forked from Minki/linux
x86/alternative: Use .ibt_endbr_seal to seal indirect calls
Objtool's --ibt option generates .ibt_endbr_seal which lists superfluous ENDBR instructions. That is those instructions for which the function is never indirectly called. Overwrite these ENDBR instructions with a NOP4 such that these function can never be indirect called, reducing the number of viable ENDBR targets in the kernel. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Link: https://lore.kernel.org/r/20220308154319.822545231@infradead.org
This commit is contained in:
Peter Zijlstra
parent
89bc853eae
commit
ed53a0d971
@ -424,6 +424,10 @@ void __init check_bugs(void)
|
||||
os_check_bugs();
|
||||
}
|
||||
|
||||
void apply_ibt_endbr(s32 *start, s32 *end)
|
||||
{
|
||||
}
|
||||
|
||||
void apply_retpolines(s32 *start, s32 *end)
|
||||
{
|
||||
}
|
||||
|
||||
@ -1873,7 +1873,7 @@ config CC_HAS_IBT
|
||||
config X86_KERNEL_IBT
|
||||
prompt "Indirect Branch Tracking"
|
||||
bool
|
||||
depends on X86_64 && CC_HAS_IBT
|
||||
depends on X86_64 && CC_HAS_IBT && STACK_VALIDATION
|
||||
help
|
||||
Build the kernel with support for Indirect Branch Tracking, a
|
||||
hardware support course-grain forward-edge Control Flow Integrity
|
||||
@ -1881,6 +1881,13 @@ config X86_KERNEL_IBT
|
||||
an ENDBR instruction, as such, the compiler will instrument the
|
||||
code with them to make this happen.
|
||||
|
||||
In addition to building the kernel with IBT, seal all functions that
|
||||
are not indirect call targets, avoiding them ever becomming one.
|
||||
|
||||
This requires LTO like objtool runs and will slow down the build. It
|
||||
does significantly reduce the number of ENDBR instructions in the
|
||||
kernel image.
|
||||
|
||||
config X86_INTEL_MEMORY_PROTECTION_KEYS
|
||||
prompt "Memory Protection Keys"
|
||||
def_bool y
|
||||
|
||||
@ -76,6 +76,7 @@ extern int alternatives_patched;
|
||||
extern void alternative_instructions(void);
|
||||
extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
|
||||
extern void apply_retpolines(s32 *start, s32 *end);
|
||||
extern void apply_ibt_endbr(s32 *start, s32 *end);
|
||||
|
||||
struct module;
|
||||
|
||||
|
||||
@ -46,8 +46,20 @@ static inline __attribute_const__ u32 gen_endbr(void)
|
||||
return endbr;
|
||||
}
|
||||
|
||||
static inline __attribute_const__ u32 gen_endbr_poison(void)
|
||||
{
|
||||
/*
|
||||
* 4 byte NOP that isn't NOP4 (in fact it is OSP NOP3), such that it
|
||||
* will be unique to (former) ENDBR sites.
