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Subject[PATCH v2 27/31] arm64: Loadable modules
Date
From: Will Deacon <will.deacon@arm.com>

This patch adds support for loadable modules. Loadable modules are
loaded 64MB below the kernel image due to branch relocation restrictions
(see Documentation/arm64/memory.txt).

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
---
arch/arm64/include/asm/module.h | 23 ++
arch/arm64/kernel/module.c | 456 +++++++++++++++++++++++++++++++++++++++
2 files changed, 479 insertions(+), 0 deletions(-)
create mode 100644 arch/arm64/include/asm/module.h
create mode 100644 arch/arm64/kernel/module.c

diff --git a/arch/arm64/include/asm/module.h b/arch/arm64/include/asm/module.h
new file mode 100644
index 0000000..e80e232
--- /dev/null
+++ b/arch/arm64/include/asm/module.h
@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef __ASM_MODULE_H
+#define __ASM_MODULE_H
+
+#include <asm-generic/module.h>
+
+#define MODULE_ARCH_VERMAGIC "aarch64"
+
+#endif /* __ASM_MODULE_H */
diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c
new file mode 100644
index 0000000..ca0e3d5
--- /dev/null
+++ b/arch/arm64/kernel/module.c
@@ -0,0 +1,456 @@
+/*
+ * AArch64 loadable module support.
+ *
+ * Copyright (C) 2012 ARM Limited
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Author: Will Deacon <will.deacon@arm.com>
+ */
+
+#include <linux/bitops.h>
+#include <linux/elf.h>
+#include <linux/gfp.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/moduleloader.h>
+#include <linux/vmalloc.h>
+
+void *module_alloc(unsigned long size)
+{
+ return __vmalloc_node_range(size, 1, MODULES_VADDR, MODULES_END,
+ GFP_KERNEL, PAGE_KERNEL_EXEC, -1,
+ __builtin_return_address(0));
+}
+
+enum aarch64_reloc_op {
+ RELOC_OP_NONE,
+ RELOC_OP_ABS,
+ RELOC_OP_PREL,
+ RELOC_OP_PAGE,
+};
+
+static u64 do_reloc(enum aarch64_reloc_op reloc_op, void *place, u64 val)
+{
+ switch (reloc_op) {
+ case RELOC_OP_ABS:
+ return val;
+ case RELOC_OP_PREL:
+ return val - (u64)place;
+ case RELOC_OP_PAGE:
+ return (val & ~0xfff) - ((u64)place & ~0xfff);
+ case RELOC_OP_NONE:
+ return 0;
+ }
+
+ pr_err("do_reloc: unknown relocation operation %d\n", reloc_op);
+ return 0;
+}
+
+static int reloc_data(enum aarch64_reloc_op op, void *place, u64 val, int len)
+{
+ u64 imm_mask = (1 << len) - 1;
+ s64 sval = do_reloc(op, place, val);
+
+ switch (len) {
+ case 16:
+ *(s16 *)place = sval;
+ break;
+ case 32:
+ *(s32 *)place = sval;
+ break;
+ case 64:
+ *(s64 *)place = sval;
+ break;
+ default:
+ pr_err("Invalid length (%d) for data relocation\n", len);
+ return 0;
+ }
+
+ /*
+ * Extract the upper value bits (including the sign bit) and
+ * shift them to bit 0.
+ */
+ sval = (s64)(sval & ~(imm_mask >> 1)) >> (len - 1);
+
+ /*
+ * Overflow has occurred if the value is not representable in
+ * len bits (i.e the bottom len bits are not sign-extended and
+ * the top bits are not all zero).
