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

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Message-ID: <20181023024801.GA25978@localhost.localdomain>
Date:   Tue, 23 Oct 2018 10:48:02 +0800
From:   Chao Fan <fanc.fnst@...fujitsu.com>
To:     Masayoshi Mizuma <msys.mizuma@...il.com>
CC:     Borislav Petkov <bp@...en8.de>, Baoquan He <bhe@...hat.com>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        <linux-kernel@...r.kernel.org>, <x86@...nel.org>,
        <linux-efi@...r.kernel.org>, <linux-acpi@...r.kernel.org>,
        <mingo@...hat.com>, <hpa@...or.com>, <keescook@...omium.org>,
        <rjw@...ysocki.net>, <lenb@...nel.org>,
        <ard.biesheuvel@...aro.org>, <indou.takao@...fujitsu.com>,
        <caoj.fnst@...fujitsu.com>
Subject: Re: [PATCH v8 0/3] x86/boot/KASLR: Parse ACPI table and limit kaslr
 in immovable memory

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