| Message ID | 20230213161352.17199-3-pierrick.bouvier@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | Adds support for running QEMU natively on windows-arm64 | expand |
Hi Pierrick, On 13/2/23 17:13, Pierrick Bouvier wrote: > Windows implementation of setjmp/longjmp is done in > C:/WINDOWS/system32/ucrtbase.dll. Alas, on arm64, it seems to *always* > perform stack unwinding, which crashes from generated code. > > By using alternative implementation built in mingw, we avoid doing stack > unwinding and this fixes crash when calling longjmp. > > Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org> > --- > include/sysemu/os-win32.h | 18 ++++++++++++++++-- > 1 file changed, 16 insertions(+), 2 deletions(-) > > diff --git a/include/sysemu/os-win32.h b/include/sysemu/os-win32.h > index 5b38c7bd04..84f62d0a17 100644 > --- a/include/sysemu/os-win32.h > +++ b/include/sysemu/os-win32.h > @@ -51,14 +51,28 @@ typedef struct sockaddr_un { > extern "C" { > #endif > > -#if defined(_WIN64) > +#if defined(__aarch64__) Shouldn't we check for __MINGW64__? #if defined(__aarch64__) && defined(__MINGW64__) > +/* On windows-arm64, setjmp is available in only one variant, and longjmp always > + * does stack unwinding. This crash with generated code. > + * Thus, we use another implementation of setjmp (not windows one), coming from > + * mingw, which never performs stack unwinding. */ > +#undef setjmp > +#undef longjmp > +/* These functions are not declared in setjmp.h because __aarch64__ defines > + * setjmp to _setjmpex instead. However, they are still defined in libmingwex.a, > + * which gets linked automatically. */ So this is not stable. Better would be to check the symbols availability at link-time via meson; see for example glusterfs_ftruncate_has_stat which defines CONFIG_GLUSTERFS_FTRUNCATE_HAS_STAT. A similar check could define CONFIG_MINGW64_HAS_SETJMP_LONGJMP. > +extern int __mingw_setjmp(jmp_buf); > +extern void __attribute__((noreturn)) __mingw_longjmp(jmp_buf, int); > +#define setjmp(env) __mingw_setjmp(env) > +#define longjmp(env, val) __mingw_longjmp(env, val) > +#elif defined(_WIN64) > /* On w64, setjmp is implemented by _setjmp which needs a second parameter. > * If this parameter is NULL, longjump does no stack unwinding. > * That is what we need for QEMU. Passing the value of register rsp (default) > * lets longjmp try a stack unwinding which will crash with generated code. */ > # undef setjmp > # define setjmp(env) _setjmp(env, NULL) > -#endif > +#endif /* __aarch64__ */ > /* QEMU uses sigsetjmp()/siglongjmp() as the portable way to specify > * "longjmp and don't touch the signal masks". Since we know that the > * savemask parameter will always be zero we can safely define these Regards, Phil.
On 2/14/23 08:11, Philippe Mathieu-Daudé wrote: > Hi Pierrick, > > On 13/2/23 17:13, Pierrick Bouvier wrote: >> Windows implementation of setjmp/longjmp is done in >> C:/WINDOWS/system32/ucrtbase.dll. Alas, on arm64, it seems to *always* >> perform stack unwinding, which crashes from generated code. >> >> By using alternative implementation built in mingw, we avoid doing stack >> unwinding and this fixes crash when calling longjmp. >> >> Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org> >> --- >> include/sysemu/os-win32.h | 18 ++++++++++++++++-- >> 1 file changed, 16 insertions(+), 2 deletions(-) >> >> diff --git a/include/sysemu/os-win32.h b/include/sysemu/os-win32.h >> index 5b38c7bd04..84f62d0a17 100644 >> --- a/include/sysemu/os-win32.h >> +++ b/include/sysemu/os-win32.h >> @@ -51,14 +51,28 @@ typedef struct sockaddr_un { >> extern "C" { >> #endif >> >> -#if defined(_WIN64) >> +#if defined(__aarch64__) > > Shouldn't we check for __MINGW64__? > > #if defined(__aarch64__) && defined(__MINGW64__) > I thought QEMU was only compiled using MinGW under Windows, (from CI, that's the case, [1], [2]), but maybe that's a wrong assumption. [1] https://gitlab.com/qemu-project/qemu/-/blob/master/.gitlab-ci.d/windows.yml [2] https://gitlab.com/qemu-project/qemu/-/blob/master/tests/docker/dockerfiles/fedora-win64-cross.docker For windows-arm64, we need an alternative