This is a note to let you know that I've just added the patch titled
x86,objtool: Create .return_sites
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-objtool-create-.return_sites.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Tue Jul 12 05:06:57 PM CEST 2022
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Tue, 14 Jun 2022 23:15:38 +0200
Subject: x86,objtool: Create .return_sites
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
commit d9e9d2300681d68a775c28de6aa6e5290ae17796 upstream.
Find all the return-thunk sites and record them in a .return_sites
section such that the kernel can undo this.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Reviewed-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
[cascardo: conflict fixup because of functions added to support IBT]
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
tools/objtool/arch/x86/decode.c | 5 ++
tools/objtool/check.c | 75 ++++++++++++++++++++++++++++++++
tools/objtool/include/objtool/arch.h | 1
tools/objtool/include/objtool/elf.h | 1
tools/objtool/include/objtool/objtool.h | 1
tools/objtool/objtool.c | 1
6 files changed, 84 insertions(+)
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -722,3 +722,8 @@ bool arch_is_retpoline(struct symbol *sy
{
return !strncmp(sym->name, "__x86_indirect_", 15);
}
+
+bool arch_is_rethunk(struct symbol *sym)
+{
+ return !strcmp(sym->name, "__x86_return_thunk");
+}
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -654,6 +654,52 @@ static int create_retpoline_sites_sectio
return 0;
}
+static int create_return_sites_sections(struct objtool_file *file)
+{
+ struct instruction *insn;
+ struct section *sec;
+ int idx;
+
+ sec = find_section_by_name(file->elf, ".return_sites");
+ if (sec) {
+ WARN("file already has .return_sites, skipping");
+ return 0;
+ }
+
+ idx = 0;
+ list_for_each_entry(insn, &file->return_thunk_list, call_node)
+ idx++;
+
+ if (!idx)
+ return 0;
+
+ sec = elf_create_section(file->elf, ".return_sites", 0,
+ sizeof(int), idx);
+ if (!sec) {
+ WARN("elf_create_section: .return_sites");
+ return -1;
+ }
+
+ idx = 0;
+ list_for_each_entry(insn, &file->return_thunk_list, call_node) {
+
+ int *site = (int *)sec->data->d_buf + idx;
+ *site = 0;
+
+ if (elf_add_reloc_to_insn(file->elf, sec,
+ idx * sizeof(int),
+ R_X86_64_PC32,
+ insn->sec, insn->offset)) {
+ WARN("elf_add_reloc_to_insn: .return_sites");
+ return -1;
+ }
+
+ idx++;
+ }
+
+ return 0;
+}
+
static int create_mcount_loc_sections(struct objtool_file *file)
{
struct section *sec;
@@ -932,6 +978,11 @@ __weak bool arch_is_retpoline(struct sym
return false;
}
+__weak bool arch_is_rethunk(struct symbol *sym)
+{
+ return false;
+}
+
#define NEGATIVE_RELOC ((void *)-1L)
static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn)
@@ -1092,6 +1143,19 @@ static void add_retpoline_call(struct ob
annotate_call_site(file, insn, false);
}
+
+static void add_return_call(struct objtool_file *file, struct instruction *insn)
+{
+ /*
+ * Return thunk tail calls are really just returns in disguise,
+ * so convert them accordingly.
+ */
+ insn->type = INSN_RETURN;
+ insn->retpoline_safe = true;
+
+ list_add_tail(&insn->call_node, &file->return_thunk_list);
+}
+
/*
* Find the destination instructions for all jumps.
