I created a GitHub repository demonstrating the issue, together with
instructions on how to build it.
https://github.com/Fighter19/hello-world-arm-efi
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+fighte...@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/ : {
