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7a5a9824c1
linux-next/arch/x86/entry/ia32entry.S
Denys Vlasenko 7a5a9824c1 x86/asm/entry/32: Remove unnecessary optimization in stub32_clone 
Really swap arguments #4 and #5 in stub32_clone instead of
"optimizing" it into a move.

Yes, tls_val is currently unused. Yes, on some CPUs XCHG is a
little bit more expensive than MOV. But a cycle or two on an
expensive syscall like clone() is way below noise floor, and
this optimization is simply not worth the obfuscation of logic.

[ There's also ongoing work on the clone() ABI by Josh Triplett
  that will depend on this change later on. ]

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1433339930-20880-2-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-06-05 13:41:28 +02:00

548 lines
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/*
* Compatibility mode system call entry point for x86-64.
*
* Copyright 2000-2002 Andi Kleen, SuSE Labs.
*/
#include "calling.h"
#include <asm/asm-offsets.h>
#include <asm/current.h>
#include <asm/errno.h>
#include <asm/ia32_unistd.h>
#include <asm/thread_info.h>
#include <asm/segment.h>
#include <asm/irqflags.h>
#include <asm/asm.h>
#include <asm/smap.h>
#include <linux/linkage.h>
#include <linux/err.h>
/* Avoid __ASSEMBLER__'ifying <linux/audit.h> just for this. */
#include <linux/elf-em.h>
#define AUDIT_ARCH_I386 (EM_386|__AUDIT_ARCH_LE)
#define __AUDIT_ARCH_LE 0x40000000
#ifndef CONFIG_AUDITSYSCALL
# define sysexit_audit ia32_ret_from_sys_call
# define sysretl_audit ia32_ret_from_sys_call
#endif
.section .entry.text, "ax"
#ifdef CONFIG_PARAVIRT
ENTRY(native_usergs_sysret32)
swapgs
sysretl
ENDPROC(native_usergs_sysret32)
#endif
/*
* 32-bit SYSENTER instruction entry.
*
* SYSENTER loads ss, rsp, cs, and rip from previously programmed MSRs.
* IF and VM in rflags are cleared (IOW: interrupts are off).
* SYSENTER does not save anything on the stack,
* and does not save old rip (!!!) and rflags.
*
* Arguments:
* eax system call number
* ebx arg1
* ecx arg2
* edx arg3
* esi arg4
* edi arg5
* ebp user stack
* 0(%ebp) arg6
*
* This is purely a fast path. For anything complicated we use the int 0x80
* path below. We set up a complete hardware stack frame to share code
* with the int 0x80 path.
*/
ENTRY(ia32_sysenter_target)
/*
* Interrupts are off on entry.
* We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON,
* it is too small to ever cause noticeable irq latency.
*/
SWAPGS_UNSAFE_STACK
movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
ENABLE_INTERRUPTS(CLBR_NONE)
/* Zero-extending 32-bit regs, do not remove */
movl %ebp, %ebp
movl %eax, %eax
movl ASM_THREAD_INFO(TI_sysenter_return, %rsp, 0), %r10d
/* Construct struct pt_regs on stack */
pushq $__USER32_DS /* pt_regs->ss */
pushq %rbp /* pt_regs->sp */
pushfq /* pt_regs->flags */
pushq $__USER32_CS /* pt_regs->cs */
pushq %r10 /* pt_regs->ip = thread_info->sysenter_return */
pushq %rax /* pt_regs->orig_ax */
pushq %rdi /* pt_regs->di */
pushq %rsi /* pt_regs->si */
pushq %rdx /* pt_regs->dx */
pushq %rcx /* pt_regs->cx */
pushq $-ENOSYS /* pt_regs->ax */
cld
sub $(10*8), %rsp /* pt_regs->r8-11, bp, bx, r12-15 not saved */
/*
* no need to do an access_ok check here because rbp has been
* 32-bit zero extended
*/
ASM_STAC
1: movl (%rbp), %ebp
_ASM_EXTABLE(1b, ia32_badarg)
ASM_CLAC
/*
* Sysenter doesn't filter flags, so we need to clear NT
* ourselves. To save a few cycles, we can check whether
* NT was set instead of doing an unconditional popfq.
