Commit be242261 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Jiri Kosina
Browse files

s390/module: Use s390_kernel_write() for late relocations 



Because of late module patching, a livepatch module needs to be able to
apply some of its relocations well after it has been loaded.  Instead of
playing games with module_{dis,en}able_ro(), use existing text poking
mechanisms to apply relocations after module loading.

So far only x86, s390 and Power have HAVE_LIVEPATCH but only the first
two also have STRICT_MODULE_RWX.

This will allow removal of the last module_disable_ro() usage in
livepatch.  The ultimate goal is to completely disallow making
executable mappings writable.

[ jpoimboe: Split up patches.  Use mod state to determine whether
	    memcpy() can be used.  Test and add fixes. ]

Cc: linux-s390@vger.kernel.org
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Suggested-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarJoe Lawrence <joe.lawrence@redhat.com>
Acked-by: default avatarMiroslav Benes <mbenes@suse.cz>
Acked-by: Gerald Schaefer <gerald.schaefer@de.ibm.com> # s390
Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
parent cb2cceae

arch/s390/kernel/module.c

+88 −59
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ 
#include <linux/kasan.h>

#include <linux/moduleloader.h>

#include <linux/bug.h>

#include <linux/memory.h>

#include <asm/alternative.h>

#include <asm/nospec-branch.h>

#include <asm/facility.h>
@@ -174,10 +175,12 @@ int module_frob_arch_sections(Elf_Ehdr *hdr, Elf_Shdr *sechdrs, 
}



static int apply_rela_bits(Elf_Addr loc, Elf_Addr val,

			   int sign, int bits, int shift)

			   int sign, int bits, int shift,

			   void *(*write)(void *dest, const void *src, size_t len))

{

	unsigned long umax;

	long min, max;

	void *dest = (void *)loc;



	if (val & ((1UL << shift) - 1))

		return -ENOEXEC;
@@ -194,26 +197,33 @@ static int apply_rela_bits(Elf_Addr loc, Elf_Addr val, 
			return -ENOEXEC;

	}



	if (bits == 8)

		*(unsigned char *) loc = val;

	else if (bits == 12)

		*(unsigned short *) loc = (val & 0xfff) |

	if (bits == 8) {

		unsigned char tmp = val;

		write(dest, &tmp, 1);

	} else if (bits == 12) {

		unsigned short tmp = (val & 0xfff) |

			(*(unsigned short *) loc & 0xf000);

	else if (bits == 16)

		*(unsigned short *) loc = val;

	else if (bits == 20)

		*(unsigned int *) loc = (val & 0xfff) << 16 |

			(val & 0xff000) >> 4 |

			(*(unsigned int *) loc & 0xf00000ff);

	else if (bits == 32)

		*(unsigned int *) loc = val;

	else if (bits == 64)

		*(unsigned long *) loc = val;

		write(dest, &tmp, 2);

	} else if (bits == 16) {

		unsigned short tmp = val;

		write(dest, &tmp, 2);

	} else if (bits == 20) {

		unsigned int tmp = (val & 0xfff) << 16 |

			(val & 0xff000) >> 4 | (*(unsigned int *) loc & 0xf00000ff);

		write(dest, &tmp, 4);

	} else if (bits == 32) {

		unsigned int tmp = val;

		write(dest, &tmp, 4);

	} else if (bits == 64) {

		unsigned long tmp = val;

		write(dest, &tmp, 8);

	}

	return 0;

}



static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab,

		      const char *strtab, struct module *me)

		      const char *strtab, struct module *me,

		      void *(*write)(void *dest, const void *src, size_t len))

{

	struct mod_arch_syminfo *info;

	Elf_Addr loc, val;
@@ -241,17 +251,17 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab, 
	case R_390_64:		/* Direct 64 bit.  */

		val += rela->r_addend;

		if (r_type == R_390_8)

			rc = apply_rela_bits(loc, val, 0, 8, 0);

			rc = apply_rela_bits(loc, val, 0, 8, 0, write);

		else if (r_type == R_390_12)

			rc = apply_rela_bits(loc, val, 0, 12, 0);

			rc = apply_rela_bits(loc, val, 0, 12, 0, write);

		else if (r_type == R_390_16)

			rc = apply_rela_bits(loc, val, 0, 16, 0);

			rc = apply_rela_bits(loc, val, 0, 16, 0, write);

		else if (r_type == R_390_20)

			rc = apply_rela_bits(loc, val, 1, 20, 0);

			rc = apply_rela_bits(loc, val, 1, 20, 0, write);

		else if (r_type == R_390_32)

			rc = apply_rela_bits(loc, val, 0, 32, 0);

			rc = apply_rela_bits(loc, val, 0, 32, 0, write);

		else if (r_type == R_390_64)

			rc = apply_rela_bits(loc, val, 0, 64, 0);

			rc = apply_rela_bits(loc, val, 0, 64, 0, write);

