svn commit: r338211 - in head/sys: amd64/amd64 arm/arm arm64/arm64 i386/i386 kern mips/mips powerpc/powerpc riscv/riscv sparc64/sparc64 sys
Mark Johnston
markj at FreeBSD.org
Wed Aug 22 20:44:33 UTC 2018
Author: markj
Date: Wed Aug 22 20:44:30 2018
New Revision: 338211
URL: https://svnweb.freebsd.org/changeset/base/338211
Log:
Prepare the kernel linker to handle PC-relative ifunc relocations.
The boot-time ifunc resolver assumes that it only needs to apply
IRELATIVE relocations to PLT entries. With an upcoming optimization,
this assumption no longer holds, so add the support required to handle
PC-relative relocations targeting GNU_IFUNC symbols.
- Provide a custom symbol lookup routine that can be used in early boot.
The default lookup routine uses kobj, which is not functional at that
point.
- Apply all existing relocations during boot rather than filtering
IRELATIVE relocations.
- Ensure that we continue to apply ifunc relocations in a second pass
when loading a kernel module.
Reviewed by: kib
MFC after: 1 month
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D16749
Modified:
head/sys/amd64/amd64/elf_machdep.c
head/sys/arm/arm/elf_machdep.c
head/sys/arm64/arm64/elf_machdep.c
head/sys/i386/i386/elf_machdep.c
head/sys/kern/link_elf.c
head/sys/kern/link_elf_obj.c
head/sys/mips/mips/elf_machdep.c
head/sys/powerpc/powerpc/elf32_machdep.c
head/sys/powerpc/powerpc/elf64_machdep.c
head/sys/riscv/riscv/elf_machdep.c
head/sys/sparc64/sparc64/elf_machdep.c
head/sys/sys/linker.h
Modified: head/sys/amd64/amd64/elf_machdep.c
==============================================================================
--- head/sys/amd64/amd64/elf_machdep.c Wed Aug 22 20:23:08 2018 (r338210)
+++ head/sys/amd64/amd64/elf_machdep.c Wed Aug 22 20:44:30 2018 (r338211)
@@ -175,13 +175,17 @@ elf64_dump_thread(struct thread *td, void *dst, size_t
*off = len;
}
-#define ERI_LOCAL 0x0001
-#define ERI_ONLYIFUNC 0x0002
+bool
+elf_is_ifunc_reloc(Elf_Size r_info)
+{
+ return (ELF_R_TYPE(r_info) == R_X86_64_IRELATIVE);
+}
+
/* Process one elf relocation with addend. */
static int
elf_reloc_internal(linker_file_t lf, Elf_Addr relocbase, const void *data,
- int type, elf_lookup_fn lookup, int flags)
+ int type, elf_lookup_fn lookup)
{
Elf64_Addr *where, val;
Elf32_Addr *where32, val32;
@@ -221,9 +225,6 @@ elf_reloc_internal(linker_file_t lf, Elf_Addr relocbas
panic("unknown reloc type %d\n", type);
}
- if (((flags & ERI_ONLYIFUNC) == 0) ^ (rtype != R_X86_64_IRELATIVE))
- return (0);
-
switch (rtype) {
case R_X86_64_NONE: /* none */
break;
@@ -300,20 +301,11 @@ elf_reloc_internal(linker_file_t lf, Elf_Addr relocbas
}
int
-elf_reloc_ifunc(linker_file_t lf, Elf_Addr relocbase, const void *data,
- int type, elf_lookup_fn lookup)
-{
-
- return (elf_reloc_internal(lf, relocbase, data, type, lookup,
- ERI_ONLYIFUNC));
-}
-
-int
elf_reloc(linker_file_t lf, Elf_Addr relocbase, const void *data, int type,
elf_lookup_fn lookup)
{
- return (elf_reloc_internal(lf, relocbase, data, type, lookup, 0));
+ return (elf_reloc_internal(lf, relocbase, data, type, lookup));
}
int
@@ -321,8 +313,7 @@ elf_reloc_local(linker_file_t lf, Elf_Addr relocbase,
int type, elf_lookup_fn lookup)
{
- return (elf_reloc_internal(lf, relocbase, data, type, lookup,
- ERI_LOCAL));
+ return (elf_reloc_internal(lf, relocbase, data, type, lookup));
}
int
Modified: head/sys/arm/arm/elf_machdep.c
==============================================================================
--- head/sys/arm/arm/elf_machdep.c Wed Aug 22 20:23:08 2018 (r338210)
+++ head/sys/arm/arm/elf_machdep.c Wed Aug 22 20:44:30 2018 (r338211)
@@ -149,6 +149,13 @@ elf32_dump_thread(struct thread *td, void *dst, size_t
#endif
}
+bool
+elf_is_ifunc_reloc(Elf_Size r_info __unused)
+{
+
+ return (false);
+}
+
/*
* It is possible for the compiler to emit relocations for unaligned data.
