Hi
On Tue, Jan 9, 2018 at 12:09 PM, Philippe Mathieu-Daudé <f4...@amsat.org> wrote:
> Hi Marc-André,
>
> On 01/04/2018 01:05 PM, Marc-André Lureau wrote:
>> It helps ASAN to detect more leaks on coroutine stacks, as found in
>> the following patch.
>>
>> A similar work would need to be done for sigaltstack & windows fibers
>> to have similar coverage. Since ucontext is preferred, I didn't bother
>> checking the other coroutine implementations for now.
>>
>> Signed-off-by: Marc-André Lureau <marcandre.lur...@redhat.com>
>> Reviewed-by: Philippe Mathieu-Daudé <f4...@amsat.org>
>> Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
>> ---
>> include/qemu/compiler.h | 4 ++++
>> util/coroutine-ucontext.c | 46
>> ++++++++++++++++++++++++++++++++++++++++++++++
>> 2 files changed, 50 insertions(+)
>>
>> diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h
>> index 340e5fdc09..5fcc4f7ec7 100644
>> --- a/include/qemu/compiler.h
>> +++ b/include/qemu/compiler.h
>> @@ -111,4 +111,8 @@
>> #define GCC_FMT_ATTR(n, m)
>> #endif
>>
>> +#ifndef __has_feature
>> +#define __has_feature(x) 0 /* compatibility with non-clang compilers */
>> +#endif
>> +
>> #endif /* COMPILER_H */
>> diff --git a/util/coroutine-ucontext.c b/util/coroutine-ucontext.c
>> index 6621f3f692..e78eae8766 100644
>> --- a/util/coroutine-ucontext.c
>> +++ b/util/coroutine-ucontext.c
>> @@ -31,6 +31,11 @@
>> #include <valgrind/valgrind.h>
>> #endif
>>
>> +#if defined(__SANITIZE_ADDRESS__) || __has_feature(address_sanitizer)
>> +#define CONFIG_ASAN 1
>> +#include <sanitizer/asan_interface.h>
>> +#endif
>
> Sadly this fails on Travis:
>
> $ export CONFIG="--enable-debug --enable-debug-tcg
> --enable-trace-backends=log"
> $ export CC=gcc
> $ ./configure ${CONFIG}
> C compiler gcc
> Host C compiler cc
> C++ compiler c++
> Objective-C compiler clang
> CFLAGS -Wno-maybe-uninitialized -Og -fsanitize=address -g
> [...]
> CC util/qemu-coroutine.o
> CC util/qemu-coroutine-lock.o
> CC util/qemu-coroutine-io.o
> CC util/qemu-coroutine-sleep.o
> CC util/coroutine-ucontext.o
> util/coroutine-ucontext.c:36:38: fatal error:
> sanitizer/asan_interface.h: No such file or directory
> #include <sanitizer/asan_interface.h>
> ^
> compilation terminated.
> make: *** [util/coroutine-ucontext.o] Error 1
>
> You simply need to update the .travis.yml, but does that mean your
I think we need libgcc-6-dev.
> previous patch "Enable ASAN/UBSan by default if the compiler supports
> it." isn't correct?
No, the problematic patch is "ucontext: annotate coroutine stack for
ASAN", it should probably check for asan_interface.h before using it.
Print a warning if it's not there during configure, as ASAN
experience/reports will be inferior.
>
>> +
>> typedef struct {
>> Coroutine base;
>> void *stack;
>> @@ -59,11 +64,37 @@ union cc_arg {
>> int i[2];
>> };
>>
>> +static void finish_switch_fiber(void *fake_stack_save)
>> +{
>> +#ifdef CONFIG_ASAN
>> + const void *bottom_old;
>> + size_t size_old;
>> +
>> + __sanitizer_finish_switch_fiber(fake_stack_save, &bottom_old,
>> &size_old);
>> +
>> + if (!leader.stack) {
>> + leader.stack = (void *)bottom_old;
>> + leader.stack_size = size_old;
>> + }
>> +#endif
>> +}
>> +
>> +static void start_switch_fiber(void **fake_stack_save,
>> + const void *bottom, size_t size)
>> +{
>> +#ifdef CONFIG_ASAN
>> + __sanitizer_start_switch_fiber(fake_stack_save, bottom, size);
>> +#endif
>> +}
>> +
>> static void coroutine_trampoline(int i0, int i1)
>> {
>> union cc_arg arg;
>> CoroutineUContext *self;
>> Coroutine *co;
>> + void *fake_stack_save = NULL;
>> +
>> + finish_switch_fiber(NULL);
>>
>> arg.i[0] = i0;
>> arg.i[1] = i1;
>> @@ -72,9 +103,13 @@ static void coroutine_trampoline(int i0, int i1)
>>
>> /* Initialize longjmp environment and switch back the caller */
>> if (!sigsetjmp(self->env, 0)) {
>> + start_switch_fiber(&fake_stack_save,
>> + leader.stack, leader.stack_size);
>> siglongjmp(*(sigjmp_buf *)co->entry_arg, 1);
>> }
>>
>> + finish_switch_fiber(fake_stack_save);
>> +
>> while (true) {
>> co->entry(co->entry_arg);
>> qemu_coroutine_switch(co, co->caller, COROUTINE_TERMINATE);
>> @@ -87,6 +122,7 @@ Coroutine *qemu_coroutine_new(void)
>> ucontext_t old_uc, uc;
>> sigjmp_buf old_env;
>> union cc_arg arg = {0};
>> + void *fake_stack_save = NULL;
>>
>> /* The ucontext functions preserve signal masks which incurs a
>> * system call overhead. sigsetjmp(buf, 0)/siglongjmp() does not
>> @@ -122,8 +158,12 @@ Coroutine *qemu_coroutine_new(void)
>>
>> /* swapcontext() in, siglongjmp() back out */
>> if (!sigsetjmp(old_env, 0)) {
>> + start_switch_fiber(&fake_stack_save, co->stack, co->stack_size);
>> swapcontext(&old_uc, &uc);
>> }
>> +
>> + finish_switch_fiber(fake_stack_save);
>> +
>> return &co->base;
>> }
>>
>> @@ -169,13 +209,19 @@ qemu_coroutine_switch(Coroutine *from_, Coroutine *to_,
>> CoroutineUContext *from = DO_UPCAST(CoroutineUContext, base, from_);
>> CoroutineUContext *to = DO_UPCAST(CoroutineUContext, base, to_);
>> int ret;
>> + void *fake_stack_save = NULL;
>>
>> current = to_;
>>
>> ret = sigsetjmp(from->env, 0);
>> if (ret == 0) {
>> + start_switch_fiber(action == COROUTINE_TERMINATE ?
>> + NULL : &fake_stack_save, to->stack,
>> to->stack_size);
>> siglongjmp(to->env, action);
>> }
>> +
>> + finish_switch_fiber(fake_stack_save);
>> +
>> return ret;
>> }
>>
>>
>
--
Marc-André Lureau
