sysfs: add /sys/firmware/memmap
This patch adds /sys/firmware/memmap interface that represents the BIOS
(or Firmware) provided memory map. The tree looks like:
/sys/firmware/memmap/0/start (hex number)
end (hex number)
type (string)
... /1/start
end
type
With the following shell snippet one can print the memory map in the same form
the kernel prints itself when booting on x86 (the E820 map).
--------- 8< --------------------------
#!/bin/sh
cd /sys/firmware/memmap
for dir in * ; do
start=$(cat $dir/start)
end=$(cat $dir/end)
type=$(cat $dir/type)
printf "%016x-%016x (%s)\n" $start $[ $end +1] "$type"
done
--------- >8 --------------------------
That patch only provides the needed interface:
1. The sysfs interface.
2. The structure and enumeration definition.
3. The function firmware_map_add() and firmware_map_add_early()
that should be called from architecture code (E820/EFI, for
example) to add the contents to the interface.
If the kernel is compiled without CONFIG_FIRMWARE_MEMMAP, the interface does
nothing without cluttering the architecture-specific code with #ifdef's.
The purpose of the new interface is kexec: While /proc/iomem represents
the *used* memory map (e.g. modified via kernel parameters like 'memmap'
and 'mem'), the /sys/firmware/memmap tree represents the unmodified memory
map provided via the firmware. So kexec can:
- use the original memory map for rebooting,
- use the /proc/iomem for setting up the ELF core headers for kdump
case that should only represent the memory of the system.
The patch has been tested on i386 and x86_64.
Signed-off-by: Bernhard Walle <bwalle@suse.de>
Acked-by: Greg KH <gregkh@suse.de>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Cc: kexec@lists.infradead.org
Cc: yhlu.kernel@gmail.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
index dc2cec6..ebb9e51 100644
--- a/drivers/firmware/Kconfig
+++ b/drivers/firmware/Kconfig
@@ -26,6 +26,16 @@
kernel. Say N if you want EDD enabled by default. EDD can be dynamically set
using the kernel parameter 'edd={on|skipmbr|off}'.
+config FIRMWARE_MEMMAP
+ bool "Add firmware-provided memory map to sysfs" if EMBEDDED
+ default (X86_64 || X86_32)
+ help
+ Add the firmware-provided (unmodified) memory map to /sys/firmware/memmap.
+ That memory map is used for example by kexec to set up parameter area
+ for the next kernel, but can also be used for debugging purposes.
+
+ See also Documentation/ABI/testing/sysfs-firmware-memmap.
+
config EFI_VARS
tristate "EFI Variable Support via sysfs"
depends on EFI