*/
testl $X86_EFLAGS_NT, EFLAGS(%rsp)
jnz sysenter_fix_flags
sysenter_flags_fixed:
orl $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
jnz sysenter_tracesys
sysenter_do_call:
/* 32-bit syscall -> 64-bit C ABI argument conversion */
movl %edi, %r8d /* arg5 */
movl %ebp, %r9d /* arg6 */
xchg %ecx, %esi /* rsi:arg2, rcx:arg4 */
movl %ebx, %edi /* arg1 */
movl %edx, %edx /* arg3 (zero extension) */
sysenter_dispatch:
cmpq $(IA32_NR_syscalls-1), %rax
ja 1f
call *ia32_sys_call_table(, %rax, 8)
movq %rax, RAX(%rsp)
1:
DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
testl $_TIF_ALLWORK_MASK, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
jnz sysexit_audit
sysexit_from_sys_call:
/*
* NB: SYSEXIT is not obviously safe for 64-bit kernels -- an
* NMI between STI and SYSEXIT has poorly specified behavior,
* and and NMI followed by an IRQ with usergs is fatal. So
* we just pretend we're using SYSEXIT but we really use
* SYSRETL instead.
*
* This code path is still called 'sysexit' because it pairs
* with 'sysenter' and it uses the SYSENTER calling convention.
*/
andl $~TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
movl RIP(%rsp), %ecx /* User %eip */
RESTORE_RSI_RDI
xorl %edx, %edx /* Do not leak kernel information */
xorq %r8, %r8
xorq %r9, %r9
xorq %r10, %r10
movl EFLAGS(%rsp), %r11d /* User eflags */
TRACE_IRQS_ON
/*
* SYSRETL works even on Intel CPUs. Use it in preference to SYSEXIT,
* since it avoids a dicey window with interrupts enabled.
*/
movl RSP(%rsp), %esp
/*
* USERGS_SYSRET32 does:
* gsbase = user's gs base
* eip = ecx
* rflags = r11
* cs = __USER32_CS
* ss = __USER_DS
*
* The prologue set RIP(%rsp) to VDSO32_SYSENTER_RETURN, which does:
*
* pop %ebp
* pop %edx
* pop %ecx
*
* Therefore, we invoke SYSRETL with EDX and R8-R10 zeroed to
* avoid info leaks. R11 ends up with VDSO32_SYSENTER_RETURN's
* address (already known to user code), and R12-R15 are
* callee-saved and therefore don't contain any interesting
* kernel data.
*/
USERGS_SYSRET32
#ifdef CONFIG_AUDITSYSCALL
.macro auditsys_entry_common
movl %esi, %r8d /* 5th arg: 4th syscall arg */
movl %ecx, %r9d /* swap with edx */
movl %edx, %ecx /* 4th arg: 3rd syscall arg */
movl %r9d, %edx /* 3rd arg: 2nd syscall arg */
movl %ebx, %esi /* 2nd arg: 1st syscall arg */
movl %eax, %edi /* 1st arg: syscall number */
call __audit_syscall_entry
movl ORIG_RAX(%rsp), %eax /* reload syscall number */
movl %ebx, %edi /* reload 1st syscall arg */
movl RCX(%rsp), %esi /* reload 2nd syscall arg */
movl RDX(%rsp), %edx /* reload 3rd syscall arg */
movl RSI(%rsp), %ecx /* reload 4th syscall arg */
movl RDI(%rsp), %r8d /* reload 5th syscall arg */
.endm
.macro auditsys_exit exit
testl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT), ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
jnz ia32_ret_from_sys_call
TRACE_IRQS_ON
ENABLE_INTERRUPTS(CLBR_NONE)