* We handle this situation with these inlines.
Modified: head/sys/arm64/arm64/elf_machdep.c
==============================================================================
--- head/sys/arm64/arm64/elf_machdep.c Wed Aug 22 20:23:08 2018 (r338210)
+++ head/sys/arm64/arm64/elf_machdep.c Wed Aug 22 20:44:30 2018 (r338211)
@@ -129,6 +129,13 @@ elf64_dump_thread(struct thread *td __unused, void *ds
}
+bool
+elf_is_ifunc_reloc(Elf_Size r_info __unused)
+{
+
+ return (false);
+}
+
static int
elf_reloc_internal(linker_file_t lf, Elf_Addr relocbase, const void *data,
int type, int local, elf_lookup_fn lookup)
Modified: head/sys/i386/i386/elf_machdep.c
==============================================================================
--- head/sys/i386/i386/elf_machdep.c Wed Aug 22 20:23:08 2018 (r338210)
+++ head/sys/i386/i386/elf_machdep.c Wed Aug 22 20:44:30 2018 (r338211)
@@ -159,8 +159,14 @@ elf32_dump_thread(struct thread *td, void *dst, size_t
*off = len;
}
+bool
+elf_is_ifunc_reloc(Elf_Size r_info)
+{
+
+ return (ELF_R_TYPE(r_info) == R_386_IRELATIVE);
+}
+
#define ERI_LOCAL 0x0001
-#define ERI_ONLYIFUNC 0x0002
/* Process one elf relocation with addend. */
static int
@@ -194,9 +200,6 @@ elf_reloc_internal(linker_file_t lf, Elf_Addr relocbas
panic("unknown reloc type %d\n", type);
}
- if (((flags & ERI_ONLYIFUNC) == 0) ^ (rtype != R_386_IRELATIVE))
- return (0);
-
if ((flags & ERI_LOCAL) != 0) {
if (rtype == R_386_RELATIVE) { /* A + B */
addr = elf_relocaddr(lf, relocbase + addend);
@@ -261,15 +264,6 @@ elf_reloc_internal(linker_file_t lf, Elf_Addr relocbas
return -1;
}
return(0);
-}
-
-int
-elf_reloc_ifunc(linker_file_t lf, Elf_Addr relocbase, const void *data,
- int type, elf_lookup_fn lookup)
-{
-
- return (elf_reloc_internal(lf, relocbase, data, type, lookup,
- ERI_ONLYIFUNC));
}
int
Modified: head/sys/kern/link_elf.c
==============================================================================
--- head/sys/kern/link_elf.c Wed Aug 22 20:23:08 2018 (r338210)
+++ head/sys/kern/link_elf.c Wed Aug 22 20:44:30 2018 (r338211)
@@ -188,11 +188,13 @@ static struct linker_class link_elf_class = {
link_elf_methods, sizeof(struct elf_file)
};
+typedef int (*elf_reloc_fn)(linker_file_t lf, Elf_Addr relocbase,
+ const void *data, int type, elf_lookup_fn lookup);
+
static int parse_dynamic(elf_file_t);
static int relocate_file(elf_file_t);
-static int relocate_file1(elf_file_t ef, int (*elf_reloc_func)(
- linker_file_t lf, Elf_Addr relocbase, const void *data,
- int type, elf_lookup_fn lookup));
+static int relocate_file1(elf_file_t ef, elf_lookup_fn lookup,
+ elf_reloc_fn reloc, bool ifuncs);
static int link_elf_preload_parse_symbols(elf_file_t);
static struct elf_set_head set_pcpu_list;
@@ -1185,96 +1187,61 @@ symbol_name(elf_file_t ef, Elf_Size r_info)
}
static int
-relocate_file1(elf_file_t ef, int (*elf_reloc_func)(linker_file_t lf,
- Elf_Addr relocbase, const void *data, int type, elf_lookup_fn lookup))
+symbol_type(elf_file_t ef, Elf_Size r_info)
{
- const Elf_Rel *rellim;
+ const Elf_Sym *ref;
+
+ if (ELF_R_SYM(r_info)) {
+ ref = ef->symtab + ELF_R_SYM(r_info);
+ return (ELF_ST_TYPE(ref->st_info));
+ }
+ return (STT_NOTYPE);
+}
+
+static int
+relocate_file1(elf_file_t ef, elf_lookup_fn lookup, elf_reloc_fn reloc,
+ bool ifuncs)
+{
const Elf_Rel *rel;
- const Elf_Rela *relalim;
const Elf_Rela *rela;
const char *symname;
