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Changes for this cycle:

Browse source 
- Micro-optimize and standardize the do_syscall_64() calling convention
  - Make syscall entry flags clearing more conservative
  - Clean up syscall table handling
  - Clean up & standardize assembly macros, in preparation of FRED
  - Misc cleanups and fixes
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'x86-asm-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 asm updates from Ingo Molnar:

 - Micro-optimize and standardize the do_syscall_64() calling convention

 - Make syscall entry flags clearing more conservative

 - Clean up syscall table handling

 - Clean up & standardize assembly macros, in preparation of FRED

 - Misc cleanups and fixes

* tag 'x86-asm-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/asm: Make <asm/asm.h> valid on cross-builds as well
  x86/regs: Syscall_get_nr() returns -1 for a non-system call
  x86/entry: Split PUSH_AND_CLEAR_REGS into two submacros
  x86/syscall: Maximize MSR_SYSCALL_MASK
  x86/syscall: Unconditionally prototype {ia32,x32}_sys_call_table[]
  x86/entry: Reverse arguments to do_syscall_64()
  x86/entry: Unify definitions from <asm/calling.h> and <asm/ptrace-abi.h>
  x86/asm: Use _ASM_BYTES() in <asm/nops.h>
  x86/asm: Add _ASM_BYTES() macro for a .byte ... opcode sequence
  x86/asm: Have the __ASM_FORM macros handle commas in arguments
This commit is contained in:
Linus Torvalds 2021-06-28 12:57:11 -07:00
commit 909489bf9f
12 changed files with 262 additions and 94 deletions
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45
arch/x86/entry/calling.h
View file

@ -6,6 +6,7 @@
#include <asm/percpu.h>
#include <asm/asm-offsets.h>
#include <asm/processor-flags.h>
#include <asm/ptrace-abi.h>
/*
@ -62,42 +63,7 @@ For 32-bit we have the following conventions - kernel is built with
* for assembly code:
*/
/* The layout forms the "struct pt_regs" on the stack: */
/*
* C ABI says these regs are callee-preserved. They aren't saved on kernel entry
* unless syscall needs a complete, fully filled "struct pt_regs".
*/
#define R15 0*8
#define R14 1*8
#define R13 2*8
#define R12 3*8
#define RBP 4*8
#define RBX 5*8
/* These regs are callee-clobbered. Always saved on kernel entry. */
#define R11 6*8
#define R10 7*8
#define R9 8*8
#define R8 9*8
#define RAX 10*8
#define RCX 11*8
#define RDX 12*8
#define RSI 13*8
#define RDI 14*8
/*
* On syscall entry, this is syscall#. On CPU exception, this is error code.
* On hw interrupt, it's IRQ number:
*/
#define ORIG_RAX 15*8
/* Return frame for iretq */
#define RIP 16*8
#define CS 17*8
#define EFLAGS 18*8
#define RSP 19*8
#define SS 20*8
#define SIZEOF_PTREGS 21*8
.macro PUSH_AND_CLEAR_REGS rdx=%rdx rax=%rax save_ret=0
.macro PUSH_REGS rdx=%rdx rax=%rax save_ret=0
.if \save_ret
pushq %rsi /* pt_regs->si */
movq 8(%rsp), %rsi /* temporarily store the return address in %rsi */
@ -124,7 +90,9 @@ For 32-bit we have the following conventions - kernel is built with
.if \save_ret
pushq %rsi /* return address on top of stack */
.endif
.endm
.macro CLEAR_REGS
/*
* Sanitize registers of values that a speculation attack might
* otherwise want to exploit. The lower registers are likely clobbered
@ -146,6 +114,11 @@ For 32-bit we have the following conventions - kernel is built with
.endm
.macro PUSH_AND_CLEAR_REGS rdx=%rdx rax=%rax save_ret=0
PUSH_REGS rdx=\rdx, rax=\rax, save_ret=\save_ret
CLEAR_REGS
.endm
.macro POP_REGS pop_rdi=1 skip_r11rcx=0
popq %r15
popq %r14

