Re: [PATCH v7 3/5] powerpc: Rework and improve STRICT_KERNEL_RWX patching

On Sat, Mar 12, 2022 at 6:30 PM Christophe Leroy
[off-list ref] wrote:

Hi Jordan

Le 10/11/2021 à 01:37, Jordan Niethe a écrit :

quoted

From: "Christopher M. Riedl" <redacted>

Rework code-patching with STRICT_KERNEL_RWX to prepare for a later patch
which uses a temporary mm for patching under the Book3s64 Radix MMU.
Make improvements by adding a WARN_ON when the patchsite doesn't match
after patching and return the error from __patch_instruction() properly.

Signed-off-by: Christopher M. Riedl <redacted>
Signed-off-by: Jordan Niethe <redacted>
---
v7: still pass addr to map_patch_area()

This patch doesn-t apply, can you rebase the series ?

Yep, will do.

Thanks
Christophe

quoted

---
  arch/powerpc/lib/code-patching.c | 20 ++++++++++----------
  1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index 29a30c3068ff..d586bf9c7581 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c

@@ -75,6 +75,7 @@ static inline void stop_using_temp_mm(struct temp_mm_state prev_state)
  }

  static DEFINE_PER_CPU(struct vm_struct *, text_poke_area);
+static DEFINE_PER_CPU(unsigned long, cpu_patching_addr);

  static int text_area_cpu_up(unsigned int cpu)
  {

@@ -87,6 +88,7 @@ static int text_area_cpu_up(unsigned int cpu)
              return -1;
      }
      this_cpu_write(text_poke_area, area);
+     this_cpu_write(cpu_patching_addr, (unsigned long)area->addr);

      return 0;
  }

@@ -172,11 +174,10 @@ static inline int unmap_patch_area(unsigned long addr)

  static int do_patch_instruction(u32 *addr, struct ppc_inst instr)
  {
-     int err;
+     int err, rc = 0;
      u32 *patch_addr = NULL;
      unsigned long flags;
      unsigned long text_poke_addr;
-     unsigned long kaddr = (unsigned long)addr;

      /*
       * During early early boot patch_instruction is called

@@ -188,15 +189,13 @@ static int do_patch_instruction(u32 *addr, struct ppc_inst instr)

      local_irq_save(flags);

-     text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr;
-     if (map_patch_area(addr, text_poke_addr)) {
-             err = -1;
+     text_poke_addr = __this_cpu_read(cpu_patching_addr);
+     err = map_patch_area(addr, text_poke_addr);
+     if (err)
              goto out;
-     }
-
-     patch_addr = (u32 *)(text_poke_addr + (kaddr & ~PAGE_MASK));

-     __patch_instruction(addr, instr, patch_addr);
+     patch_addr = (u32 *)(text_poke_addr | offset_in_page(addr));
+     rc = __patch_instruction(addr, instr, patch_addr);

      err = unmap_patch_area(text_poke_addr);
      if (err)

@@ -204,8 +203,9 @@ static int do_patch_instruction(u32 *addr, struct ppc_inst instr)

  out:
      local_irq_restore(flags);
+     WARN_ON(!ppc_inst_equal(ppc_inst_read(addr), instr));

-     return err;
+     return rc ? rc : err;
  }
  #else /* !CONFIG_STRICT_KERNEL_RWX */