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

Masayoshi Mizuma
2018-10-24T19:21:36Z

On Tue, Oct 23, 2018 at 10:48:02AM +0800, Chao Fan wrote:
> On Mon, Oct 22, 2018 at 11:42:05AM -0400, Masayoshi Mizuma wrote:
> >Hi Boris,
>
> Hi Mizuma-san,
>
> I have several questions:

Thank you for your comments! I think your suggestions are
right.
However, the prototype patch works EFI environment only.
The memory hot-plug affinity in SRAT and KASLR are also available
on legacy BIOS environment, so I need to get the patch useful
for legacy BIOS as well, but I have no idea to add such things...
If you have ideas, could you let me know?

Probably I should have another idea, for example,
add the SRAT parsing code, looks like you are adding to
arch/x86/boot/compressed/acpitb.c, to arch/x86/mm/kaslr.c.

Thanks,
Masa

>
> >+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
>
>