*/
@@ -1116,6 +1180,9 @@ static int add_jump_destinations(struct
} else if (reloc->sym->retpoline_thunk) {
add_retpoline_call(file, insn);
continue;
+ } else if (reloc->sym->return_thunk) {
+ add_return_call(file, insn);
+ continue;
} else if (insn->func) {
/* internal or external sibling call (with reloc) */
add_call_dest(file, insn, reloc->sym, true);
@@ -1937,6 +2004,9 @@ static int classify_symbols(struct objto
if (arch_is_retpoline(func))
func->retpoline_thunk = true;
+ if (arch_is_rethunk(func))
+ func->return_thunk = true;
+
if (!strcmp(func->name, "__fentry__"))
func->fentry = true;
@@ -3413,6 +3483,11 @@ int check(struct objtool_file *file)
if (ret < 0)
goto out;
warnings += ret;
+
+ ret = create_return_sites_sections(file);
+ if (ret < 0)
+ goto out;
+ warnings += ret;
}
if (mcount) {
--- a/tools/objtool/include/objtool/arch.h
+++ b/tools/objtool/include/objtool/arch.h
@@ -88,6 +88,7 @@ const char *arch_ret_insn(int len);
int arch_decode_hint_reg(u8 sp_reg, int *base);
bool arch_is_retpoline(struct symbol *sym);
+bool arch_is_rethunk(struct symbol *sym);
int arch_rewrite_retpolines(struct objtool_file *file);
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -57,6 +57,7 @@ struct symbol {
u8 uaccess_safe : 1;
u8 static_call_tramp : 1;
u8 retpoline_thunk : 1;
+ u8 return_thunk : 1;
u8 fentry : 1;
u8 kcov : 1;
};
--- a/tools/objtool/include/objtool/objtool.h
+++ b/tools/objtool/include/objtool/objtool.h
@@ -19,6 +19,7 @@ struct objtool_file {
struct list_head insn_list;
DECLARE_HASHTABLE(insn_hash, 20);
struct list_head retpoline_call_list;
+ struct list_head return_thunk_list;
struct list_head static_call_list;
struct list_head mcount_loc_list;
bool ignore_unreachables, c_file, hints, rodata;
--- a/tools/objtool/objtool.c
+++ b/tools/objtool/objtool.c
@@ -126,6 +126,7 @@ struct objtool_file *objtool_open_read(c
INIT_LIST_HEAD(&file.insn_list);
hash_init(file.insn_hash);
INIT_LIST_HEAD(&file.retpoline_call_list);
+ INIT_LIST_HEAD(&file.return_thunk_list);
INIT_LIST_HEAD(&file.static_call_list);
INIT_LIST_HEAD(&file.mcount_loc_list);
file.c_file = !vmlinux && find_section_by_name(file.elf, ".comment");
Patches currently in stable-queue which might be from peterz@xxxxxxxxxxxxx are
queue-5.15/x86-sev-avoid-using-__x86_return_thunk.patch
queue-5.15/x86-ftrace-use-alternative-ret-encoding.patch
queue-5.15/objtool-re-add-unwind_hint_-save_restore.patch
queue-5.15/x86-bugs-add-retbleed-ibpb.patch
queue-5.15/x86-bugs-enable-stibp-for-jmp2ret.patch
queue-5.15/x86-retpoline-cleanup-some-ifdefery.patch
queue-5.15/kvm-vmx-flatten-__vmx_vcpu_run.patch
queue-5.15/x86-kvm-vmx-make-noinstr-clean.patch
queue-5.15/objtool-x86-replace-alternatives-with-.retpoline_sites.patch
queue-5.15/x86-retbleed-add-fine-grained-kconfig-knobs.patch
queue-5.15/x86-cpu-amd-add-spectral-chicken.patch
queue-5.15/kvm-vmx-fix-ibrs-handling-after-vmexit.patch
queue-5.15/kvm-vmx-prevent-guest-rsb-poisoning-attacks-with-eibrs.patch
queue-5.15/x86-vsyscall_emu-64-don-t-use-ret-in-vsyscall-emulation.patch
