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linux-2.6/arch/i386/kernel/entry.S

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/*
* linux/arch/i386/entry.S
*
* Copyright (C) 1991, 1992 Linus Torvalds
*/
/*
* entry.S contains the system-call and fault low-level handling routines.
* This also contains the timer-interrupt handler, as well as all interrupts
* and faults that can result in a task-switch.
*
* NOTE: This code handles signal-recognition, which happens every time
* after a timer-interrupt and after each system call.
*
* I changed all the .align's to 4 (16 byte alignment), as that's faster
* on a 486.
*
* Stack layout in 'ret_from_system_call':
* ptrace needs to have all regs on the stack.
* if the order here is changed, it needs to be
* updated in fork.c:copy_process, signal.c:do_signal,
* ptrace.c and ptrace.h
*
* 0(%esp) - %ebx
* 4(%esp) - %ecx
* 8(%esp) - %edx
* C(%esp) - %esi
* 10(%esp) - %edi
* 14(%esp) - %ebp
* 18(%esp) - %eax
* 1C(%esp) - %ds
* 20(%esp) - %es
* 24(%esp) - orig_eax
* 28(%esp) - %eip
* 2C(%esp) - %cs
* 30(%esp) - %eflags
* 34(%esp) - %oldesp
* 38(%esp) - %oldss
*
* "current" is in register %ebx during any slow entries.
*/
#include <linux/config.h>
#include <linux/linkage.h>
#include <asm/thread_info.h>
#include <asm/errno.h>
#include <asm/segment.h>
#include <asm/smp.h>
#include <asm/page.h>
#include <asm/desc.h>
#include "irq_vectors.h"
#define nr_syscalls ((syscall_table_size)/4)
EBX = 0x00
ECX = 0x04
EDX = 0x08
ESI = 0x0C
EDI = 0x10
EBP = 0x14
EAX = 0x18
DS = 0x1C
ES = 0x20
ORIG_EAX = 0x24
EIP = 0x28
CS = 0x2C
EFLAGS = 0x30
OLDESP = 0x34
OLDSS = 0x38
CF_MASK = 0x00000001
TF_MASK = 0x00000100
IF_MASK = 0x00000200
DF_MASK = 0x00000400
NT_MASK = 0x00004000
VM_MASK = 0x00020000
#ifdef CONFIG_PREEMPT
#define preempt_stop cli
#else
#define preempt_stop
#define resume_kernel restore_nocheck
#endif
#define SAVE_ALL \
cld; \
pushl %es; \
pushl %ds; \
pushl %eax; \
pushl %ebp; \
pushl %edi; \
pushl %esi; \
pushl %edx; \
pushl %ecx; \
pushl %ebx; \
movl $(__USER_DS), %edx; \
movl %edx, %ds; \
movl %edx, %es;
#define RESTORE_INT_REGS \
popl %ebx; \
popl %ecx; \
popl %edx; \
popl %esi; \
popl %edi; \
popl %ebp; \
popl %eax
#define RESTORE_REGS \
RESTORE_INT_REGS; \
1: popl %ds; \
2: popl %es; \
.section .fixup,"ax"; \
3: movl $0,(%esp); \
jmp 1b; \
4: movl $0,(%esp); \
jmp 2b; \
.previous; \
.section __ex_table,"a";\
.align 4; \
.long 1b,3b; \
.long 2b,4b; \
.previous
ENTRY(ret_from_fork)
pushl %eax
call schedule_tail
GET_THREAD_INFO(%ebp)
popl %eax
jmp syscall_exit
/*
* Return to user mode is not as complex as all this looks,
* but we want the default path for a system call return to
* go as quickly as possible which is why some of this is
* less clear than it otherwise should be.
*/
# userspace resumption stub bypassing syscall exit tracing
ALIGN
ret_from_exception:
preempt_stop
ret_from_intr:
GET_THREAD_INFO(%ebp)
movl EFLAGS(%esp), %eax # mix EFLAGS and CS
movb CS(%esp), %al
testl $(VM_MASK | 3), %eax
jz resume_kernel
ENTRY(resume_userspace)
cli # make sure we don't miss an interrupt
# setting need_resched or sigpending
# between sampling and the iret
movl TI_flags(%ebp), %ecx
andl $_TIF_WORK_MASK, %ecx # is there any work to be done on
# int/exception return?
jne work_pending
jmp restore_all
#ifdef CONFIG_PREEMPT
ENTRY(resume_kernel)
cli
cmpl $0,TI_preempt_count(%ebp) # non-zero preempt_count ?
jnz restore_nocheck
need_resched:
movl TI_flags(%ebp), %ecx # need_resched set ?
testb $_TIF_NEED_RESCHED, %cl
jz restore_all
testl $IF_MASK,EFLAGS(%esp) # interrupts off (exception path) ?
jz restore_all
call preempt_schedule_irq
jmp need_resched
#endif
/* SYSENTER_RETURN points to after the "sysenter" instruction in
the vsyscall page. See vsyscall-sysentry.S, which defines the symbol. */
# sysenter call handler stub
ENTRY(sysenter_entry)
movl TSS_sysenter_esp0(%esp),%esp
sysenter_past_esp:
sti
pushl $(__USER_DS)
pushl %ebp
pushfl
pushl $(__USER_CS)
pushl $SYSENTER_RETURN
/*
* Load the potential sixth argument from user stack.