- /* Perform relocations without addend if there are any: */
- rel = ef->rel;
- if (rel != NULL) {
- rellim = (const Elf_Rel *)
- ((const char *)ef->rel + ef->relsize);
- while (rel < rellim) {
- if (elf_reloc_func(&ef->lf, (Elf_Addr)ef->address, rel,
- ELF_RELOC_REL, elf_lookup)) {
- symname = symbol_name(ef, rel->r_info);
- printf("link_elf: symbol %s undefined\n", symname);
- return (ENOENT);
- }
- rel++;
- }
- }
+#define APPLY_RELOCS(iter, tbl, tblsize, type) do { \
+ for ((iter) = (tbl); (iter) != NULL && \
+ (iter) < (tbl) + (tblsize) / sizeof(*(iter)); (iter)++) { \
+ if ((symbol_type(ef, (iter)->r_info) == \
+ STT_GNU_IFUNC || \
+ elf_is_ifunc_reloc((iter)->r_info)) != ifuncs) \
+ continue; \
+ if (reloc(&ef->lf, (Elf_Addr)ef->address, \
+ (iter), (type), lookup)) { \
+ symname = symbol_name(ef, (iter)->r_info); \
+ printf("link_elf: symbol %s undefined\n", \
+ symname); \
+ return (ENOENT); \
+ } \
+ } \
+} while (0)
- /* Perform relocations with addend if there are any: */
- rela = ef->rela;
- if (rela != NULL) {
- relalim = (const Elf_Rela *)
- ((const char *)ef->rela + ef->relasize);
- while (rela < relalim) {
- if (elf_reloc_func(&ef->lf, (Elf_Addr)ef->address, rela,
- ELF_RELOC_RELA, elf_lookup)) {
- symname = symbol_name(ef, rela->r_info);
- printf("link_elf: symbol %s undefined\n",
- symname);
- return (ENOENT);
- }
- rela++;
- }
- }
+ APPLY_RELOCS(rel, ef->rel, ef->relsize, ELF_RELOC_REL);
+ APPLY_RELOCS(rela, ef->rela, ef->relasize, ELF_RELOC_RELA);
+ APPLY_RELOCS(rel, ef->pltrel, ef->pltrelsize, ELF_RELOC_REL);
+ APPLY_RELOCS(rela, ef->pltrela, ef->pltrelasize, ELF_RELOC_RELA);
- /* Perform PLT relocations without addend if there are any: */
- rel = ef->pltrel;
- if (rel != NULL) {
- rellim = (const Elf_Rel *)
- ((const char *)ef->pltrel + ef->pltrelsize);
- while (rel < rellim) {
- if (elf_reloc_func(&ef->lf, (Elf_Addr)ef->address, rel,
- ELF_RELOC_REL, elf_lookup)) {
- symname = symbol_name(ef, rel->r_info);
- printf("link_elf: symbol %s undefined\n",
- symname);
- return (ENOENT);
- }
- rel++;
- }
- }
+#undef APPLY_RELOCS
- /* Perform relocations with addend if there are any: */
- rela = ef->pltrela;
- if (rela != NULL) {
- relalim = (const Elf_Rela *)
- ((const char *)ef->pltrela + ef->pltrelasize);
- while (rela < relalim) {
- if (elf_reloc_func(&ef->lf, (Elf_Addr)ef->address, rela,
- ELF_RELOC_RELA, elf_lookup)) {
- symname = symbol_name(ef, rela->r_info);
- printf("link_elf: symbol %s undefined\n",
- symname);
- return (ENOENT);
- }
- rela++;
- }
- }
-
return (0);
}
static int
relocate_file(elf_file_t ef)
{
- int e;
+ int error;
- e = relocate_file1(ef, elf_reloc);
-#if defined(__i386__) || defined(__amd64__)
- if (e == 0)
- e = relocate_file1(ef, elf_reloc_ifunc);
-#endif
- return (e);
+ error = relocate_file1(ef, elf_lookup, elf_reloc, false);
+ if (error == 0)
+ error = relocate_file1(ef, elf_lookup, elf_reloc, true);
+ return (error);
}
/*
@@ -1298,7 +1265,7 @@ elf_hash(const char *name)
}
static int
-link_elf_lookup_symbol(linker_file_t lf, const char* name, c_linker_sym_t* sym)
+link_elf_lookup_symbol(linker_file_t lf, const char *name, c_linker_sym_t *sym)
{
elf_file_t ef = (elf_file_t) lf;
unsigned long symnum;
@@ -1687,6 +1654,29 @@ link_elf_strtab_get(linker_file_t lf, caddr_t *strtab)
}
#if defined(__i386__) || defined(__amd64__)
+/*
+ * Use this lookup routine when performing relocations early during boot.