|
||||
*/
|
||||
return 0x001f0f66; /* osp nopl (%rax) */
|
||||
}
|
||||
|
||||
static inline bool is_endbr(u32 val)
|
||||
{
|
||||
if (val == gen_endbr_poison())
|
||||
return true;
|
||||
|
||||
val &= ~0x01000000U; /* ENDBR32 -> ENDBR64 */
|
||||
return val == gen_endbr();
|
||||
}
|
||||
|
||||
@ -115,6 +115,7 @@ static void __init_or_module add_nops(void *insns, unsigned int len)
|
||||
}
|
||||
|
||||
extern s32 __retpoline_sites[], __retpoline_sites_end[];
|
||||
extern s32 __ibt_endbr_seal[], __ibt_endbr_seal_end[];
|
||||
extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
|
||||
extern s32 __smp_locks[], __smp_locks_end[];
|
||||
void text_poke_early(void *addr, const void *opcode, size_t len);
|
||||
@ -512,6 +513,42 @@ void __init_or_module noinline apply_retpolines(s32 *start, s32 *end) { }
|
||||
|
||||
#endif /* CONFIG_RETPOLINE && CONFIG_STACK_VALIDATION */
|
||||
|
||||
#ifdef CONFIG_X86_KERNEL_IBT
|
||||
|
||||
/*
|
||||
* Generated by: objtool --ibt
|
||||
*/
|
||||
void __init_or_module noinline apply_ibt_endbr(s32 *start, s32 *end)
|
||||
{
|
||||
s32 *s;
|
||||
|
||||
for (s = start; s < end; s++) {
|
||||
u32 endbr, poison = gen_endbr_poison();
|
||||
void *addr = (void *)s + *s;
|
||||
|
||||
if (WARN_ON_ONCE(get_kernel_nofault(endbr, addr)))
|
||||
continue;
|
||||
|
||||
if (WARN_ON_ONCE(!is_endbr(endbr)))
|
||||
continue;
|
||||
|
||||
DPRINTK("ENDBR at: %pS (%px)", addr, addr);
|
||||
|
||||
/*
|
||||
* When we have IBT, the lack of ENDBR will trigger #CP
|
||||
*/
|
||||
DUMP_BYTES(((u8*)addr), 4, "%px: orig: ", addr);
|
||||
DUMP_BYTES(((u8*)&poison), 4, "%px: repl: ", addr);
|
||||
text_poke_early(addr, &poison, 4);
|
||||
}
|
||||
}
|
||||
|
||||
#else
|
||||
|
||||
void __init_or_module noinline apply_ibt_endbr(s32 *start, s32 *end) { }
|
||||
|
||||
#endif /* CONFIG_X86_KERNEL_IBT */
|
||||
|
||||
#ifdef CONFIG_SMP
|
||||
static void alternatives_smp_lock(const s32 *start, const s32 *end,
|
||||
u8 *text, u8 *text_end)
|
||||
@ -830,6 +867,8 @@ void __init alternative_instructions(void)
|
||||
*/
|
||||
apply_alternatives(__alt_instructions, __alt_instructions_end);
|
||||
|
||||
apply_ibt_endbr(__ibt_endbr_seal, __ibt_endbr_seal_end);
|
||||
|
||||
#ifdef CONFIG_SMP
|
||||
/* Patch to UP if other cpus not imminent. */
|
||||
if (!noreplace_smp && (num_present_cpus() == 1 || setup_max_cpus <= 1)) {
|
||||
|
||||
@ -253,7 +253,7 @@ int module_finalize(const Elf_Ehdr *hdr,
|
||||
{
|
||||
const Elf_Shdr *s, *text = NULL, *alt = NULL, *locks = NULL,
|
||||
*para = NULL, *orc = NULL, *orc_ip = NULL,
|
||||
