Re: [PATCH v4 1/4] kaslr: add immovable_mem=nn[KMG]@ss[KMG] to specify extracting memory

[Chao Fan <fanc.fnst@cn.fujitsu.com>]

On Tue, Dec 12, 2017 at 08:07:02PM +0800, Chao Fan wrote:
>In current code, kaslr may choose the memory region in movable
>nodes to extract kernel, which will make the nodes can't be hot-removed.
>To solve it, we can specify the memory region in immovable node.
>Create immovable_mem to store the regions in immovable_mem, where should
>be chosen by kaslr.
>
>Also change the "handle_mem_memmap" to "handle_mem_filter", since
>it will not only handle memmap parameter now.
>Since "immovable_mem=" only works with "movable_node", so "immovable_mem="
>doesn't work alone. If specify "movable_node" without "immovable_mem=",
>disable KASLR.
>
>Multiple regions can be specified, comma delimited.
>Considering the usage of memory, only support for 4 regions.
>4 regions contains 2 nodes at least, enough for kernel to extract.
>
>Signed-off-by: Chao Fan <fanc.fnst@cn.fujitsu.com>
>---
> arch/x86/boot/compressed/kaslr.c | 112 +++++++++++++++++++++++++++++++++++++--
> 1 file changed, 109 insertions(+), 3 deletions(-)
>
>diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
>index 8199a6187251..40f299d8cd34 100644
>--- a/arch/x86/boot/compressed/kaslr.c
>+++ b/arch/x86/boot/compressed/kaslr.c
>@@ -108,6 +108,19 @@ enum mem_avoid_index {
> 
> static struct mem_vector mem_avoid[MEM_AVOID_MAX];
> 
>+#ifdef CONFIG_MEMORY_HOTPLUG
>+/* Only supporting at most 4 immovable memory regions with kaslr */
>+#define MAX_IMMOVABLE_MEM	4
>+
>+static bool lack_immovable_mem;
>+
>+/* Store the memory regions in immovable node */
>+static struct mem_vector immovable_mem[MAX_IMMOVABLE_MEM];
>+
>+/* The immovable regions user specify, not more than 4 */
>+static int num_immovable_region;
>+#endif
>+

Hi Kees,

I put all the functions and variables about immovable_mem to the #ifdefs
and make some adjustments according to this change.

I try to reuse some codes, but found that '!' '@' '#' '$' work in
memmap, but can't work in "immovable_mem=", then the reuse will make
codes look strange.

So how do you think about this version.

Thanks,
Chao Fan

> static bool mem_overlaps(struct mem_vector *one, struct mem_vector *two)
> {
> 	/* Item one is entirely before item two. */
>@@ -206,17 +219,99 @@ static void mem_avoid_memmap(char *str)
> 		memmap_too_large = true;
> }
> 
>-static int handle_mem_memmap(void)
>+#ifdef CONFIG_MEMORY_HOTPLUG
>+static int parse_immovable_mem(char *p,
>+			       unsigned long long *start,
>+			       unsigned long long *size)
>+{
>+	char *oldp;
>+
>+	if (!p)
>+		return -EINVAL;
>+
>+	oldp = p;
>+	*size = memparse(p, &p);
>+	if (p == oldp)
>+		return -EINVAL;
>+
>+	switch (*p) {
>+	case '@':
>+		*start = memparse(p + 1, &p);
>+		return 0;
>+	default:
>+		/*
>+		 * If w/o offset, only size specified, immovable_mem=nn[KMG]
>+		 * has the same behaviour as immovable_mem=nn[KMG]@0. It means
>+		 * the region starts from 0.
>+		 */
>+		*start = 0;
>+		return 0;
>+	}
>+
>+	return -EINVAL;
>+}
>+
>+static void parse_immovable_mem_regions(char *str)
>+{
>+	static int i;
>+
>+	while (str && (i < MAX_IMMOVABLE_MEM)) {
>+		int rc;
>+		unsigned long long start, size;
>+		char *k = strchr(str, ',');
>+
>+		if (k)
>+			*k++ = 0;
>+
>+		rc = parse_immovable_mem(str, &start, &size);
>+		if (rc < 0)
>+			break;
>+		str = k;
>+
>+		immovable_mem[i].start = start;
>+		immovable_mem[i].size = size;
>+		i++;
>+	}
>+	num_immovable_region = i;
>+}
>+#else
>+static inline void parse_immovable_mem_regions(char *str)
>+{
>+}
>+#endif
>+
>+static int handle_mem_filter(void)
> {
> 	char *args = (char *)get_cmd_line_ptr();
> 	size_t len = strlen((char *)args);
>+	bool exist_movable_node = false;
> 	char *tmp_cmdline;
> 	char *param, *val;
> 	u64 mem_size;
> 
>-	if (!strstr(args, "memmap=") && !strstr(args, "mem="))
>+	if (!strstr(args, "memmap=") && !strstr(args, "mem=") &&
>+	    !strstr(args, "movable_node"))
> 		return 0;
> 
>+#ifdef CONFIG_MEMORY_HOTPLUG
>+	if (strstr(args, "movable_node")) {
>+		/*
>+		 * Confirm "movable_node" specified, otherwise
>+		 * "immovable_mem=" doesn't work.
>+		 */
>+		exist_movable_node = true;
>+
>+		/*
>+		 * If only specify "movable_node" without "immovable_mem=",
>+		 * disable KASLR.
>+		 */
>+		if (!strstr(args, "immovable_mem=")) {
>+			lack_immovable_mem = true;
>+			return 0;
>+		}
>+	}
>+#endif
>+
> 	tmp_cmdline = malloc(len + 1);
> 	if (!tmp_cmdline)
> 		error("Failed to allocate space for tmp_cmdline");
>@@ -239,6 +334,9 @@ static int handle_mem_memmap(void)
> 
> 		if (!strcmp(param, "memmap")) {
> 			mem_avoid_memmap(val);
>+		} else if (!strcmp(param, "immovable_mem=") &&
>+			   exist_movable_node) {
>+			parse_immovable_mem_regions(val);
> 		} else if (!strcmp(param, "mem")) {
> 			char *p = val;
> 
>@@ -378,7 +476,7 @@ static void mem_avoid_init(unsigned long input, unsigned long input_size,
> 	/* We don't need to set a mapping for setup_data. */
> 
> 	/* Mark the memmap regions we need to avoid */
>-	handle_mem_memmap();
>+	handle_mem_filter();
> 
> #ifdef CONFIG_X86_VERBOSE_BOOTUP
> 	/* Make sure video RAM can be used. */
>@@ -673,6 +771,14 @@ static unsigned long find_random_phys_addr(unsigned long minimum,
> 		return 0;
> 	}
> 
>+#ifdef CONFIG_MEMORY_HOTPLUG
>+	/* Check if specify "movable_node" without "immovable_mem=". */
>+	if (lack_immovable_mem) {
>+		debug_putstr("Fail KASLR when movable_node specified without immovable_mem=.\n");
>+		return 0;
>+	}
>+#endif
>+
> 	/* Make sure minimum is aligned. */
> 	minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN);
> 
>-- 
>2.14.3
>