Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753843AbbLIVo2 (ORCPT ); Wed, 9 Dec 2015 16:44:28 -0500 Received: from smtp.outflux.net ([198.145.64.163]:46355 "EHLO smtp.outflux.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753264AbbLIVoV (ORCPT ); Wed, 9 Dec 2015 16:44:21 -0500 From: Kees Cook To: linux-kernel@vger.kernel.org Cc: Kees Cook , Ingo Molnar , Andy Lutomirski , "H. Peter Anvin" , Michael Ellerman , Mathias Krause , Thomas Gleixner , x86@kernel.org, Arnd Bergmann , PaX Team , Emese Revfy , kernel-hardening@lists.openwall.com, linux-arch Subject: [PATCH v3 4/8] init: create cmdline param to disable readonly Date: Wed, 9 Dec 2015 13:43:20 -0800 Message-Id: <1449697404-21076-5-git-send-email-keescook@chromium.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1449697404-21076-1-git-send-email-keescook@chromium.org> References: <1449697404-21076-1-git-send-email-keescook@chromium.org> X-HELO: www.outflux.net Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3422 Lines: 107 It may be useful to debug writes to the readonly sections of memory, so provide a cmdline "rodata=off" to allow for this. This can be expanded in the future to support "log" and "write" modes, but that will need to be architecture-specific. Suggested-by: H. Peter Anvin Signed-off-by: Kees Cook --- Documentation/kernel-parameters.txt | 4 ++++ init/main.c | 27 +++++++++++++++++++++++---- kernel/debug/kdb/kdb_bp.c | 4 +--- 3 files changed, 28 insertions(+), 7 deletions(-) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 742f69d18fc8..21cf76dbba90 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -3409,6 +3409,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted. ro [KNL] Mount root device read-only on boot + rodata= [KNL] + on Mark read-only kernel memory as read-only (default). + off Leave read-only kernel memory writable for debugging. + root= [KNL] Root filesystem See name_to_dev_t comment in init/do_mounts.c. diff --git a/init/main.c b/init/main.c index 9e64d7097f1a..fbafa271531c 100644 --- a/init/main.c +++ b/init/main.c @@ -93,9 +93,6 @@ static int kernel_init(void *); extern void init_IRQ(void); extern void fork_init(void); extern void radix_tree_init(void); -#ifndef CONFIG_DEBUG_RODATA -static inline void mark_rodata_ro(void) { } -#endif /* * Debug helper: via this flag we know that we are in 'early bootup code' @@ -929,6 +926,28 @@ static int try_to_run_init_process(const char *init_filename) static noinline void __init kernel_init_freeable(void); +#ifdef CONFIG_DEBUG_RODATA +static bool rodata_enabled = true; +static int __init set_debug_rodata(char *str) +{ + return strtobool(str, &rodata_enabled); +} +__setup("rodata=", set_debug_rodata); + +static void mark_readonly(void) +{ + if (rodata_enabled) + mark_rodata_ro(); + else + pr_info("Kernel memory protection disabled.\n"); +} +#else +static inline void mark_readonly(void) +{ + pr_warn("This architecture does not have kernel memory protection.\n"); +} +#endif + static int __ref kernel_init(void *unused) { int ret; @@ -937,7 +956,7 @@ static int __ref kernel_init(void *unused) /* need to finish all async __init code before freeing the memory */ async_synchronize_full(); free_initmem(); - mark_rodata_ro(); + mark_readonly(); system_state = SYSTEM_RUNNING; numa_default_policy(); diff --git a/kernel/debug/kdb/kdb_bp.c b/kernel/debug/kdb/kdb_bp.c index e1dbf4a2c69e..90ff129c88a2 100644 --- a/kernel/debug/kdb/kdb_bp.c +++ b/kernel/debug/kdb/kdb_bp.c @@ -153,13 +153,11 @@ static int _kdb_bp_install(struct pt_regs *regs, kdb_bp_t *bp) } else { kdb_printf("%s: failed to set breakpoint at 0x%lx\n", __func__, bp->bp_addr); -#ifdef CONFIG_DEBUG_RODATA if (!bp->bp_type) { kdb_printf("Software breakpoints are unavailable.\n" - " Change the kernel CONFIG_DEBUG_RODATA=n\n" + " Boot the kernel with rodata=off\n" " OR use hw breaks: help bph\n"); } -#endif return 1; } return 0; -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/