Re: [PATCH v2 08/10] powerpc/fsl_booke/kaslr: clear the original kernel if randomized

[Christophe Leroy]

Le 30/07/2019 à 09:42, Jason Yan a écrit :

The original kernel still exists in the memory, clear it now.

Signed-off-by: Jason Yan <yanai...@huawei.com>
Cc: Diana Craciun <diana.crac...@nxp.com>
Cc: Michael Ellerman <m...@ellerman.id.au>
Cc: Christophe Leroy <christophe.le...@c-s.fr>
Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org>
Cc: Paul Mackerras <pau...@samba.org>
Cc: Nicholas Piggin <npig...@gmail.com>
Cc: Kees Cook <keesc...@chromium.org>

Reviewed-by: Christophe Leroy <christophe.le...@c-s.fr>

Is kaslr_second_init() the best name ?
What about kaslr_late_init() or kaslr_clear_early_kernel() or ... ?

Christophe

---
  arch/powerpc/kernel/kaslr_booke.c  | 11 +++++++++++
  arch/powerpc/mm/mmu_decl.h         |  2 ++
  arch/powerpc/mm/nohash/fsl_booke.c |  1 +
  3 files changed, 14 insertions(+)

diff --git a/arch/powerpc/kernel/kaslr_booke.c 
b/arch/powerpc/kernel/kaslr_booke.c
index 0bb02e45b928..f032ac119457 100644
--- a/arch/powerpc/kernel/kaslr_booke.c
+++ b/arch/powerpc/kernel/kaslr_booke.c
@@ -412,3 +412,14 @@ notrace void __init kaslr_early_init(void *dt_ptr, 
phys_addr_t size)

reloc_kernel_entry(dt_ptr, kimage_vaddr);

  }
+
+void __init kaslr_second_init(void)
+{
+       /* If randomized, clear the original kernel */
+       if (kimage_vaddr != KERNELBASE) {
+               unsigned long kernel_sz;
+
+               kernel_sz = (unsigned long)_end - kimage_vaddr;
+               memzero_explicit((void *)KERNELBASE, kernel_sz);
+       }
+}
diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h
index 9332772c8a66..550c8d742f88 100644
--- a/arch/powerpc/mm/mmu_decl.h
+++ b/arch/powerpc/mm/mmu_decl.h
@@ -150,8 +150,10 @@ extern void loadcam_multi(int first_idx, int num, int 
tmp_idx);

#ifdef CONFIG_RANDOMIZE_BASE

  void kaslr_early_init(void *dt_ptr, phys_addr_t size);
+void kaslr_second_init(void);
  #else
  static inline void kaslr_early_init(void *dt_ptr, phys_addr_t size) {}
+static inline void kaslr_second_init(void) {}
  #endif

struct tlbcam {

diff --git a/arch/powerpc/mm/nohash/fsl_booke.c 
b/arch/powerpc/mm/nohash/fsl_booke.c
index 8d25a8dc965f..fa5a87f5c08e 100644
--- a/arch/powerpc/mm/nohash/fsl_booke.c
+++ b/arch/powerpc/mm/nohash/fsl_booke.c
@@ -269,6 +269,7 @@ notrace void __init relocate_init(u64 dt_ptr, phys_addr_t 
start)
        kernstart_addr = start;
        if (is_second_reloc) {
                virt_phys_offset = PAGE_OFFSET - memstart_addr;
+               kaslr_second_init();
                return;
        }