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x86,objtool: Separate unret validation from unwind hints

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The ENTRY unwind hint type is serving double duty as both an empty
unwind hint and an unret validation annotation.

Unret validation is unrelated to unwinding. Separate it out into its own
annotation.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/ff7448d492ea21b86d8a90264b105fbd0d751077.1677683419.git.jpoimboe@kernel.org
This commit is contained in:
Josh Poimboeuf 2023-03-01 07:13:11 -08:00 committed by Peter Zijlstra
parent f902cfdd46
commit 4708ea14be
9 changed files with 85 additions and 45 deletions
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14
arch/x86/entry/entry_64.S
View File

@ -388,9 +388,9 @@ SYM_CODE_START(\asmsym)
.if \vector == X86_TRAP_BP
/* #BP advances %rip to the next instruction */
UNWIND_HINT_IRET_REGS offset=\has_error_code*8 signal=0
UNWIND_HINT_IRET_ENTRY offset=\has_error_code*8 signal=0
.else
UNWIND_HINT_IRET_REGS offset=\has_error_code*8
UNWIND_HINT_IRET_ENTRY offset=\has_error_code*8
.endif
ENDBR
@ -461,7 +461,7 @@ SYM_CODE_END(\asmsym)
*/
.macro idtentry_mce_db vector asmsym cfunc
SYM_CODE_START(\asmsym)
UNWIND_HINT_IRET_REGS
UNWIND_HINT_IRET_ENTRY
ENDBR
ASM_CLAC
cld
@ -518,7 +518,7 @@ SYM_CODE_END(\asmsym)
*/
.macro idtentry_vc vector asmsym cfunc
SYM_CODE_START(\asmsym)
UNWIND_HINT_IRET_REGS
UNWIND_HINT_IRET_ENTRY
ENDBR
ASM_CLAC
cld
@ -582,7 +582,7 @@ SYM_CODE_END(\asmsym)
*/
.macro idtentry_df vector asmsym cfunc
SYM_CODE_START(\asmsym)
UNWIND_HINT_IRET_REGS offset=8
UNWIND_HINT_IRET_ENTRY offset=8
ENDBR
ASM_CLAC
cld
@ -1107,7 +1107,7 @@ SYM_CODE_START(error_entry)
FENCE_SWAPGS_KERNEL_ENTRY
CALL_DEPTH_ACCOUNT
leaq 8(%rsp), %rax /* return pt_regs pointer */
ANNOTATE_UNRET_END
VALIDATE_UNRET_END
RET
.Lbstep_iret:
@ -1153,7 +1153,7 @@ SYM_CODE_END(error_return)
* when PAGE_TABLE_ISOLATION is in use. Do not clobber.
*/
SYM_CODE_START(asm_exc_nmi)
UNWIND_HINT_IRET_REGS
UNWIND_HINT_IRET_ENTRY
ENDBR
/*

8
arch/x86/include/asm/nospec-branch.h
View File

@ -210,8 +210,8 @@
* Abuse ANNOTATE_RETPOLINE_SAFE on a NOP to indicate UNRET_END, should
* eventually turn into it's own annotation.
*/
.macro ANNOTATE_UNRET_END
#ifdef CONFIG_DEBUG_ENTRY
.macro VALIDATE_UNRET_END
#if defined(CONFIG_NOINSTR_VALIDATION) && defined(CONFIG_CPU_UNRET_ENTRY)
ANNOTATE_RETPOLINE_SAFE
nop
#endif
@ -286,7 +286,7 @@
.macro UNTRAIN_RET
#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
defined(CONFIG_CALL_DEPTH_TRACKING)
ANNOTATE_UNRET_END
VALIDATE_UNRET_END
ALTERNATIVE_3 "", \
CALL_ZEN_UNTRAIN_RET, X86_FEATURE_UNRET, \
"call entry_ibpb", X86_FEATURE_ENTRY_IBPB, \
@ -297,7 +297,7 @@
.macro UNTRAIN_RET_FROM_CALL
#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_IBPB_ENTRY) || \
defined(CONFIG_CALL_DEPTH_TRACKING)
ANNOTATE_UNRET_END
VALIDATE_UNRET_END
ALTERNATIVE_3 "", \
CALL_ZEN_UNTRAIN_RET, X86_FEATURE_UNRET, \
"call entry_ibpb", X86_FEATURE_ENTRY_IBPB, \

