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authorPeter Zijlstra <peterz@infradead.org>2022-03-08 16:30:56 +0100
committerPeter Zijlstra <peterz@infradead.org>2022-03-15 10:32:47 +0100
commited53a0d971926e484d86cce617ec02a7ee85c3fe (patch)
tree1423484f3912113c56c0b77fa5b0397113040828 /scripts
parent89bc853eae4ad125030ef99f207ba76c2f00a26e (diff)
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
Diffstat (limited to 'scripts')
-rw-r--r--scripts/Makefile.build47
-rwxr-xr-xscripts/link-vmlinux.sh10
2 files changed, 46 insertions, 11 deletions
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index a4b89b757287..926d2549a59c 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -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 $*.o \
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 9b08dca26f99..f704034ebbe6 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -108,7 +108,9 @@ objtool_link()
local objtoolcmd;
local objtoolopt;
- if is_enabled CONFIG_LTO_CLANG && is_enabled CONFIG_STACK_VALIDATION; then
+ if is_enabled CONFIG_STACK_VALIDATION && \
+ ( is_enabled CONFIG_LTO_CLANG || is_enabled CONFIG_X86_KERNEL_IBT ); then
+
# Don't perform vmlinux validation unless explicitly requested,
# but run objtool on vmlinux.o now that we have an object file.
if is_enabled CONFIG_UNWINDER_ORC; then
@@ -117,6 +119,10 @@ objtool_link()
objtoolopt="${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=