RISC-V: Add sections of PLT and GOT for kernel module
The address of external symbols will locate more than 32-bit offset
in 64-bit kernel with sv39 or sv48 virtual addressing.
Module loader emits the GOT and PLT entries for data symbols and
function symbols respectively.
The PLT entry is a trampoline code for jumping to the 64-bit
real address. The GOT entry is just the data symbol address.
Signed-off-by: Zong Li <zong@andestech.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
diff --git a/arch/riscv/include/asm/module.h b/arch/riscv/include/asm/module.h
new file mode 100644
index 0000000..e61d73f
--- /dev/null
+++ b/arch/riscv/include/asm/module.h
@@ -0,0 +1,103 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2017 Andes Technology Corporation */
+
+#ifndef _ASM_RISCV_MODULE_H
+#define _ASM_RISCV_MODULE_H
+
+#include <asm-generic/module.h>
+
+#define MODULE_ARCH_VERMAGIC "riscv"
+
+u64 module_emit_got_entry(struct module *mod, u64 val);
+u64 module_emit_plt_entry(struct module *mod, u64 val);
+
+#ifdef CONFIG_MODULE_SECTIONS
+struct mod_section {
+ struct elf64_shdr *shdr;
+ int num_entries;
+ int max_entries;
+};
+
+struct mod_arch_specific {
+ struct mod_section got;
+ struct mod_section plt;
+};
+
+struct got_entry {
+ u64 symbol_addr; /* the real variable address */
+};
+
+static inline struct got_entry emit_got_entry(u64 val)
+{
+ return (struct got_entry) {val};
+}
+
+static inline struct got_entry *get_got_entry(u64 val,
+ const struct mod_section *sec)
+{
+ struct got_entry *got = (struct got_entry *)sec->shdr->sh_addr;
+ int i;
+ for (i = 0; i < sec->num_entries; i++) {
+ if (got[i].symbol_addr == val)
+ return &got[i];
+ }
+ return NULL;
+}
+
+struct plt_entry {
+ /*
+ * Trampoline code to real target address. The return address
+ * should be the original (pc+4) before entring plt entry.
+ * For 8 byte alignment of symbol_addr,
+ * don't pack structure to remove the padding.
+ */
+ u32 insn_auipc; /* auipc t0, 0x0 */
+ u32 insn_ld; /* ld t1, 0x10(t0) */
+ u32 insn_jr; /* jr t1 */
+ u64 symbol_addr; /* the real jump target address */
+};
+
+#define OPC_AUIPC 0x0017
+#define OPC_LD 0x3003
+#define OPC_JALR 0x0067
+#define REG_T0 0x5
+#define REG_T1 0x6
+#define IMM_OFFSET 0x10
+
+static inline struct plt_entry emit_plt_entry(u64 val)
+{
+ /*
+ * U-Type encoding:
+ * +------------+----------+----------+
+ * | imm[31:12] | rd[11:7] | opc[6:0] |
+ * +------------+----------+----------+
+ *
+ * I-Type encoding:
+ * +------------+------------+--------+----------+----------+
+ * | imm[31:20] | rs1[19:15] | funct3 | rd[11:7] | opc[6:0] |
+ * +------------+------------+--------+----------+----------+
+ *
+ */
+ return (struct plt_entry) {
+ OPC_AUIPC | (REG_T0 << 7),
+ OPC_LD | (IMM_OFFSET << 20) | (REG_T0 << 15) | (REG_T1 << 7),
+ OPC_JALR | (REG_T1 << 15),
+ val
+ };
+}
+
+static inline struct plt_entry *get_plt_entry(u64 val,
+ const struct mod_section *sec)
+{
+ struct plt_entry *plt = (struct plt_entry *)sec->shdr->sh_addr;
+ int i;
+ for (i = 0; i < sec->num_entries; i++) {
+ if (plt[i].symbol_addr == val)
+ return &plt[i];
+ }
+ return NULL;
+}
+
+#endif /* CONFIG_MODULE_SECTIONS */
+
+#endif /* _ASM_RISCV_MODULE_H */