2
arch/x86/entry/common.c
View file

@ -36,7 +36,7 @@
#include <asm/irq_stack.h>
#ifdef CONFIG_X86_64
__visible noinstr void do_syscall_64(unsigned long nr, struct pt_regs *regs)
__visible noinstr void do_syscall_64(struct pt_regs *regs, unsigned long nr)
{
add_random_kstack_offset();
nr = syscall_enter_from_user_mode(regs, nr);

4
arch/x86/entry/entry_64.S
View file

@ -107,8 +107,8 @@ SYM_INNER_LABEL(entry_SYSCALL_64_after_hwframe, SYM_L_GLOBAL)
PUSH_AND_CLEAR_REGS rax=$-ENOSYS
/* IRQs are off. */
movq %rax, %rdi
movq %rsp, %rsi
movq %rsp, %rdi
movq %rax, %rsi
call do_syscall_64 /* returns with IRQs disabled */
/*

27
arch/x86/include/asm/asm.h
View file

@ -3,25 +3,26 @@
#define _ASM_X86_ASM_H
#ifdef __ASSEMBLY__
# define __ASM_FORM(x) x
# define __ASM_FORM_RAW(x) x
# define __ASM_FORM_COMMA(x) x,
# define __ASM_FORM(x, ...) x,## __VA_ARGS__
# define __ASM_FORM_RAW(x, ...) x,## __VA_ARGS__
# define __ASM_FORM_COMMA(x, ...) x,## __VA_ARGS__,
#else
#include <linux/stringify.h>
# define __ASM_FORM(x) " " __stringify(x) " "
# define __ASM_FORM_RAW(x) __stringify(x)
# define __ASM_FORM_COMMA(x) " " __stringify(x) ","
# define __ASM_FORM(x, ...) " " __stringify(x,##__VA_ARGS__) " "
# define __ASM_FORM_RAW(x, ...) __stringify(x,##__VA_ARGS__)
# define __ASM_FORM_COMMA(x, ...) " " __stringify(x,##__VA_ARGS__) ","
#endif
#define _ASM_BYTES(x, ...) __ASM_FORM(.byte x,##__VA_ARGS__ ;)
#ifndef __x86_64__
/* 32 bit */
# define __ASM_SEL(a,b) __ASM_FORM(a)
# define __ASM_SEL_RAW(a,b) __ASM_FORM_RAW(a)
# define __ASM_SEL(a,b) __ASM_FORM(a)
# define __ASM_SEL_RAW(a,b) __ASM_FORM_RAW(a)
#else
/* 64 bit */
# define __ASM_SEL(a,b) __ASM_FORM(b)
# define __ASM_SEL_RAW(a,b) __ASM_FORM_RAW(b)
# define __ASM_SEL(a,b) __ASM_FORM(b)
# define __ASM_SEL_RAW(a,b) __ASM_FORM_RAW(b)
#endif
#define __ASM_SIZE(inst, ...) __ASM_SEL(inst##l##__VA_ARGS__, \
@ -119,6 +120,8 @@
# define CC_OUT(c) [_cc_ ## c] "=qm"
#endif
#ifdef __KERNEL__
/* Exception table entry */
#ifdef __ASSEMBLY__
# define _ASM_EXTABLE_HANDLE(from, to, handler) \
@ -185,4 +188,6 @@ register unsigned long current_stack_pointer asm(_ASM_SP);
#define ASM_CALL_CONSTRAINT "+r" (current_stack_pointer)
#endif /* __ASSEMBLY__ */
#endif /* __KERNEL__ */
#endif /* _ASM_X86_ASM_H */

