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

Charlie Jenkins <charlie@rivosinc.com> 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] https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/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/20231101-module_relocations-v9-0-8dfa3483c400@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

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

arch/riscv/kernel/tests/Kconfig.debug

@@ -0,0 +1,35 @@
+# SPDX-License-Identifier: GPL-2.0-only
+menu "arch/riscv/kernel Testing and Coverage"
+
+config AS_HAS_ULEB128
+	def_bool $(as-instr,.reloc label$(comma) R_RISCV_SET_ULEB128$(comma) 127\n.reloc label$(comma) R_RISCV_SUB_ULEB128$(comma) 127\nlabel:\n.word 0)
+
+menuconfig RUNTIME_KERNEL_TESTING_MENU
+       bool "arch/riscv/kernel runtime Testing"
+       def_bool y
+       help
+         Enable riscv kernel runtime testing.
+
+if RUNTIME_KERNEL_TESTING_MENU
+
+config RISCV_MODULE_LINKING_KUNIT
+       bool "KUnit test riscv module linking at runtime" if !KUNIT_ALL_TESTS
+       depends on KUNIT
+       default KUNIT_ALL_TESTS
+       help
+         Enable this option to test riscv module linking at boot. This will
+	 enable a module called "test_module_linking".
+
+         KUnit tests run during boot and output the results to the debug log
+         in TAP format (http://testanything.org/). Only useful for kernel devs
+         running the KUnit test harness, and not intended for inclusion into a
+         production build.
+
+         For more information on KUnit and unit tests in general please refer
+         to the KUnit documentation in Documentation/dev-tools/kunit/.
+
+         If unsure, say N.
+
+endif # RUNTIME_TESTING_MENU
+
+endmenu # "arch/riscv/kernel runtime Testing"

arch/riscv/kernel/tests/Makefile

@@ -0,0 +1 @@
+obj-$(CONFIG_RISCV_MODULE_LINKING_KUNIT)	+= module_test/

arch/riscv/kernel/tests/module_test/Makefile

@@ -0,0 +1,15 @@
+obj-m += test_module_linking.o
+
+test_sub := test_sub6.o test_sub8.o test_sub16.o test_sub32.o test_sub64.o
+
+test_set := test_set6.o test_set8.o test_set16.o test_set32.o
+
+test_module_linking-objs += $(test_sub)
+
+test_module_linking-objs += $(test_set)
+
+ifeq ($(CONFIG_AS_HAS_ULEB128),y)
+test_module_linking-objs += test_uleb128.o
+endif
+
+test_module_linking-objs += test_module_linking_main.o

arch/riscv/kernel/tests/module_test/test_module_linking_main.c

@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2023 Rivos Inc.
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <kunit/test.h>
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Test module linking");
+
+extern int test_set32(void);
+extern int test_set16(void);
+extern int test_set8(void);
+extern int test_set6(void);
+extern long test_sub64(void);
+extern int test_sub32(void);
+extern int test_sub16(void);
+extern int test_sub8(void);
+extern int test_sub6(void);
+
+#ifdef CONFIG_AS_HAS_ULEB128
+extern int test_uleb_basic(void);
+extern int test_uleb_large(void);
+#endif
+
+#define CHECK_EQ(lhs, rhs) KUNIT_ASSERT_EQ(test, lhs, rhs)
+
+void run_test_set(struct kunit *test);
+void run_test_sub(struct kunit *test);
+void run_test_uleb(struct kunit *test);
+
+void run_test_set(struct kunit *test)
+{
+	int val32 = test_set32();
+	int val16 = test_set16();
+	int val8 = test_set8();
+	int val6 = test_set6();
+
+	CHECK_EQ(val32, 0);
+	CHECK_EQ(val16, 0);
+	CHECK_EQ(val8, 0);
+	CHECK_EQ(val6, 0);
+}
+
+void run_test_sub(struct kunit *test)
+{
+	int val64 = test_sub64();
+	int val32 = test_sub32();
+	int val16 = test_sub16();
+	int val8 = test_sub8();
+	int val6 = test_sub6();
+
+	CHECK_EQ(val64, 0);
+	CHECK_EQ(val32, 0);
+	CHECK_EQ(val16, 0);
+	CHECK_EQ(val8, 0);
+	CHECK_EQ(val6, 0);
+}
+
+#ifdef CONFIG_AS_HAS_ULEB128
+void run_test_uleb(struct kunit *test)
+{
+	int val_uleb = test_uleb_basic();
+	int val_uleb2 = test_uleb_large();
+
+	CHECK_EQ(val_uleb, 0);
+	CHECK_EQ(val_uleb2, 0);
+}
+#endif
+
+static struct kunit_case __refdata riscv_module_linking_test_cases[] = {
+	KUNIT_CASE(run_test_set),
+	KUNIT_CASE(run_test_sub),
+#ifdef CONFIG_AS_HAS_ULEB128
+	KUNIT_CASE(run_test_uleb),
+#endif
+	{}
+};
+
+static struct kunit_suite riscv_module_linking_test_suite = {
+	.name = "riscv_checksum",
+	.test_cases = riscv_module_linking_test_cases,
+};
+
+kunit_test_suites(&riscv_module_linking_test_suite);