* Careful about security.
*/
cmpl $__PAGE_OFFSET-3,%ebp
jae syscall_fault
1: movl (%ebp),%ebp
.section __ex_table,"a"
.align 4
.long 1b,syscall_fault
.previous
pushl %eax
SAVE_ALL
GET_THREAD_INFO(%ebp)
/* Note, _TIF_SECCOMP is bit number 8, and so it needs testw and not testb */
[PATCH] UML Support - Ptrace: adds the host SYSEMU support, for UML and general usage Jeff Dike <jdike@addtoit.com>, Paolo 'Blaisorblade' Giarrusso <blaisorblade_spam@yahoo.it>, Bodo Stroesser <bstroesser@fujitsu-siemens.com> Adds a new ptrace(2) mode, called PTRACE_SYSEMU, resembling PTRACE_SYSCALL except that the kernel does not execute the requested syscall; this is useful to improve performance for virtual environments, like UML, which want to run the syscall on their own. In fact, using PTRACE_SYSCALL means stopping child execution twice, on entry and on exit, and each time you also have two context switches; with SYSEMU you avoid the 2nd stop and so save two context switches per syscall. Also, some architectures don't have support in the host for changing the syscall number via ptrace(), which is currently needed to skip syscall execution (UML turns any syscall into getpid() to avoid it being executed on the host). Fixing that is hard, while SYSEMU is easier to implement. * This version of the patch includes some suggestions of Jeff Dike to avoid adding any instructions to the syscall fast path, plus some other little changes, by myself, to make it work even when the syscall is executed with SYSENTER (but I'm unsure about them). It has been widely tested for quite a lot of time. * Various fixed were included to handle the various switches between various states, i.e. when for instance a syscall entry is traced with one of PT_SYSCALL / _SYSEMU / _SINGLESTEP and another one is used on exit. Basically, this is done by remembering which one of them was used even after the call to ptrace_notify(). * We're combining TIF_SYSCALL_EMU with TIF_SYSCALL_TRACE or TIF_SINGLESTEP to make do_syscall_trace() notice that the current syscall was started with SYSEMU on entry, so that no notification ought to be done in the exit path; this is a bit of a hack, so this problem is solved in another way in next patches. * Also, the effects of the patch: "Ptrace - i386: fix Syscall Audit interaction with singlestep" are cancelled; they are restored back in the last patch of this series. Detailed descriptions of the patches doing this kind of processing follow (but I've already summed everything up). * Fix behaviour when changing interception kind #1. In do_syscall_trace(), we check the status of the TIF_SYSCALL_EMU flag only after doing the debugger notification; but the debugger might have changed the status of this flag because he continued execution with PTRACE_SYSCALL, so this is wrong. This patch fixes it by saving the flag status before calling ptrace_notify(). * Fix behaviour when changing interception kind #2: avoid intercepting syscall on return when using SYSCALL again. A guest process switching from using PTRACE_SYSEMU to PTRACE_SYSCALL crashes. The problem is in arch/i386/kernel/entry.S. The current SYSEMU patch inhibits the syscall-handler to be called, but does not prevent do_syscall_trace() to be called after this for syscall completion interception. The appended patch fixes this. It reuses the flag TIF_SYSCALL_EMU to remember "we come from PTRACE_SYSEMU and now are in PTRACE_SYSCALL", since the flag is unused in the depicted situation. * Fix behaviour when changing interception kind #3: avoid intercepting syscall on return when using SINGLESTEP. When testing 2.6.9 and the skas3.v6 patch, with my latest patch and had problems with singlestepping on UML in SKAS with SYSEMU. It looped receiving SIGTRAPs without moving forward. EIP of the traced process was the same for all SIGTRAPs. What's missing is to handle switching from PTRACE_SYSCALL_EMU to PTRACE_SINGLESTEP in a way very similar to what is done for the change from PTRACE_SYSCALL_EMU to PTRACE_SYSCALL_TRACE. I.e., after calling ptrace(PTRACE_SYSEMU), on the return path, the debugger is notified and then wake ups the process; the syscall is executed (or skipped, when do_syscall_trace() returns 0, i.e. when using PTRACE_SYSEMU), and do_syscall_trace() is called again. Since we are on the return path of a SYSEMU'd syscall, if the wake up is performed through ptrace(PTRACE_SYSCALL), we must still avoid notifying the parent of the syscall exit. Now, this behaviour is extended even to resuming with PTRACE_SINGLESTEP. Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> Cc: Jeff Dike <jdike@addtoit.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-09-03 22:57:18 +00:00
