target/linux/generic/pending-6.1/350-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 4. Enable this feature only for 32-bit CPUs. Currently, only ath79 and
  11    ralink CPUs are using it.
  12
  13 [1] 439a1bcac648 ("fortify: Use __builtin_dynamic_object_size() when available")
  14 Signed-off-by: Shiji Yang <yangshiji66@outlook.com>
  15 ---
  16  arch/mips/include/asm/bootinfo.h |  2 ++
  17  arch/mips/kernel/setup.c         | 17 ++++++++++++-----
  18  2 files changed, 14 insertions(+), 5 deletions(-)
  19
  20 --- a/arch/mips/include/asm/bootinfo.h
  21 +++ b/arch/mips/include/asm/bootinfo.h
  22 @@ -93,7 +93,9 @@ const char *get_system_type(void);
  23
  24  extern unsigned long mips_machtype;
  25
  26 +#ifndef CONFIG_64BIT
  27  extern void detect_memory_region(phys_addr_t start, phys_addr_t sz_min,  phys_addr_t sz_max);
  28 +#endif
  29
  30  extern void prom_init(void);
  31  extern void prom_free_prom_memory(void);
  32 --- a/arch/mips/kernel/setup.c
  33 +++ b/arch/mips/kernel/setup.c
  34 @@ -90,21 +90,27 @@ static struct resource bss_resource = {
  35  unsigned long __kaslr_offset __ro_after_init;
  36  EXPORT_SYMBOL(__kaslr_offset);
  37
  38 -static void *detect_magic __initdata = detect_memory_region;
  39 -
  40  #ifdef CONFIG_MIPS_AUTO_PFN_OFFSET
  41  unsigned long ARCH_PFN_OFFSET;
  42  EXPORT_SYMBOL(ARCH_PFN_OFFSET);
  43  #endif
  44
  45 +#ifndef CONFIG_64BIT
  46 +static u32 detect_magic __initdata;
  47 +#define MIPS_MEM_TEST_PATTERN          0xaa5555aa
  48 +
  49  void __init detect_memory_region(phys_addr_t start, phys_addr_t sz_min, phys_addr_t sz_max)
  50  {
  51 -       void *dm = &detect_magic;
  52 +       void *dm = (void *)KSEG1ADDR(&detect_magic);
  53         phys_addr_t size;
  54
  55         for (size = sz_min; size < sz_max; size <<= 1) {
  56 -               if (!memcmp(dm, dm + size, sizeof(detect_magic)))
  57 -                       break;
  58 +               __raw_writel(MIPS_MEM_TEST_PATTERN, dm);
  59 +               if (__raw_readl(dm) == __raw_readl(dm + size)) {
  60 +                       __raw_writel(~MIPS_MEM_TEST_PATTERN, dm);
  61 +                       if (__raw_readl(dm) == __raw_readl(dm + size))
  62 +                               break;
  63 +               }
  64         }
  65
  66         pr_debug("Memory: %lluMB of RAM detected at 0x%llx (min: %lluMB, max: %lluMB)\n",
  67 @@ -115,6 +121,7 @@ void __init detect_memory_region(phys_ad
  68
  69         memblock_add(start, size);
  70  }
  71 +#endif /* CONFIG_64BIT */
  72
  73  /*
  74   * Manage initrd