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x86/ibt,entry: Sprinkle ENDBR dust

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Kernel entry points should be having ENDBR on for IBT configs.

The SYSCALL entry points are found through taking their respective
address in order to program them in the MSRs, while the exception
entry points are found through UNWIND_HINT_IRET_REGS.

The rule is that any UNWIND_HINT_IRET_REGS at sym+0 should have an
ENDBR, see the later objtool ibt validation patch.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20220308154317.933157479@infradead.org
This commit is contained in:
Peter Zijlstra 2022-03-08 16:30:24 +01:00
parent 5b2fc51576
commit 8f93402b92
6 changed files with 29 additions and 13 deletions
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7
arch/x86/entry/entry_64.S
View File

@ -86,6 +86,7 @@
SYM_CODE_START(entry_SYSCALL_64)
UNWIND_HINT_EMPTY
ENDBR
swapgs
/* tss.sp2 is scratch space. */
@ -350,6 +351,7 @@ SYM_CODE_END(ret_from_fork)
.macro idtentry vector asmsym cfunc has_error_code:req
SYM_CODE_START(\asmsym)
UNWIND_HINT_IRET_REGS offset=\has_error_code*8
ENDBR
ASM_CLAC
.if \has_error_code == 0
@ -417,6 +419,7 @@ SYM_CODE_END(\asmsym)
.macro idtentry_mce_db vector asmsym cfunc
SYM_CODE_START(\asmsym)
UNWIND_HINT_IRET_REGS
ENDBR
ASM_CLAC
pushq $-1 /* ORIG_RAX: no syscall to restart */
@ -472,6 +475,7 @@ SYM_CODE_END(\asmsym)
.macro idtentry_vc vector asmsym cfunc
SYM_CODE_START(\asmsym)
UNWIND_HINT_IRET_REGS
ENDBR
ASM_CLAC
/*
@ -533,6 +537,7 @@ SYM_CODE_END(\asmsym)
.macro idtentry_df vector asmsym cfunc
SYM_CODE_START(\asmsym)
UNWIND_HINT_IRET_REGS offset=8
ENDBR
ASM_CLAC
/* paranoid_entry returns GS information for paranoid_exit in EBX. */
@ -1069,6 +1074,7 @@ SYM_CODE_END(error_return)
*/
SYM_CODE_START(asm_exc_nmi)
UNWIND_HINT_IRET_REGS
ENDBR
/*
* We allow breakpoints in NMIs. If a breakpoint occurs, then
@ -1427,6 +1433,7 @@ SYM_CODE_END(asm_exc_nmi)
*/
SYM_CODE_START(ignore_sysret)
UNWIND_HINT_EMPTY
ENDBR
mov $-ENOSYS, %eax
sysretl
SYM_CODE_END(ignore_sysret)

3
arch/x86/entry/entry_64_compat.S
View File

@ -48,6 +48,7 @@
*/
SYM_CODE_START(entry_SYSENTER_compat)
UNWIND_HINT_EMPTY
ENDBR
/* Interrupts are off on entry. */
SWAPGS
@ -198,6 +199,7 @@ SYM_CODE_END(entry_SYSENTER_compat)
*/
SYM_CODE_START(entry_SYSCALL_compat)
UNWIND_HINT_EMPTY
ENDBR
/* Interrupts are off on entry. */
swapgs
@ -340,6 +342,7 @@ SYM_CODE_END(entry_SYSCALL_compat)
*/
SYM_CODE_START(entry_INT80_compat)
UNWIND_HINT_EMPTY
ENDBR
/*
* Interrupts are off on entry.
*/

