[RFC PATCH 2/4] arm: Prepare linker scripts for memory permissions
Jerome Forissier
jerome.forissier at linaro.org
Thu Jan 30 10:27:29 CET 2025
On 1/30/25 10:19, Ilias Apalodimas wrote:
> On Thu, 30 Jan 2025 at 11:09, Jerome Forissier
> <jerome.forissier at linaro.org> wrote:
>>
>> Hi Ilias,
>>
>> On 1/30/25 08:20, Ilias Apalodimas wrote:
>>> Upcoming patches are switching the memory mappings to RW, RO, RW^X page
>>> permissions after the U-Boot binary and its data are relocated. Add
>>> annotations in the linker scripts to and mark text, data, rodata etc
>>> sections and align them to a page boundary
>>>
>>> Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
>>> ---
>>> Makefile | 15 +++++++++------
>>> arch/arm/cpu/armv8/u-boot.lds | 32 +++++++++++++++++++-------------
>>> include/asm-generic/sections.h | 2 ++
>>> lib/efi_loader/efi_runtime.c | 2 ++
>>> 4 files changed, 32 insertions(+), 19 deletions(-)
>>>
>>> diff --git a/Makefile b/Makefile
>>> index 33bb86343c5b..8d7c062ec830 100644
>>> --- a/Makefile
>>> +++ b/Makefile
>>> @@ -2176,13 +2176,16 @@ System.map: u-boot
>>> # ARM relocations should all be R_ARM_RELATIVE (32-bit) or
>>> # R_AARCH64_RELATIVE (64-bit).
>>> checkarmreloc: u-boot
>>> - @RELOC="`$(CROSS_COMPILE)readelf -r -W $< | cut -d ' ' -f 4 | \
>>> + @RELOCS="`$(CROSS_COMPILE)readelf -r -W $< | cut -d ' ' -f 4 | \
>>> grep R_A | sort -u`"; \
>>> - if test "$$RELOC" != "R_ARM_RELATIVE" -a \
>>> - "$$RELOC" != "R_AARCH64_RELATIVE"; then \
>>> - echo "$< contains unexpected relocations: $$RELOC"; \
>>> - false; \
>>> - fi
>>> + for reloc in $$RELOCS; do \
>>> + if [ "$$reloc" != "R_ARM_RELATIVE" -a \
>>> + "$$reloc" != "R_AARCH64_RELATIVE" -a \
>>> + "$$reloc" != "R_AARCH64_NONE" ]; then \
>>> + echo "$< contains unexpected relocations: $$reloc"; \
>>> + false; \
>>
>> s/false/exit 1/ otherwise the loop won't break and make won't get a
>> failure status unless the error is on the last reloc.
>>
>>> + fi; \
>>> + done
>>
>> This Makefile change seems unrelated to the current patch. Should it
>> go into a separate fixup patch?
>>
>>> tools/version.h: include/version.h
>>> $(Q)mkdir -p $(dir $@)
>>> diff --git a/arch/arm/cpu/armv8/u-boot.lds b/arch/arm/cpu/armv8/u-boot.lds
>>> index 857f44412e07..18e168e27135 100644
>>> --- a/arch/arm/cpu/armv8/u-boot.lds
>>> +++ b/arch/arm/cpu/armv8/u-boot.lds
>>> @@ -22,7 +22,7 @@ SECTIONS
>>>
>>> . = ALIGN(8);
>>> __image_copy_start = ADDR(.text);
>>> - .text :
>>> + .text ALIGN(4096):
>>> {
>>> CPUDIR/start.o (.text*)
>>> }
>>> @@ -36,9 +36,12 @@ SECTIONS
>>> __efi_runtime_stop = .;
>>> }
>>>
>>> - .text_rest :
>>> + .text_rest ALIGN(4096) :
>>> {
>>> + __text_start = .;
>>> *(.text*)
>>> + . = ALIGN(4096);
>>> + __text_end = .;
>>> }
>>>
>>> #ifdef CONFIG_ARMV8_PSCI
>>> @@ -98,27 +101,30 @@ SECTIONS
>>> }
>>> #endif
>>>
>>> - . = ALIGN(8);
>>> - .rodata : { *(SORT_BY_ALIGNMENT(SORT_BY_NAME(.rodata*))) }