setjmp/longjmp implementation (__builtin_setjmp and __builtin_longjmp in clang are not available), thus, that makes MinGW mandatory, at least for this platform. Would adding this be satisfying? Or better to add this check in Meson? #ifndef __MINGW64__ #error MinGW must be available for this platform #endif >> +/* On windows-arm64, setjmp is available in only one variant, and longjmp always >> + * does stack unwinding. This crash with generated code. >> + * Thus, we use another implementation of setjmp (not windows one), coming from >> + * mingw, which never performs stack unwinding. */ >> +#undef setjmp >> +#undef longjmp >> +/* These functions are not declared in setjmp.h because __aarch64__ defines >> + * setjmp to _setjmpex instead. However, they are still defined in libmingwex.a, >> + * which gets linked automatically. */ > > So this is not stable. Better would be to check the symbols availability > at link-time via meson; see for example glusterfs_ftruncate_has_stat > which defines CONFIG_GLUSTERFS_FTRUNCATE_HAS_STAT. > > A similar check could define CONFIG_MINGW64_HAS_SETJMP_LONGJMP. > You're right, it's not stable. Checking this using meson sounds a good approach. >> +extern int __mingw_setjmp(jmp_buf); >> +extern void __attribute__((noreturn)) __mingw_longjmp(jmp_buf, int); >> +#define setjmp(env) __mingw_setjmp(env) >> +#define longjmp(env, val) __mingw_longjmp(env, val) >> +#elif defined(_WIN64) >> /* On w64, setjmp is implemented by _setjmp which needs a second parameter. >> * If this parameter is NULL, longjump does no stack unwinding. >> * That is what we need for QEMU. Passing the value of register rsp (default) >> * lets longjmp try a stack unwinding which will crash with generated code. */ >> # undef setjmp >> # define setjmp(env) _setjmp(env, NULL) >> -#endif >> +#endif /* __aarch64__ */ >> /* QEMU uses sigsetjmp()/siglongjmp() as the portable way to specify >> * "longjmp and don't touch the signal masks". Since we know that the >> * savemask parameter will always be zero we can safely define these > > Regards, > > Phil.
diff --git a/include/sysemu/os-win32.h b/include/sysemu/os-win32.h index 5b38c7bd04..84f62d0a17 100644 --- a/include/sysemu/os-win32.h +++ b/include/sysemu/os-win32.h @@ -51,14 +51,28 @@ typedef struct sockaddr_un { extern "C" { #endif -#if defined(_WIN64) +#if defined(__aarch64__) +/* On windows-arm64, setjmp is available in only one variant, and longjmp always + * does stack unwinding. This crash with generated code. + * Thus, we use another implementation of setjmp (not windows one), coming from + * mingw, which never performs stack unwinding. */ +#undef setjmp +#undef longjmp +/* These functions are not declared in setjmp.h because __aarch64__ defines + * setjmp to _setjmpex instead. However, they are still defined in libmingwex.a, + * which gets linked automatically. */ +extern int __mingw_setjmp(jmp_buf); +extern void __attribute__((noreturn)) __mingw_longjmp(jmp_buf, int); +#define setjmp(env) __mingw_setjmp(env) +#define longjmp(env, val) __mingw_longjmp(env, val) +#elif defined(_WIN64) /* On w64, setjmp is implemented by _setjmp which needs a second parameter. * If this parameter is NULL, longjump does no stack unwinding. * That is what we need for QEMU. Passing the value of register rsp (default) * lets longjmp try a stack unwinding which will crash with generated code. */ # undef setjmp # define setjmp(env) _setjmp(env, NULL) -#endif +#endif /* __aarch64__ */ /* QEMU uses sigsetjmp()/siglongjmp() as the portable way to specify * "longjmp and don't touch the signal masks". Since we know that the * savemask parameter will always be zero we can safely define these
Windows implementation of setjmp/longjmp is done in C:/WINDOWS/system32/ucrtbase.dll. Alas, on arm64, it seems to *always* perform stack unwinding, which crashes from generated code. By using alternative implementation built in mingw, we avoid doing stack unwinding and this fixes crash when calling longjmp. Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org> --- include/sysemu/os-win32.h | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-)