Am 6. November 2022 19:36:15 MEZ schrieb Patrick Zacharias littlefighter19@web.de:
I created a GitHub repository demonstrating the issue, together with instructions on how to build it.
Please, check the instructions in
https://doc.rust-lang.org/rustc/platform-support/unknown-uefi.html
Best regards
Heinrich
Currently, when using the old linker file, it will crash. Personally, to test it, I built U-Boot for QEMU and loaded the EFI file via TFTP.
Am 06.11.22 um 18:03 schrieb Patrick Zacharias:
Hi Heinrich,
Thanks for the information, I'll make sure to use it for future contributions.
I encountered this issue, while building a custom EFI application using Rust by linking the following files:
./arch/arm/lib/reloc_arm_efi.c ./arch/arm/lib/crt0_arm_efi.S ./arch/arm/lib/elf_arm_efi.lds
As well as the custom application built as a library, that exports "efi_main".
Thus, the relocations were caused by the "write_fmt" functions that Rust provides. I encountered it, when concatenating two strings. format!("Test {}", "Test2");
The relocation was not applied and therefor lead to a crash.
From my understanding these relocations are ELF relocations and are therefor applied by the _relocate function (inside the built application) and not by the EFI loader. This is why I assumed, that it's fine for these relocations to reside in the data section.
I noticed, that in the _relocate function in ./arch/arm/lib/reloc_arm_efi.c, that the case R_ARM_RELATIVE was never entered, even though the generated shared object included them. I then looked at the EFI header file (crt0_arm_efi.S) and noticed, that it specifies only up to _edata to be loaded.
I concluded that _edata needs to be extended to include the ELF relocations as well.
After I decided to place it after the relocations, I noticed, that _edata is already specified at the same (new position) in gnu-efi. This reaffirmed me to contribute the patch as it currently is.
I assumed, that on x86, that the linker treats the ELF relocations (.rela.*) as if it was part of the data section. From my understanding the EFI relocations are in .reloc while the ELF relocations are in .rela.*. I might be mistaken, however.
Greetings, Patrick
Am 06.11.22 um 10:20 schrieb Heinrich Schuchardt:
On 10/31/22 21:01, Patrick Zacharias wrote:
Prior to this commit, the relocations would not get loaded by the efi loader.
This lead to none of the relocations being applied.
Signed-off-by: Fighter19 1475802+Fighter19@users.noreply.github.com
Thanks Patrick for your contribution.
You can use scripts/get_maintainer.pl to determine to whom a patch should be sent.
Where did you actually see relocations? Which code is not position independent?
arch/arm/lib/elf_aarch64_efi.lds | 2 +- arch/arm/lib/elf_arm_efi.lds | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/arm/lib/elf_aarch64_efi.lds b/arch/arm/lib/elf_aarch64_efi.lds index c0604dad46..1982864d17 100644 --- a/arch/arm/lib/elf_aarch64_efi.lds +++ b/arch/arm/lib/elf_aarch64_efi.lds @@ -46,12 +46,12 @@ SECTIONS *(COMMON) . = ALIGN(512); _bss_end = .; - _edata = .; } .rela.dyn : { *(.rela.dyn) } .rela.plt : { *(.rela.plt) } .rela.got : { *(.rela.got) } .rela.data : { *(.rela.data) *(.rela.data*) } + _edata = .; _data_size = . - _etext;
. = ALIGN(4096); diff --git a/arch/arm/lib/elf_arm_efi.lds b/arch/arm/lib/elf_arm_efi.lds index 767ebda635..c1b58a8033 100644 --- a/arch/arm/lib/elf_arm_efi.lds +++ b/arch/arm/lib/elf_arm_efi.lds @@ -46,12 +46,12 @@ SECTIONS *(COMMON) . = ALIGN(512); _bss_end = .; - _edata = .; } .rel.dyn : { *(.rel.dyn) } .rel.plt : { *(.rel.plt) } .rel.got : { *(.rel.got) } .rel.data : { *(.rel.data) *(.rel.data*) } + _edata = .;
Relocations (if they exist) should be in the .reloc section, not in the .data section.
If we want to create a .reloc section, we have to change arch/arm/lib/crt0_*_efi.S too. Furthermore the relocation section must be pointed to by field BaseRelocationTable of the Optional Header Data Directories (see PE-COFF specification).
Please, consider the other UEFI architectures (x86 and RISC-V) too.
Best regards
Heinrich
_data_size = . - _etext;
/DISCARD/ : {