+ * The generic lookup routine depends on kobj, which is not initialized
+ * at that point.
+ */
+static int
+elf_lookup_ifunc(linker_file_t lf, Elf_Size symidx, int deps __unused,
+ Elf_Addr *res)
+{
+ elf_file_t ef;
+ const Elf_Sym *symp;
+ caddr_t val;
+
+ ef = (elf_file_t)lf;
+ symp = ef->symtab + symidx;
+ if (ELF_ST_TYPE(symp->st_info) == STT_GNU_IFUNC) {
+ val = (caddr_t)ef->address + symp->st_value;
+ *res = ((Elf_Addr (*)(void))val)();
+ return (0);
+ }
+ return (ENOENT);
+}
+
void
link_elf_ireloc(caddr_t kmdp)
{
@@ -1695,7 +1685,7 @@ link_elf_ireloc(caddr_t kmdp)
volatile char *c;
size_t i;
- ef = &eff;
+ ef = &eff;
/* Do not use bzero/memset before ireloc is done. */
for (c = (char *)ef, i = 0; i < sizeof(*ef); i++)
@@ -1706,6 +1696,6 @@ link_elf_ireloc(caddr_t kmdp)
parse_dynamic(ef);
ef->address = 0;
link_elf_preload_parse_symbols(ef);
- relocate_file1(ef, elf_reloc_ifunc);
+ relocate_file1(ef, elf_lookup_ifunc, elf_reloc, true);
}
#endif
Modified: head/sys/kern/link_elf_obj.c
==============================================================================
--- head/sys/kern/link_elf_obj.c Wed Aug 22 20:23:08 2018 (r338210)
+++ head/sys/kern/link_elf_obj.c Wed Aug 22 20:44:30 2018 (r338211)
@@ -1521,15 +1521,10 @@ link_elf_reloc_local(linker_file_t lf, bool ifuncs)
/* Only do local relocs */
if (ELF_ST_BIND(sym->st_info) != STB_LOCAL)
continue;
- if ((ELF_ST_TYPE(sym->st_info) == STT_GNU_IFUNC) ==
- ifuncs)
+ if ((ELF_ST_TYPE(sym->st_info) == STT_GNU_IFUNC ||
+ elf_is_ifunc_reloc(rel->r_info)) == ifuncs)
elf_reloc_local(lf, base, rel, ELF_RELOC_REL,
elf_obj_lookup);
-#if defined(__i386__) || defined(__amd64__)
- else if (ifuncs)
- elf_reloc_ifunc(lf, base, rel, ELF_RELOC_REL,
- elf_obj_lookup);
-#endif
}
}
@@ -1554,15 +1549,10 @@ link_elf_reloc_local(linker_file_t lf, bool ifuncs)
/* Only do local relocs */
if (ELF_ST_BIND(sym->st_info) != STB_LOCAL)
continue;
- if ((ELF_ST_TYPE(sym->st_info) == STT_GNU_IFUNC) ==
- ifuncs)
+ if ((ELF_ST_TYPE(sym->st_info) == STT_GNU_IFUNC ||
+ elf_is_ifunc_reloc(rela->r_info)) == ifuncs)
elf_reloc_local(lf, base, rela, ELF_RELOC_RELA,
elf_obj_lookup);
-#if defined(__i386__) || defined(__amd64__)
- else if (ifuncs)
- elf_reloc_ifunc(lf, base, rela, ELF_RELOC_RELA,
- elf_obj_lookup);
-#endif
}
}
return (0);
Modified: head/sys/mips/mips/elf_machdep.c
==============================================================================
--- head/sys/mips/mips/elf_machdep.c Wed Aug 22 20:23:08 2018 (r338210)
+++ head/sys/mips/mips/elf_machdep.c Wed Aug 22 20:44:30 2018 (r338211)
@@ -295,6 +295,13 @@ mips_tmp_reloc_free(struct mips_tmp_reloc *r)
free(r, M_TEMP);
}
+bool
+elf_is_ifunc_reloc(Elf_Size r_info __unused)
+{
+
+ return (false);
+}
+
/* Process one elf relocation with addend. */
static int
elf_reloc_internal(linker_file_t lf, Elf_Addr relocbase, const void *data,
Modified: head/sys/powerpc/powerpc/elf32_machdep.c
==============================================================================
