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Subject[PATCH v3 3/3] x86/boot: Introduce the setup_indirect
Date
The setup_data is a bit awkward to use for extremely large data objects,
both because the setup_data header has to be adjacent to the data object
and because it has a 32-bit length field. However, it is important that
intermediate stages of the boot process have a way to identify which
chunks of memory are occupied by kernel data. Thus we introduce an uniform
way to specify such indirect data as setup_indirect struct and
SETUP_INDIRECT type.

Suggested-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Ross Philipson <ross.philipson@oracle.com>
---
v3 - suggestions/fixes:
- add setup_indirect mapping/KASLR avoidance/etc. code
(suggested by H. Peter Anvin),
- the SETUP_INDIRECT sets most significant bit right now;
this way it is possible to differentiate regular setup_data
and setup_indirect objects in the debugfs filesystem.

v2 - suggestions/fixes:
- add setup_indirect usage example
(suggested by Eric Snowberg and Ross Philipson).
---
Documentation/x86/boot.rst | 40 +++++++++++++++++++++++++++++++++++
arch/x86/boot/compressed/kaslr.c | 12 +++++++++++
arch/x86/include/uapi/asm/bootparam.h | 16 +++++++++++---
arch/x86/kernel/e820.c | 11 ++++++++++
arch/x86/kernel/kdebugfs.c | 20 ++++++++++++++----
arch/x86/kernel/ksysfs.c | 30 ++++++++++++++++++++------
arch/x86/kernel/setup.c | 4 ++++
arch/x86/mm/ioremap.c | 11 ++++++++++
8 files changed, 130 insertions(+), 14 deletions(-)

diff --git a/Documentation/x86/boot.rst b/Documentation/x86/boot.rst
index 4c536bc8816d..d6d03b00b594 100644
--- a/Documentation/x86/boot.rst
+++ b/Documentation/x86/boot.rst
@@ -827,6 +827,46 @@ Protocol: 2.09+
sure to consider the case where the linked list already contains
entries.

+ The setup_data is a bit awkward to use for extremely large data objects,
+ both because the setup_data header has to be adjacent to the data object
+ and because it has a 32-bit length field. However, it is important that
+ intermediate stages of the boot process have a way to identify which
+ chunks of memory are occupied by kernel data.
+
+ Thus setup_indirect struct and SETUP_INDIRECT type were introduced in
+ protocol 2.15.
+
+ struct setup_indirect {
+ __u32 type;
+ __u32 reserved; /* Reserved, must be set to zero. */
+ __u64 len;
+ __u64 addr;
+ };
+
+ The type member is a SETUP_INDIRECT | SETUP_* type. However, it cannot be
+ SETUP_INDIRECT itself since making the setup_indirect a tree structure
+ could require a lot of stack space in something that needs to parse it
+ and stack space can be limited in boot contexts.
+
+ Let's give an example how to point to SETUP_E820_EXT data using setup_indirect.
+ In this case setup_data and setup_indirect will look like this:
+
+ struct setup_data {
+ __u64 next = 0 or <addr_of_next_setup_data_struct>;
+ __u32 type = SETUP_INDIRECT;
+ __u32 len = sizeof(setup_data);
+ __u8 data[sizeof(setup_indirect)] = struct setup_indirect {
+ __u32 type = SETUP_INDIRECT | SETUP_E820_EXT;
+ __u32 reserved = 0;
+ __u64 len = <len_of_SETUP_E820_EXT_data>;
+ __u64 addr = <addr_of_SETUP_E820_EXT_data>;
+ }
+ }
+
+ Note: SETUP_INDIRECT | SETUP_NONE objects cannot be properly distinguished
+ from SETUP_INDIRECT itself. So, this kind of objects cannot be provided
+ by the bootloaders.
+
============ ============
Field name: pref_address
Type: read (reloc)
diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 2e53c056ba20..bb9bfef174ae 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -459,6 +459,18 @@ static bool mem_avoid_overlap(struct mem_vector *img,
is_overlapping = true;
}