*retpolines = NULL;
|
||||
*retpolines = NULL, *ibt_endbr = NULL;
|
||||
char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
|
||||
|
||||
for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
|
||||
@ -271,6 +271,8 @@ int module_finalize(const Elf_Ehdr *hdr,
|
||||
orc_ip = s;
|
||||
if (!strcmp(".retpoline_sites", secstrings + s->sh_name))
|
||||
retpolines = s;
|
||||
if (!strcmp(".ibt_endbr_seal", secstrings + s->sh_name))
|
||||
ibt_endbr = s;
|
||||
}
|
||||
|
||||
/*
|
||||
@ -290,6 +292,10 @@ int module_finalize(const Elf_Ehdr *hdr,
|
||||
void *aseg = (void *)alt->sh_addr;
|
||||
apply_alternatives(aseg, aseg + alt->sh_size);
|
||||
}
|
||||
if (ibt_endbr) {
|
||||
void *iseg = (void *)ibt_endbr->sh_addr;
|
||||
apply_ibt_endbr(iseg, iseg + ibt_endbr->sh_size);
|
||||
}
|
||||
if (locks && text) {
|
||||
void *lseg = (void *)locks->sh_addr;
|
||||
void *tseg = (void *)text->sh_addr;
|
||||
|
||||
@ -86,12 +86,18 @@ ifdef need-builtin
|
||||
targets-for-builtin += $(obj)/built-in.a
|
||||
endif
|
||||
|
||||
targets-for-modules := $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
|
||||
targets-for-modules :=
|
||||
|
||||
ifdef CONFIG_LTO_CLANG
|
||||
targets-for-modules += $(patsubst %.o, %.lto.o, $(filter %.o, $(obj-m)))
|
||||
endif
|
||||
|
||||
ifdef CONFIG_X86_KERNEL_IBT
|
||||
targets-for-modules += $(patsubst %.o, %.objtool, $(filter %.o, $(obj-m)))
|
||||
endif
|
||||
|
||||
targets-for-modules += $(patsubst %.o, %.mod, $(filter %.o, $(obj-m)))
|
||||
|
||||
ifdef need-modorder
|
||||
targets-for-modules += $(obj)/modules.order
|
||||
endif
|
||||
@ -230,6 +236,7 @@ objtool := $(objtree)/tools/objtool/objtool
|
||||
objtool_args = \
|
||||
$(if $(CONFIG_UNWINDER_ORC),orc generate,check) \
|
||||
$(if $(part-of-module), --module) \
|
||||
$(if $(CONFIG_X86_KERNEL_IBT), --lto --ibt) \
|
||||
$(if $(CONFIG_FRAME_POINTER),, --no-fp) \
|
||||
$(if $(CONFIG_GCOV_KERNEL)$(CONFIG_LTO_CLANG), --no-unreachable)\
|
||||
$(if $(CONFIG_RETPOLINE), --retpoline) \
|
||||
@ -237,8 +244,8 @@ objtool_args = \
|
||||
$(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount) \
|
||||
$(if $(CONFIG_SLS), --sls)
|
||||
|
||||
cmd_objtool = $(if $(objtool-enabled), ; $(objtool) $(objtool_args) $@)
|
||||
cmd_gen_objtooldep = $(if $(objtool-enabled), { echo ; echo '$@: $$(wildcard $(objtool))' ; } >> $(dot-target).cmd)
|
||||
cmd_objtool = $(if $(objtool-enabled), ; $(objtool) $(objtool_args) $(@:.objtool=.o))
|
||||
cmd_gen_objtooldep = $(if $(objtool-enabled), { echo ; echo '$(@:.objtool=.o): $$(wildcard $(objtool))' ; } >> $(dot-target).cmd)
