Re: [PATCH v8 0/3] x86/boot/KASLR: Parse ACPI table and limit kaslr in immovable memory

Masayoshi Mizuma
2018-10-16T15:13:54Z

Hi Boris, Baoquan and all,

I have created a RFC patch for adjust KASLR padding size.
This patch is based on Can's v8 patch [1/3], and the Can's patch
will be changed in the future, so this patch is just RFC.

Welcome to any comments and suggestions. Thanks!

---
arch/x86/boot/compressed/acpitb.c | 8 ++++++-
arch/x86/include/uapi/asm/bootparam.h | 3 ++-
arch/x86/mm/kaslr.c | 31 ++++++++++++++++++++++++++-
3 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/arch/x86/boot/compressed/acpitb.c b/arch/x86/boot/compressed/acpitb.c
index 6b869e3f9780..1504b46f2a04 100644
--- a/arch/x86/boot/compressed/acpitb.c
+++ b/arch/x86/boot/compressed/acpitb.c
@@ -367,6 +367,7 @@ void get_immovable_mem(void)
struct acpi_subtable_header *table;
struct acpi_srat_mem_affinity *ma;
unsigned long table_end;
+ unsigned long long possible_addr, max_possible_addr = 0;
int i = 0;

if (!strstr(args, "movable_node") || strstr(args, "acpi=off"))
@@ -384,7 +385,11 @@ void get_immovable_mem(void)
while (((unsigned long)table) + table->length < table_end) {
if (table->type == 1) {
ma = (struct acpi_srat_mem_affinity *)table;
- if (!(ma->flags & ACPI_SRAT_MEM_HOT_PLUGGABLE)) {
+ if (ma->flags & ACPI_SRAT_MEM_HOT_PLUGGABLE) {
+ possible_addr = ma->base_address + ma->length;
+ if (possible_addr > max_possible_addr)
+ max_possible_addr = possible_addr;
+ } else {
immovable_mem[i].start = ma->base_address;
immovable_mem[i].size = ma->length;
i++;
@@ -397,6 +402,7 @@ void get_immovable_mem(void)
((unsigned long)table + table->length);
}
num_immovable_mem = i;
+ boot_params->possible_mem_addr = max_possible_addr;
}
#else
void get_immovable_mem(void)
diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h
index a06cbf019744..c987c725e93a 100644
--- a/arch/x86/include/uapi/asm/bootparam.h
+++ b/arch/x86/include/uapi/asm/bootparam.h
@@ -191,7 +191,8 @@ struct boot_params {
__u8 _pad7[0x290-0x1f1-sizeof(struct setup_header)];
__u32 edd_mbr_sig_buffer[EDD_MBR_SIG_MAX]; /* 0x290 */
struct boot_e820_entry e820_table[E820_MAX_ENTRIES_ZEROPAGE]; /* 0x2d0 */
- __u8 _pad8[48]; /* 0xcd0 */
+ __u8 _pad8[40]; /* 0xcd0 */
+ __u64 possible_mem_addr; /* 0xcf8 */
struct edd_info eddbuf[EDDMAXNR]; /* 0xd00 */
__u8 _pad9[276]; /* 0xeec */
} __attribute__((packed));
diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c
index 61db77b0eda9..8c5aca792b51 100644
--- a/arch/x86/mm/kaslr.c
+++ b/arch/x86/mm/kaslr.c
@@ -69,6 +69,35 @@ static inline bool kaslr_memory_enabled(void)
return kaslr_enabled() && !IS_ENABLED(CONFIG_KASAN);
}

+#ifdef CONFIG_MEMORY_HOTPLUG
+static unsigned int __init kaslr_padding(void)
+{
+ unsigned long long max_possible_phys, max_actual_phys, threshold;
+ unsigned int rand_mem_physical_padding =
+ CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING;
+
+ if (!boot_params.possible_mem_addr)
+ goto out;
+
+ max_actual_phys = roundup(PFN_PHYS(max_pfn), 1ULL << TB_SHIFT);
+ max_possible_phys = roundup(boot_params.possible_mem_addr,
+ 1ULL << TB_SHIFT);
+ threshold = max_actual_phys +
+ ((unsigned long long)rand_mem_physical_padding << TB_SHIFT);
+
+ if (max_possible_phys > threshold)
+ rand_mem_physical_padding =
+ (max_possible_phys - max_actual_phys) >> TB_SHIFT;
+out:
+ return rand_mem_physical_padding;
+}
+#else
+static unsigned int __init kaslr_padding(void)
+{
+ return CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING;
+}
+#endif
+
/* Initialize base and padding for each memory region randomized with KASLR */
void __init kernel_randomize_memory(void)
{
@@ -102,7 +131,7 @@ void __init kernel_randomize_memory(void)
*/
BUG_ON(kaslr_regions[0].base != &page_offset_base);
memory_tb = DIV_ROUND_UP(max_pfn << PAGE_SHIFT, 1UL << TB_SHIFT) +
- CONFIG_RANDOMIZE_MEMORY_PHYSICAL_PADDING;
+ kaslr_padding();

/* Adapt phyiscal memory region size based on available memory */
if (memory_tb < kaslr_regions[0].size_tb)
--
2.18.0

- Masa