movl %eax, %esi /* second arg, syscall return value */
cmpl $-MAX_ERRNO, %eax /* is it an error ? */
jbe 1f
movslq %eax, %rsi /* if error sign extend to 64 bits */
1: setbe %al /* 1 if error, 0 if not */
movzbl %al, %edi /* zero-extend that into %edi */
call __audit_syscall_exit
movq RAX(%rsp), %rax /* reload syscall return value */
movl $(_TIF_ALLWORK_MASK & ~_TIF_SYSCALL_AUDIT), %edi
DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
testl %edi, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
jz \exit
xorl %eax, %eax /* Do not leak kernel information */
movq %rax, R11(%rsp)
movq %rax, R10(%rsp)
movq %rax, R9(%rsp)
movq %rax, R8(%rsp)
jmp int_with_check
.endm
sysenter_auditsys:
auditsys_entry_common
movl %ebp, %r9d /* reload 6th syscall arg */
jmp sysenter_dispatch
sysexit_audit:
auditsys_exit sysexit_from_sys_call
#endif
sysenter_fix_flags:
pushq $(X86_EFLAGS_IF|X86_EFLAGS_FIXED)
popfq
jmp sysenter_flags_fixed
sysenter_tracesys:
#ifdef CONFIG_AUDITSYSCALL
testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT), ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
jz sysenter_auditsys
#endif
SAVE_EXTRA_REGS
xorl %eax, %eax /* Do not leak kernel information */
movq %rax, R11(%rsp)
movq %rax, R10(%rsp)
movq %rax, R9(%rsp)
movq %rax, R8(%rsp)
movq %rsp, %rdi /* &pt_regs -> arg1 */
call syscall_trace_enter
/* Reload arg registers from stack. (see sysenter_tracesys) */
movl RCX(%rsp), %ecx
movl RDX(%rsp), %edx
movl RSI(%rsp), %esi
movl RDI(%rsp), %edi
movl %eax, %eax /* zero extension */
RESTORE_EXTRA_REGS
jmp sysenter_do_call
ENDPROC(ia32_sysenter_target)
/*
* 32-bit SYSCALL instruction entry.
*
* 32-bit SYSCALL saves rip to rcx, clears rflags.RF, then saves rflags to r11,
* then loads new ss, cs, and rip from previously programmed MSRs.
* rflags gets masked by a value from another MSR (so CLD and CLAC
* are not needed). SYSCALL does not save anything on the stack
* and does not change rsp.
*
* Note: rflags saving+masking-with-MSR happens only in Long mode
* (in legacy 32-bit mode, IF, RF and VM bits are cleared and that's it).
* Don't get confused: rflags saving+masking depends on Long Mode Active bit
* (EFER.LMA=1), NOT on bitness of userspace where SYSCALL executes
* or target CS descriptor's L bit (SYSCALL does not read segment descriptors).
*
* Arguments:
* eax system call number
* ecx return address
* ebx arg1
* ebp arg2 (note: not saved in the stack frame, should not be touched)
* edx arg3
* esi arg4
* edi arg5
* esp user stack
* 0(%esp) arg6
*
* This is purely a fast path. For anything complicated we use the int 0x80
* path below. We set up a complete hardware stack frame to share code
* with the int 0x80 path.
*/
ENTRY(ia32_cstar_target)
/*
* Interrupts are off on entry.
* We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON,
* it is too small to ever cause noticeable irq latency.
