bsd-user: define max args in terms of pages

For 32-bit platforms, pass in up to 256k of args. For 64-bit, bump that
to 512k.

Signed-off-by: Kyle Evans <kevans@freebsd.org>
Signed-off-by: Warner Losh <imp@bsdimp.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

bsd-user/qemu.h

@@ -20,6 +20,7 @@
 
 #include "qemu/osdep.h"
 #include "cpu.h"
+#include "qemu/units.h"
 #include "exec/cpu_ldst.h"
 #include "exec/exec-all.h"
 
@@ -101,11 +102,17 @@ extern const char *qemu_uname_release;
 extern unsigned long mmap_min_addr;
 
 /*
- * MAX_ARG_PAGES defines the number of pages allocated for arguments
- * and envelope for the new program. 32 should suffice, this gives
- * a maximum env+arg of 128kB w/4KB pages!
+ * TARGET_ARG_MAX defines the number of bytes allocated for arguments
+ * and envelope for the new program. 256k should suffice for a reasonable
+ * maxiumum env+arg in 32-bit environments, bump it up to 512k for !ILP32
+ * platforms.
  */
-#define MAX_ARG_PAGES 32
+#if TARGET_ABI_BITS > 32
+#define TARGET_ARG_MAX (512 * KiB)
+#else
+#define TARGET_ARG_MAX (256 * KiB)
+#endif
+#define MAX_ARG_PAGES (TARGET_ARG_MAX / TARGET_PAGE_SIZE)
 
 /*
  * This structure is used to hold the arguments that are