+ */
+ if ((u64)(sval + 1) > 2)
+ return -ERANGE;
+
+ return 0;
+}
+
+enum aarch64_imm_type {
+ INSN_IMM_MOVNZ,
+ INSN_IMM_MOVK,
+ INSN_IMM_ADR,
+ INSN_IMM_26,
+ INSN_IMM_19,
+ INSN_IMM_16,
+ INSN_IMM_14,
+ INSN_IMM_12,
+ INSN_IMM_9,
+};
+
+static u32 encode_insn_immediate(enum aarch64_imm_type type, u32 insn, u64 imm)
+{
+ u32 immlo, immhi, lomask, himask, mask;
+ int shift;
+
+ switch (type) {
+ case INSN_IMM_MOVNZ:
+ /*
+ * For signed MOVW relocations, we have to manipulate the
+ * instruction encoding depending on whether or not the
+ * immediate is less than zero.
+ */
+ insn &= ~(3 << 29);
+ if ((s64)imm >= 0) {
+ /* >=0: Set the instruction to MOVZ (opcode 10b). */
+ insn |= 2 << 29;
+ } else {
+ /*
+ * <0: Set the instruction to MOVN (opcode 00b).
+ * Since we've masked the opcode already, we
+ * don't need to do anything other than
+ * inverting the new immediate field.
+ */
+ imm = ~imm;
+ }
+ case INSN_IMM_MOVK:
+ mask = BIT(16) - 1;
+ shift = 5;
+ break;
+ case INSN_IMM_ADR:
+ lomask = 0x3;
+ himask = 0x7ffff;
+ immlo = imm & lomask;
+ imm >>= 2;
+ immhi = imm & himask;
+ imm = (immlo << 24) | (immhi);
+ mask = (lomask << 24) | (himask);
+ shift = 5;
+ break;
+ case INSN_IMM_26:
+ mask = BIT(26) - 1;
+ shift = 0;
+ break;
+ case INSN_IMM_19:
+ mask = BIT(19) - 1;
+ shift = 5;
+ break;
+ case INSN_IMM_16:
+ mask = BIT(16) - 1;
+ shift = 5;
+ break;
+ case INSN_IMM_14:
+ mask = BIT(14) - 1;
+ shift = 5;
+ break;
+ case INSN_IMM_12:
+ mask = BIT(12) - 1;
+ shift = 10;
+ break;
+ case INSN_IMM_9:
+ mask = BIT(9) - 1;
+ shift = 12;
+ break;
+ default:
+ pr_err("encode_insn_immediate: unknown immediate encoding %d\n",
+ type);
+ return 0;
+ }
+
+ /* Update the immediate field. */
+ insn &= ~(mask << shift);
+ insn |= (imm & mask) << shift;
+
+ return insn;
+}
+
+static int reloc_insn_movw(enum aarch64_reloc_op op, void *place, u64 val,
+ int lsb, enum aarch64_imm_type imm_type)
+{
+ u64 imm, limit = 0;
+ s64 sval;
+ u32 insn = *(u32 *)place;
+
+ sval = do_reloc(op, place, val);
+ sval >>= lsb;
+ imm = sval & 0xffff;
+
+ /* Update the instruction with the new encoding. */
+ *(u32 *)place = encode_insn_immediate(imm_type, insn, imm);
+
+ /* Shift out the immediate field. */
+ sval >>= 16;
+
+ /*
+ * For unsigned immediates, the overflow check is straightforward.
+ * For signed immediates, the sign bit is actually the bit past the
+ * most significant bit of the field.
+ * The INSN_IMM_16 immediate type is unsigned.
+ */
+ if (imm_type != INSN_IMM_16) {
+ sval++;
+ limit++;
+ }
+
+ /* Check the upper bits depending on the sign of the immediate. */
+ if ((u64)sval > limit)
+ return -ERANGE;
+
+ return 0;
+}
+
+static int reloc_insn_imm(enum aarch64_reloc_op op, void *place, u64 val,
+ int lsb, int len, enum aarch64_imm_type imm_type)
+{
+ u64 imm, imm_mask;
+ s64 sval;
+ u32 insn = *(u32 *)place;
+
+ /* Calculate the relocation value. */
+ sval = do_reloc(op, place, val);
+ sval >>= lsb;
+
+ /* Extract the value bits and shift them to bit 0. */
+ imm_mask = (BIT(lsb + len) - 1) >> lsb;
+ imm = sval & imm_mask;
+
+ /* Update the instruction's immediate field. */
+ *(u32 *)place = encode_insn_immediate(imm_type, insn, imm);
+
+ /*
+ * Extract the upper value bits (including the sign bit) and
+ * shift them to bit 0.