		break;

	case R_390_PC16:	/* PC relative 16 bit.  */

	case R_390_PC16DBL:	/* PC relative 16 bit shifted by 1.  */
@@ -260,15 +270,15 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab, 
	case R_390_PC64:	/* PC relative 64 bit.	*/

		val += rela->r_addend - loc;

		if (r_type == R_390_PC16)

			rc = apply_rela_bits(loc, val, 1, 16, 0);

			rc = apply_rela_bits(loc, val, 1, 16, 0, write);

		else if (r_type == R_390_PC16DBL)

			rc = apply_rela_bits(loc, val, 1, 16, 1);

			rc = apply_rela_bits(loc, val, 1, 16, 1, write);

		else if (r_type == R_390_PC32DBL)

			rc = apply_rela_bits(loc, val, 1, 32, 1);

			rc = apply_rela_bits(loc, val, 1, 32, 1, write);

		else if (r_type == R_390_PC32)

			rc = apply_rela_bits(loc, val, 1, 32, 0);

			rc = apply_rela_bits(loc, val, 1, 32, 0, write);

		else if (r_type == R_390_PC64)

			rc = apply_rela_bits(loc, val, 1, 64, 0);

			rc = apply_rela_bits(loc, val, 1, 64, 0, write);

		break;

	case R_390_GOT12:	/* 12 bit GOT offset.  */

	case R_390_GOT16:	/* 16 bit GOT offset.  */
@@ -283,33 +293,33 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab, 
	case R_390_GOTPLT64:	/* 64 bit offset to jump slot.	*/

	case R_390_GOTPLTENT:	/* 32 bit rel. offset to jump slot >> 1. */

		if (info->got_initialized == 0) {

			Elf_Addr *gotent;



			gotent = me->core_layout.base + me->arch.got_offset +

			Elf_Addr *gotent = me->core_layout.base +

					   me->arch.got_offset +

					   info->got_offset;

			*gotent = val;



			write(gotent, &val, sizeof(*gotent));

			info->got_initialized = 1;

		}

		val = info->got_offset + rela->r_addend;

		if (r_type == R_390_GOT12 ||

		    r_type == R_390_GOTPLT12)

			rc = apply_rela_bits(loc, val, 0, 12, 0);

			rc = apply_rela_bits(loc, val, 0, 12, 0, write);

		else if (r_type == R_390_GOT16 ||

			 r_type == R_390_GOTPLT16)

			rc = apply_rela_bits(loc, val, 0, 16, 0);

			rc = apply_rela_bits(loc, val, 0, 16, 0, write);

		else if (r_type == R_390_GOT20 ||

			 r_type == R_390_GOTPLT20)

			rc = apply_rela_bits(loc, val, 1, 20, 0);

			rc = apply_rela_bits(loc, val, 1, 20, 0, write);

		else if (r_type == R_390_GOT32 ||

			 r_type == R_390_GOTPLT32)

			rc = apply_rela_bits(loc, val, 0, 32, 0);

			rc = apply_rela_bits(loc, val, 0, 32, 0, write);

		else if (r_type == R_390_GOT64 ||

			 r_type == R_390_GOTPLT64)

			rc = apply_rela_bits(loc, val, 0, 64, 0);

			rc = apply_rela_bits(loc, val, 0, 64, 0, write);

		else if (r_type == R_390_GOTENT ||

			 r_type == R_390_GOTPLTENT) {

			val += (Elf_Addr) me->core_layout.base - loc;

			rc = apply_rela_bits(loc, val, 1, 32, 1);

			rc = apply_rela_bits(loc, val, 1, 32, 1, write);

		}

		break;

	case R_390_PLT16DBL:	/* 16 bit PC rel. PLT shifted by 1.  */
@@ -320,25 +330,29 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab, 
	case R_390_PLTOFF32:	/* 32 bit offset from GOT to PLT. */

	case R_390_PLTOFF64:	/* 16 bit offset from GOT to PLT. */

		if (info->plt_initialized == 0) {

			unsigned int *ip;

			ip = me->core_layout.base + me->arch.plt_offset +

			unsigned int insn[5];

			unsigned int *ip = me->core_layout.base +

					   me->arch.plt_offset +

					   info->plt_offset;

			ip[0] = 0x0d10e310;	/* basr 1,0  */

			ip[1] = 0x100a0004;	/* lg	1,10(1) */



			insn[0] = 0x0d10e310;	/* basr 1,0  */

			insn[1] = 0x100a0004;	/* lg	1,10(1) */

			if (IS_ENABLED(CONFIG_EXPOLINE) && !nospec_disable) {

				unsigned int *ij;

				ij = me->core_layout.base +

					me->arch.plt_offset +

					me->arch.plt_size - PLT_ENTRY_SIZE;

				ip[2] = 0xa7f40000 +	/* j __jump_r1 */

				insn[2] = 0xa7f40000 +	/* j __jump_r1 */

					(unsigned int)(u16)

