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

On Wed Jun 3, 2020 at 9:14 AM, Christophe Leroy wrote:

Le 03/06/2020 à 07:19, Christopher M. Riedl a écrit :

quoted

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/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 df0765845204..c23453049116 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c

@@ -52,6 +52,13 @@ int raw_patch_instruction(struct ppc_inst *addr, struct ppc_inst 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)

If this fonction is not static, it means it is intended to be used from
some other C file, so it should be declared in a .h too.

Yup agreed. This was left-over from the RFC to simplify using the LKDTM
test on a tree without this series. Will fix this in the next spin.

Christophe

quoted

+{
+	return patching_addr;
+}
+#endif
+
  void __init poking_init(void)
  {
  	spinlock_t *ptl; /* for protecting pte table */