Clang generates jump tables in .rodata.cst* instead of custom .rodata.<section> causing EFI runtime failures #161055
Description
When compiling u-boot with Clang, we observed that certain functions marked with a custom section attribute (e.g. .text.efi_runtime) may produce jump tables in a separate .rodata.cst* section. This behavior breaks the expected layout, because the U-Boot linker script only includes .rodata.efi_runtime* but not .rodata.cst*.
This leads to missing jump tables at runtime and ultimately boot failure.
GCC does not show this issue:
GCC emits jump tables into .rodata.efi_runtime., which naturally matches the linker script.
Clang emits jump tables into .rodata.cst, which is excluded by the current linker script.
Reproducer: u-boot: psci.c
unsigned long invoke_psci_fn(unsigned long, unsigned long, unsigned long, unsigned long);
enum efi_reset_type {
EFI_RESET_COLD = 0,
EFI_RESET_WARM = 1,
EFI_RESET_SHUTDOWN = 2,
EFI_RESET_PLATFORM_SPECIFIC = 3,
};
typedef unsigned long efi_status_t;
__attribute__((__section__(".text.efi_runtime")))
void efi_reset_system(enum efi_reset_type reset_type,
efi_status_t reset_status,
unsigned long data_size,
void *reset_data) {
if (reset_type == EFI_RESET_COLD ||
reset_type == EFI_RESET_WARM ||
reset_type == EFI_RESET_PLATFORM_SPECIFIC) {
invoke_psci_fn((0x84000000 + 9), 0, 0, 0);
} else if (reset_type == EFI_RESET_SHUTDOWN) {
invoke_psci_fn((0x84000000 + 8), 0, 0, 0);
}
while (1) ;
}
The linker script only collects: u-boot: u-boot.lds
.efi_runtime : {
__efi_runtime_start = .;
*(.text.efi_runtime*)
*(.rodata.efi_runtime*)
*(.data.efi_runtime*)
__efi_runtime_stop = .;
}
https://godbolt.org/z/nr5qahqsf
Actual behavior (Clang)
- Jump table emitted into .rodata.cst*
- Not captured by .efi_runtime in the linker script
Expected behavior (GCC-compatible)
- Jump table emitted into .rodata.efi_runtime.*
- Automatically included in .efi_runtime section by existing linker script
It seems GCC propagates the custom section naming to associated constant data (such as jump tables), while Clang defaults to placing them into .rodata.cst*.
Possible solutions:
Clang to emit jump tables into a section derived from the enclosing function’s custom section (e.g., .rodata.efi_runtime.*).
Or provide an attribute / option to control jump table section placement explicitly.