Thumb-2: Add support for loadable modules
Modules compiled to Thumb-2 have two additional relocations needing to
be resolved at load time, R_ARM_THM_CALL and R_ARM_THM_JUMP24, for BL
and B.W instructions. The maximum Thumb-2 addressing range is +/-2^24
(+/-16MB) therefore the MODULES_VADDR macro in asm/memory.h is set to
(MODULES_END - 8MB) for the Thumb-2 compiled kernel.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
diff --git a/arch/arm/include/asm/elf.h b/arch/arm/include/asm/elf.h
index c207504..c3b911e 100644
--- a/arch/arm/include/asm/elf.h
+++ b/arch/arm/include/asm/elf.h
@@ -55,6 +55,9 @@
#define R_ARM_MOVW_ABS_NC 43
#define R_ARM_MOVT_ABS 44
+#define R_ARM_THM_CALL 10
+#define R_ARM_THM_JUMP24 30
+
/*
* These are used to set parameters in the core dumps.
*/
diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
index 85763db..376be1a 100644
--- a/arch/arm/include/asm/memory.h
+++ b/arch/arm/include/asm/memory.h
@@ -44,7 +44,13 @@
* The module space lives between the addresses given by TASK_SIZE
* and PAGE_OFFSET - it must be within 32MB of the kernel text.
*/
+#ifndef CONFIG_THUMB2_KERNEL
#define MODULES_VADDR (PAGE_OFFSET - 16*1024*1024)
+#else
+/* smaller range for Thumb-2 symbols relocation (2^24)*/
+#define MODULES_VADDR (PAGE_OFFSET - 8*1024*1024)
+#endif
+
#if TASK_SIZE > MODULES_VADDR
#error Top of user space clashes with start of module space
#endif
diff --git a/arch/arm/kernel/module.c b/arch/arm/kernel/module.c
index bac03c8..f28c5e9 100644
--- a/arch/arm/kernel/module.c
+++ b/arch/arm/kernel/module.c
@@ -102,6 +102,7 @@
unsigned long loc;
Elf32_Sym *sym;
s32 offset;
+ u32 upper, lower, sign, j1, j2;
offset = ELF32_R_SYM(rel->r_info);
if (offset < 0 || offset > (symsec->sh_size / sizeof(Elf32_Sym))) {
@@ -184,6 +185,58 @@
(offset & 0x0fff);
break;
+ case R_ARM_THM_CALL:
+ case R_ARM_THM_JUMP24:
+ upper = *(u16 *)loc;
+ lower = *(u16 *)(loc + 2);
+
+ /*
+ * 25 bit signed address range (Thumb-2 BL and B.W
+ * instructions):
+ * S:I1:I2:imm10:imm11:0
+ * where:
+ * S = upper[10] = offset[24]
+ * I1 = ~(J1 ^ S) = offset[23]
+ * I2 = ~(J2 ^ S) = offset[22]
+ * imm10 = upper[9:0] = offset[21:12]
+ * imm11 = lower[10:0] = offset[11:1]
+ * J1 = lower[13]
+ * J2 = lower[11]
+ */
+ sign = (upper >> 10) & 1;
+ j1 = (lower >> 13) & 1;
+ j2 = (lower >> 11) & 1;
+ offset = (sign << 24) | ((~(j1 ^ sign) & 1) << 23) |
+ ((~(j2 ^ sign) & 1) << 22) |
+ ((upper & 0x03ff) << 12) |
+ ((lower & 0x07ff) << 1);
+ if (offset & 0x01000000)
+ offset -= 0x02000000;
+ offset += sym->st_value - loc;
+
+ /* only Thumb addresses allowed (no interworking) */
+ if (!(offset & 1) ||
+ offset <= (s32)0xff000000 ||
+ offset >= (s32)0x01000000) {
+ printk(KERN_ERR
+ "%s: relocation out of range, section "
+ "%d reloc %d sym '%s'\n", module->name,
+ relindex, i, strtab + sym->st_name);
+ return -ENOEXEC;
+ }
+
+ sign = (offset >> 24) & 1;
+ j1 = sign ^ (~(offset >> 23) & 1);
+ j2 = sign ^ (~(offset >> 22) & 1);
+ *(u16 *)loc = (u16)((upper & 0xf800) | (sign << 10) |
+ ((offset >> 12) & 0x03ff));
+ *(u16 *)(loc + 2) = (u16)((lower & 0xd000) |
+ (j1 << 13) | (j2 << 11) |
+ ((offset >> 1) & 0x07ff));
+ upper = *(u16 *)loc;
+ lower = *(u16 *)(loc + 2);
+ break;
+
default:
printk(KERN_ERR "%s: unknown relocation: %u\n",
module->name, ELF32_R_TYPE(rel->r_info));