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arm64: Enable RW, RX and RO mappings for the relocated binary

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Now that we have everything in place switch the page permissions for
.rodata, .text and .data just after we relocate everything in top of the
RAM.

Unfortunately we can't enable this by default, since we have examples of
U-Boot crashing due to invalid access. This usually happens because code
defines const variables that it later writes. So hide it behind a Kconfig
option until we sort it out.

It's worth noting that EFI runtime services are not covered by this
patch on purpose. Since the OS can call SetVirtualAddressMap which can
relocate runtime services, we need to set them to RX initially but remap
them as RWX right before ExitBootServices.

Link: https://lore.kernel.org/u-boot/20250129-rockchip-pinctrl-const-v1-0-450ccdadfa7e@cherry.de/
Link: https://lore.kernel.org/u-boot/20250130133646.2177194-1-andre.przywara@arm.com/
Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
This commit is contained in:
Ilias Apalodimas 2025-02-20 15:54:43 +02:00
parent ec1c6cfb1c
commit fb553201b6
2 changed files with 33 additions and 0 deletions
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13
common/Kconfig
View file

@ -914,6 +914,19 @@ config STACKPROTECTOR
Enable stack smash detection through compiler's stack-protector
canary logic
config MMU_PGPROT
bool "Enable RO, RW and RX mappings"
help
U-Boot maps all pages as RWX. If selected pages will
be marked as RO(.rodata), RX(.text), RW(.data) right after
we relocate. Since code sections needs to be page aligned
the final binary size will increase. The mappings can be dumped
using the 'meminfo' command.
Enabling this feature can expose bugs in U-Boot where we have
code that violates read-only permissions for example. Use this
feature with caution.
config SPL_STACKPROTECTOR
bool "Stack Protector buffer overflow detection for SPL"
depends on STACKPROTECTOR && SPL

20
common/board_r.c
View file

@ -170,7 +170,27 @@ static int initr_reloc_global_data(void)
efi_save_gd();
efi_runtime_relocate(gd->relocaddr, NULL);
#endif
/*
* We are done with all relocations change the permissions of the binary
* NOTE: __start_rodata etc are defined in arm64 linker scripts and
* sections.h. If you want to add support for your platform you need to
* add the symbols on your linker script, otherwise they will point to
* random addresses.
*
*/
if (IS_ENABLED(CONFIG_MMU_PGPROT)) {
pgprot_set_attrs((phys_addr_t)(uintptr_t)(__start_rodata),
(size_t)(uintptr_t)(__end_rodata - __start_rodata),
MMU_ATTR_RO);
pgprot_set_attrs((phys_addr_t)(uintptr_t)(__start_data),
(size_t)(uintptr_t)(__end_data - __start_data),
MMU_ATTR_RW);
pgprot_set_attrs((phys_addr_t)(uintptr_t)(__text_start),
(size_t)(uintptr_t)(__text_end - __text_start),
MMU_ATTR_RX);
}
return 0;
}