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

[Masayoshi Mizuma <msys.mizuma@gmail.com>]

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
> 
>