[RFC PATCH v2 4/5] powerpc/lib: Add LKDTM accessor for patching addr

From: "Christopher M. Riedl" <cmr@informatik.wtf>
To: linuxppc-dev@lists.ozlabs.org, kernel-hardening@lists.openwall.com
Subject: [RFC PATCH v2 4/5] powerpc/lib: Add LKDTM accessor for patching addr
Date: Tue, 28 Apr 2020 21:05:30 -0500	[thread overview]
Message-ID: <20200429020531.20684-5-cmr@informatik.wtf> (raw)
In-Reply-To: <20200429020531.20684-1-cmr@informatik.wtf>

When live patching a STRICT_RWX kernel, a mapping is installed at a
"patching address" with temporary write permissions. Provide a
LKDTM-only accessor function for this address in preparation for a LKDTM
test which attempts to "hijack" this mapping by writing to it from
another CPU.

Signed-off-by: Christopher M. Riedl <cmr@informatik.wtf>
---
 arch/powerpc/lib/code-patching.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index 26f06cdb5d7e..cfbdef90384e 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -46,6 +46,13 @@ int raw_patch_instruction(unsigned int *addr, unsigned int instr)
 static struct mm_struct *patching_mm __ro_after_init;
 static unsigned long patching_addr __ro_after_init;
 
+#ifdef CONFIG_LKDTM
+unsigned long read_cpu_patching_addr(unsigned int cpu)
+{
+	return patching_addr;
+}
+#endif
+
 void __init poking_init(void)
 {
 	spinlock_t *ptl; /* for protecting pte table */
-- 
2.26.1

