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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>
This commit is contained in:
Catalin Marinas 2009-07-24 12:32:59 +01:00
parent 0e056f20f1
commit adca6dc23b
3 changed files with 62 additions and 0 deletions
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3
arch/arm/include/asm/elf.h
View File

@ -55,6 +55,9 @@ typedef struct user_fp elf_fpregset_t;
#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.
*/

6
arch/arm/include/asm/memory.h
View File

@ -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

53
arch/arm/kernel/module.c
View File

@ -102,6 +102,7 @@ apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex,
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 @@ apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex,
(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));