*/
SWAPGS_UNSAFE_STACK
movl %esp, %r8d
movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
ENABLE_INTERRUPTS(CLBR_NONE)
/* Zero-extending 32-bit regs, do not remove */
movl %eax, %eax
/* Construct struct pt_regs on stack */
pushq $__USER32_DS /* pt_regs->ss */
pushq %r8 /* pt_regs->sp */
pushq %r11 /* pt_regs->flags */
pushq $__USER32_CS /* pt_regs->cs */
pushq %rcx /* pt_regs->ip */
pushq %rax /* pt_regs->orig_ax */
pushq %rdi /* pt_regs->di */
pushq %rsi /* pt_regs->si */
pushq %rdx /* pt_regs->dx */
pushq %rbp /* pt_regs->cx */
movl %ebp, %ecx
pushq $-ENOSYS /* pt_regs->ax */
sub $(10*8), %rsp /* pt_regs->r8-11, bp, bx, r12-15 not saved */
/*
* No need to do an access_ok check here because r8 has been
* 32-bit zero extended:
*/
ASM_STAC
1: movl (%r8), %ebp
_ASM_EXTABLE(1b, ia32_badarg)
ASM_CLAC
orl $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
jnz cstar_tracesys
cstar_do_call:
/* 32-bit syscall -> 64-bit C ABI argument conversion */
movl %edi, %r8d /* arg5 */
movl %ebp, %r9d /* arg6 */
xchg %ecx, %esi /* rsi:arg2, rcx:arg4 */
movl %ebx, %edi /* arg1 */
movl %edx, %edx /* arg3 (zero extension) */
cstar_dispatch:
cmpq $(IA32_NR_syscalls-1), %rax
ja 1f
call *ia32_sys_call_table(, %rax, 8)
movq %rax, RAX(%rsp)
1:
DISABLE_INTERRUPTS(CLBR_NONE)
TRACE_IRQS_OFF
testl $_TIF_ALLWORK_MASK, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
jnz sysretl_audit
sysretl_from_sys_call:
andl $~TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
movl RCX(%rsp), %ebp
RESTORE_RSI_RDI_RDX
movl RIP(%rsp), %ecx
movl EFLAGS(%rsp), %r11d
xorq %r10, %r10
xorq %r9, %r9
xorq %r8, %r8
TRACE_IRQS_ON
movl RSP(%rsp), %esp
/*
* 64-bit->32-bit SYSRET restores eip from ecx,
* eflags from r11 (but RF and VM bits are forced to 0),
* cs and ss are loaded from MSRs.
* (Note: 32-bit->32-bit SYSRET is different: since r11
* does not exist, it merely sets eflags.IF=1).
*
* NB: On AMD CPUs with the X86_BUG_SYSRET_SS_ATTRS bug, the ss
* descriptor is not reinitialized. This means that we must
* avoid SYSRET with SS == NULL, which could happen if we schedule,
* exit the kernel, and re-enter using an interrupt vector. (All
* interrupt entries on x86_64 set SS to NULL.) We prevent that
* from happening by reloading SS in __switch_to.
*/
USERGS_SYSRET32
#ifdef CONFIG_AUDITSYSCALL
cstar_auditsys:
auditsys_entry_common
movl %ebp, %r9d /* reload 6th syscall arg */
jmp cstar_dispatch
sysretl_audit:
auditsys_exit sysretl_from_sys_call
#endif
cstar_tracesys:
#ifdef CONFIG_AUDITSYSCALL
testl $(_TIF_WORK_SYSCALL_ENTRY & ~_TIF_SYSCALL_AUDIT), ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
jz cstar_auditsys
#endif
SAVE_EXTRA_REGS
xorl %eax, %eax /* Do not leak kernel information */
movq %rax, R11(%rsp)
movq %rax, R10(%rsp)
movq %rax, R9(%rsp)
movq %rax, R8(%rsp)
movq %rsp, %rdi /* &pt_regs -> arg1 */
call syscall_trace_enter
/* Reload arg registers from stack. (see sysenter_tracesys) */
movl RCX(%rsp), %ecx
movl RDX(%rsp), %edx
movl RSI(%rsp), %esi
movl RDI(%rsp), %edi
movl %eax, %eax /* zero extension */
RESTORE_EXTRA_REGS
jmp cstar_do_call
END(ia32_cstar_target)
ia32_badarg:
ASM_CLAC
movq $-EFAULT, %rax
jmp ia32_sysret
ia32_ret_from_sys_call:
xorl %eax, %eax /* Do not leak kernel information */
movq %rax, R11(%rsp)
movq %rax, R10(%rsp)
movq %rax, R9(%rsp)
movq %rax, R8(%rsp)
jmp int_ret_from_sys_call
/*
* Emulated IA32 system calls via int 0x80.
