6-0001Ph-0L for qemu-devel@nongnu.org; Tue, 27 Sep 2016 09:54:35 -0400 From: Kevin Wolf Date: Tue, 27 Sep 2016 15:53:55 +0200 Message-Id: <1474984441-28516-13-git-send-email-kwolf@redhat.com> In-Reply-To: <1474984441-28516-1-git-send-email-kwolf@redhat.com> References: <1474984441-28516-1-git-send-email-kwolf@redhat.com> Subject: [Qemu-devel] [PULL 12/18] oslib-posix: add helpers for stack alloc and free List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-block@nongnu.org Cc: kwolf@redhat.com, qemu-devel@nongnu.org From: Peter Lieven 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 Signed-off-by: Kevin Wolf --- 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..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); +} -- 1.8.3.1