					(((unsigned long) ij - 8 -

					  (unsigned long) ip) / 2);

			} else {

				ip[2] = 0x07f10000;	/* br %r1 */

				insn[2] = 0x07f10000;	/* br %r1 */

			}

			ip[3] = (unsigned int) (val >> 32);

			ip[4] = (unsigned int) val;

			insn[3] = (unsigned int) (val >> 32);

			insn[4] = (unsigned int) val;



			write(ip, insn, sizeof(insn));

			info->plt_initialized = 1;

		}

		if (r_type == R_390_PLTOFF16 ||
@@ -357,17 +371,17 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab, 
			val += rela->r_addend - loc;

		}

		if (r_type == R_390_PLT16DBL)

			rc = apply_rela_bits(loc, val, 1, 16, 1);

			rc = apply_rela_bits(loc, val, 1, 16, 1, write);

		else if (r_type == R_390_PLTOFF16)

			rc = apply_rela_bits(loc, val, 0, 16, 0);

			rc = apply_rela_bits(loc, val, 0, 16, 0, write);

		else if (r_type == R_390_PLT32DBL)

			rc = apply_rela_bits(loc, val, 1, 32, 1);

			rc = apply_rela_bits(loc, val, 1, 32, 1, write);

		else if (r_type == R_390_PLT32 ||

			 r_type == R_390_PLTOFF32)

			rc = apply_rela_bits(loc, val, 0, 32, 0);

			rc = apply_rela_bits(loc, val, 0, 32, 0, write);

		else if (r_type == R_390_PLT64 ||

			 r_type == R_390_PLTOFF64)

			rc = apply_rela_bits(loc, val, 0, 64, 0);

			rc = apply_rela_bits(loc, val, 0, 64, 0, write);

		break;

	case R_390_GOTOFF16:	/* 16 bit offset to GOT.  */

	case R_390_GOTOFF32:	/* 32 bit offset to GOT.  */
@@ -375,20 +389,20 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab, 
		val = val + rela->r_addend -

			((Elf_Addr) me->core_layout.base + me->arch.got_offset);

		if (r_type == R_390_GOTOFF16)

			rc = apply_rela_bits(loc, val, 0, 16, 0);

			rc = apply_rela_bits(loc, val, 0, 16, 0, write);

		else if (r_type == R_390_GOTOFF32)

			rc = apply_rela_bits(loc, val, 0, 32, 0);

			rc = apply_rela_bits(loc, val, 0, 32, 0, write);

		else if (r_type == R_390_GOTOFF64)

			rc = apply_rela_bits(loc, val, 0, 64, 0);

			rc = apply_rela_bits(loc, val, 0, 64, 0, write);

		break;

	case R_390_GOTPC:	/* 32 bit PC relative offset to GOT. */

	case R_390_GOTPCDBL:	/* 32 bit PC rel. off. to GOT shifted by 1. */

		val = (Elf_Addr) me->core_layout.base + me->arch.got_offset +

			rela->r_addend - loc;

		if (r_type == R_390_GOTPC)

			rc = apply_rela_bits(loc, val, 1, 32, 0);

			rc = apply_rela_bits(loc, val, 1, 32, 0, write);

		else if (r_type == R_390_GOTPCDBL)

			rc = apply_rela_bits(loc, val, 1, 32, 1);

			rc = apply_rela_bits(loc, val, 1, 32, 1, write);

		break;

	case R_390_COPY:

	case R_390_GLOB_DAT:	/* Create GOT entry.  */
@@ -412,9 +426,10 @@ static int apply_rela(Elf_Rela *rela, Elf_Addr base, Elf_Sym *symtab, 
	return 0;

}



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

static int __apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,

		       unsigned int symindex, unsigned int relsec,

		       struct module *me)

		       struct module *me,

		       void *(*write)(void *dest, const void *src, size_t len))

{

	Elf_Addr base;

	Elf_Sym *symtab;
@@ -430,13 +445,27 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab, 
	n = sechdrs[relsec].sh_size / sizeof(Elf_Rela);



	for (i = 0; i < n; i++, rela++) {

		rc = apply_rela(rela, base, symtab, strtab, me);

		rc = apply_rela(rela, base, symtab, strtab, me, write);

		if (rc)

			return rc;

	}

	return 0;

}



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

		       unsigned int symindex, unsigned int relsec,

		       struct module *me)

{

	bool early = me->state == MODULE_STATE_UNFORMED;

	void *(*write)(void *, const void *, size_t) = memcpy;



	if (!early)

		write = s390_kernel_write;



	return __apply_relocate_add(sechdrs, strtab, symindex, relsec, me,

				    write);

}



int module_finalize(const Elf_Ehdr *hdr,

		    const Elf_Shdr *sechdrs,

		    struct module *me)