--- head/sys/powerpc/powerpc/elf32_machdep.c Wed Aug 22 20:23:08 2018 (r338210)
+++ head/sys/powerpc/powerpc/elf32_machdep.c Wed Aug 22 20:44:30 2018 (r338211)
@@ -214,6 +214,13 @@ elf32_dump_thread(struct thread *td, void *dst, size_t
}
#ifndef __powerpc64__
+bool
+elf_is_ifunc_reloc(Elf_Size r_info __unused)
+{
+
+ return (false);
+}
+
/* Process one elf relocation with addend. */
static int
elf_reloc_internal(linker_file_t lf, Elf_Addr relocbase, const void *data,
Modified: head/sys/powerpc/powerpc/elf64_machdep.c
==============================================================================
--- head/sys/powerpc/powerpc/elf64_machdep.c Wed Aug 22 20:23:08 2018 (r338210)
+++ head/sys/powerpc/powerpc/elf64_machdep.c Wed Aug 22 20:44:30 2018 (r338211)
@@ -276,6 +276,12 @@ elf64_dump_thread(struct thread *td, void *dst, size_t
*off = len;
}
+bool
+elf_is_ifunc_reloc(Elf_Size r_info __unused)
+{
+
+ return (false);
+}
/* Process one elf relocation with addend. */
static int
Modified: head/sys/riscv/riscv/elf_machdep.c
==============================================================================
--- head/sys/riscv/riscv/elf_machdep.c Wed Aug 22 20:23:08 2018 (r338210)
+++ head/sys/riscv/riscv/elf_machdep.c Wed Aug 22 20:44:30 2018 (r338211)
@@ -259,6 +259,13 @@ reloctype_to_str(int type)
return "*unknown*";
}
+bool
+elf_is_ifunc_reloc(Elf_Size r_info __unused)
+{
+
+ return (false);
+}
+
/*
* Currently kernel loadable module for RISCV is compiled with -fPIC option.
* (see also additional CFLAGS definition for RISCV in sys/conf/kmod.mk)
Modified: head/sys/sparc64/sparc64/elf_machdep.c
==============================================================================
--- head/sys/sparc64/sparc64/elf_machdep.c Wed Aug 22 20:23:08 2018 (r338210)
+++ head/sys/sparc64/sparc64/elf_machdep.c Wed Aug 22 20:44:30 2018 (r338211)
@@ -312,6 +312,13 @@ static const long reloc_target_bitmask[] = {
};
#define RELOC_VALUE_BITMASK(t) (reloc_target_bitmask[t])
+bool
+elf_is_ifunc_reloc(Elf_Size r_info __unused)
+{
+
+ return (false);
+}
+
int
elf_reloc_local(linker_file_t lf, Elf_Addr relocbase, const void *data,
int type, elf_lookup_fn lookup __unused)
Modified: head/sys/sys/linker.h
==============================================================================
--- head/sys/sys/linker.h Wed Aug 22 20:23:08 2018 (r338210)
+++ head/sys/sys/linker.h Wed Aug 22 20:44:30 2018 (r338211)
@@ -272,9 +272,8 @@ extern int kld_debug;
typedef int elf_lookup_fn(linker_file_t, Elf_Size, int, Elf_Addr *);
/* Support functions */
+bool elf_is_ifunc_reloc(Elf_Size r_info);
int elf_reloc(linker_file_t _lf, Elf_Addr base, const void *_rel,
- int _type, elf_lookup_fn _lu);
-int elf_reloc_ifunc(linker_file_t _lf, Elf_Addr base, const void *_rel,
int _type, elf_lookup_fn _lu);
int elf_reloc_local(linker_file_t _lf, Elf_Addr base, const void *_rel,
int _type, elf_lookup_fn _lu);
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