uname -m/-p for compat32 binaries

[Kostik Belousov]

On Tue, Jul 20, 2010 at 03:48:57PM -0500, Nathan Whitehorn wrote:
> On 07/20/10 08:07, John Baldwin wrote:
> >On Monday, July 19, 2010 5:30:54 pm Kostik Belousov wrote:
> >   
> >>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 ?
> >>     
> >Presumably ia64 and powerpc64 would need a similar change as well?  It 
> >looks
> >fine to me.  I suspect Y! used the UNAME_* approach as it didn't add yet-
> >another local diff to maintain in the kernel, and the uname fixes at Y! 
> >might
> >have predated SCTL_MASK32.
> >   
> Maybe it makes sense to define a MACHINE_ARCH32 in machine/param.h, as 
> is done for ELF_ARCH32 in machine/elf.h? This would keep the MI code in 
> the kernel MI, and ever-so-slightly simplify implementation for ia64, 
> mips, and powerpc64. Thanks for doing this!

See below. Also, I painted red another wall, adding a sysctl to turn
the adaptive behaviour off.

diff --git a/sys/amd64/amd64/identcpu.c b/sys/amd64/amd64/identcpu.c
index 52e7568..914f4d2 100644
--- a/sys/amd64/amd64/identcpu.c
+++ b/sys/amd64/amd64/identcpu.c
@@ -76,8 +76,28 @@ 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");
+
+extern int adaptive_machine_arch;
+
+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 && adaptive_machine_arch)
+		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/amd64/include/param.h b/sys/amd64/include/param.h
index c940597..9a742f9 100644
--- a/sys/amd64/include/param.h
+++ b/sys/amd64/include/param.h
@@ -59,6 +59,9 @@
 #ifndef MACHINE_ARCH
 #define	MACHINE_ARCH	"amd64"
 #endif
+#ifndef MACHINE_ARCH32
+#define	MACHINE_ARCH32	"i386"
+#endif
 
 #if defined(SMP) || defined(KLD_MODULE)
 #define MAXCPU		32
diff --git a/sys/ia64/include/param.h b/sys/ia64/include/param.h
index ba26290..36b27e0 100644
--- a/sys/ia64/include/param.h
+++ b/sys/ia64/include/param.h
@@ -57,6 +57,9 @@
 #ifndef MACHINE_ARCH
 #define	MACHINE_ARCH	"ia64"
 #endif
+#ifndef MACHINE_ARCH32
+#define	MACHINE_ARCH32	"i386"
+#endif
 
 #if defined(SMP) || defined(KLD_MODULE)
 #define	MAXCPU		32
diff --git a/sys/kern/kern_mib.c b/sys/kern/kern_mib.c
index 7ef580f..3bfecea 100644
--- a/sys/kern/kern_mib.c
+++ b/sys/kern/kern_mib.c
@@ -232,9 +232,28 @@ 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");
+int adaptive_machine_arch = 1;
+static int
+sysctl_hw_machine_arch(SYSCTL_HANDLER_ARGS)
+{
+	int error;
+	static const char machine_arch[] = MACHINE_ARCH;
+#ifdef SCTL_MASK32
+	static const char machine_arch32[] = MACHINE_ARCH32;
+
+	if ((req->flags & SCTL_MASK32) != 0 && adaptive_machine_arch)
+		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");
+SYSCTL_INT(_debug, OID_AUTO, adaptive_machine_arch, CTLFLAG_RW,
+    &adaptive_machine_arch, 1,
+    "Adapt reported machine architecture to the ABI of the binary");
 
 static int
 sysctl_hostname(SYSCTL_HANDLER_ARGS)
diff --git a/sys/powerpc/include/param.h b/sys/powerpc/include/param.h
index 4aeabe7..91bb238 100644
--- a/sys/powerpc/include/param.h
+++ b/sys/powerpc/include/param.h
@@ -61,6 +61,11 @@
 #endif
 #endif
 #define	MID_MACHINE	MID_POWERPC
+#ifdef __powerpc64__
+#ifndef	MACHINE_ARCH32
+#define	MACHINE_ARCH32	"powerpc"
+#endif
+#endif
 
 #if defined(SMP) || defined(KLD_MODULE)
 #define	MAXCPU		2
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