24
arch/x86/include/asm/nops.h
View file

@ -2,6 +2,8 @@
#ifndef _ASM_X86_NOPS_H
#define _ASM_X86_NOPS_H
#include <asm/asm.h>
/*
* Define nops for use with alternative() and for tracing.
*/
@ -57,20 +59,14 @@
#endif /* CONFIG_64BIT */
#ifdef __ASSEMBLY__
#define _ASM_MK_NOP(x) .byte x
#else
#define _ASM_MK_NOP(x) ".byte " __stringify(x) "\n"
#endif
#define ASM_NOP1 _ASM_MK_NOP(BYTES_NOP1)
#define ASM_NOP2 _ASM_MK_NOP(BYTES_NOP2)
#define ASM_NOP3 _ASM_MK_NOP(BYTES_NOP3)
#define ASM_NOP4 _ASM_MK_NOP(BYTES_NOP4)
#define ASM_NOP5 _ASM_MK_NOP(BYTES_NOP5)
#define ASM_NOP6 _ASM_MK_NOP(BYTES_NOP6)
#define ASM_NOP7 _ASM_MK_NOP(BYTES_NOP7)
#define ASM_NOP8 _ASM_MK_NOP(BYTES_NOP8)
#define ASM_NOP1 _ASM_BYTES(BYTES_NOP1)
#define ASM_NOP2 _ASM_BYTES(BYTES_NOP2)
#define ASM_NOP3 _ASM_BYTES(BYTES_NOP3)
#define ASM_NOP4 _ASM_BYTES(BYTES_NOP4)
#define ASM_NOP5 _ASM_BYTES(BYTES_NOP5)
#define ASM_NOP6 _ASM_BYTES(BYTES_NOP6)
#define ASM_NOP7 _ASM_BYTES(BYTES_NOP7)
#define ASM_NOP8 _ASM_BYTES(BYTES_NOP8)
#define ASM_NOP_MAX 8

13
arch/x86/include/asm/syscall.h
View file

@ -21,13 +21,12 @@ extern const sys_call_ptr_t sys_call_table[];
#if defined(CONFIG_X86_32)
#define ia32_sys_call_table sys_call_table
#endif
#if defined(CONFIG_IA32_EMULATION)
#else
/*
* These may not exist, but still put the prototypes in so we
* can use IS_ENABLED().
*/
extern const sys_call_ptr_t ia32_sys_call_table[];
#endif
#ifdef CONFIG_X86_X32_ABI
extern const sys_call_ptr_t x32_sys_call_table[];
#endif
@ -160,7 +159,7 @@ static inline int syscall_get_arch(struct task_struct *task)
? AUDIT_ARCH_I386 : AUDIT_ARCH_X86_64;
}
void do_syscall_64(unsigned long nr, struct pt_regs *regs);
void do_syscall_64(struct pt_regs *regs, unsigned long nr);
void do_int80_syscall_32(struct pt_regs *regs);
long do_fast_syscall_32(struct pt_regs *regs);

12
arch/x86/kernel/cpu/common.c
View file

@ -1773,10 +1773,16 @@ void syscall_init(void)
wrmsrl_safe(MSR_IA32_SYSENTER_EIP, 0ULL);
#endif
/* Flags to clear on syscall */
/*
* Flags to clear on syscall; clear as much as possible
* to minimize user space-kernel interference.
*/
wrmsrl(MSR_SYSCALL_MASK,
X86_EFLAGS_TF|X86_EFLAGS_DF|X86_EFLAGS_IF|
X86_EFLAGS_IOPL|X86_EFLAGS_AC|X86_EFLAGS_NT);
X86_EFLAGS_CF|X86_EFLAGS_PF|X86_EFLAGS_AF|
X86_EFLAGS_ZF|X86_EFLAGS_SF|X86_EFLAGS_TF|
X86_EFLAGS_IF|X86_EFLAGS_DF|X86_EFLAGS_OF|
X86_EFLAGS_IOPL|X86_EFLAGS_NT|X86_EFLAGS_RF|
X86_EFLAGS_AC|X86_EFLAGS_ID);
}
#else /* CONFIG_X86_64 */

