[PATCH v3 2/6] x86: Add LKDTM accessor for patching addr
From: Christopher M. Riedl <hidden>
Date: 2020-08-27 06:13:28
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
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 <redacted> --- 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 6593b42cb379..f67b4dd30bf8 100644
--- a/arch/x86/include/asm/text-patching.h
+++ b/arch/x86/include/asm/text-patching.h@@ -148,4 +148,8 @@ void int3_emulate_call(struct pt_regs *regs, unsigned long func) } #endif /* !CONFIG_UML_X86 */ +#ifdef 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 c3daf0aaa0ee..c16833f35a1f 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c@@ -843,6 +843,13 @@ 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; +#ifdef 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;
--
2.28.0