target/linux/generic/pending-6.6/350-mips-kernel-fix-detect_memory_region-function.patch

   1 From: Shiji Yang <yangshiji66@outlook.com>
   2 Date: Wed, 13 Mar 2024 20:28:37 +0800
   3 Subject: [PATCH] mips: kernel: fix detect_memory_region() function
   4
   5 1. Do not use memcmp() on unallocated memory, as the new introduced
   6    fortify dynamic object size check[1] will report unexpected result.
   7 2. Use a fixed pattern instead of a random function pointer as the
   8    magic value.
   9 3. Flip magic value and double check it.
  10
  11 [1] 439a1bcac648 ("fortify: Use __builtin_dynamic_object_size() when available")
  12 Signed-off-by: Shiji Yang <yangshiji66@outlook.com>
  13 ---
  14  arch/mips/kernel/setup.c | 16 +++++++++++-----
  15  1 file changed, 11 insertions(+), 5 deletions(-)
  16
  17 --- a/arch/mips/kernel/setup.c
  18 +++ b/arch/mips/kernel/setup.c
  19 @@ -46,6 +46,8 @@
  20  #include <asm/prom.h>
  21  #include <asm/fw/fw.h>
  22
  23 +#define MIPS_MEM_TEST_PATTERN          0xaa5555aa
  24 +
  25  #ifdef CONFIG_MIPS_ELF_APPENDED_DTB
  26  char __section(".appended_dtb") __appended_dtb[0x100000];
  27  #endif /* CONFIG_MIPS_ELF_APPENDED_DTB */
  28 @@ -90,7 +92,7 @@ static struct resource bss_resource = {
  29  unsigned long __kaslr_offset __ro_after_init;
  30  EXPORT_SYMBOL(__kaslr_offset);
  31
  32 -static void *detect_magic __initdata = detect_memory_region;
  33 +static u32 detect_magic __initdata;
  34
  35  #ifdef CONFIG_MIPS_AUTO_PFN_OFFSET
  36  unsigned long ARCH_PFN_OFFSET;
  37 @@ -99,12 +101,16 @@ EXPORT_SYMBOL(ARCH_PFN_OFFSET);
  38
  39  void __init detect_memory_region(phys_addr_t start, phys_addr_t sz_min, phys_addr_t sz_max)
  40  {
  41 -       void *dm = &detect_magic;
  42 +       void *dm = (void *)KSEG1ADDR(&detect_magic);
  43         phys_addr_t size;
  44
  45         for (size = sz_min; size < sz_max; size <<= 1) {
  46 -               if (!memcmp(dm, dm + size, sizeof(detect_magic)))
  47 -                       break;
  48 +               __raw_writel(MIPS_MEM_TEST_PATTERN, dm);
  49 +               if (__raw_readl(dm) == __raw_readl(dm + size)) {
  50 +                       __raw_writel(~MIPS_MEM_TEST_PATTERN, dm);
  51 +                       if (__raw_readl(dm) == __raw_readl(dm + size))
  52 +                               break;
  53 +               }
  54         }
  55
  56         pr_debug("Memory: %lluMB of RAM detected at 0x%llx (min: %lluMB, max: %lluMB)\n",