| Message ID | 20220304161531.1558318-1-martin@martin.st |
|---|---|
| State | New |
| Headers | show |
| Series | [FFmpeg-devel] ntdll: Zero-initialize the syscall_frame used for starting threads on ARM/ARM64 | expand |
| Context | Check | Description |
|---|---|---|
| andriy/configure_aarch64_jetson | warning | Failed to apply patch |
On Fri, 4 Mar 2022, Martin Storsjö wrote: Sorry, I sent this to the entirely wrong mailing list... // Martin
diff --git a/dlls/ntdll/unix/signal_arm.c b/dlls/ntdll/unix/signal_arm.c index a1bcb0ddd32..1fea76f6563 100644 --- a/dlls/ntdll/unix/signal_arm.c +++ b/dlls/ntdll/unix/signal_arm.c @@ -1105,6 +1105,7 @@ void DECLSPEC_HIDDEN call_init_thunk( LPTHREAD_START_ROUTINE entry, void *arg, B ctx = (CONTEXT *)((ULONG_PTR)context.Sp & ~15) - 1; *ctx = context; ctx->ContextFlags = CONTEXT_FULL; + memset( frame, 0, sizeof(*frame) ); NtSetContextThread( GetCurrentThread(), ctx ); frame->sp = (DWORD)ctx; diff --git a/dlls/ntdll/unix/signal_arm64.c b/dlls/ntdll/unix/signal_arm64.c index 94f280e218a..1df97f16f13 100644 --- a/dlls/ntdll/unix/signal_arm64.c +++ b/dlls/ntdll/unix/signal_arm64.c @@ -1202,6 +1202,7 @@ void DECLSPEC_HIDDEN call_init_thunk( LPTHREAD_START_ROUTINE entry, void *arg, B ctx = (CONTEXT *)((ULONG_PTR)context.Sp & ~15) - 1; *ctx = context; ctx->ContextFlags = CONTEXT_FULL; + memset( frame, 0, sizeof(*frame) ); NtSetContextThread( GetCurrentThread(), ctx ); frame->sp = (ULONG64)ctx;
This fixes an inconsistency since fed7e7a78b4bea183d0cbb107953e275f17baa4f (ntdll: Simulate a syscall return when starting a thread); in that commit, on i386 and x86_64, the syscall_frame used for starting the thread was zeroed with a memset, while it wasn't on arm and arm64. This had a noticable effect on float maths, where the uninitialized frame->restore_flags field could have the CONTEXT_FLOATING_POINT bit set. (call_init_thunk only ORs in CONTEXT_INTEGER into the restore_flags field, on all architectures). If that bit was set, it would restore uninitialized data into the fpscr register, possibly setting the FPU in a nondefault rounding mode. Signed-off-by: Martin Storsjö <martin@martin.st> --- dlls/ntdll/unix/signal_arm.c | 1 + dlls/ntdll/unix/signal_arm64.c | 1 + 2 files changed, 2 insertions(+)