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Commit 5d3c7925 authored by Paul Burton's avatar Paul Burton Committed by Ralf Baechle
Browse files

MIPS: Support R_MIPS_PC{16,21,26} rel-style relocs 



MIPS32 code uses rel-style relocs, and MIPS32r6 modules may include
R_MIPS_PC16, R_MIPS_PC21 & R_MIPS_PC26 relocations. We thus need to
support these relocations in order to load MIPS32r6 kernel modules. This
patch adds such support, which is similar to the rela-style support in
module-rela.c but making use of the implicit addend from the instruction
encoding.

Signed-off-by: default avatarPaul Burton <paul.burton@imgtec.com>
Cc: Steven J. Hill <sjhill@realitydiluted.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/12435/


Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
parent ad8319ea

arch/mips/kernel/module.c

+50 −1
Original line number Diff line number Diff line
@@ -182,13 +182,62 @@ static int apply_r_mips_lo16_rel(struct module *me, u32 *location, Elf_Addr v) 
	return -ENOEXEC;

}



static int apply_r_mips_pc_rel(struct module *me, u32 *location, Elf_Addr v,

			       unsigned bits)

{

	unsigned long mask = GENMASK(bits - 1, 0);

	unsigned long se_bits;

	long offset;



	if (v % 4) {

		pr_err("module %s: dangerous R_MIPS_PC%u REL relocation\n",

		       me->name, bits);

		return -ENOEXEC;

	}



	/* retrieve & sign extend implicit addend */

	offset = *location & mask;

	offset |= (offset & BIT(bits - 1)) ? ~mask : 0;



	offset += ((long)v - (long)location) >> 2;



	/* check the sign bit onwards are identical - ie. we didn't overflow */

	se_bits = (offset & BIT(bits - 1)) ? ~0ul : 0;

	if ((offset & ~mask) != (se_bits & ~mask)) {

		pr_err("module %s: relocation overflow\n", me->name);

		return -ENOEXEC;

	}



	*location = (*location & ~mask) | (offset & mask);



	return 0;

}



static int apply_r_mips_pc16_rel(struct module *me, u32 *location, Elf_Addr v)

{

	return apply_r_mips_pc_rel(me, location, v, 16);

}



static int apply_r_mips_pc21_rel(struct module *me, u32 *location, Elf_Addr v)

{

	return apply_r_mips_pc_rel(me, location, v, 21);

}



static int apply_r_mips_pc26_rel(struct module *me, u32 *location, Elf_Addr v)

{

	return apply_r_mips_pc_rel(me, location, v, 26);

}



static int (*reloc_handlers_rel[]) (struct module *me, u32 *location,

				Elf_Addr v) = {

	[R_MIPS_NONE]		= apply_r_mips_none,

	[R_MIPS_32]		= apply_r_mips_32_rel,

	[R_MIPS_26]		= apply_r_mips_26_rel,

	[R_MIPS_HI16]		= apply_r_mips_hi16_rel,

	[R_MIPS_LO16]		= apply_r_mips_lo16_rel

	[R_MIPS_LO16]		= apply_r_mips_lo16_rel,

	[R_MIPS_PC16]		= apply_r_mips_pc16_rel,

	[R_MIPS_PC21_S2]	= apply_r_mips_pc21_rel,

	[R_MIPS_PC26_S2]	= apply_r_mips_pc26_rel,

};



int apply_relocate(Elf_Shdr *sechdrs, const char *strtab,