When live patching with STRICT_KERNEL_RWX 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 <c...@bluescreens.de>
---
arch/x86/include/asm/text-patching.h | 4 ++++
arch/x86/kernel/alternative.c | 7 +++++++
2 files changed, 11 insertions(+)
diff --git a/arch/x86/include/asm/text-patching.h
b/arch/x86/include/asm/text-patching.h
index b7421780e4e92..f0caf9ee13bd8 100644
--- a/arch/x86/include/asm/text-patching.h
+++ b/arch/x86/include/asm/text-patching.h
@@ -167,4 +167,8 @@ void int3_emulate_ret(struct pt_regs *regs)
}
#endif /* !CONFIG_UML_X86 */
+#if IS_BUILTIN(CONFIG_LKDTM)
+unsigned long read_cpu_patching_addr(unsigned int cpu);
+#endif
+
#endif /* _ASM_X86_TEXT_PATCHING_H */
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 8d778e46725d2..4c95fdd9b1965 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -852,6 +852,13 @@ static inline void unuse_temporary_mm(temp_mm_state_t
prev_state)
__ro_after_init struct mm_struct *poking_mm;
__ro_after_init unsigned long poking_addr;
+#if IS_BUILTIN(CONFIG_LKDTM)
+unsigned long read_cpu_patching_addr(unsigned int cpu)
+{
+ return poking_addr;
+}
+#endif
+
static void *__text_poke(void *addr, const void *opcode, size_t len)
{
bool cross_page_boundary = offset_in_page(addr) + len > PAGE_SIZE;
--
2.26.1