arch/riscv/kernel/tests/module_test/test_set16.S

@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2023 Rivos Inc.
+ */
+
+.text
+.global test_set16
+test_set16:
+	lw	a0, set16
+	la	t0, set16
+#ifdef CONFIG_32BIT
+	slli	t0, t0, 16
+	srli	t0, t0, 16
+#else
+	slli	t0, t0, 48
+	srli	t0, t0, 48
+#endif
+	sub	a0, a0, t0
+	ret
+.data
+set16:
+	.reloc set16, R_RISCV_SET16, set16
+	.word 0

arch/riscv/kernel/tests/module_test/test_set32.S

@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2023 Rivos Inc.
+ */
+
+.text
+.global test_set32
+test_set32:
+	lw	a0, set32
+	la	t0, set32
+#ifndef CONFIG_32BIT
+	slli	t0, t0, 32
+	srli	t0, t0, 32
+#endif
+	sub	a0, a0, t0
+	ret
+.data
+set32:
+	.reloc set32, R_RISCV_SET32, set32
+	.word 0

arch/riscv/kernel/tests/module_test/test_set6.S

@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2023 Rivos Inc.
+ */
+
+.text
+.global test_set6
+test_set6:
+	lw	a0, set6
+	la	t0, set6
+#ifdef CONFIG_32BIT
+	slli	t0, t0, 26
+	srli	t0, t0, 26
+#else
+	slli	t0, t0, 58
+	srli	t0, t0, 58
+#endif
+	sub	a0, a0, t0
+	ret
+.data
+set6:
+	.reloc set6, R_RISCV_SET6, set6
+	.word 0

arch/riscv/kernel/tests/module_test/test_set8.S

@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2023 Rivos Inc.
+ */
+
+.text
+.global test_set8
+test_set8:
+	lw	a0, set8
+	la	t0, set8
+#ifdef CONFIG_32BIT
+	slli	t0, t0, 24
+	srli	t0, t0, 24
+#else
+	slli	t0, t0, 56
+	srli	t0, t0, 56
+#endif
+	sub	a0, a0, t0
+	ret
+.data
+set8:
+	.reloc set8, R_RISCV_SET8, set8
+	.word 0

arch/riscv/kernel/tests/module_test/test_sub16.S

@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2023 Rivos Inc.
+ */
+
+.text
+.global test_sub16
+test_sub16:
+	lh	a0, sub16
+	addi	a0, a0, -32
+	ret
+first:
+	.space 32
+second:
+
+.data
+sub16:
+	.reloc		sub16, R_RISCV_ADD16, second
+	.reloc		sub16, R_RISCV_SUB16, first
+	.half		0

arch/riscv/kernel/tests/module_test/test_sub32.S

@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2023 Rivos Inc.
+ */
+
+.text
+.global test_sub32
+test_sub32:
+	lw	a0, sub32
+	addi	a0, a0, -32
+	ret
+first:
+	.space 32
+second:
+
+.data
+sub32:
+	.reloc		sub32, R_RISCV_ADD32, second
+	.reloc		sub32, R_RISCV_SUB32, first
+	.word		0

arch/riscv/kernel/tests/module_test/test_sub6.S

@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2023 Rivos Inc.
+ */
+
+.text
+.global test_sub6
+test_sub6:
+	lb	a0, sub6
+	addi	a0, a0, -32
+	ret
+first:
+	.space 32
+second:
+
+.data
+sub6:
+	.reloc		sub6, R_RISCV_SET6, second
+	.reloc		sub6, R_RISCV_SUB6, first
+	.byte		0

arch/riscv/kernel/tests/module_test/test_sub64.S

@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2023 Rivos Inc.
+ */
+
+.text
+.global test_sub64
+test_sub64:
+#ifdef CONFIG_32BIT
+	lw	a0, sub64
+#else
+	ld	a0, sub64
+#endif
+	addi	a0, a0, -32
+	ret
+first:
+	.space 32
+second:
+
+.data
+sub64:
+	.reloc		sub64, R_RISCV_ADD64, second
+	.reloc		sub64, R_RISCV_SUB64, first
+	.word		0
+	.word		0

arch/riscv/kernel/tests/module_test/test_sub8.S

@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2023 Rivos Inc.
+ */
+
+.text
+.global test_sub8
+test_sub8:
+	lb	a0, sub8
+	addi	a0, a0, -32
+	ret
+first:
+	.space 32
+second:
+
+.data
+sub8:
+	.reloc		sub8, R_RISCV_ADD8, second
+	.reloc		sub8, R_RISCV_SUB8, first
+	.byte		0

arch/riscv/kernel/tests/module_test/test_uleb128.S

@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2023 Rivos Inc.
+ */
+
+.text
+.global test_uleb_basic
+test_uleb_basic:
+	ld	a0, second
+	addi	a0, a0, -127
+	ret
+
+.global test_uleb_large
+test_uleb_large:
+	ld	a0, fourth
+	addi	a0, a0, -0x07e8
+	ret
+
+.data
+first:
+	.space 127
+second:
+	.reloc second, R_RISCV_SET_ULEB128, second
+	.reloc second, R_RISCV_SUB_ULEB128, first
+	.dword 0
+third:
+	.space 1000
+fourth:
+	.reloc fourth, R_RISCV_SET_ULEB128, fourth
+	.reloc fourth, R_RISCV_SUB_ULEB128, third
+	.dword 0