8
arch/x86/include/asm/unwind_hints.h
View File

@ -12,7 +12,8 @@
.endm
.macro UNWIND_HINT_ENTRY
UNWIND_HINT type=UNWIND_HINT_TYPE_ENTRY end=1
VALIDATE_UNRET_BEGIN
UNWIND_HINT_EMPTY
.endm
.macro UNWIND_HINT_REGS base=%rsp offset=0 indirect=0 extra=1 partial=0 signal=1
@ -52,6 +53,11 @@
UNWIND_HINT_REGS base=\base offset=\offset partial=1 signal=\signal
.endm
.macro UNWIND_HINT_IRET_ENTRY base=%rsp offset=0 signal=1
VALIDATE_UNRET_BEGIN
UNWIND_HINT_IRET_REGS base=\base offset=\offset signal=\signal
.endm
.macro UNWIND_HINT_FUNC
UNWIND_HINT sp_reg=ORC_REG_SP sp_offset=8 type=UNWIND_HINT_TYPE_FUNC
.endm

5
arch/x86/kernel/head_64.S
View File

@ -390,8 +390,6 @@ SYM_CODE_START_NOALIGN(vc_boot_ghcb)
UNWIND_HINT_IRET_REGS offset=8
ENDBR
ANNOTATE_UNRET_END
/* Build pt_regs */
PUSH_AND_CLEAR_REGS
@ -451,7 +449,6 @@ SYM_CODE_END(early_idt_handler_array)
SYM_CODE_START_LOCAL(early_idt_handler_common)
UNWIND_HINT_IRET_REGS offset=16
ANNOTATE_UNRET_END
/*
* The stack is the hardware frame, an error code or zero, and the
* vector number.
@ -501,8 +498,6 @@ SYM_CODE_START_NOALIGN(vc_no_ghcb)
UNWIND_HINT_IRET_REGS offset=8
ENDBR
ANNOTATE_UNRET_END
/* Build pt_regs */
PUSH_AND_CLEAR_REGS

16
include/linux/objtool.h
View File

@ -124,6 +124,22 @@
.popsection
.endm
/*
* Use objtool to validate the entry requirement that all code paths do
* VALIDATE_UNRET_END before RET.
*
* NOTE: The macro must be used at the beginning of a global symbol, otherwise
* it will be ignored.
*/
.macro VALIDATE_UNRET_BEGIN
#if defined(CONFIG_NOINSTR_VALIDATION) && defined(CONFIG_CPU_UNRET_ENTRY)
.Lhere_\@:
.pushsection .discard.validate_unret
.long .Lhere_\@ - .
.popsection
#endif
.endm
.macro REACHABLE
.Lhere_\@:
.pushsection .discard.reachable

5
include/linux/objtool_types.h
View File

@ -42,8 +42,7 @@ struct unwind_hint {
#define UNWIND_HINT_TYPE_REGS_PARTIAL 2
/* The below hint types don't have corresponding ORC types */
#define UNWIND_HINT_TYPE_FUNC 3
#define UNWIND_HINT_TYPE_ENTRY 4
#define UNWIND_HINT_TYPE_SAVE 5
#define UNWIND_HINT_TYPE_RESTORE 6
#define UNWIND_HINT_TYPE_SAVE 4
#define UNWIND_HINT_TYPE_RESTORE 5
#endif /* _LINUX_OBJTOOL_TYPES_H */

5
tools/include/linux/objtool_types.h
View File

@ -42,8 +42,7 @@ struct unwind_hint {
#define UNWIND_HINT_TYPE_REGS_PARTIAL 2
/* The below hint types don't have corresponding ORC types */
#define UNWIND_HINT_TYPE_FUNC 3
#define UNWIND_HINT_TYPE_ENTRY 4
#define UNWIND_HINT_TYPE_SAVE 5
#define UNWIND_HINT_TYPE_RESTORE 6
#define UNWIND_HINT_TYPE_SAVE 4
#define UNWIND_HINT_TYPE_RESTORE 5
#endif /* _LINUX_OBJTOOL_TYPES_H */

