1. Do not use memcmp() on unallocated memory, as the new introduced
fortify dynamic object size check[1] will report unexpected result.
2. Use a fixed pattern instead of a random function pointer as the
magic value.
3. Flip magic value and double check it.
[1] 439a1bcac648 ("fortify: Use __builtin_dynamic_object_size() when available")
Signed-off-by: Shiji Yang <yangshiji66@xxxxxxxxxxx>
---
arch/mips/kernel/setup.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 9c30de151..354458fa9 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -46,6 +46,8 @@
#include <asm/prom.h>
#include <asm/fw/fw.h>
+#define MIPS_MEM_TEST_PATTERN 0xaa5555aa
+
#ifdef CONFIG_MIPS_ELF_APPENDED_DTB
char __section(".appended_dtb") __appended_dtb[0x100000];
#endif /* CONFIG_MIPS_ELF_APPENDED_DTB */
@@ -86,7 +88,7 @@ static struct resource bss_resource = { .name = "Kernel bss", };
unsigned long __kaslr_offset __ro_after_init;
EXPORT_SYMBOL(__kaslr_offset);
-static void *detect_magic __initdata = detect_memory_region;
+static u32 detect_magic __initdata;
#ifdef CONFIG_MIPS_AUTO_PFN_OFFSET
unsigned long ARCH_PFN_OFFSET;
@@ -95,12 +97,16 @@ EXPORT_SYMBOL(ARCH_PFN_OFFSET);
void __init detect_memory_region(phys_addr_t start, phys_addr_t sz_min, phys_addr_t sz_max)
{
- void *dm = &detect_magic;
+ void *dm = (void *)KSEG1ADDR(&detect_magic);
phys_addr_t size;
for (size = sz_min; size < sz_max; size <<= 1) {
- if (!memcmp(dm, dm + size, sizeof(detect_magic)))
- break;
+ __raw_writel(MIPS_MEM_TEST_PATTERN, dm);
+ if (__raw_readl(dm) == __raw_readl(dm + size)) {
+ __raw_writel(~MIPS_MEM_TEST_PATTERN, dm);
+ if (__raw_readl(dm) == __raw_readl(dm + size))
+ break;
+ }
}
pr_debug("Memory: %lluMB of RAM detected at 0x%llx (min: %lluMB, max: %lluMB)\n",
--
2.44.0