testw $(_TIF_SYSCALL_EMU|_TIF_SYSCALL_TRACE|_TIF_SECCOMP|_TIF_SYSCALL_AUDIT),TI_flags(%ebp)
jnz syscall_trace_entry
cmpl $(nr_syscalls), %eax
jae syscall_badsys
call *sys_call_table(,%eax,4)
movl %eax,EAX(%esp)
cli
movl TI_flags(%ebp), %ecx
testw $_TIF_ALLWORK_MASK, %cx
jne syscall_exit_work
/* if something modifies registers it must also disable sysexit */
movl EIP(%esp), %edx
movl OLDESP(%esp), %ecx
xorl %ebp,%ebp
sti
sysexit
# system call handler stub
ENTRY(system_call)
pushl %eax # save orig_eax
SAVE_ALL
GET_THREAD_INFO(%ebp)
[PATCH] i386: fix singlestep through an int80 syscall Using PTRACE_SINGLESTEP on a child that does an int80 syscall misses the SIGTRAP that should be delivered upon syscall exit. Fix that by setting TIF_SINGLESTEP when entering the kernel via int80 with TF set. /* Test whether singlestep through an int80 syscall works. */ #define _GNU_SOURCE #include <stdio.h> #include <unistd.h> #include <fcntl.h> #include <sys/ptrace.h> #include <sys/wait.h> #include <sys/mman.h> #include <asm/user.h> static int child, status; static struct user_regs_struct regs; static void do_child() { ptrace(PTRACE_TRACEME, 0, 0, 0); kill(getpid(), SIGUSR1); asm ("int $0x80" : : "a" (20)); /* getpid */ } static void do_parent() { unsigned long eip, expected = 0; again: waitpid(child, &status, 0); if (WIFEXITED(status) || WIFSIGNALED(status)) return; if (WIFSTOPPED(status)) { ptrace(PTRACE_GETREGS, child, 0, &regs); eip = regs.eip; if (expected) fprintf(stderr, "child stop @ %08x, expected %08x %s\n", eip, expected, eip == expected ? "" : " <== ERROR"); if (*(unsigned short *)eip == 0x80cd) { fprintf(stderr, "int 0x80 at %08x\n", (unsigned int)eip); expected = eip + 2; } else expected = 0; ptrace(PTRACE_SINGLESTEP, child, NULL, NULL); } goto again; } int main(int argc, char * const argv[]) { child = fork(); if (child) do_parent(); else do_child(); return 0; } Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-23 10:59:48 +00:00
testl $TF_MASK,EFLAGS(%esp)
jz no_singlestep
orl $_TIF_SINGLESTEP,TI_flags(%ebp)
no_singlestep:
[PATCH] UML Support - Ptrace: adds the host SYSEMU support, for UML and general usage Jeff Dike <jdike@addtoit.com>, Paolo 'Blaisorblade' Giarrusso <blaisorblade_spam@yahoo.it>, Bodo Stroesser <bstroesser@fujitsu-siemens.com> Adds a new ptrace(2) mode, called PTRACE_SYSEMU, resembling PTRACE_SYSCALL except that the kernel does not execute the requested syscall; this is useful to improve performance for virtual environments, like UML, which want to run the syscall on their own. In fact, using PTRACE_SYSCALL means stopping child execution twice, on entry and on exit, and each time you also have two context switches; with SYSEMU you avoid the 2nd stop and so save two context switches per syscall. Also, some architectures don't have support in the host for changing the syscall number via ptrace(), which is currently needed to skip syscall execution (UML turns any syscall into getpid() to avoid it being executed on the host). Fixing that is hard, while SYSEMU is easier to implement. * This version of the patch includes some suggestions of Jeff Dike to avoid adding any instructions to the syscall fast path, plus some other little changes, by myself, to make it work even when the syscall is executed with SYSENTER (but I'm unsure about them). It has been widely tested for quite a lot of time. * Various fixed were included to handle the various switches between various states, i.e. when for instance a syscall entry is traced with one of PT_SYSCALL / _SYSEMU / _SINGLESTEP and another one is used on exit. Basically, this is done by remembering which one of them was used even after the call to ptrace_notify(). * We're combining TIF_SYSCALL_EMU with TIF_SYSCALL_TRACE or TIF_SINGLESTEP to make do_syscall_trace() notice that the current syscall was started with SYSEMU on entry, so that no notification ought to be done in the exit path; this is a bit of a hack, so this problem is solved in another way in next patches. * Also, the effects of the patch: "Ptrace - i386: fix Syscall Audit interaction with singlestep" are cancelled; they are restored back in the last patch of this series. Detailed descriptions of the patches doing this kind of processing follow (but I've already summed everything up). * Fix behaviour when changing interception kind #1. In do_syscall_trace(), we check the status of the TIF_SYSCALL_EMU flag only after doing the debugger notification; but the debugger might have changed the status of this flag because he continued execution with PTRACE_SYSCALL, so this is wrong. This patch fixes it by saving the flag status before calling