From: Daniele Buono <dbu...@linux.vnet.ibm.com> Current implementation of LLVM's SafeStack is not compatible with code that uses an alternate stack created with sigaltstack(). Since coroutine-sigaltstack relies on sigaltstack(), it is not compatible with SafeStack. The resulting binary is incorrect, with different coroutines sharing the same unsafe stack and producing undefined behavior at runtime.
In the future LLVM may provide a SafeStack implementation compatible with sigaltstack(). In the meantime, if SafeStack is desired, the coroutine implementation from coroutine-ucontext should be used. As a safety check, add a control in coroutine-sigaltstack to throw a preprocessor #error if SafeStack is enabled and we are trying to use coroutine-sigaltstack to implement coroutines. Signed-off-by: Daniele Buono <dbu...@linux.vnet.ibm.com> Message-id: 20200529205122.714-3-dbu...@linux.vnet.ibm.com Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com> --- util/coroutine-sigaltstack.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/util/coroutine-sigaltstack.c b/util/coroutine-sigaltstack.c index f6fc49a0e5..aade82afb8 100644 --- a/util/coroutine-sigaltstack.c +++ b/util/coroutine-sigaltstack.c @@ -30,6 +30,10 @@ #include "qemu-common.h" #include "qemu/coroutine_int.h" +#ifdef CONFIG_SAFESTACK +#error "SafeStack is not compatible with code run in alternate signal stacks" +#endif + typedef struct { Coroutine base; void *stack; -- 2.26.2