From b8bde0ef12bd43f013d879973a1900930bfb95ee Mon Sep 17 00:00:00 2001 From: Zong Li Date: Thu, 15 Mar 2018 16:50:42 +0800 Subject: RISC-V: Add section of GOT.PLT for kernel module Separate the function symbol address from .plt to .got.plt section. The original plt entry has trampoline code with symbol address, there is a 32-bit padding bwtween jar instruction and symbol address. Extract the symbol address to .got.plt to reduce the module size. Signed-off-by: Zong Li Signed-off-by: Palmer Dabbelt --- arch/riscv/include/asm/module.h | 40 +++++++++++++++++++++++-------------- arch/riscv/kernel/module-sections.c | 21 +++++++++++++++++-- arch/riscv/kernel/module.lds | 1 + 3 files changed, 45 insertions(+), 17 deletions(-) (limited to 'arch/riscv') diff --git a/arch/riscv/include/asm/module.h b/arch/riscv/include/asm/module.h index e61d73f82d4d..349df33808c4 100644 --- a/arch/riscv/include/asm/module.h +++ b/arch/riscv/include/asm/module.h @@ -21,6 +21,7 @@ struct mod_section { struct mod_arch_specific { struct mod_section got; struct mod_section plt; + struct mod_section got_plt; }; struct got_entry { @@ -48,13 +49,10 @@ 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 @@ -62,9 +60,8 @@ struct plt_entry { #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) +static inline struct plt_entry emit_plt_entry(u64 val, u64 plt, u64 got_plt) { /* * U-Type encoding: @@ -78,24 +75,37 @@ static inline struct plt_entry emit_plt_entry(u64 val) * +------------+------------+--------+----------+----------+ * */ + u64 offset = got_plt - plt; + u32 hi20 = (offset + 0x800) & 0xfffff000; + u32 lo12 = (offset - hi20); 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 + OPC_AUIPC | (REG_T0 << 7) | hi20, + OPC_LD | (lo12 << 20) | (REG_T0 << 15) | (REG_T1 << 7), + OPC_JALR | (REG_T1 << 15) }; } -static inline struct plt_entry *get_plt_entry(u64 val, - const struct mod_section *sec) +static inline int get_got_plt_idx(u64 val, const struct mod_section *sec) { - struct plt_entry *plt = (struct plt_entry *)sec->shdr->sh_addr; + struct got_entry *got_plt = (struct got_entry *)sec->shdr->sh_addr; int i; for (i = 0; i < sec->num_entries; i++) { - if (plt[i].symbol_addr == val) - return &plt[i]; + if (got_plt[i].symbol_addr == val) + return i; } - return NULL; + return -1; +} + +static inline struct plt_entry *get_plt_entry(u64 val, + const struct mod_section *sec_plt, + const struct mod_section *sec_got_plt) +{ + struct plt_entry *plt = (struct plt_entry *)sec_plt->shdr->sh_addr; + int got_plt_idx = get_got_plt_idx(val, sec_got_plt); + if (got_plt_idx >= 0) + return plt + got_plt_idx; + else + return NULL; } #endif /* CONFIG_MODULE_SECTIONS */ diff --git a/arch/riscv/kernel/module-sections.c b/arch/riscv/kernel/module-sections.c index 94ba1551eac3..bbbd26e19bfd 100644 --- a/arch/riscv/kernel/module-sections.c +++ b/arch/riscv/kernel/module-sections.c @@ -30,18 +30,23 @@ u64 module_emit_got_entry(struct module *mod, u64 val) u64 module_emit_plt_entry(struct module *mod, u64 val) { + struct mod_section *got_plt_sec = &mod->arch.got_plt; + struct got_entry *got_plt; struct mod_section *plt_sec = &mod->arch.plt; - struct plt_entry *plt = get_plt_entry(val, plt_sec); + struct plt_entry *plt = get_plt_entry(val, plt_sec, got_plt_sec); int i = plt_sec->num_entries; if (plt) return (u64)plt; /* There is no duplicate entry, create a new one */ + got_plt = (struct got_entry *)got_plt_sec->shdr->sh_addr; + got_plt[i] = emit_got_entry(val); plt = (struct plt_entry *)plt_sec->shdr->sh_addr; - plt[i] = emit_plt_entry(val); + plt[i] = emit_plt_entry(val, (u64)&plt[i], (u64)&got_plt[i]); plt_sec->num_entries++; + got_plt_sec->num_entries++; BUG_ON(plt_sec->num_entries > plt_sec->max_entries); return (u64)&plt[i]; @@ -94,6 +99,8 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, mod->arch.plt.shdr = sechdrs + i; else if (!strcmp(secstrings + sechdrs[i].sh_name, ".got")) mod->arch.got.shdr = sechdrs + i; + else if (!strcmp(secstrings + sechdrs[i].sh_name, ".got.plt")) + mod->arch.got_plt.shdr = sechdrs + i; } if (!mod->arch.plt.shdr) { @@ -104,6 +111,10 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, pr_err("%s: module GOT section(s) missing\n", mod->name); return -ENOEXEC; } + if (!mod->arch.got_plt.shdr) { + pr_err("%s: module GOT.PLT section(s) missing\n", mod->name); + return -ENOEXEC; + } /* Calculate the maxinum number of entries */ for (i = 0; i < ehdr->e_shnum; i++) { @@ -135,5 +146,11 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, mod->arch.got.num_entries = 0; mod->arch.got.max_entries = num_gots; + mod->arch.got_plt.shdr->sh_type = SHT_NOBITS; + mod->arch.got_plt.shdr->sh_flags = SHF_ALLOC; + mod->arch.got_plt.shdr->sh_addralign = L1_CACHE_BYTES; + mod->arch.got_plt.shdr->sh_size = (num_plts + 1) * sizeof(struct got_entry); + mod->arch.got_plt.num_entries = 0; + mod->arch.got_plt.max_entries = num_plts; return 0; } diff --git a/arch/riscv/kernel/module.lds b/arch/riscv/kernel/module.lds index 7ef580e62883..295ecfb341a2 100644 --- a/arch/riscv/kernel/module.lds +++ b/arch/riscv/kernel/module.lds @@ -4,4 +4,5 @@ SECTIONS { .plt (NOLOAD) : { BYTE(0) } .got (NOLOAD) : { BYTE(0) } + .got.plt (NOLOAD) : { BYTE(0) } } -- cgit v1.2.3