uname -m/-p for compat32 binaries

[Kostik Belousov]

Hi,
I intend to commit the following change, that makes sysctls
hw.machine_arch and hw.machine to return "i386" for 32 bit
binaries run on amd64. In particular, 32 bit uname -m and uname -p
print "i386", that is good for i386 jails on amd64 kernels.

I find the change very useful for me, but I wonder why such trivial
modification is not yet done. Can anybody note a possible fallout from
it ?

diff --git a/sys/amd64/amd64/identcpu.c b/sys/amd64/amd64/identcpu.c
index 52e7568..68de22b 100644
--- a/sys/amd64/amd64/identcpu.c
+++ b/sys/amd64/amd64/identcpu.c
@@ -76,8 +76,26 @@ static void print_via_padlock_info(void);
 
 int	cpu_class;
 char machine[] = "amd64";
-SYSCTL_STRING(_hw, HW_MACHINE, machine, CTLFLAG_RD, 
-    machine, 0, "Machine class");
+
+static int
+sysctl_hw_machine(SYSCTL_HANDLER_ARGS)
+{
+#ifdef SCTL_MASK32
+	static const char machine32[] = "i386";
+#endif
+	int error;
+
+#ifdef SCTL_MASK32
+	if ((req->flags & SCTL_MASK32) != 0)
+		error = SYSCTL_OUT(req, machine32, sizeof(machine32));
+	else
+#endif
+		error = SYSCTL_OUT(req, machine, sizeof(machine));
+	return (error);
+
+}
+SYSCTL_PROC(_hw, HW_MACHINE, machine, CTLTYPE_STRING | CTLFLAG_RD,
+    NULL, 0, sysctl_hw_machine, "A", "Machine class");
 
 static char cpu_model[128];
 SYSCTL_STRING(_hw, HW_MODEL, model, CTLFLAG_RD, 
diff --git a/sys/kern/kern_mib.c b/sys/kern/kern_mib.c
index 7ef580f..0b7d27f 100644
--- a/sys/kern/kern_mib.c
+++ b/sys/kern/kern_mib.c
@@ -232,9 +232,31 @@ sysctl_hw_pagesizes(SYSCTL_HANDLER_ARGS)
 SYSCTL_PROC(_hw, OID_AUTO, pagesizes, CTLTYPE_ULONG | CTLFLAG_RD,
     NULL, 0, sysctl_hw_pagesizes, "LU", "Supported page sizes");
 
-static char	machine_arch[] = MACHINE_ARCH;
-SYSCTL_STRING(_hw, HW_MACHINE_ARCH, machine_arch, CTLFLAG_RD,
-    machine_arch, 0, "System architecture");
+static int
+sysctl_hw_machine_arch(SYSCTL_HANDLER_ARGS)
+{
+	static const char machine_arch[] = MACHINE_ARCH;
+#ifdef SCTL_MASK32
+	static const char machine_arch32[] = 
+#if defined(__amd64__) || defined(__ia64__)
+		"i386";
+#else
+		MACHINE_ARCH;
+#endif
+#endif
+	int error;
+
+#ifdef SCTL_MASK32
+	if ((req->flags & SCTL_MASK32) != 0)
+		error = SYSCTL_OUT(req, machine_arch32, sizeof(machine_arch32));
+	else
+#endif
+		error = SYSCTL_OUT(req, machine_arch, sizeof(machine_arch));
+	return (error);
+
+}
+SYSCTL_PROC(_hw, HW_MACHINE_ARCH, machine_arch, CTLTYPE_STRING | CTLFLAG_RD,
+    NULL, 0, sysctl_hw_machine_arch, "A", "System architecture");
 
 static int
 sysctl_hostname(SYSCTL_HANDLER_ARGS)
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