65
tools/objtool/check.c
View File

@ -2307,16 +2307,9 @@ static int read_unwind_hints(struct objtool_file *file)
WARN_FUNC("UNWIND_HINT_IRET_REGS without ENDBR",
insn->sec, insn->offset);
}
insn->entry = 1;
}
}
if (hint->type == UNWIND_HINT_TYPE_ENTRY) {
hint->type = UNWIND_HINT_TYPE_CALL;
insn->entry = 1;
}
if (hint->type == UNWIND_HINT_TYPE_FUNC) {
insn->cfi = &func_cfi;
continue;
@ -2449,6 +2442,34 @@ static int read_instr_hints(struct objtool_file *file)
return 0;
}
static int read_validate_unret_hints(struct objtool_file *file)
{
struct section *sec;
struct instruction *insn;
struct reloc *reloc;
sec = find_section_by_name(file->elf, ".rela.discard.validate_unret");
if (!sec)
return 0;
list_for_each_entry(reloc, &sec->reloc_list, list) {
if (reloc->sym->type != STT_SECTION) {
WARN("unexpected relocation symbol type in %s", sec->name);
return -1;
}
insn = find_insn(file, reloc->sym->sec, reloc->addend);
if (!insn) {
WARN("bad .discard.instr_end entry");
return -1;
}
insn->unret = 1;
}
return 0;
}
static int read_intra_function_calls(struct objtool_file *file)
{
struct instruction *insn;
@ -2667,6 +2688,10 @@ static int decode_sections(struct objtool_file *file)
if (ret)
return ret;
ret = read_validate_unret_hints(file);
if (ret)
return ret;
return 0;
}
@ -3863,10 +3888,10 @@ static int validate_unwind_hints(struct objtool_file *file, struct section *sec)
/*
* Validate rethunk entry constraint: must untrain RET before the first RET.
*
* Follow every branch (intra-function) and ensure ANNOTATE_UNRET_END comes
* Follow every branch (intra-function) and ensure VALIDATE_UNRET_END comes
* before an actual RET instruction.
*/
static int validate_entry(struct objtool_file *file, struct instruction *insn)
static int validate_unret(struct objtool_file *file, struct instruction *insn)
{
struct instruction *next, *dest;
int ret, warnings = 0;
@ -3874,10 +3899,10 @@ static int validate_entry(struct objtool_file *file, struct instruction *insn)
for (;;) {
next = next_insn_to_validate(file, insn);
if (insn->visited & VISITED_ENTRY)
if (insn->visited & VISITED_UNRET)
return 0;
insn->visited |= VISITED_ENTRY;
insn->visited |= VISITED_UNRET;
if (!insn->ignore_alts && insn->alts) {
struct alternative *alt;
@ -3887,7 +3912,7 @@ static int validate_entry(struct objtool_file *file, struct instruction *insn)
if (alt->skip_orig)
skip_orig = true;
ret = validate_entry(file, alt->insn);
ret = validate_unret(file, alt->insn);
if (ret) {
if (opts.backtrace)
BT_FUNC("(alt)", insn);
@ -3915,7 +3940,7 @@ static int validate_entry(struct objtool_file *file, struct instruction *insn)
insn->sec, insn->offset);
return -1;
}
ret = validate_entry(file, insn->jump_dest);
ret = validate_unret(file, insn->jump_dest);
if (ret) {
if (opts.backtrace) {
BT_FUNC("(branch%s)", insn,
@ -3940,7 +3965,7 @@ static int validate_entry(struct objtool_file *file, struct instruction *insn)
return -1;
}
ret = validate_entry(file, dest);
ret = validate_unret(file, dest);
if (ret) {
if (opts.backtrace)
BT_FUNC("(call)", insn);
@ -3976,19 +4001,19 @@ static int validate_entry(struct objtool_file *file, struct instruction *insn)
}
/*
* Validate that all branches starting at 'insn->entry' encounter UNRET_END
* before RET.
* Validate that all branches starting at VALIDATE_UNRET_BEGIN encounter
* VALIDATE_UNRET_END before RET.
*/
static int validate_unret(struct objtool_file *file)
static int validate_unrets(struct objtool_file *file)
{
struct instruction *insn;
int ret, warnings = 0;
for_each_insn(file, insn) {
if (!insn->entry)
if (!insn->unret)
continue;
ret = validate_entry(file, insn);
ret = validate_unret(file, insn);
if (ret < 0) {
WARN_FUNC("Failed UNRET validation", insn->sec, insn->offset);
return ret;
@ -4607,7 +4632,7 @@ int check(struct objtool_file *file)
* Must be after validate_branch() and friends, it plays
* further games with insn->visited.
*/
ret = validate_unret(file);
ret = validate_unrets(file);
if (ret < 0)
return ret;
warnings += ret;

4
tools/objtool/include/objtool/check.h
View File

@ -61,7 +61,7 @@ struct instruction {
restore : 1,
retpoline_safe : 1,
noendbr : 1,
entry : 1,
unret : 1,
visited : 4,
no_reloc : 1;
/* 10 bit hole */
@ -92,7 +92,7 @@ static inline struct symbol *insn_func(struct instruction *insn)
#define VISITED_BRANCH 0x01
#define VISITED_BRANCH_UACCESS 0x02
#define VISITED_BRANCH_MASK 0x03
#define VISITED_ENTRY 0x04
#define VISITED_UNRET 0x04
static inline bool is_static_jump(struct instruction *insn)
{