Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751707AbaG1FWn (ORCPT ); Mon, 28 Jul 2014 01:22:43 -0400 Received: from mail7.hitachi.co.jp ([133.145.228.42]:59894 "EHLO mail7.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750867AbaG1FWi (ORCPT ); Mon, 28 Jul 2014 01:22:38 -0400 Subject: [PATCH ftrace/core v4 2/4] ftrace, kprobes: Support IPMODIFY flag to find IP modify conflict From: Masami Hiramatsu To: Steven Rostedt , Josh Poimboeuf Cc: Ingo Molnar , Namhyung Kim , Ananth N Mavinakayanahalli , Linux Kernel Mailing List Date: Mon, 28 Jul 2014 05:22:29 +0000 Message-ID: <20140728052229.29491.71944.stgit@kbuild-fedora.novalocal> In-Reply-To: <20140728052215.29491.23631.stgit@kbuild-fedora.novalocal> References: <20140728052215.29491.23631.stgit@kbuild-fedora.novalocal> User-Agent: StGit/0.17-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Introduce FTRACE_OPS_FL_IPMODIFY to avoid conflict among ftrace users who may modify regs->ip to change the execution path. If two or more users modify the regs->ip on the same function entry, one of them will be broken. So they must add IPMODIFY flag and make sure that ftrace_set_filter_ip() succeeds. Note that ftrace doesn't allow ftrace_ops which has IPMODIFY flag to have notrace hash, and the ftrace_ops must have a filter hash (so that the ftrace_ops can hook only specific entries), because it strongly depends on the address and must be allowed for only few selected functions. Changes in v4: - Split kprobe's part from this patch. - Add no-notrace hash check. - Reject if the filter_hash is empty. Since IPMODIFY action is very address sensitive, empty hash (means hooking all functions) must not be allowed. Changes in v3: - Update for the latest ftrace/core. - Add a comment about FTRACE_OPS_FL_* attribute flags. - Don't check FTRACE_OPS_FL_SAVE_REGS in __ftrace_hash_update_ipmodify(). - Fix comments. Changes in v2: - Add a description how __ftrace_hash_update_ipmodify() will handle the given hashes (NULL and EMPTY_HASH cases). - Clear FTRACE_OPS_FL_ENABLED after calling __unregister_ftrace_function() in error path. Signed-off-by: Masami Hiramatsu Cc: Ananth N Mavinakayanahalli Cc: Steven Rostedt Cc: Josh Poimboeuf Cc: Namhyung Kim --- Documentation/trace/ftrace.txt | 5 + include/linux/ftrace.h | 16 ++++ kernel/trace/ftrace.c | 143 +++++++++++++++++++++++++++++++++++++++- 3 files changed, 160 insertions(+), 4 deletions(-) diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt index 2479b2a..aa7e5bd 100644 --- a/Documentation/trace/ftrace.txt +++ b/Documentation/trace/ftrace.txt @@ -234,6 +234,11 @@ of ftrace. Here is a list of some of the key files: will be displayed on the same line as the function that is returning registers. + If the callback registered to be traced by a function with + the "ip modify" attribute (thus the regs->ip can be changed), + an 'I' will be displayed on the same line as the function that + can be overridden. + function_profile_enabled: When set it will enable all functions with either the function diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 6bb5e3f..905ec9f 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -59,6 +59,11 @@ typedef void (*ftrace_func_t)(unsigned long ip, unsigned long parent_ip, /* * FTRACE_OPS_FL_* bits denote the state of ftrace_ops struct and are * set in the flags member. + * CONTROL, SAVE_REGS, SAVE_REGS_IF_SUPPORTED, RECURSION_SAFE, STUB and + * IPMODIFY are a kind of attribute flags which can be set only before + * registering the ftrace_ops, and can not be modified while registered. + * Changing those attribute flags after regsitering ftrace_ops will + * cause unexpected