+ if (ptr->type == SETUP_INDIRECT &&
+ ((struct setup_indirect *)ptr->data)->type != SETUP_INDIRECT) {
+ avoid.start = ((struct setup_indirect *)ptr->data)->addr;
+ avoid.size = ((struct setup_indirect *)ptr->data)->len;
+
+ if (mem_overlaps(img, &avoid) && (avoid.start < earliest)) {
+ *overlap = avoid;
+ earliest = overlap->start;
+ is_overlapping = true;
+ }
+ }
+
ptr = (struct setup_data *)(unsigned long)ptr->next;
}

diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h
index dbb41128e5a0..949066b5398a 100644
--- a/arch/x86/include/uapi/asm/bootparam.h
+++ b/arch/x86/include/uapi/asm/bootparam.h
@@ -2,7 +2,7 @@
#ifndef _ASM_X86_BOOTPARAM_H
#define _ASM_X86_BOOTPARAM_H

-/* setup_data types */
+/* setup_data/setup_indirect types */
#define SETUP_NONE 0
#define SETUP_E820_EXT 1
#define SETUP_DTB 2
@@ -11,8 +11,10 @@
#define SETUP_APPLE_PROPERTIES 5
#define SETUP_JAILHOUSE 6

-/* max(SETUP_*) */
-#define SETUP_TYPE_MAX SETUP_JAILHOUSE
+#define SETUP_INDIRECT (1<<31)
+
+/* SETUP_INDIRECT | max(SETUP_*) */
+#define SETUP_TYPE_MAX (SETUP_INDIRECT | SETUP_JAILHOUSE)

/* ram_size flags */
#define RAMDISK_IMAGE_START_MASK 0x07FF
@@ -52,6 +54,14 @@ struct setup_data {
__u8 data[0];
};

+/* extensible setup indirect data node */
+struct setup_indirect {
+ __u32 type;
+ __u32 reserved; /* Reserved, must be set to zero. */
+ __u64 len;
+ __u64 addr;
+};
+
struct setup_header {
__u8 setup_sects;
__u16 root_flags;
diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 7da2bcd2b8eb..0bfe9a685b3b 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -999,6 +999,17 @@ void __init e820__reserve_setup_data(void)
data = early_memremap(pa_data, sizeof(*data));
e820__range_update(pa_data, sizeof(*data)+data->len, E820_TYPE_RAM, E820_TYPE_RESERVED_KERN);
e820__range_update_kexec(pa_data, sizeof(*data)+data->len, E820_TYPE_RAM, E820_TYPE_RESERVED_KERN);
+
+ if (data->type == SETUP_INDIRECT &&
+ ((struct setup_indirect *)data->data)->type != SETUP_INDIRECT) {
+ e820__range_update(((struct setup_indirect *)data->data)->addr,
+ ((struct setup_indirect *)data->data)->len,
+ E820_TYPE_RAM, E820_TYPE_RESERVED_KERN);
+ e820__range_update_kexec(((struct setup_indirect *)data->data)->addr,
+ ((struct setup_indirect *)data->data)->len,
+ E820_TYPE_RAM, E820_TYPE_RESERVED_KERN);
+ }
+
pa_data = data->next;
early_memunmap(data, sizeof(*data));
}
diff --git a/arch/x86/kernel/kdebugfs.c b/arch/x86/kernel/kdebugfs.c
index edaa30b20841..701a98300f86 100644
--- a/arch/x86/kernel/kdebugfs.c
+++ b/arch/x86/kernel/kdebugfs.c
@@ -44,7 +44,11 @@ static ssize_t setup_data_read(struct file *file, char __user *user_buf,
if (count > node->len - pos)
count = node->len - pos;

- pa = node->paddr + sizeof(struct setup_data) + pos;
+ pa = node->paddr + pos;
+
+ if (!(node->type & SETUP_INDIRECT) || node->type == SETUP_INDIRECT)
+ pa += sizeof(struct setup_data);
+
p = memremap(pa, count, MEMREMAP_WB);
if (!p)
return -ENOMEM;
@@ -108,9 +112,17 @@ static int __init create_setup_data_nodes(struct dentry *parent)
goto err_dir;
}