6
arch/x86/kernel/head_64.S
View file

@ -62,7 +62,7 @@ SYM_CODE_START_NOALIGN(startup_64)
*/
/* Set up the stack for verify_cpu(), similar to initial_stack below */
leaq (__end_init_task - SIZEOF_PTREGS)(%rip), %rsp
leaq (__end_init_task - FRAME_SIZE)(%rip), %rsp
leaq _text(%rip), %rdi
pushq %rsi
@ -343,10 +343,10 @@ SYM_DATA(initial_vc_handler, .quad handle_vc_boot_ghcb)
#endif
/*
* The SIZEOF_PTREGS gap is a convention which helps the in-kernel unwinder
* The FRAME_SIZE gap is a convention which helps the in-kernel unwinder
* reliably detect the end of the stack.
*/
SYM_DATA(initial_stack, .quad init_thread_union + THREAD_SIZE - SIZEOF_PTREGS)
SYM_DATA(initial_stack, .quad init_thread_union + THREAD_SIZE - FRAME_SIZE)
__FINITDATA
__INIT

2
arch/x86/kernel/ptrace.c
View file

@ -911,7 +911,7 @@ static int putreg32(struct task_struct *child, unsigned regno, u32 value)
* syscall with TS_COMPAT still set.
*/
regs->orig_ax = value;
if (syscall_get_nr(child, regs) >= 0)
if (syscall_get_nr(child, regs) != -1)
child->thread_info.status |= TS_I386_REGS_POKED;
break;

4
arch/x86/kernel/signal.c
View file

@ -713,7 +713,7 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs)
save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL);
/* Are we from a system call? */
if (syscall_get_nr(current, regs) >= 0) {
if (syscall_get_nr(current, regs) != -1) {
/* If so, check system call restarting.. */
switch (syscall_get_error(current, regs)) {
case -ERESTART_RESTARTBLOCK:
@ -793,7 +793,7 @@ void arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal)
}
/* Did we come from a system call? */
if (syscall_get_nr(current, regs) >= 0) {
if (syscall_get_nr(current, regs) != -1) {
/* Restart the system call - no handlers present */
switch (syscall_get_error(current, regs)) {
case -ERESTARTNOHAND:

