From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60745) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bWpJR-0005NS-5j for qemu-devel@nongnu.org; Mon, 08 Aug 2016 14:30:10 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bWpJN-0006cC-Sb for qemu-devel@nongnu.org; Mon, 08 Aug 2016 14:30:09 -0400 Received: from mx-v6.kamp.de ([2a02:248:0:51::16]:58834 helo=mx01.kamp.de) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bWpJN-0006ao-IF for qemu-devel@nongnu.org; Mon, 08 Aug 2016 14:30:05 -0400 Message-ID: <57A8CFA6.5070503@kamp.de> Date: Mon, 08 Aug 2016 20:29:58 +0200 From: Peter Lieven MIME-Version: 1.0 References: <1468340586-19304-1-git-send-email-pl@kamp.de> <1468340586-19304-2-git-send-email-pl@kamp.de> <20160808103750.GA30105@stefanha-x1.localdomain> In-Reply-To: <20160808103750.GA30105@stefanha-x1.localdomain> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH V5 1/6] oslib-posix: add helpers for stack alloc and free List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: qemu-devel@nongnu.org, kwolf@redhat.com, peter.maydell@linaro.org, mst@redhat.com, armbru@redhat.com, dgilbert@redhat.com, mreitz@redhat.com, pbonzini@redhat.com, rth@twiddle.net Am 08.08.2016 um 12:37 schrieb Stefan Hajnoczi: > On Tue, Jul 12, 2016 at 06:23:01PM +0200, Peter Lieven wrote: >> 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 >> --- >> include/sysemu/os-posix.h | 23 +++++++++++++++++++++++ >> util/oslib-posix.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++ >> 2 files changed, 69 insertions(+) >> >> diff --git a/include/sysemu/os-posix.h b/include/sysemu/os-posix.h >> index 9c7dfdf..7630665 100644 >> --- a/include/sysemu/os-posix.h >> +++ b/include/sysemu/os-posix.h >> @@ -60,4 +60,27 @@ int qemu_utimens(const char *path, const qemu_timespec *times); >> >> bool is_daemonized(void); >> >> +/** >> + * qemu_alloc_stack: >> + * @sz: size of required stack in bytes >> + * >> + * 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()). >> + * >> + * 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(). >> + */ >> +void qemu_free_stack(void *stack, size_t sz); >> + >> #endif >> diff --git a/util/oslib-posix.c b/util/oslib-posix.c >> index e2e1d4d..2303ca6 100644 >> --- a/util/oslib-posix.c >> +++ b/util/oslib-posix.c >> @@ -497,3 +497,49 @@ pid_t qemu_fork(Error **errp) >> } >> return pid; >> } >> + >> +static size_t adjust_stack_size(size_t sz) >> +{ >> +#ifdef _SC_THREAD_STACK_MIN >> + /* avoid stacks smaller than _SC_THREAD_STACK_MIN */ >> + sz = MAX(MAX(sysconf(_SC_THREAD_STACK_MIN), 0), sz); >> +#endif >> + /* adjust stack size to a multiple of the page size */ >> + sz = ROUND_UP(sz, getpagesize()); >> + return sz; >> +} >> + >> +void *qemu_alloc_stack(size_t sz) >> +{ >> + void *ptr, *guardpage; >> + size_t pagesz = getpagesize(); >> + sz = adjust_stack_size(sz); >> + >> + ptr = mmap(NULL, sz, PROT_READ | PROT_WRITE, > It's cleaner to count for the guard page separately and give the caller > the sz bytes they expected: > > sz + pagesz I don't mind to change that, but the glibc stack allocation routine does it exactly this way. (see glibc/nptl/allocatestack.c). As we already used other parts (minimal stack size, positioning of the guard page), we mimicked this as well. Peter