[PATCH 0/1] MR10319: server: On ARM64, only list 32-bit ARM as a supported architecture if the CPU supports it.

[Brendan Shanks (＠bshanks)]

Using `personality(PER_LINUX32)` was inspired by a [mailing list thread](https://www.spinics.net/lists/arm-kernel/msg746756.html) about detecting AArch32 support from an AArch64 process in user space. The `personality` call only succeeds when `ID_AA64PFR0_EL1` indicates that the CPU supports AArch32 in EL0 (`system_supports_32bit_el0()` in the kernel).

I unfortunately don't have AArch32-capable hardware to test this on, but on AArch64-only CPUs the `personality` call fails as expected.
Also, on AArch64-only CPUs this matches the current behavior of Windows 11 which has dropped support for 32-bit ARM on all hardware.

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/10319

[PATCH 1/1] server: On ARM64, only list 32-bit ARM as a supported architecture if the CPU supports it.

[Brendan Shanks]

From: Brendan Shanks <[e-mail]>

---
 configure.ac      |  1 +
 server/registry.c | 20 +++++++++++++++++++-
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index c28bb4c3703..2cf181c3c9e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -778,6 +778,7 @@ AC_CHECK_HEADERS(\
 	sys/modem.h \
 	sys/mtio.h \
 	sys/param.h \
+	sys/personality.h \
 	sys/prctl.h \
 	sys/ptrace.h \
 	sys/queue.h \
diff --git a/server/registry.c b/server/registry.c
index 9642116d40b..28da803b230 100644
--- a/server/registry.c
+++ b/server/registry.c
@@ -29,6 +29,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <limits.h>
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdarg.h>
 #include <string.h>
@@ -36,6 +37,9 @@
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
+#ifdef HAVE_SYS_PERSONALITY_H
+#include <sys/personality.h>
+#endif
 
 #include "ntstatus.h"
 #include "object.h"
@@ -1844,6 +1848,20 @@ static WCHAR *format_user_registry_path( const struct sid *sid, struct unicode_s
     return ascii_to_unicode_str( buffer, path );
 }
 
+#ifdef __aarch64__
+static bool supports_aarch32(void)
+{
+#if defined(HAVE_SYS_PERSONALITY_H)
+    int old = personality(PER_LINUX32);
+    if (old == -1)
+        return false;
+    personality(old);
+    return true;
+#endif
+    return false;
+}
+#endif
+
 static void init_supported_machines(void)
 {
     unsigned int count = 0;
@@ -1859,7 +1877,7 @@ static void init_supported_machines(void)
     {
         supported_machines[count++] = IMAGE_FILE_MACHINE_ARM64;
         supported_machines[count++] = IMAGE_FILE_MACHINE_I386;
-        supported_machines[count++] = IMAGE_FILE_MACHINE_ARMNT;
+        if (supports_aarch32()) supported_machines[count++] = IMAGE_FILE_MACHINE_ARMNT;
     }
 #else
 #error Unsupported machine
-- 
GitLab

https://gitlab.winehq.org/wine/wine/-/merge_requests/10319