virt_to_phys.sh also works with nopat

buildroot_config_fragment

@@ -58,8 +58,11 @@ BR2_PACKAGE_HOST_DTC=y
 #
 # - https://superuser.com/questions/71389/what-is-dev-mem/1214662#1214662
 # - https://unix.stackexchange.com/questions/4948/shell-command-to-read-device-registers
+# - man mem
 #
 # TODO: why with mmap MAP_PRIVATE (used in my previous custom naive version),
 # the entire register page is read?;
 #
+# TODO: have a look at: https://github.com/kaiwan/device-memory-readwrite
+#
 BR2_PACKAGE_DEVMEM2=y

kernel_module/user/usermem.c

@@ -4,7 +4,7 @@ Only tested in x86_64.
 Provide an allocated userland memory address for us to test out kernel memory APIs, including:
 
 - /proc/pid/maps
-- /proc/pid/pagemap
+- /proc/pid/pagemap. See also: https://stackoverflow.com/questions/17021214/decode-proc-pid-pagemap-entry/45126141#45126141
 - /dev/mem
 
 Usage:
@@ -18,13 +18,13 @@ Outputs address and pid, e.g.:
 
 Now translate the virtual address to physical for the given PID:
 
-	/pagemap2.out 110 | grep 0x600000
+	/pagemap_dump.out 110 | grep 0x600000
 
 where 0x600000 is the page that contains 0x600800.
 
 This produces a line of type:
 
-	0x600000 0x7c7b 0 0 0 1 /pagemap_test.out
+	0x600000 0x7c7b 0 0 0 1 /usermem.out
 
 where 0x7c7b is the PFN. To get the physical address, just add three zeros back:
 

kernel_module/virt_to_phys.c

@@ -1,9 +1,5 @@
 /*
-TODO not working. Tested with both:
-
-	/virt_to_phys.sh
-
-and on QEMU monitor:
+Also try on QEMU monitor:
 
 	xp 0x<vaddr>
 

rootfs_overlay/virt_to_phys.sh

@@ -3,8 +3,10 @@ set -ex
 insmod /virt_to_phys.ko
 cd /sys/kernel/debug
 cat lkmc_virt_to_phys
+# *i = 0x12345678
 addr=$(grep virt_to_phys lkmc_virt_to_phys | cut -d ' ' -f 2)
 devmem2 "$addr"
 devmem2 "$addr" w 0x9ABCDEF0
 cat lkmc_virt_to_phys
+# *i = 0x9ABCDEF0
 rmmod virt_to_phys