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Re: [Qemu-devel] [PATCH V9 1/7] oslib-posix: add helpers for stack alloc
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] [PATCH V9 1/7] oslib-posix: add helpers for stack alloc and free |
Date: |
Tue, 27 Sep 2016 13:59:39 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
Am 27.09.2016 um 11:58 hat Peter Lieven geschrieben:
> 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);
s/sz/*sz/
> +#elif defined(HOST_HPPA)
> + /* stack grows up */
> + guardpage = ptr + sz - pagesz;
Here too. I can fix both while applying the series.
> +#else
> + /* stack grows down */
> + guardpage = ptr;
> +#endif
> + if (mprotect(guardpage, pagesz, PROT_NONE) != 0) {
> + abort();
> + }
> +
> + return ptr;
> +}
Kevin
- [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, 2016/09/27
- Re: [Qemu-devel] [PATCH V9 1/7] oslib-posix: add helpers for stack alloc and free,
Kevin Wolf <=
- [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
- [Qemu-devel] [PATCH V9 4/7] coroutine-ucontext: use helper for allocating stack memory, Peter Lieven, 2016/09/27