Currently, unwinding the unix libraries (or full ELF builds) requires having libunwind available.
When starting up a wine environment, an exception of type `RPC_S_SERVER_UNAVAILABLE` gets thrown - and if libunwind isn't available, this breaks the startup. Thus, currently on ARM/ARM64, libunwind is essentially mandatory.
Additionally, at least on ARM, libunwind seems brittle (commits in latest git master breaks the unwinding use cases in Wine, see e.g. https://github.com/libunwind/libunwind/pull/203#issuecomment-984126066.
This MR tries to resolve all of this, by including the preexisting DWARF parser from x86_64 in the aarch64 version too. This bit was mostly quite straightforward.
For ARM, libunwind has currently relied on DWARF debug info in the `.debug_frame` section, since Linux on ARM doesn't use DWARF for runtime unwinding. This MR adds ARM EHABI unwind opcodes where necessary, and adds a local reimplementation of an ARM EHABI/EXIDX/EXTBL unwinder, similar to the DWARF one.
With these changes, unwinding on both ARM and ARM64 seems to work fine, even without libunwind.
See the individual commit messages for more commentary on the decisions taken so far (I've tried to write up all relevant considerations there - it's a fair amount of commentery).
A couple open questions:
- So far, the shared DWARF code was put in a header, `dwarf.h`. Do you want to make this a proper standalone `.c` file too?
- I wrote the ARM EHABI unwind code mostly with `stdint.h` types like `uint32_t`(as it's in the ntdll/unix directory anyway), but I can rewrite it with `DWORD` or similar if that's preferred.
- The ARM EHABI opcodes are enabled for `defined(__arm__) && defined(__ELF__) && defined(__GNUC__) && !defined(__SEH__) && !defined(__ARM_DWARF_EH__)` - there's no define to check for for knowing it's used and enabled, but it has to be implicitly assumed if no other other unwind mechanism is signaled.
- The `dl_iterate_phdr` function, used for finding the EXIDX section for locating ARM EHABI unwind info, is used within `#ifdef linux`. It might be available on other OSes too (like FreeBSD etc). Or should I go ahead and add a configure check for it?
CC @julliard @rbernon @AndreRH
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https://gitlab.winehq.org/wine/wine/-/merge_requests/1134
As far as my testing goes, the message box is never shown on Windows when abort() is called with retail runtime is used, regardless of error mode and abort behaviour. That is not the case with _assert which still can show a dialog even in release mode.
It happens rather often that an app meets the error condition during the process exit and that goes silent on Windows while we display the abort dialog on app's exit.
The test program below shows that (and the same behaviour is, e. g., with ucrtbase vs ucrtbased).
```
#include <windows.h>
#include <stdio.h>
#include <stdlib.h>
void CDECL _set_app_type(int app_type);
#define D(name) static typeof(name) *p_##name
#define L(name) p_##name = (void *)GetProcAddress(hdll, #name); if (!p_##name) printf("NULL %s.\n", #name)
D(abort);
D(_set_app_type);
D(_set_abort_behavior);
D(_set_error_mode);
int main(int argc, char *argv[])
{
HMODULE hdll = LoadLibraryA("msvcrt.dll");
printf("hdll %p.\n", hdll);
L(_set_app_type);
if (!p__set_app_type)
if (!(p__set_app_type = (void *)GetProcAddress(hdll, "__set_app_type")))
printf("NULL p__set_app_type.\n");
L(abort);
L(_set_abort_behavior);
L(_set_error_mode);
p__set_app_type(2);
if (p__set_abort_behavior)
p__set_abort_behavior(_WRITE_ABORT_MSG, _WRITE_ABORT_MSG);
p__set_error_mode(_OUT_TO_MSGBOX);
p_abort();
}
```
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https://gitlab.winehq.org/wine/wine/-/merge_requests/1128
On Fri Oct 21 09:44:38 2022 +0000, Rémi Bernon wrote:
> I suggested to do that so we can use these tokens in the macros, which
> need to stringify their value for the `.cfi_escape` strings.
Oh, I see - thanks, that makes sense.
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https://gitlab.winehq.org/wine/wine/-/merge_requests/1065#note_11683
On Fri Oct 21 09:29:30 2022 +0000, Martin Storsjö wrote:
> Out of curiosity - was there any specific reason for changing these
> enums into defines (or was this maybe an artifact from how this patch
> evolved from earlier forms)?
I suggested to do that so we can use these tokens in the macros, which need to stringify their value for the `.cfi_escape` strings.
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https://gitlab.winehq.org/wine/wine/-/merge_requests/1065#note_11674