results. * * ENABLED - set/unset when ftrace_ops is registered/unregistered * DYNAMIC - set when ftrace_ops is registered to denote dynamically @@ -89,6 +94,10 @@ typedef void (*ftrace_func_t)(unsigned long ip, unsigned long parent_ip, * INITIALIZED - The ftrace_ops has already been initialized (first use time * register_ftrace_function() is called, it will initialized the ops) * DELETED - The ops are being deleted, do not let them be registered again. + * IPMODIFY - The ops can modify the IP register. This can only be set with + * SAVE_REGS. If another ops is already registered for any of the + * functions that this ops will be registered for, then this ops + * will fail to register or set_filter_ip. */ enum { FTRACE_OPS_FL_ENABLED = 1 << 0, @@ -100,6 +109,7 @@ enum { FTRACE_OPS_FL_STUB = 1 << 6, FTRACE_OPS_FL_INITIALIZED = 1 << 7, FTRACE_OPS_FL_DELETED = 1 << 8, + FTRACE_OPS_FL_IPMODIFY = 1 << 9, }; /* @@ -281,6 +291,7 @@ extern int ftrace_nr_registered_ops(void); * ENABLED - the function is being traced * REGS - the record wants the function to save regs * REGS_EN - the function is set up to save regs. + * IPMODIFY - the record allows for the IP address to be changed. * * When a new ftrace_ops is registered and wants a function to save * pt_regs, the rec->flag REGS is set. When the function has been @@ -294,10 +305,11 @@ enum { FTRACE_FL_REGS_EN = (1UL << 29), FTRACE_FL_TRAMP = (1UL << 28), FTRACE_FL_TRAMP_EN = (1UL << 27), + FTRACE_FL_IPMODIFY = (1UL << 26), }; -#define FTRACE_REF_MAX_SHIFT 27 -#define FTRACE_FL_BITS 5 +#define FTRACE_REF_MAX_SHIFT 26 +#define FTRACE_FL_BITS 6 #define FTRACE_FL_MASKED_BITS ((1UL << FTRACE_FL_BITS) - 1) #define FTRACE_FL_MASK (FTRACE_FL_MASKED_BITS << FTRACE_REF_MAX_SHIFT) #define FTRACE_REF_MAX ((1UL << FTRACE_REF_MAX_SHIFT) - 1) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 979bd8c..788c500 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -1292,6 +1292,9 @@ ftrace_hash_rec_disable(struct ftrace_ops *ops, int filter_hash); static void ftrace_hash_rec_enable(struct ftrace_ops *ops, int filter_hash); +static int ftrace_hash_ipmodify_update(struct ftrace_ops *ops, + struct ftrace_hash *new_hash); + static int ftrace_hash_move(struct ftrace_ops *ops, int enable, struct ftrace_hash **dst, struct ftrace_hash *src) @@ -1303,8 +1306,13 @@ ftrace_hash_move(struct ftrace_ops *ops, int enable, struct ftrace_hash *new_hash; int size = src->count; int bits = 0; + int ret; int i; + /* Reject setting notrace hash on IPMODIFY ftrace_ops */ + if (ops->flags & FTRACE_OPS_FL_IPMODIFY && !enable) + return -EINVAL; + /* * If the new source is empty, just free dst and assign it * the empty_hash. @@ -1338,6 +1346,16 @@ ftrace_hash_move(struct ftrace_ops *ops, int enable, } update: + /* Make sure this can be applied if it is IPMODIFY ftrace_ops */ + if (enable) { + /* IPMODIFY should be updated only when filter_hash updating */ + ret = ftrace_hash_ipmodify_update(ops, new_hash); + if (ret < 0) { + free_ftrace_hash(new_hash); + return ret; + } + } + /* * Remove the current set, update the hash and add * them back. @@ -1682,6 +1700,115 @@ static void ftrace_hash_rec_enable(struct ftrace_ops *ops, __ftrace_hash_rec_update(ops, filter_hash, 1); } +/* + * Try to update IPMODIFY flag on each ftrace_rec. Return 0 if it is OK + * or no-needed to update, -EBUSY if it detects a conflict of the flag + * on a ftrace_rec, and -EINVAL if the new_hash tries to trace all recs. + * Note that old_hash and new_hash has below meanings + * - If the hash is NULL, it hits all recs (if IPMODIFY is set, this is rejected) + * - If the hash is EMPTY_HASH, it hits nothing + * - Anything else hits the recs which match the hash entries. + */ +static int __ftrace_hash_update_ipmodify(struct ftrace_ops *ops, + struct ftrace_hash *old_hash, + struct ftrace_hash *new_hash) +{ + struct ftrace_page *pg; + struct dyn_ftrace *rec, *end = NULL; + int in_old, in_new; + + /* Only update if the ops has been registered */ + if (!