queue-5.15/x86-add-magic-amd-return-thunk.patch
queue-5.15/x86-bugs-keep-a-per-cpu-ia32_spec_ctrl-value.patch
queue-5.15/x86-objtool-create-.return_sites.patch
queue-5.15/x86-alternative-handle-jcc-__x86_indirect_thunk_-reg.patch
queue-5.15/x86-kvm-fix-setcc-emulation-for-return-thunks.patch
queue-5.15/x86-retpoline-swizzle-retpoline-thunk.patch
queue-5.15/x86-speculation-fix-firmware-entry-spec_ctrl-handling.patch
queue-5.15/x86-retpoline-remove-unused-replacement-symbols.patch
queue-5.15/x86-speculation-add-spectre_v2-ibrs-option-to-support-kernel-ibrs.patch
queue-5.15/x86-xen-add-untrain_ret.patch
queue-5.15/bpf-x86-respect-x86_feature_retpoline.patch
queue-5.15/x86-undo-return-thunk-damage.patch
queue-5.15/x86-entry-avoid-very-early-ret.patch
queue-5.15/x86-entry-move-push_and_clear_regs-back-into-error_entry.patch
queue-5.15/x86-retpoline-create-a-retpoline-thunk-array.patch
queue-5.15/x86-asm-fix-register-order.patch
queue-5.15/x86-speculation-fill-rsb-on-vmexit-for-ibrs.patch
queue-5.15/objtool-add-entry-unret-validation.patch
queue-5.15/objtool-shrink-struct-instruction.patch
queue-5.15/kvm-vmx-convert-launched-argument-to-flags.patch
queue-5.15/x86-bpf-use-alternative-ret-encoding.patch
queue-5.15/x86-common-stamp-out-the-stepping-madness.patch
queue-5.15/x86-bugs-split-spectre_v2_select_mitigation-and-spectre_v2_user_select_mitigation.patch
queue-5.15/x86-bugs-report-intel-retbleed-vulnerability.patch
queue-5.15/bpf-x86-simplify-computing-label-offsets.patch
queue-5.15/x86-cpufeatures-move-retpoline-flags-to-word-11.patch
queue-5.15/x86-speculation-fix-spec_ctrl-write-on-smt-state-change.patch
queue-5.15/x86-retpoline-use-mfunction-return.patch
queue-5.15/x86-xen-rename-sys-entry-points.patch
queue-5.15/x86-bugs-optimize-spec_ctrl-msr-writes.patch
queue-5.15/x86-bugs-report-amd-retbleed-vulnerability.patch
queue-5.15/x86-static_call-use-alternative-ret-encoding.patch
queue-5.15/x86-speculation-fix-rsb-filling-with-config_retpoline-n.patch
queue-5.15/x86-asm-fixup-odd-gen-for-each-reg.h-usage.patch
queue-5.15/x86-alternative-add-debug-prints-to-apply_retpolines.patch
queue-5.15/x86-use-return-thunk-in-asm-code.patch
queue-5.15/objtool-classify-symbols.patch
queue-5.15/intel_idle-disable-ibrs-during-long-idle.patch
queue-5.15/x86-retpoline-move-the-retpoline-thunk-declarations-to-nospec-branch.h.patch
queue-5.15/x86-alternative-implement-.retpoline_sites-support.patch
queue-5.15/x86-alternative-try-inline-spectre_v2-retpoline-amd.patch
queue-5.15/x86-entry-remove-skip_r11rcx.patch
queue-5.15/objtool-explicitly-avoid-self-modifying-code-in-.altinstr_replacement.patch
queue-5.15/x86-speculation-use-cached-host-spec_ctrl-value-for-guest-entry-exit.patch
queue-5.15/x86-bugs-add-amd-retbleed-boot-parameter.patch
queue-5.15/x86-entry-add-kernel-ibrs-implementation.patch
queue-5.15/objtool-treat-.text.__x86.-as-noinstr.patch
queue-5.15/objtool-introduce-cfi-hash.patch
queue-5.15/objtool-default-ignore-int3-for-unreachable.patch
queue-5.15/objtool-update-retpoline-validation.patch
