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SubjectRe: [PATCH v6 1/5] kaslr: add kaslr_mem=nn[KMG]@ss[KMG] to specify extracting memory
On Mon, Jan 15, 2018 at 08:40:12PM +0800, Chao Fan wrote:
>In current code, kaslr only has a method to avoid some memory regions,
>but no method to specify the regions for kaslr to extract. So kaslr
>may choose the wrong position sometimes, which will cause some other
>features fail.
>
>Here is a problem that 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 "kaslr_mem=" to store the regions in immovable nodes, 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.
>
>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 | 73 ++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 70 insertions(+), 3 deletions(-)
>
>diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
>index 8199a6187251..b071f6edd7b2 100644
>--- a/arch/x86/boot/compressed/kaslr.c
>+++ b/arch/x86/boot/compressed/kaslr.c
>@@ -108,6 +108,15 @@ enum mem_avoid_index {
>
> static struct mem_vector mem_avoid[MEM_AVOID_MAX];
>
>+/* Only support at most 4 usable memory regions specified for kaslr */
>+#define MAX_KASLR_MEM_USABLE 4
>+
>+/* Store the usable memory regions for kaslr */
>+static struct mem_vector mem_usable[MAX_KASLR_MEM_USABLE];

Here it may should be "kaslr_mem", but there is mem_avoid in current
code, so I name it as "mem_usable" to be symmetrical with "mem_avoid".
We can see more in PATCH 05.

Thanks,
Chao Fan

>+
>+/* The amount of usable regions for kaslr user specify, not more than 4 */
>+static int num_usable_region;
>+
> static bool mem_overlaps(struct mem_vector *one, struct mem_vector *two)
> {
> /* Item one is entirely before item two. */
>@@ -206,7 +215,62 @@ static void mem_avoid_memmap(char *str)
> memmap_too_large = true;
> }
>
>-static int handle_mem_memmap(void)
>+static int parse_kaslr_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, kaslr_mem=nn[KMG]
>+ * has the same behaviour as kaslr_mem=nn[KMG]@0. It means
>+ * the region starts from 0.
>+ */
>+ *start = 0;
>+ return 0;
>+ }
>+
>+ return -EINVAL;
>+}
>+
>+static void parse_kaslr_mem_regions(char *str)
>+{
>+ static int i;
>+
>+ while (str && (i < MAX_KASLR_MEM_USABLE)) {
>+ int rc;
>+ unsigned long long start, size;
>+ char *k = strchr(str, ',');
>+
>+ if (k)
>+ *k++ = 0;
>+
>+ rc = parse_kaslr_mem(str, &start, &size);
>+ if (rc < 0)
>+ break;
>+ str = k;
>+
>+ mem_usable[i].start = start;
>+ mem_usable[i].size = size;
>+ i++;
>+ }
>+ num_usable_region = i;
>+}
>+
>+static int handle_mem_filter(void)
> {
> char *args = (char *)get_cmd_line_ptr();
> size_t len = strlen((char *)args);
>@@ -214,7 +278,8 @@ static int handle_mem_memmap(void)
> char *param, *val;
> u64 mem_size;
>
>- if (!strstr(args, "memmap=") && !strstr(args, "mem="))
>+ if (!strstr(args, "memmap=") && !strstr(args, "mem=") &&
>+ !strstr(args, "kaslr_mem="))
> return 0;
>
> tmp_cmdline = malloc(len + 1);
>@@ -239,6 +304,8 @@ static int handle_mem_memmap(void)
>
> if (!strcmp(param, "memmap")) {
> mem_avoid_memmap(val);
>+ } else if (!strcmp(param, "kaslr_mem")) {
>+ parse_kaslr_mem_regions(val);
> } else if (!strcmp(param, "mem")) {
> char *p = val;
>
>@@ -378,7 +445,7 @@ 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. */
>--
>2.14.3
>


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