mirror of
https://github.com/cirosantilli/linux-kernel-module-cheat.git
synced 2026-01-23 02:05:57 +01:00
virt_to_phys: fix %p vs %px
Move doc to README
This commit is contained in:
Ciro Santilli
52
README.adoc
52
README.adoc
@@ -4127,7 +4127,9 @@ The module also shows which handlers are registered for each IRQ, as we have obs
|
||||
|
||||
When in text mode, we can also observe interrupt line 4 with handler `ttyS0` increase continuously as IO goes through the UART.
|
||||
|
||||
=== Linux kernel utility functions
|
||||
=== Kernel utility functions
|
||||
|
||||
https://github.com/torvalds/linux/blob/v4.17/Documentation/core-api/kernel-api.rst
|
||||
|
||||
==== kstrto
|
||||
|
||||
@@ -4151,6 +4153,54 @@ Sources:
|
||||
|
||||
Bibliography: https://stackoverflow.com/questions/6139493/how-convert-char-to-int-in-linux-kernel/49811658#49811658
|
||||
|
||||
==== virt_to_phys
|
||||
|
||||
Convert a virtual address to physical:
|
||||
|
||||
....
|
||||
insmod /virt_to_phys.ko
|
||||
cat /sys/kernel/debug/lkmc_virt_to_phys
|
||||
....
|
||||
|
||||
Source: link:kernel_module/virt_to_phys.c[]
|
||||
|
||||
Sample output:
|
||||
|
||||
....
|
||||
*kmalloc_ptr = 0x12345678
|
||||
kmalloc_ptr = ffff88000e169ae8
|
||||
virt_to_phys(kmalloc_ptr) = 0xe169ae8
|
||||
static_var = 0x12345678
|
||||
&static_var = ffffffffc0002308
|
||||
virt_to_phys(&static_var) = 0x40002308
|
||||
....
|
||||
|
||||
We can confirm that the `kmalloc_ptr` translation worked with:
|
||||
|
||||
....
|
||||
./qemumonitor 'xp 0xe169ae8'
|
||||
....
|
||||
|
||||
which reads four bytes from a given physical address, and gives the expected:
|
||||
|
||||
....
|
||||
000000000e169ae8: 0x12345678
|
||||
....
|
||||
|
||||
TODO it only works for kmalloc however, for the static variable:
|
||||
|
||||
....
|
||||
./qemumonitor 'xp 0x40002308'
|
||||
....
|
||||
|
||||
it gave a wrong value of `00000000`.
|
||||
|
||||
Bibliography:
|
||||
|
||||
* https://stackoverflow.com/questions/5748492/is-there-any-api-for-determining-the-physical-address-from-virtual-address-in-li/45128487#45128487
|
||||
* https://stackoverflow.com/questions/39134990/mmap-of-dev-mem-fails-with-invalid-argument-for-virt-to-phys-address-but-addre/45127582#45127582
|
||||
* https://stackoverflow.com/questions/43325205/can-we-use-virt-to-phys-for-user-space-memory-in-kernel-module
|
||||
|
||||
=== Linux kernel tracing
|
||||
|
||||
Good overviews:
|
||||
|
||||
@@ -10,7 +10,6 @@ Our kernel modules!
|
||||
.. link:work_from_work.c[]
|
||||
.. link:workqueue_cheat.c[]
|
||||
. Misc
|
||||
.. link:virt_to_phys.c[]
|
||||
.. link:netlink.c[]
|
||||
. Hardening
|
||||
.. link:strlen_overflow.c[]
|
||||
|
||||
@@ -1,16 +1,4 @@
|
||||
/*
|
||||
Also try on QEMU monitor:
|
||||
|
||||
xp 0x<vaddr>
|
||||
|
||||
Only works for kmalloc.
|
||||
|
||||
static inline phys_addr_t virt_to_phys(volatile void *address)
|
||||
|
||||
- https://stackoverflow.com/questions/5748492/is-there-any-api-for-determining-the-physical-address-from-virtual-address-in-li
|
||||
- https://stackoverflow.com/questions/43325205/can-we-use-virt-to-phys-for-user-space-memory-in-kernel-module
|
||||
- https://stackoverflow.com/questions/39134990/mmap-of-dev-mem-fails-with-invalid-argument-but-address-is-page-aligned
|
||||
*/
|
||||
/* https://github.com/cirosantilli/linux-kernel-module-cheat#virt_to_phys */
|
||||
|
||||
#include <asm/io.h> /* virt_to_phys */
|
||||
#include <linux/debugfs.h>
|
||||
@@ -21,26 +9,26 @@ static inline phys_addr_t virt_to_phys(volatile void *address)
|
||||
#include <linux/seq_file.h> /* single_open, single_release */
|
||||
#include <linux/slab.h> /* kmalloc, kfree */
|
||||
|
||||
static volatile u32 *k;
|
||||
static volatile u32 i;
|
||||
static volatile u32 *kmalloc_ptr;
|
||||
static volatile u32 static_var;
|
||||
|
||||
static struct dentry *debugfs_file;
|
||||
|
||||
static int show(struct seq_file *m, void *v)
|
||||
{
|
||||
seq_printf(m,
|
||||
"k 0x%llx\n"
|
||||
"addr_k %p\n"
|
||||
"virt_to_phys_k 0x%llx\n"
|
||||
"i 0x%llx\n"
|
||||
"addr_i %p\n"
|
||||
"virt_to_phys_i 0x%llx\n",
|
||||
(unsigned long long)*k,
|
||||
k,
|
||||
(unsigned long long)virt_to_phys((void *)k),
|
||||
(unsigned long long)i,
|
||||
&i,
|
||||
(unsigned long long)virt_to_phys((void *)&i)
|
||||
"*kmalloc_ptr = 0x%llx\n"
|
||||
"kmalloc_ptr = %px\n"
|
||||
"virt_to_phys(kmalloc_ptr) = 0x%llx\n"
|
||||
"static_var = 0x%llx\n"
|
||||
"&static_var = %px\n"
|
||||
"virt_to_phys(&static_var) = 0x%llx\n",
|
||||
(unsigned long long)*kmalloc_ptr,
|
||||
kmalloc_ptr,
|
||||
(unsigned long long)virt_to_phys((void *)kmalloc_ptr),
|
||||
(unsigned long long)static_var,
|
||||
&static_var,
|
||||
(unsigned long long)virt_to_phys((void *)&static_var)
|
||||
);
|
||||
return 0;
|
||||
}
|
||||
@@ -60,18 +48,17 @@ static const struct file_operations fops = {
|
||||
|
||||
static int myinit(void)
|
||||
{
|
||||
k = kmalloc(sizeof(k), GFP_KERNEL);
|
||||
*k = 0x12345678;
|
||||
i = 0x12345678;
|
||||
debugfs_file = debugfs_create_file(
|
||||
"lkmc_virt_to_phys", S_IRUSR, NULL, NULL, &fops);
|
||||
kmalloc_ptr = kmalloc(sizeof(kmalloc_ptr), GFP_KERNEL);
|
||||
*kmalloc_ptr = 0x12345678;
|
||||
static_var = 0x12345678;
|
||||
debugfs_file = debugfs_create_file("lkmc_virt_to_phys", S_IRUSR, NULL, NULL, &fops);
|
||||
return 0;
|
||||
}
|
||||
|
||||
static void myexit(void)
|
||||
{
|
||||
debugfs_remove(debugfs_file);
|
||||
kfree((void *)k);
|
||||
kfree((void *)kmalloc_ptr);
|
||||
}
|
||||
|
||||
module_init(myinit)
|
||||
|
||||
Reference in New Issue
Block a user