193
tools/arch/x86/include/asm/asm.h Normal file
View file

@ -0,0 +1,193 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_X86_ASM_H
#define _ASM_X86_ASM_H
#ifdef __ASSEMBLY__
# define __ASM_FORM(x, ...) x,## __VA_ARGS__
# define __ASM_FORM_RAW(x, ...) x,## __VA_ARGS__
# define __ASM_FORM_COMMA(x, ...) x,## __VA_ARGS__,
#else
#include <linux/stringify.h>
# define __ASM_FORM(x, ...) " " __stringify(x,##__VA_ARGS__) " "
# define __ASM_FORM_RAW(x, ...) __stringify(x,##__VA_ARGS__)
# define __ASM_FORM_COMMA(x, ...) " " __stringify(x,##__VA_ARGS__) ","
#endif
#define _ASM_BYTES(x, ...) __ASM_FORM(.byte x,##__VA_ARGS__ ;)
#ifndef __x86_64__
/* 32 bit */
# define __ASM_SEL(a,b) __ASM_FORM(a)
# define __ASM_SEL_RAW(a,b) __ASM_FORM_RAW(a)
#else
/* 64 bit */
# define __ASM_SEL(a,b) __ASM_FORM(b)
# define __ASM_SEL_RAW(a,b) __ASM_FORM_RAW(b)
#endif
#define __ASM_SIZE(inst, ...) __ASM_SEL(inst##l##__VA_ARGS__, \
inst##q##__VA_ARGS__)
#define __ASM_REG(reg) __ASM_SEL_RAW(e##reg, r##reg)
#define _ASM_PTR __ASM_SEL(.long, .quad)
#define _ASM_ALIGN __ASM_SEL(.balign 4, .balign 8)
#define _ASM_MOV __ASM_SIZE(mov)
#define _ASM_INC __ASM_SIZE(inc)
#define _ASM_DEC __ASM_SIZE(dec)
#define _ASM_ADD __ASM_SIZE(add)
#define _ASM_SUB __ASM_SIZE(sub)
#define _ASM_XADD __ASM_SIZE(xadd)
#define _ASM_MUL __ASM_SIZE(mul)
#define _ASM_AX __ASM_REG(ax)
#define _ASM_BX __ASM_REG(bx)
#define _ASM_CX __ASM_REG(cx)
#define _ASM_DX __ASM_REG(dx)
#define _ASM_SP __ASM_REG(sp)
#define _ASM_BP __ASM_REG(bp)
#define _ASM_SI __ASM_REG(si)
#define _ASM_DI __ASM_REG(di)
#ifndef __x86_64__
/* 32 bit */
#define _ASM_ARG1 _ASM_AX
#define _ASM_ARG2 _ASM_DX
#define _ASM_ARG3 _ASM_CX
#define _ASM_ARG1L eax
#define _ASM_ARG2L edx
#define _ASM_ARG3L ecx
#define _ASM_ARG1W ax
#define _ASM_ARG2W dx
#define _ASM_ARG3W cx
#define _ASM_ARG1B al
#define _ASM_ARG2B dl
#define _ASM_ARG3B cl
#else
/* 64 bit */
#define _ASM_ARG1 _ASM_DI
#define _ASM_ARG2 _ASM_SI
#define _ASM_ARG3 _ASM_DX
#define _ASM_ARG4 _ASM_CX
#define _ASM_ARG5 r8
#define _ASM_ARG6 r9
#define _ASM_ARG1Q rdi
#define _ASM_ARG2Q rsi
#define _ASM_ARG3Q rdx
#define _ASM_ARG4Q rcx
#define _ASM_ARG5Q r8
#define _ASM_ARG6Q r9
#define _ASM_ARG1L edi
#define _ASM_ARG2L esi
#define _ASM_ARG3L edx
#define _ASM_ARG4L ecx
#define _ASM_ARG5L r8d
#define _ASM_ARG6L r9d
#define _ASM_ARG1W di
#define _ASM_ARG2W si
#define _ASM_ARG3W dx
#define _ASM_ARG4W cx
#define _ASM_ARG5W r8w
#define _ASM_ARG6W r9w
#define _ASM_ARG1B dil
#define _ASM_ARG2B sil
#define _ASM_ARG3B dl
#define _ASM_ARG4B cl
#define _ASM_ARG5B r8b
#define _ASM_ARG6B r9b
#endif
/*
* Macros to generate condition code outputs from inline assembly,
* The output operand must be type "bool".
*/
#ifdef __GCC_ASM_FLAG_OUTPUTS__
# define CC_SET(c) "\n\t/* output condition code " #c "*/\n"
# define CC_OUT(c) "=@cc" #c
#else
# define CC_SET(c) "\n\tset" #c " %[_cc_" #c "]\n"
# define CC_OUT(c) [_cc_ ## c] "=qm"
#endif
#ifdef __KERNEL__
/* Exception table entry */
#ifdef __ASSEMBLY__
# define _ASM_EXTABLE_HANDLE(from, to, handler) \
.pushsection "__ex_table","a" ; \
.balign 4 ; \
.long (from) - . ; \
.long (to) - . ; \
.long (handler) - . ; \
.popsection
# define _ASM_EXTABLE(from, to) \
_ASM_EXTABLE_HANDLE(from, to, ex_handler_default)
# define _ASM_EXTABLE_UA(from, to) \
_ASM_EXTABLE_HANDLE(from, to, ex_handler_uaccess)
# define _ASM_EXTABLE_CPY(from, to) \
_ASM_EXTABLE_HANDLE(from, to, ex_handler_copy)
# define _ASM_EXTABLE_FAULT(from, to) \
_ASM_EXTABLE_HANDLE(from, to, ex_handler_fault)
# ifdef CONFIG_KPROBES
# define _ASM_NOKPROBE(entry) \
.pushsection "_kprobe_blacklist","aw" ; \
_ASM_ALIGN ; \
_ASM_PTR (entry); \
.popsection
# else
# define _ASM_NOKPROBE(entry)
# endif
#else /* ! __ASSEMBLY__ */
# define _EXPAND_EXTABLE_HANDLE(x) #x
# define _ASM_EXTABLE_HANDLE(from, to, handler) \
" .pushsection \"__ex_table\",\"a\"\n" \
" .balign 4\n" \
" .long (" #from ") - .\n" \
" .long (" #to ") - .\n" \
" .long (" _EXPAND_EXTABLE_HANDLE(handler) ") - .\n" \
" .popsection\n"
# define _ASM_EXTABLE(from, to) \
_ASM_EXTABLE_HANDLE(from, to, ex_handler_default)
# define _ASM_EXTABLE_UA(from, to) \
_ASM_EXTABLE_HANDLE(from, to, ex_handler_uaccess)
# define _ASM_EXTABLE_CPY(from, to) \
_ASM_EXTABLE_HANDLE(from, to, ex_handler_copy)
# define _ASM_EXTABLE_FAULT(from, to) \
_ASM_EXTABLE_HANDLE(from, to, ex_handler_fault)
/* For C file, we already have NOKPROBE_SYMBOL macro */
/*
* This output constraint should be used for any inline asm which has a "call"
* instruction. Otherwise the asm may be inserted before the frame pointer
* gets set up by the containing function. If you forget to do this, objtool
* may print a "call without frame pointer save/setup" warning.
*/
register unsigned long current_stack_pointer asm(_ASM_SP);
#define ASM_CALL_CONSTRAINT "+r" (current_stack_pointer)
#endif /* __ASSEMBLY__ */
#endif /* __KERNEL__ */
#endif /* _ASM_X86_ASM_H */

