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

Chao Fan
2018-10-23T02:48:02Z

On Mon, Oct 22, 2018 at 11:42:05AM -0400, Masayoshi Mizuma wrote:
>Hi Boris,

Hi Mizuma-san,

I have several questions:

>+static void store_possible_addr(unsigned long long possible)
>+{
>+ struct setup_data *data;
>+
>+ data = (struct setup_data *)(unsigned long)boot_params->hdr.setup_data;
I suggest you add check:

if (!data) {
debug_putstr("No setup_data found.\n");
return;
}

>+ while (data) {
>+ if (data->type == SETUP_KASLR) {
>+ *(unsigned long long *)data->data = possible;
>+ return;
>+ }
>+ data = (struct setup_data *)(unsigned long)data->next;
>+ }
>+}
>+
> /*
> * According to ACPI table, filter the immvoable memory regions
> * and store them in immovable_mem[].
>@@ -319,6 +333,7 @@ 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 (!cmdline_find_option_bool("movable_node") ||
>@@ -338,7 +353,12 @@ void get_immovable_mem(void)
> sizeof(struct acpi_subtable_header) < table_end) {
> if (table->type == ACPI_SRAT_TYPE_MEMORY_AFFINITY) {
> 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++;
>@@ -351,4 +371,5 @@ void get_immovable_mem(void)
> ((unsigned long)table + table->length);
> }
> num_immovable_mem = i;
>+ store_possible_addr(max_possible_addr);
> }
>diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
>index 1458b17..9b95fba 100644
>--- a/arch/x86/boot/compressed/eboot.c
>+++ b/arch/x86/boot/compressed/eboot.c
>@@ -192,6 +192,40 @@ static void setup_efi_pci(struct boot_params *params)
> efi_call_early(free_pool, pci_handle);
> }
>
>+#ifdef CONFIG_RANDOMIZE_MEMORY
>+static void setup_kaslr(struct boot_params *params)
>+{
>+ struct setup_data *kaslr_data = NULL;
>+ struct setup_data *data;
>+ unsigned long size;
>+ efi_status_t status;
>+
>+ size = sizeof(struct setup_data) + sizeof(unsigned long long);
>+
>+ status = efi_call_early(allocate_pool, EFI_LOADER_DATA,
>+ size, (void **)&kaslr_data);
>+ if (status != EFI_SUCCESS) {
>+ efi_printk(sys_table, "Failed to allocate memory for 'kaslr_data'\n");
>+ return;
>+ }
>+
>+ kaslr_data->type = SETUP_KASLR;
>+ kaslr_data->next = 0;
>+ kaslr_data->len = size;
>+
>+ data = (struct setup_data *)(unsigned long)params->hdr.setup_data;
>+ if (data)
>+ data->next = (unsigned long)kaslr_data;
Why just put the kaslr_data in data->next. You can't make sure
data->next was NULL.
>+ else {
If data is NULL, go to this else{}, so these two lines below work?
>+ while (data->next)
>+ data = (struct setup_data *)(unsigned long)data->next;
>+ data->next = (unsigned long)kaslr_data;
>+ }
If my understanding is not wrong, it should be:

data = (struct setup_data *)(unsigned long)params->hdr.setup_data;
if (!data)
params->hdr.setup_data = (unsigned long)kaslr_data;
else {
while (data->next)
data = (struct setup_data *)(unsigned long)data->next;
data->next = (unsigned long)kaslr_data;
}

If I misunderstand something, please tell me.

Thanks,
Chao Fan