|
||||
|
||||
endif # CONFIG_STACK_VALIDATION
|
||||
|
||||
@ -247,6 +254,21 @@ ifdef CONFIG_LTO_CLANG
|
||||
# Skip objtool for LLVM bitcode
|
||||
$(obj)/%.o: objtool-enabled :=
|
||||
|
||||
# objtool was skipped for LLVM bitcode, run it now that we have compiled
|
||||
# modules into native code
|
||||
$(obj)/%.lto.o: objtool-enabled = y
|
||||
$(obj)/%.lto.o: part-of-module := y
|
||||
|
||||
else ifdef CONFIG_X86_KERNEL_IBT
|
||||
|
||||
# Skip objtool on individual files
|
||||
$(obj)/%.o: objtool-enabled :=
|
||||
|
||||
# instead run objtool on the module as a whole, right before
|
||||
# the final link pass with the linker script.
|
||||
$(obj)/%.objtool: objtool-enabled = y
|
||||
$(obj)/%.objtool: part-of-module := y
|
||||
|
||||
else
|
||||
|
||||
# 'OBJECT_FILES_NON_STANDARD := y': skip objtool checking for a directory
|
||||
@ -292,18 +314,13 @@ ifdef CONFIG_LTO_CLANG
|
||||
# Module .o files may contain LLVM bitcode, compile them into native code
|
||||
# before ELF processing
|
||||
quiet_cmd_cc_lto_link_modules = LTO [M] $@
|
||||
cmd_cc_lto_link_modules = \
|
||||
cmd_cc_lto_link_modules = \
|
||||
$(LD) $(ld_flags) -r -o $@ \
|
||||
$(shell [ -s $(@:.lto.o=.o.symversions) ] && \
|
||||
echo -T $(@:.lto.o=.o.symversions)) \
|
||||
--whole-archive $(filter-out FORCE,$^) \
|
||||
$(cmd_objtool)
|
||||
|
||||
# objtool was skipped for LLVM bitcode, run it now that we have compiled
|
||||
# modules into native code
|
||||
$(obj)/%.lto.o: objtool-enabled = y
|
||||
$(obj)/%.lto.o: part-of-module := y
|
||||
|
||||
$(obj)/%.lto.o: $(obj)/%.o FORCE
|
||||
$(call if_changed,cc_lto_link_modules)
|
||||
endif
|
||||
@ -316,6 +333,18 @@ cmd_mod = { \
|
||||
$(obj)/%.mod: $(obj)/%$(mod-prelink-ext).o FORCE
|
||||
$(call if_changed,mod)
|
||||
|
||||
#
|
||||
# Since objtool will re-write the file it will change the timestamps, therefore
|
||||
# it is critical that the %.objtool file gets a timestamp *after* objtool runs.
|
||||
#
|
||||
# Additionally, care must be had with ordering this rule against the other rules
|
||||
# that take %.o as a dependency.
|
||||
#
|
||||
cmd_objtool_mod = true $(cmd_objtool) ; touch $@
|
||||
|
||||
$(obj)/%.objtool: $(obj)/%$(mod-prelink-ext).o FORCE
|
||||
$(call if_changed,objtool_mod)
|
||||
|
||||
quiet_cmd_cc_lst_c = MKLST $@
|
||||
cmd_cc_lst_c = $(CC) $(c_flags) -g -c -o $*.o $< && \
|
||||
$(CONFIG_SHELL) $(srctree)/scripts/makelst $*.o \
|
||||
|
||||
@ -108,7 +108,9 @@ objtool_link()
|
||||
local objtoolcmd;
|
||||
local objtoolopt;
|
||||
|
||||
if is_enabled CONFIG_LTO_CLANG && is_enabled CONFIG_STACK_VALIDATION; then
|
||||
if is_enabled CONFIG_STACK_VALIDATION && \
|
||||
( is_enabled CONFIG_LTO_CLANG || is_enabled CONFIG_X86_KERNEL_IBT ); then
|
||||
|
||||
# Don't perform vmlinux validation unless explicitly requested,
|
||||
# but run objtool on vmlinux.o now that we have an object file.
|
||||
if is_enabled CONFIG_UNWINDER_ORC; then
|
||||
@ -117,6 +119,10 @@ objtool_link()
|
||||
|
||||
objtoolopt="${objtoolopt} --lto"
|
||||
|
||||
if is_enabled CONFIG_X86_KERNEL_IBT; then
|
||||
objtoolopt="${objtoolopt} --ibt"
|
||||
fi
|
||||
|
||||
if is_enabled CONFIG_FTRACE_MCOUNT_USE_OBJTOOL; then
|
||||
objtoolopt="${objtoolopt} --mcount"
|
||||
fi
|
||||
@ -168,7 +174,7 @@ vmlinux_link()
|
||||
# skip output file argument
|
||||
shift
|
||||
|
||||
if is_enabled CONFIG_LTO_CLANG; then
|
||||
if is_enabled CONFIG_LTO_CLANG || is_enabled CONFIG_X86_KERNEL_IBT; then
|
||||
# Use vmlinux.o instead of performing the slow LTO link again.
|
||||
objs=vmlinux.o
|
||||
libs=
|
||||
|
||||
Loading…
Reference in New Issue
Block a user