linux-kernel - [PATCH] x86/hw_breakpoints, kprobes: Remove kprobes ifdeffery

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Date:   Sun, 27 Jan 2019 14:12:37 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     X86 ML <x86@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Frederic Weisbecker <frederic@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH] x86/hw_breakpoints, kprobes: Remove kprobes ifdeffery

From: Borislav Petkov <bp@...e.de>

Remove the ifdeffery in the breakpoint parsing arch_build_bp_info() by
adding a within_kprobe_blacklist() stub for the !CONFIG_KPROBES case.

It is returning true when kprobes are not enabled to mean that any
address is within the kprobes blacklist on such kernels and thus not
allow kernel breakpoints on non-kprobes kernels.

Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Frederic Weisbecker <frederic@...nel.org>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/kernel/hw_breakpoint.c | 4 ----
 include/linux/kprobes.h         | 5 +++++
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c
index 7d6f91f2869a..ff9bfd40429e 100644
--- a/arch/x86/kernel/hw_breakpoint.c
+++ b/arch/x86/kernel/hw_breakpoint.c
@@ -261,12 +261,8 @@ static int arch_build_bp_info(struct perf_event *bp,
 		 * allow kernel breakpoints at all.
 		 */
 		if (attr->bp_addr >= TASK_SIZE_MAX) {
-#ifdef CONFIG_KPROBES
 			if (within_kprobe_blacklist(attr->bp_addr))
 				return -EINVAL;
-#else
-			return -EINVAL;
-#endif
 		}
 
 		hw->type = X86_BREAKPOINT_EXECUTE;
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index e07e91daaacc..201f0f2683f2 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -442,6 +442,11 @@ static inline int enable_kprobe(struct kprobe *kp)
 {
 	return -ENOSYS;
 }
+
+static inline bool within_kprobe_blacklist(unsigned long addr)
+{
+	return true;
+}
 #endif /* CONFIG_KPROBES */
 static inline int disable_kretprobe(struct kretprobe *rp)
 {
-- 
2.19.1