Hi Ilias,
On 30/01/25 12:50 pm, Ilias Apalodimas wrote:
U-Boot maps all pages as RWX. Sadly it's not not 1990 anymore and we are
better off mapping binaries with proper permissions.
This is an attempt to map the U-Boot binary properly, but leave the
area we load binaries unaffected and RWX.
patch #1 adds printing capabilities for page permissions in meminfo
patch #2 prepares our linker scripts, aligns sections in page boundaries etc
patch #3 is adding a function to change page tables
patch #4 sets the permissions for .rodata, .text and .data
There's a few problems problem in this RFC ...
- U-Boot has no MMU APIs in place. As a result I just wired up the function
changing the page permissions in board_r.c but only for arm64. In the long
term we should add an API that other archs can use if they wish/can
- meminfo doesn't align all results properly (Caleb?)
- I am not setting the permissions of EFI runtime services section on purpose.
Since the OS is allowed to call SetVirtualAddressMap, we need to reset the
pages to RWX just before ExitBootServices, so the OS can relocate that code.
In arm64 this isn't a huge problem, because we explicitly disable SVAM if
if VA_BITS > 39, but other OSes/archs will have a problem.
# TODO:
- Long term. Add an MMU API and use that instead of exporting arch specific
functions
- Add an enum in mmu_set_attrs() instead of 1,2,3 arguments
- Set the permissions of EFI runtime services anbd reset them before EBS()
- Fix alignment when printing pages & information
- Add a Kconfig option so the feature can be turned off.
The reason is that QEMU CI and some boards, fail because they are trying to
write RO pages. This usually happens due to variables being wrongly defined
as
const, but with the updated page permissions this leads to a crash [0] [1].
In both cases the reported ESR is 0x9600004f which translates to
"Abort caused by writing to memory" "Permission fault, level 3.". On top of
that not setting pages as RO (and only setting .data and .text sections)
works
fine. So until we find and fix the bugs above we can't turn this on
unconditionally.
# Open questions
- Is initr_reloc_global_data() the right place to change permissions? Or is
there
a better/safer place to do that?
# How to test patches
- Aplly them an enable
CONFIG_CMD_MEMINFO=y
CONFIG_CMD_MEMINFO_MAP=y
'meminfo' should print something along the lines of
=> meminfo
DRAM: 8 GiB
Walking pagetable at 000000023ffe0000, va_bits: 40. Using 4 levels
[0x23ffe1000] | Table | |
[0x23ffe2000] | Table | |
[0x000000000 - 0x008000000] | Block | RWX | Normal |
Inner-shareable
[0x008000000 - 0x040000000] | Block | RW | Device-nGnRnE | Non-shareable
[0x040000000 - 0x200000000] | Block | RWX | Normal |
Inner-shareable
[0x23ffea000] | Table | |
[0x200000000 - 0x23f600000] | Block | RWX | Normal |
Inner-shareable
[0x23ffeb000] | Table | |
[0x23f600000 - 0x23f68b000] | Pages | RWX | Normal |
Inner-shareable
[0x23f68b000 - 0x23f74e000] | Pages | RX | Normal |
Inner-shareable
[0x23f74e000 - 0x23f793000] | Pages | RO | Normal |
Inner-shareable
[0x23f793000 - 0x23f794000] | Pages | RWX | Normal |
Inner-shareable
[0x23f794000 - 0x23f79d000] | Pages | RW | Normal |
Inner-shareable
[0x23f79d000 - 0x23f800000] | Pages | RWX | Normal |
Inner-shareable
[0x23f800000 - 0x240000000] | Block | RWX | Normal |
Inner-shareable
[0x240000000 - 0x4000000000] | Block | RWX | Normal |
Inner-shareable
[0x23ffe3000] | Table | |
[0x4010000000 - 0x4020000000] | Block | RW | Device-nGnRnE |
Non-shareable
[0x23ffe4000] | Table | |
[0x8000000000 - 0x10000000000] | Block | RW | Device-nGnRnE |
Non-shareable
[0]
https://lore.kernel.org/u-boot/20250129-rockchip-pinctrl-const-v1-0-450ccdadf...@cherry.de/
[1] https://source.denx.de/u-boot/custodians/u-boot-tpm/-/jobs/1008714
Ilias Apalodimas (4):
meminfo: add memory details for armv8
arm: Prepare linker scripts for memory permissions
arm64: mmu_change_region_attr() add an option not to break PTEs
arm64: Change mapping for data/rodata/text
Makefile | 15 +++++----
arch/arm/cpu/armv8/cache_v8.c | 45 +++++++++++++++++++++++--
arch/arm/cpu/armv8/fsl-layerscape/cpu.c | 10 +++---
arch/arm/cpu/armv8/u-boot.lds | 32 +++++++++++-------
arch/arm/include/asm/armv8/mmu.h | 2 ++
arch/arm/include/asm/system.h | 3 +-
arch/arm/mach-snapdragon/board.c | 2 +-
cmd/meminfo.c | 5 +++
common/board_r.c | 7 ++++
include/asm-generic/sections.h | 2 ++
lib/efi_loader/efi_runtime.c | 2 ++
11 files changed, 97 insertions(+), 28 deletions(-)
This patch series is increasing u-boot size by 13kB which is breaking
our mini u-boot configurations.
Without patch:
text data bss dec hex filename
0 115632 0 115632 1c3b0 u-boot.elf
With patch:
text data bss dec hex filename
0 128688 0 128688 1f6b0 u-boot.elf
Regards,
Love Kumar
--
2.43.0