24
tools/arch/x86/include/asm/nops.h
View file

@ -2,6 +2,8 @@
#ifndef _ASM_X86_NOPS_H
#define _ASM_X86_NOPS_H
#include <asm/asm.h>
/*
* Define nops for use with alternative() and for tracing.
*/
@ -57,20 +59,14 @@
#endif /* CONFIG_64BIT */
#ifdef __ASSEMBLY__
#define _ASM_MK_NOP(x) .byte x
#else
#define _ASM_MK_NOP(x) ".byte " __stringify(x) "\n"
#endif
#define ASM_NOP1 _ASM_MK_NOP(BYTES_NOP1)
#define ASM_NOP2 _ASM_MK_NOP(BYTES_NOP2)
#define ASM_NOP3 _ASM_MK_NOP(BYTES_NOP3)
#define ASM_NOP4 _ASM_MK_NOP(BYTES_NOP4)
#define ASM_NOP5 _ASM_MK_NOP(BYTES_NOP5)
#define ASM_NOP6 _ASM_MK_NOP(BYTES_NOP6)
#define ASM_NOP7 _ASM_MK_NOP(BYTES_NOP7)
#define ASM_NOP8 _ASM_MK_NOP(BYTES_NOP8)
#define ASM_NOP1 _ASM_BYTES(BYTES_NOP1)
#define ASM_NOP2 _ASM_BYTES(BYTES_NOP2)
#define ASM_NOP3 _ASM_BYTES(BYTES_NOP3)
#define ASM_NOP4 _ASM_BYTES(BYTES_NOP4)
#define ASM_NOP5 _ASM_BYTES(BYTES_NOP5)
#define ASM_NOP6 _ASM_BYTES(BYTES_NOP6)
#define ASM_NOP7 _ASM_BYTES(BYTES_NOP7)
#define ASM_NOP8 _ASM_BYTES(BYTES_NOP8)
#define ASM_NOP_MAX 8