(ops->flags & FTRACE_OPS_FL_ENABLED)) + return 0; + + if (!(ops->flags & FTRACE_OPS_FL_IPMODIFY)) + return 0; + + /* + * Since the IPMODIFY is very address sensitive action, we do not allow + * ftrace_ops to set all functions to new hash. + */ + if (!new_hash || !old_hash) + return -EINVAL; + + /* Update rec->flags */ + do_for_each_ftrace_rec(pg, rec) { + /* We need to update only differences of filter_hash */ + in_old = !!ftrace_lookup_ip(old_hash, rec->ip); + in_new = !!ftrace_lookup_ip(new_hash, rec->ip); + if (in_old == in_new) + continue; + + if (in_new) { + /* New entries must ensure no others are using it */ + if (rec->flags & FTRACE_FL_IPMODIFY) + goto rollback; + rec->flags |= FTRACE_FL_IPMODIFY; + } else /* Removed entry */ + rec->flags &= ~FTRACE_FL_IPMODIFY; + } while_for_each_ftrace_rec(); + + return 0; + +rollback: + end = rec; + + /* Roll back what we did above */ + do_for_each_ftrace_rec(pg, rec) { + if (rec == end) + goto err_out; + + in_old = !!ftrace_lookup_ip(old_hash, rec->ip); + in_new = !!ftrace_lookup_ip(new_hash, rec->ip); + if (in_old == in_new) + continue; + + if (in_new) + rec->flags &= ~FTRACE_FL_IPMODIFY; + else + rec->flags |= FTRACE_FL_IPMODIFY; + } while_for_each_ftrace_rec(); + +err_out: + return -EBUSY; +} + +static int ftrace_hash_ipmodify_enable(struct ftrace_ops *ops) +{ + struct ftrace_hash *hash = ops->filter_hash; + + if (ftrace_hash_empty(hash)) + hash = NULL; + + return __ftrace_hash_update_ipmodify(ops, EMPTY_HASH, hash); +} + +/* Disabling always succeeds */ +static void ftrace_hash_ipmodify_disable(struct ftrace_ops *ops) +{ + struct ftrace_hash *hash = ops->filter_hash; + + if (ftrace_hash_empty(hash)) + hash = NULL; + + __ftrace_hash_update_ipmodify(ops, hash, EMPTY_HASH); +} + +static int ftrace_hash_ipmodify_update(struct ftrace_ops *ops, + struct ftrace_hash *new_hash) +{ + struct ftrace_hash *old_hash = ops->filter_hash; + + if (ftrace_hash_empty(old_hash)) + old_hash = NULL; + + if (ftrace_hash_empty(new_hash)) + new_hash = NULL; + + return __ftrace_hash_update_ipmodify(ops, old_hash, new_hash); +} + + static void print_ip_ins(const char *fmt, unsigned char *p) { int i; @@ -2322,6 +2449,15 @@ static int ftrace_startup(struct ftrace_ops *ops, int command) ops->flags |= FTRACE_OPS_FL_ENABLED; + ret = ftrace_hash_ipmodify_enable(ops); + if (ret < 0) { + /* Rollback registration process */ + __unregister_ftrace_function(ops); + ftrace_start_up--; + ops->flags &= ~FTRACE_OPS_FL_ENABLED; + return ret; + } + ftrace_hash_rec_enable(ops, 1); ftrace_startup_enable(command); @@ -2348,6 +2484,8 @@ static int ftrace_shutdown(struct ftrace_ops *ops, int command) */ WARN_ON_ONCE(ftrace_start_up < 0); + /* Disabling ipmodify never fails */ + ftrace_hash_ipmodify_disable(ops); ftrace_hash_rec_disable(ops, 1); ops->flags &= ~FTRACE_OPS_FL_ENABLED; @@ -2898,9 +3036,10 @@ static int t_show(struct seq_file *m, void *v) seq_printf(m, "%ps", (void *)rec->ip); if (iter->flags & FTRACE_ITER_ENABLED) { - seq_printf(m, " (%ld)%s", + seq_printf(m, " (%ld)%s%s", ftrace_rec_count(rec), - rec->flags & FTRACE_FL_REGS ? " R" : " "); + rec->flags & FTRACE_FL_REGS ? " R" : " ", + rec->flags & FTRACE_FL_IPMODIFY ? " I" : " "); if (rec->flags & FTRACE_FL_TRAMP_EN) { struct ftrace_ops *ops; -- 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/