ARC: add new disp25 reloc

Add the R_ARC_S25H_PCREL relocation to the list of known
and resolve this relocation.

Replacement of jump instructions (j) to branches (b) in the .fixup
section (commit 955b7c7) cause to appearance of the new relocation
type R_ARC_S25H_PCREL, which can be added by the compiler to handle
relative offsets in kernel modules.

Fixes: 955b7c7 (ARCv3: link above 4GB: handle 64-bit literals in final link)
Signed-off-by: Pavel Kozlov <pavel.kozlov@synopsys.com>

Author: pavelvkozlov

arch/arc/include/asm/elf.h

@@ -48,6 +48,7 @@ int elf_check_arch(const struct elf32_hdr *x);
 /* ARC Relocations (kernel Modules only) */
 #define  R_ARC_32		0x4
 #define  R_ARC_64		0x5
+#define  R_ARC_S25H_PCREL	0x10
 #define  R_ARC_32_ME		0x1B
 #define  R_ARC_32_PCREL		0x31
 #define  R_ARC_LO32_ME		0x5c

arch/arc/kernel/module.c

@@ -19,6 +19,19 @@ static inline void arc_write_me(unsigned short *addr, unsigned long value)
 	*(addr + 1) = (value & 0xffff);
 }
 
+static inline void arc_write_disp25h(unsigned short *addr, unsigned long value)
+{
+	unsigned short ins = *addr & ~0x7fe;
+
+	ins |= (value & 0x03ff) << 1;
+	*addr = ins;
+
+	ins = *(addr + 1) & ~0xffcf;
+	ins |= ((value >> 10) & 0x03ff) << 6;
+	ins |= ((value >> 20) & 0x000f) << 0;
+	*(addr + 1) = ins;
+}
+
 /*
  * This gets called before relocation loop in generic loader
  * Make a note of the section index of unwinding section
@@ -105,6 +118,9 @@ int apply_relocate_add(Elf_Shdr *sechdrs,
 			*((Elf_Addr *) location) = relocation;
 		else if (R_ARC_32_PCREL == relo_type)	/* ( S + A ) - PDATA ) */
 			*((Elf_Addr *) location) = relocation - location;
+		else if (R_ARC_S25H_PCREL == relo_type)	/* ( S + A ) - PDATA ) >> 1 */
+			arc_write_disp25h((unsigned short *)location, 
+						(relocation - location) >> 1);
 #ifdef CONFIG_64BIT
 		else if (R_ARC_64 == relo_type)		/* ( S + A ) */
 			*((Elf_Addr *) location) = relocation;