From 56f15e518cfdc732bd4e4da90e0c9cf2fc4e7c1b Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Mon, 27 Jan 2014 10:25:39 +0100 Subject: [PATCH] s390/uaccess: introduce 'uaccesspt' kernel parameter The uaccesspt kernel parameter allows to enforce using the uaccess page table walk variant. This is mainly for debugging purposes, so this mode can also be enabled on machines which support the mvcos instruction. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky --- arch/s390/lib/uaccess_mvcos.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/arch/s390/lib/uaccess_mvcos.c b/arch/s390/lib/uaccess_mvcos.c index e2685ff2ec4b..ae97b8df11aa 100644 --- a/arch/s390/lib/uaccess_mvcos.c +++ b/arch/s390/lib/uaccess_mvcos.c @@ -241,9 +241,22 @@ long __strncpy_from_user(char *dst, const char __user *src, long count) } EXPORT_SYMBOL(__strncpy_from_user); +/* + * The uaccess page tabe walk variant can be enforced with the "uaccesspt" + * kernel parameter. This is mainly for debugging purposes. + */ +static int force_uaccess_pt __initdata; + +static int __init parse_uaccess_pt(char *__unused) +{ + force_uaccess_pt = 1; + return 0; +} +early_param("uaccesspt", parse_uaccess_pt); + static int __init uaccess_init(void) { - if (IS_ENABLED(CONFIG_32BIT) || !test_facility(27)) + if (IS_ENABLED(CONFIG_32BIT) || force_uaccess_pt || !test_facility(27)) static_key_slow_dec(&have_mvcos); return 0; }