*
* Arguments:
* eax system call number
* ebx arg1
* ecx arg2
* edx arg3
* esi arg4
* edi arg5
* ebp arg6 (note: not saved in the stack frame, should not be touched)
*
* Notes:
* Uses the same stack frame as the x86-64 version.
* All registers except eax must be saved (but ptrace may violate that).
* Arguments are zero extended. For system calls that want sign extension and
* take long arguments a wrapper is needed. Most calls can just be called
* directly.
* Assumes it is only called from user space and entered with interrupts off.
*/
ENTRY(ia32_syscall)
/*
* Interrupts are off on entry.
* We do not frame this tiny irq-off block with TRACE_IRQS_OFF/ON,
* it is too small to ever cause noticeable irq latency.
*/
PARAVIRT_ADJUST_EXCEPTION_FRAME
SWAPGS
ENABLE_INTERRUPTS(CLBR_NONE)
/* Zero-extending 32-bit regs, do not remove */
movl %eax, %eax
/* Construct struct pt_regs on stack (iret frame is already on stack) */
pushq %rax /* pt_regs->orig_ax */
pushq %rdi /* pt_regs->di */
pushq %rsi /* pt_regs->si */
pushq %rdx /* pt_regs->dx */
pushq %rcx /* pt_regs->cx */
pushq $-ENOSYS /* pt_regs->ax */
pushq $0 /* pt_regs->r8 */
pushq $0 /* pt_regs->r9 */
pushq $0 /* pt_regs->r10 */
pushq $0 /* pt_regs->r11 */
cld
sub $(6*8), %rsp /* pt_regs->bp, bx, r12-15 not saved */
orl $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
jnz ia32_tracesys
ia32_do_call:
/* 32-bit syscall -> 64-bit C ABI argument conversion */
movl %edi, %r8d /* arg5 */
movl %ebp, %r9d /* arg6 */
xchg %ecx, %esi /* rsi:arg2, rcx:arg4 */
movl %ebx, %edi /* arg1 */
movl %edx, %edx /* arg3 (zero extension) */
cmpq $(IA32_NR_syscalls-1), %rax
ja 1f
call *ia32_sys_call_table(, %rax, 8) /* RIP relative */
ia32_sysret:
movq %rax, RAX(%rsp)
1:
jmp int_ret_from_sys_call
ia32_tracesys:
SAVE_EXTRA_REGS
movq %rsp, %rdi /* &pt_regs -> arg1 */
call syscall_trace_enter
/*
* Reload arg registers from stack in case ptrace changed them.
* Don't reload %eax because syscall_trace_enter() returned
* the %rax value we should see. But do truncate it to 32 bits.
* If it's -1 to make us punt the syscall, then (u32)-1 is still
* an appropriately invalid value.
*/
movl RCX(%rsp), %ecx
movl RDX(%rsp), %edx
movl RSI(%rsp), %esi
movl RDI(%rsp), %edi
movl %eax, %eax /* zero extension */
RESTORE_EXTRA_REGS
jmp ia32_do_call
END(ia32_syscall)
.macro PTREGSCALL label, func
ALIGN
GLOBAL(\label)
leaq \func(%rip), %rax
jmp ia32_ptregs_common
.endm
PTREGSCALL stub32_rt_sigreturn, sys32_rt_sigreturn
PTREGSCALL stub32_sigreturn, sys32_sigreturn
PTREGSCALL stub32_fork, sys_fork
PTREGSCALL stub32_vfork, sys_vfork
ALIGN
GLOBAL(stub32_clone)
leaq sys_clone(%rip), %rax
/*
* The 32-bit clone ABI is: clone(..., int tls_val, int *child_tidptr).
* The 64-bit clone ABI is: clone(..., int *child_tidptr, int tls_val).
*
* The native 64-bit kernel's sys_clone() implements the latter,
* so we need to swap arguments here before calling it:
*/
xchg %r8, %rcx
jmp ia32_ptregs_common
ALIGN
ia32_ptregs_common:
SAVE_EXTRA_REGS 8
call *%rax
RESTORE_EXTRA_REGS 8
ret
END(ia32_ptregs_common)
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