20
arch/x86/include/asm/idtentry.h
View File

@ -5,6 +5,8 @@
/* Interrupts/Exceptions */
#include <asm/trapnr.h>
#define IDT_ALIGN (8 * (1 + HAS_KERNEL_IBT))
#ifndef __ASSEMBLY__
#include <linux/entry-common.h>
#include <linux/hardirq.h>
@ -480,7 +482,7 @@ __visible noinstr void func(struct pt_regs *regs, \
/*
* ASM code to emit the common vector entry stubs where each stub is
* packed into 8 bytes.
* packed into IDT_ALIGN bytes.
*
* Note, that the 'pushq imm8' is emitted via '.byte 0x6a, vector' because
* GCC treats the local vector variable as unsigned int and would expand
@ -492,33 +494,33 @@ __visible noinstr void func(struct pt_regs *regs, \
* point is to mask off the bits above bit 7 because the push is sign
* extending.
*/
.align 8
.align IDT_ALIGN
SYM_CODE_START(irq_entries_start)
vector=FIRST_EXTERNAL_VECTOR
.rept NR_EXTERNAL_VECTORS
UNWIND_HINT_IRET_REGS
0 :
ENDBR
.byte 0x6a, vector
jmp asm_common_interrupt
nop
/* Ensure that the above is 8 bytes max */
. = 0b + 8
/* Ensure that the above is IDT_ALIGN bytes max */
.fill 0b + IDT_ALIGN - ., 1, 0xcc
vector = vector+1
.endr
SYM_CODE_END(irq_entries_start)
#ifdef CONFIG_X86_LOCAL_APIC
.align 8
.align IDT_ALIGN
SYM_CODE_START(spurious_entries_start)
vector=FIRST_SYSTEM_VECTOR
.rept NR_SYSTEM_VECTORS
UNWIND_HINT_IRET_REGS
0 :
ENDBR
.byte 0x6a, vector
jmp asm_spurious_interrupt
nop
/* Ensure that the above is 8 bytes max */
. = 0b + 8
/* Ensure that the above is IDT_ALIGN bytes max */
.fill 0b + IDT_ALIGN - ., 1, 0xcc
vector = vector+1
.endr
SYM_CODE_END(spurious_entries_start)

3
arch/x86/include/asm/segment.h
View File

@ -4,6 +4,7 @@
#include <linux/const.h>
#include <asm/alternative.h>
#include <asm/ibt.h>
/*
* Constructor for a conventional segment GDT (or LDT) entry.
@ -275,7 +276,7 @@ static inline void vdso_read_cpunode(unsigned *cpu, unsigned *node)
* vector has no error code (two bytes), a 'push $vector_number' (two
* bytes), and a jump to the common entry code (up to five bytes).
*/
#define EARLY_IDT_HANDLER_SIZE 9
#define EARLY_IDT_HANDLER_SIZE (9 + ENDBR_INSN_SIZE)
/*
* xen_early_idt_handler_array is for Xen pv guests: for each entry in

4
arch/x86/kernel/head_64.S
View File

@ -371,9 +371,11 @@ SYM_CODE_START(early_idt_handler_array)
.rept NUM_EXCEPTION_VECTORS
.if ((EXCEPTION_ERRCODE_MASK >> i) & 1) == 0
UNWIND_HINT_IRET_REGS
ENDBR
pushq $0 # Dummy error code, to make stack frame uniform
.else
UNWIND_HINT_IRET_REGS offset=8
ENDBR
.endif
pushq $i # 72(%rsp) Vector number
jmp early_idt_handler_common
@ -381,11 +383,11 @@ SYM_CODE_START(early_idt_handler_array)
i = i + 1
.fill early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
.endr
UNWIND_HINT_IRET_REGS offset=16
SYM_CODE_END(early_idt_handler_array)
ANNOTATE_NOENDBR // early_idt_handler_array[NUM_EXCEPTION_VECTORS]
SYM_CODE_START_LOCAL(early_idt_handler_common)
UNWIND_HINT_IRET_REGS offset=16
/*
* The stack is the hardware frame, an error code or zero, and the
* vector number.

5
arch/x86/kernel/idt.c
View File

@ -10,6 +10,7 @@
#include <asm/proto.h>
#include <asm/desc.h>
#include <asm/hw_irq.h>
#include <asm/idtentry.h>
#define DPL0 0x0
#define DPL3 0x3
@ -272,7 +273,7 @@ void __init idt_setup_apic_and_irq_gates(void)
idt_setup_from_table(idt_table, apic_idts, ARRAY_SIZE(apic_idts), true);
for_each_clear_bit_from(i, system_vectors, FIRST_SYSTEM_VECTOR) {
entry = irq_entries_start + 8 * (i - FIRST_EXTERNAL_VECTOR);
entry = irq_entries_start + IDT_ALIGN * (i - FIRST_EXTERNAL_VECTOR);
set_intr_gate(i, entry);
}
@ -283,7 +284,7 @@ void __init idt_setup_apic_and_irq_gates(void)
* system_vectors bitmap. Otherwise they show up in
* /proc/interrupts.
*/
entry = spurious_entries_start + 8 * (i - FIRST_SYSTEM_VECTOR);
entry = spurious_entries_start + IDT_ALIGN * (i - FIRST_SYSTEM_VECTOR);
set_intr_gate(i, entry);
}
#endif