- node->paddr = pa_data;
- node->type = data->type;
- node->len = data->len;
+ if (data->type == SETUP_INDIRECT &&
+ ((struct setup_indirect *)data->data)->type != SETUP_INDIRECT) {
+ node->paddr = ((struct setup_indirect *)data->data)->addr;
+ node->type = ((struct setup_indirect *)data->data)->type;
+ node->len = ((struct setup_indirect *)data->data)->len;
+ } else {
+ node->paddr = pa_data;
+ node->type = data->type;
+ node->len = data->len;
+ }
+
create_setup_data_node(d, no, node);
pa_data = data->next;

diff --git a/arch/x86/kernel/ksysfs.c b/arch/x86/kernel/ksysfs.c
index 7969da939213..14ef8121aa53 100644
--- a/arch/x86/kernel/ksysfs.c
+++ b/arch/x86/kernel/ksysfs.c
@@ -100,7 +100,11 @@ static int __init get_setup_data_size(int nr, size_t *size)
if (!data)
return -ENOMEM;
if (nr == i) {
- *size = data->len;
+ if (data->type == SETUP_INDIRECT &&
+ ((struct setup_indirect *)data->data)->type != SETUP_INDIRECT)
+ *size = ((struct setup_indirect *)data->data)->len;
+ else
+ *size = data->len;
memunmap(data);
return 0;
}
@@ -130,7 +134,10 @@ static ssize_t type_show(struct kobject *kobj,
if (!data)
return -ENOMEM;

- ret = sprintf(buf, "0x%x\n", data->type);
+ if (data->type == SETUP_INDIRECT)
+ ret = sprintf(buf, "0x%x\n", ((struct setup_indirect *)data->data)->type);
+ else
+ ret = sprintf(buf, "0x%x\n", data->type);
memunmap(data);
return ret;
}
@@ -142,7 +149,7 @@ static ssize_t setup_data_data_read(struct file *fp,
loff_t off, size_t count)
{
int nr, ret = 0;
- u64 paddr;
+ u64 paddr, len;
struct setup_data *data;
void *p;

@@ -157,19 +164,28 @@ static ssize_t setup_data_data_read(struct file *fp,
if (!data)
return -ENOMEM;

- if (off > data->len) {
+ if (data->type == SETUP_INDIRECT &&
+ ((struct setup_indirect *)data->data)->type != SETUP_INDIRECT) {
+ paddr = ((struct setup_indirect *)data->data)->addr;
+ len = ((struct setup_indirect *)data->data)->len;
+ } else {
+ paddr += sizeof(*data);
+ len = data->len;
+ }
+
+ if (off > len) {
ret = -EINVAL;
goto out;
}

- if (count > data->len - off)
- count = data->len - off;
+ if (count > len - off)
+ count = len - off;

if (!count)
goto out;

ret = count;
- p = memremap(paddr + sizeof(*data), data->len, MEMREMAP_WB);
+ p = memremap(paddr, len, MEMREMAP_WB);
if (!p) {
ret = -ENOMEM;
goto out;
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 77ea96b794bd..4603702dbfc1 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -438,6 +438,10 @@ static void __init memblock_x86_reserve_range_setup_data(void)
while (pa_data) {
data = early_memremap(pa_data, sizeof(*data));
memblock_reserve(pa_data, sizeof(*data) + data->len);
+ if (data->type == SETUP_INDIRECT &&
+ ((struct setup_indirect *)data->data)->type != SETUP_INDIRECT)
+ memblock_reserve(((struct setup_indirect *)data->data)->addr,
+ ((struct setup_indirect *)data->data)->len);
pa_data = data->next;
early_memunmap(data, sizeof(*data));
}
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index a39dcdb5ae34..1ff9c2030b4f 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -626,6 +626,17 @@ static bool memremap_is_setup_data(resource_size_t phys_addr,
paddr_next = data->next;
len = data->len;

+ if ((phys_addr > paddr) && (phys_addr < (paddr + len))) {
+ memunmap(data);
+ return true;
+ }
+
+ if (data->type == SETUP_INDIRECT &&
+ ((struct setup_indirect *)data->data)->type != SETUP_INDIRECT) {
+ paddr = ((struct setup_indirect *)data->data)->addr;
+ len = ((struct setup_indirect *)data->data)->len;
+ }
+
memunmap(data);

if ((phys_addr > paddr) && (phys_addr < (paddr + len)))
--
2.11.0
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