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authorDave Martin <dave.martin@linaro.org>2011-06-16 07:09:37 -0400
committerRussell King <rmk+kernel@arm.linux.org.uk>2011-06-17 06:25:04 -0400
commit9a00318eadbb43db4e9c163c262a22a3c8b5a672 (patch)
tree139ebd71664b5d039b7e5eda7700eaaa7a9f63e1 /arch/arm
parent343fda59823ca20f48578f816ec12e741214f509 (diff)
ARM: 6963/1: Thumb-2: Relax relocation requirements for non-function symbols
The "Thumb bit" of a symbol is only really meaningful for function symbols (STT_FUNC). However, sometimes a branch is relocated against a non-function symbol; for example, PC-relative branches to anonymous assembler local symbols are typically fixed up against the start-of-section symbol, which is not a function symbol. Some inline assembler generates references of this type, such as fixup code generated by macros in <asm/uaccess.h>. The existing relocation code for R_ARM_THM_CALL/R_ARM_THM_JUMP24 interprets this case as an error, because the target symbol appears to be an ARM symbol; but this is really not the case, since the target symbol is just a base in these cases. The addend defines the precise offset to the target location, but since the addend is encoded in a non-interworking Thumb branch instruction, there is no explicit Thumb bit in the addend. Because these instructions never interwork, the implied Thumb bit in the addend is 1, and the destination is Thumb by definition. This patch removes the extraneous Thumb bit check for non-function symbols, enabling modules containing the affected relocation types to be loaded. No modification to the actual relocation code is required, since this code does not take bit[0] of the location->destination offset into account in any case. Function symbols are always checked for interworking conflicts, as before. Signed-off-by: Dave Martin <dave.martin@linaro.org> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm')
-rw-r--r--arch/arm/kernel/module.c13
1 files changed, 11 insertions, 2 deletions
diff --git a/arch/arm/kernel/module.c b/arch/arm/kernel/module.c
index fee7c36349eb..016d6a0830a3 100644
--- a/arch/arm/kernel/module.c
+++ b/arch/arm/kernel/module.c
@@ -193,8 +193,17 @@ apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex,
193 offset -= 0x02000000; 193 offset -= 0x02000000;
194 offset += sym->st_value - loc; 194 offset += sym->st_value - loc;
195 195
196 /* only Thumb addresses allowed (no interworking) */ 196 /*
197 if (!(offset & 1) || 197 * For function symbols, only Thumb addresses are
198 * allowed (no interworking).
199 *
200 * For non-function symbols, the destination
201 * has no specific ARM/Thumb disposition, so
202 * the branch is resolved under the assumption
203 * that interworking is not required.
204 */
205 if ((ELF32_ST_TYPE(sym->st_info) == STT_FUNC &&
206 !(offset & 1)) ||
198 offset <= (s32)0xff000000 || 207 offset <= (s32)0xff000000 ||
199 offset >= (s32)0x01000000) { 208 offset >= (s32)0x01000000) {
200 pr_err("%s: section %u reloc %u sym '%s': relocation %u out of range (%#lx -> %#x)\n", 209 pr_err("%s: section %u reloc %u sym '%s': relocation %u out of range (%#lx -> %#x)\n",