Merge patch series "riscv: Add remaining module relocations and tests"

Charlie Jenkins <[email protected]> says:

A handful of module relocations were missing, this patch includes the
remaining ones. I also wrote some test cases to ensure that module
loading works properly. Some relocations cannot be supported in the
kernel, these include the ones that rely on thread local storage and
dynamic linking.

This patch also overhauls the implementation of ADD/SUB/SET/ULEB128
relocations to handle overflow. "Overflow" is different for ULEB128
since it is a variable-length encoding that the compiler can be expected
to generate enough space for. Instead of overflowing, ULEB128 will
expand into the next 8-bit segment of the location.

A psABI proposal [1] was merged that mandates that SET_ULEB128 and
SUB_ULEB128 are paired, however the discussion following the merging of
the pull request revealed that while the pull request was valid, it
would be better for linkers to properly handle this overflow. This patch
proactively implements this methodology for future compatibility.

This can be tested by enabling KUNIT, RUNTIME_KERNEL_TESTING_MENU, and
RISCV_MODULE_LINKING_KUNIT.

[1] riscv-non-isa/riscv-elf-psabi-doc#403

* b4-shazam-merge:
  riscv: Add tests for riscv module loading
  riscv: Add remaining module relocations
  riscv: Avoid unaligned access when relocating modules

Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Palmer Dabbelt <[email protected]>

Author: palmer-dabbelt

arch/riscv/Kconfig.debug

@@ -0,0 +1 @@
+source "arch/riscv/kernel/tests/Kconfig.debug"

arch/riscv/include/uapi/asm/elf.h

@@ -49,6 +49,7 @@ typedef union __riscv_fp_state elf_fpregset_t;
 #define R_RISCV_TLS_DTPREL64	9
 #define R_RISCV_TLS_TPREL32	10
 #define R_RISCV_TLS_TPREL64	11
+#define R_RISCV_IRELATIVE	58
 
 /* Relocation types not used by the dynamic linker */
 #define R_RISCV_BRANCH		16
@@ -81,7 +82,6 @@ typedef union __riscv_fp_state elf_fpregset_t;
 #define R_RISCV_ALIGN		43
 #define R_RISCV_RVC_BRANCH	44
 #define R_RISCV_RVC_JUMP	45
-#define R_RISCV_LUI		46
 #define R_RISCV_GPREL_I		47
 #define R_RISCV_GPREL_S		48
 #define R_RISCV_TPREL_I		49
@@ -93,6 +93,9 @@ typedef union __riscv_fp_state elf_fpregset_t;
 #define R_RISCV_SET16		55
 #define R_RISCV_SET32		56
 #define R_RISCV_32_PCREL	57
+#define R_RISCV_PLT32		59
+#define R_RISCV_SET_ULEB128	60
+#define R_RISCV_SUB_ULEB128	61
 
 
 #endif /* _UAPI_ASM_RISCV_ELF_H */

arch/riscv/kernel/Makefile

@@ -57,6 +57,7 @@ obj-y	+= stacktrace.o
 obj-y	+= cacheinfo.o
 obj-y	+= patch.o
 obj-y	+= probes/
+obj-y	+= tests/
 obj-$(CONFIG_MMU) += vdso.o vdso/
 
 obj-$(CONFIG_RISCV_MISALIGNED)	+= traps_misaligned.o