From 0bc11ed5ab60c135aa764a62c02cd5ea68289de4 Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Thu, 25 Jul 2019 15:24:37 +0900 Subject: [PATCH] kprobes: Allow kprobes coexist with livepatch Allow kprobes which do not modify regs->ip, coexist with livepatch by dropping FTRACE_OPS_FL_IPMODIFY from ftrace_ops. User who wants to modify regs->ip (e.g. function fault injection) must set a dummy post_handler to its kprobes when registering. However, if such regs->ip modifying kprobes is set on a function, that function can not be livepatched. Link: http://lkml.kernel.org/r/156403587671.30117.5233558741694155985.stgit@devnote2 Acked-by: Joe Lawrence Signed-off-by: Masami Hiramatsu Signed-off-by: Steven Rostedt (VMware) --- kernel/kprobes.c | 56 ++++++++++++++++++++++++++++++++++-------------- 1 file changed, 40 insertions(+), 16 deletions(-) diff --git a/kernel/kprobes.c b/kernel/kprobes.c index d9770a5393c8..f57deec96ba1 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -961,9 +961,16 @@ static struct kprobe *alloc_aggr_kprobe(struct kprobe *p) #ifdef CONFIG_KPROBES_ON_FTRACE static struct ftrace_ops kprobe_ftrace_ops __read_mostly = { + .func = kprobe_ftrace_handler, + .flags = FTRACE_OPS_FL_SAVE_REGS, +}; + +static struct ftrace_ops kprobe_ipmodify_ops __read_mostly = { .func = kprobe_ftrace_handler, .flags = FTRACE_OPS_FL_SAVE_REGS | FTRACE_OPS_FL_IPMODIFY, }; + +static int kprobe_ipmodify_enabled; static int kprobe_ftrace_enabled; /* Must ensure p->addr is really on ftrace */ @@ -976,58 +983,75 @@ static int prepare_kprobe(struct kprobe *p) } /* Caller must lock kprobe_mutex */ -static int arm_kprobe_ftrace(struct kprobe *p) +static int __arm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops, + int *cnt) { int ret = 0; - ret = ftrace_set_filter_ip(&kprobe_ftrace_ops, - (unsigned long)p->addr, 0, 0); + ret = ftrace_set_filter_ip(ops, (unsigned long)p->addr, 0, 0); if (ret) { pr_debug("Failed to arm kprobe-ftrace at %pS (%d)\n", p->addr, ret); return ret; } - if (kprobe_ftrace_enabled == 0) { - ret = register_ftrace_function(&kprobe_ftrace_ops); + if (*cnt == 0) { + ret = register_ftrace_function(ops); if (ret) { pr_debug("Failed to init kprobe-ftrace (%d)\n", ret); goto err_ftrace; } } - kprobe_ftrace_enabled++; + (*cnt)++; return ret; err_ftrace: /* - * Note: Since kprobe_ftrace_ops has IPMODIFY set, and ftrace requires a - * non-empty filter_hash for IPMODIFY ops, we're safe from an accidental - * empty filter_hash which would undesirably trace all functions. + * At this point, sinec ops is not registered, we should be sefe from + * registering empty filter. */ - ftrace_set_filter_ip(&kprobe_ftrace_ops, (unsigned long)p->addr, 1, 0); + ftrace_set_filter_ip(ops, (unsigned long)p->addr, 1, 0); return ret; } +static int arm_kprobe_ftrace(struct kprobe *p) +{ + bool ipmodify = (p->post_handler != NULL); + + return __arm_kprobe_ftrace(p, + ipmodify ? &kprobe_ipmodify_ops : &kprobe_ftrace_ops, + ipmodify ? &kprobe_ipmodify_enabled : &kprobe_ftrace_enabled); +} + /* Caller must lock kprobe_mutex */ -static int disarm_kprobe_ftrace(struct kprobe *p) +static int __disarm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops, + int *cnt) { int ret = 0; - if (kprobe_ftrace_enabled == 1) { - ret = unregister_ftrace_function(&kprobe_ftrace_ops); + if (*cnt == 1) { + ret = unregister_ftrace_function(ops); if (WARN(ret < 0, "Failed to unregister kprobe-ftrace (%d)\n", ret)) return ret; } - kprobe_ftrace_enabled--; + (*cnt)--; - ret = ftrace_set_filter_ip(&kprobe_ftrace_ops, - (unsigned long)p->addr, 1, 0); + ret = ftrace_set_filter_ip(ops, (unsigned long)p->addr, 1, 0); WARN_ONCE(ret < 0, "Failed to disarm kprobe-ftrace at %pS (%d)\n", p->addr, ret); return ret; } + +static int disarm_kprobe_ftrace(struct kprobe *p) +{ + bool ipmodify = (p->post_handler != NULL); + + return __disarm_kprobe_ftrace(p, + ipmodify ? &kprobe_ipmodify_ops : &kprobe_ftrace_ops, + ipmodify ? &kprobe_ipmodify_enabled : &kprobe_ftrace_enabled); +} #else /* !CONFIG_KPROBES_ON_FTRACE */ #define prepare_kprobe(p) arch_prepare_kprobe(p) #define arm_kprobe_ftrace(p) (-ENODEV)