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Date: Tue, 12 Dec 2017 20:25:26 +0800
From: Chao Fan <fanc.fnst@...fujitsu.com>
To: <linux-kernel@...r.kernel.org>, <x86@...nel.org>, <hpa@...or.com>,
<tglx@...utronix.de>, <mingo@...hat.com>, <bhe@...hat.com>,
<keescook@...omium.org>, <yasu.isimatu@...il.com>
CC: <indou.takao@...fujitsu.com>, <caoj.fnst@...fujitsu.com>,
<douly.fnst@...fujitsu.com>
Subject: Re: [PATCH v4 1/4] kaslr: add immovable_mem=nn[KMG]@ss[KMG] to
specify extracting memory
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.
>
I tried reuse codes like this:
@@ -129,7 +142,7 @@ char *skip_spaces(const char *str)
#include "../../../../lib/cmdline.c"
static int
-parse_memmap(char *p, unsigned long long *start, unsigned long long *size)
+parse_mem_filter(char *p, unsigned long long *start, unsigned long long *size)
{
char *oldp;
@@ -149,6 +162,9 @@ parse_memmap(char *p, unsigned long long *start, unsigned long long *size)
case '#':
case '$':
case '!':
+#ifdef CONFIG_MEMORY_HOTPLUG
+ case '%':
+#endif
*start = memparse(p + 1, &p);
return 0;
case '@':
@@ -183,7 +199,7 @@ static void mem_avoid_memmap(char *str)
if (k)
*k++ = 0;
- rc = parse_memmap(str, &start, &size);
+ rc = parse_mem_filter(str, &start, &size);
if (rc < 0)
break;
str = k;
@@ -206,17 +222,68 @@ static void mem_avoid_memmap(char *str)
memmap_too_large = true;
}
-static int handle_mem_memmap(void)
+#ifdef CONFIG_MEMORY_HOTPLUG
+static void parse_immovable_mem_regions(char *str)
+{
+ static int i;
+
+ while (str && (i < MAX_IMMOVABLE_MEM)) {
+ int rc;
+ unsigned long long start, size;
+ char *k = strchr(str, ',');
+
+ if (k)
+ *k++ = 0;
+
+ rc = parse_mem_filter(str, &start, &size);
+ if (rc < 0)
+ break;
+ str = k;
+
+ immovable_mem[i].start = start;
+ immovable_mem[i].size = size;
+ i++;
+ }
+ num_immovable_region = i;
+}
+#else
+static inline void parse_immovable_mem_regions(char *str)
+{
+}
+#endif
So that we can reuse and rename parse_memmap(), then use '%' for
"immovable_mem=", but I found in this version, '!' '@' '#' '$'
will also work well as '%'. I didn't find a good method to avoid
it, so I gave up the reuse.
Thanks,
Chao Fan
>Signed-off-by: Chao Fan <fanc.fnst@...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
>+
> 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
>
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