+ */
+ sval = (s64)(sval & ~(imm_mask >> 1)) >> (len - 1);
+
+ /*
+ * Overflow has occurred if the upper bits are not all equal to
+ * the sign bit of the value.
+ */
+ if ((u64)(sval + 1) >= 2)
+ return -ERANGE;
+
+ return 0;
+}
+
+int apply_relocate_add(Elf64_Shdr *sechdrs,
+ const char *strtab,
+ unsigned int symindex,
+ unsigned int relsec,
+ struct module *me)
+{
+ unsigned int i;
+ int ovf;
+ bool overflow_check;
+ Elf64_Sym *sym;
+ void *loc;
+ u64 val;
+ Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr;
+
+ for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
+ /* loc corresponds to P in the AArch64 ELF document. */
+ loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
+ + rel[i].r_offset;
+
+ /* sym is the ELF symbol we're referring to. */
+ sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
+ + ELF64_R_SYM(rel[i].r_info);
+
+ /* val corresponds to (S + A) in the AArch64 ELF document. */
+ val = sym->st_value + rel[i].r_addend;
+
+ /* Check for overflow by default. */
+ overflow_check = true;
+
+ /* Perform the static relocation. */
+ switch (ELF64_R_TYPE(rel[i].r_info)) {
+ /* Null relocations. */
+ case R_ARM_NONE:
+ case R_AARCH64_NONE:
+ ovf = 0;
+ break;
+
+ /* Data relocations. */
+ case R_AARCH64_ABS64:
+ overflow_check = false;
+ ovf = reloc_data(RELOC_OP_ABS, loc, val, 64);
+ break;
+ case R_AARCH64_ABS32:
+ ovf = reloc_data(RELOC_OP_ABS, loc, val, 32);
+ break;
+ case R_AARCH64_ABS16:
+ ovf = reloc_data(RELOC_OP_ABS, loc, val, 16);
+ break;
+ case R_AARCH64_PREL64:
+ overflow_check = false;
+ ovf = reloc_data(RELOC_OP_PREL, loc, val, 64);
+ break;
+ case R_AARCH64_PREL32:
+ ovf = reloc_data(RELOC_OP_PREL, loc, val, 32);
+ break;
+ case R_AARCH64_PREL16:
+ ovf = reloc_data(RELOC_OP_PREL, loc, val, 16);
+ break;
+
+ /* MOVW instruction relocations. */
+ case R_AARCH64_MOVW_UABS_G0_NC:
+ overflow_check = false;
+ case R_AARCH64_MOVW_UABS_G0:
+ ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 0,
+ INSN_IMM_16);
+ break;
+ case R_AARCH64_MOVW_UABS_G1_NC:
+ overflow_check = false;
+ case R_AARCH64_MOVW_UABS_G1:
+ ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 16,
+ INSN_IMM_16);
+ break;
+ case R_AARCH64_MOVW_UABS_G2_NC:
+ overflow_check = false;
+ case R_AARCH64_MOVW_UABS_G2:
+ ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 32,
+ INSN_IMM_16);
+ break;
+ case R_AARCH64_MOVW_UABS_G3:
+ /* We're using the top bits so we can't overflow. */
+ overflow_check = false;
+ ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 48,
+ INSN_IMM_16);
+ break;
+ case R_AARCH64_MOVW_SABS_G0:
+ ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 0,
+ INSN_IMM_MOVNZ);
+ break;
+ case R_AARCH64_MOVW_SABS_G1:
+ ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 16,
+ INSN_IMM_MOVNZ);
+ break;
+ case R_AARCH64_MOVW_SABS_G2:
+ ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 32,
+ INSN_IMM_MOVNZ);
+ break;
+ case R_AARCH64_MOVW_PREL_G0_NC:
+ overflow_check = false;
+ ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 0,
+ INSN_IMM_MOVK);
+ break;
+ case R_AARCH64_MOVW_PREL_G0:
+ ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 0,
+ INSN_IMM_MOVNZ);
+ break;
+ case R_AARCH64_MOVW_PREL_G1_NC:
+ overflow_check = false;
+ ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 16,
+ INSN_IMM_MOVK);
+ break;
+ case R_AARCH64_MOVW_PREL_G1:
+ ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 16,
+ INSN_IMM_MOVNZ);
+ break;
+ case R_AARCH64_MOVW_PREL_G2_NC:
+ overflow_check = false;
+ ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 32,
+ INSN_IMM_MOVK);
+ break;
+ case R_AARCH64_MOVW_PREL_G2:
+ ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 32,
+ INSN_IMM_MOVNZ);
+ break;
+ case R_AARCH64_MOVW_PREL_G3:
+ /* We're using the top bits so we can't overflow. */
+ overflow_check = false;
+ ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 48,
+ INSN_IMM_MOVNZ);
+ break;
+
+ /* Immediate instruction relocations. */
+ case R_AARCH64_LD_PREL_LO19:
+ ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 19,
+ INSN_IMM_19);
+ break;
+ case R_AARCH64_ADR_PREL_LO21:
+ ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 0, 21,
+ INSN_IMM_ADR);
+ break;
+ case R_AARCH64_ADR_PREL_PG_HI21_NC:
+ overflow_check = false;
+ case R_AARCH64_ADR_PREL_PG_HI21:
+ ovf = reloc_insn_imm(RELOC_OP_PAGE, loc, val, 12, 21,
+ INSN_IMM_ADR);
+ break;
+ case R_AARCH64_ADD_ABS_LO12_NC:
+ case R_AARCH64_LDST8_ABS_LO12_NC:
+ overflow_check = false;
+ ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 0, 12,
+ INSN_IMM_12);
+ break;
+ case R_AARCH64_LDST16_ABS_LO12_NC:
+ overflow_check = false;
+ ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 1, 11,
+ INSN_IMM_12);
+ break;
+ case R_AARCH64_LDST32_ABS_LO12_NC:
+ overflow_check = false;
+ ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 2, 10,
+ INSN_IMM_12);
+ break;
+ case R_AARCH64_LDST64_ABS_LO12_NC:
+ overflow_check = false;
+ ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 3, 9,
+ INSN_IMM_12);
+ break;
+ case R_AARCH64_LDST128_ABS_LO12_NC:
+ overflow_check = false;
+ ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 4, 8,
+ INSN_IMM_12);
+ break;
+ case R_AARCH64_TSTBR14:
+ ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 14,
+ INSN_IMM_14);
+ break;
+ case R_AARCH64_CONDBR19:
+ ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 19,
+ INSN_IMM_19);
+ break;
+ case R_AARCH64_JUMP26:
+ case R_AARCH64_CALL26:
+ ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 26,
+ INSN_IMM_26);
+ break;
+
+ default:
+ pr_err("module %s: unsupported RELA relocation: %llu\n",
+ me->name, ELF64_R_TYPE(rel[i].r_info));
+ return -ENOEXEC;
+ }
+
+ if (overflow_check && ovf == -ERANGE)
+ goto overflow;
+
+ }
+
+ return 0;
+
+overflow:
+ pr_err("module %s: overflow in relocation type %d val %Lx\n",
+ me->name, (int)ELF64_R_TYPE(rel[i].r_info), val);
+ return -ENOEXEC;
+}


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