>>> + .rodata ALIGN(4096): {
>>> + __start_rodata = .;
>>> + *(SORT_BY_ALIGNMENT(SORT_BY_NAME(.rodata*)))
>>> + . = ALIGN(4096);
>>> + __end_rodata = .;
>>> + }
>>>
>>> - . = ALIGN(8);
>>> - .data : {
>>> + .data ALIGN(4096) : {
>>> + __start_data = .;
>>> *(.data*)
>>> + . = ALIGN(4096);
>>> + __end_data = .;
>>> }
>>>
>>> - . = ALIGN(8);
>>> -
>>> - . = .;
>>> -
>>> . = ALIGN(8);
>>> __u_boot_list : {
>>> KEEP(*(SORT(__u_boot_list*)));
>>> }
>>>
>>> - .efi_runtime_rel : {
>>> + .efi_runtime_rel ALIGN(4096) : {
>>> __efi_runtime_rel_start = .;
>>> *(.rel*.efi_runtime)
>>> *(.rel*.efi_runtime.*)
>>> + . = ALIGN(4096);
>>> __efi_runtime_rel_stop = .;
>>> }
>>>
>>> @@ -136,10 +142,10 @@ SECTIONS
>>> /*
>>> * arch/arm/lib/crt0_64.S assumes __bss_start - __bss_end % 8 == 0
>>> */
>>> - .bss ALIGN(8) : {
>>> + .bss ALIGN(4096) : {
>>> __bss_start = .;
>>> *(.bss*)
>>> - . = ALIGN(8);
>>> + . = ALIGN(4096);
>>> __bss_end = .;
>>> }
>>>
>>> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
>>> index b6bca53db10d..5626df796f33 100644
>>> --- a/include/asm-generic/sections.h
>>> +++ b/include/asm-generic/sections.h
>>> @@ -23,6 +23,7 @@ extern char __kprobes_text_start[], __kprobes_text_end[];
>>> extern char __entry_text_start[], __entry_text_end[];
>>> extern char __initdata_begin[], __initdata_end[];
>>> extern char __start_rodata[], __end_rodata[];
>>> +extern char __start_data[], __end_data[];
>>> extern char __efi_helloworld_begin[];
>>> extern char __efi_helloworld_end[];
>>> extern char __efi_var_file_begin[];
>>> @@ -63,6 +64,7 @@ static inline int arch_is_kernel_data(unsigned long addr)
>>>
>>> /* Start of U-Boot text region */
>>> extern char __text_start[];
>>> +extern char __text_end[];
>>>
>>> /* This marks the text region which must be relocated */
>>> extern char __image_copy_start[], __image_copy_end[];
>>> diff --git a/lib/efi_loader/efi_runtime.c b/lib/efi_loader/efi_runtime.c
>>> index 35eb6a777665..c10a79301a92 100644
>>> --- a/lib/efi_loader/efi_runtime.c
>>> +++ b/lib/efi_loader/efi_runtime.c
>>> @@ -742,6 +742,8 @@ void efi_runtime_relocate(ulong offset, struct efi_mem_desc *map)
>>> rel->info, *p, rel->offset);
>>>
>>> switch (rel->info & R_MASK) {
>>> + case 0:
>>> + break;
>>
>> It looks like this may need to go into the same fixup patch as the
>> Makefile changes above.
>>
>>> case R_RELATIVE:
>>> #ifdef IS_RELA
>>> newaddr = rel->addend + offset - CONFIG_TEXT_BASE;
>>
>> For the linker script changes:
>
> All of these are needed in a single patch. The alignment changes
> trigger the emitted R_AARCH64_NONE relocs.
Got it. I suggest mentioning this in the commit description.
Please do not forget my comment about the "exit 1" though ;)
Thanks,
--
Jerome
>
> Cheers
> /Ilias
>>
>> Acked-by: Jerome Forissier <jerome.forissier at linaro.org>
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