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: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Gerald Schaefer <gerald.schaefer@de.ibm.com> # s390
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

diff --git a/arch/s390/kernel/module.c b/arch/s390/kernel/module.c
index ba8f19b..4055f1c 100644 (file)
--- a/arch/s390/kernel/module.c
+++ b/arch/s390/kernel/module.c
@@ -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;
+                       Elf_Addr *gotent = me->core_layout.base +
+                                          me->arch.got_offset +
+                                          info->got_offset;
 
-                       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 +
-                               info->plt_offset;
-                       ip[0] = 0x0d10e310;     /* basr 1,0  */
-                       ip[1] = 0x100a0004;     /* lg   1,10(1) */
+                       unsigned int insn[5];
+                       unsigned int *ip = me->core_layout.base +
+                                          me->arch.plt_offset +
+                                          info->plt_offset;
+
+                       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)