ptrace_notify(). * Fix behaviour when changing interception kind #2: avoid intercepting syscall on return when using SYSCALL again. A guest process switching from using PTRACE_SYSEMU to PTRACE_SYSCALL crashes. The problem is in arch/i386/kernel/entry.S. The current SYSEMU patch inhibits the syscall-handler to be called, but does not prevent do_syscall_trace() to be called after this for syscall completion interception. The appended patch fixes this. It reuses the flag TIF_SYSCALL_EMU to remember "we come from PTRACE_SYSEMU and now are in PTRACE_SYSCALL", since the flag is unused in the depicted situation. * Fix behaviour when changing interception kind #3: avoid intercepting syscall on return when using SINGLESTEP. When testing 2.6.9 and the skas3.v6 patch, with my latest patch and had problems with singlestepping on UML in SKAS with SYSEMU. It looped receiving SIGTRAPs without moving forward. EIP of the traced process was the same for all SIGTRAPs. What's missing is to handle switching from PTRACE_SYSCALL_EMU to PTRACE_SINGLESTEP in a way very similar to what is done for the change from PTRACE_SYSCALL_EMU to PTRACE_SYSCALL_TRACE. I.e., after calling ptrace(PTRACE_SYSEMU), on the return path, the debugger is notified and then wake ups the process; the syscall is executed (or skipped, when do_syscall_trace() returns 0, i.e. when using PTRACE_SYSEMU), and do_syscall_trace() is called again. Since we are on the return path of a SYSEMU'd syscall, if the wake up is performed through ptrace(PTRACE_SYSCALL), we must still avoid notifying the parent of the syscall exit. Now, this behaviour is extended even to resuming with PTRACE_SINGLESTEP. Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> Cc: Jeff Dike <jdike@addtoit.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-09-03 22:57:18 +00:00
# system call tracing in operation / emulation
/* Note, _TIF_SECCOMP is bit number 8, and so it needs testw and not testb */
[PATCH] UML Support - Ptrace: adds the host SYSEMU support, for UML and general usage Jeff Dike <jdike@addtoit.com>, Paolo 'Blaisorblade' Giarrusso <blaisorblade_spam@yahoo.it>, Bodo Stroesser <bstroesser@fujitsu-siemens.com> Adds a new ptrace(2) mode, called PTRACE_SYSEMU, resembling PTRACE_SYSCALL except that the kernel does not execute the requested syscall; this is useful to improve performance for virtual environments, like UML, which want to run the syscall on their own. In fact, using PTRACE_SYSCALL means stopping child execution twice, on entry and on exit, and each time you also have two context switches; with SYSEMU you avoid the 2nd stop and so save two context switches per syscall. Also, some architectures don't have support in the host for changing the syscall number via ptrace(), which is currently needed to skip syscall execution (UML turns any syscall into getpid() to avoid it being executed on the host). Fixing that is hard, while SYSEMU is easier to implement. * This version of the patch includes some suggestions of Jeff Dike to avoid adding any instructions to the syscall fast path, plus some other little changes, by myself, to make it work even when the syscall is executed with SYSENTER (but I'm unsure about them). It has been widely tested for quite a lot of time. * Various fixed were included to handle the various switches between various states, i.e. when for instance a syscall entry is traced with one of PT_SYSCALL / _SYSEMU / _SINGLESTEP and another one is used on exit. Basically, this is done by remembering which one of them was used even after the call to ptrace_notify(). * We're combining TIF_SYSCALL_EMU with TIF_SYSCALL_TRACE or TIF_SINGLESTEP to make do_syscall_trace() notice that the current syscall was started with SYSEMU on entry, so that no notification ought to be done in the exit path; this is a bit of a hack, so this problem is solved in another way in next patches. * Also, the effects of the patch: "Ptrace - i386: fix Syscall Audit interaction with singlestep" are cancelled; they are restored back in the last patch of this series. Detailed descriptions of the patches doing this kind of processing follow (but I've already summed everything up). * Fix behaviour when changing interception kind #1. In do_syscall_trace(), we check the status of the TIF_SYSCALL_EMU flag only after doing the debugger notification; but the debugger might have changed the status of this flag because he continued execution with PTRACE_SYSCALL, so this is wrong. This patch fixes it by saving the flag status before calling ptrace_notify(). * Fix behaviour when changing interception kind #2: avoid intercepting syscall on return when using SYSCALL again. A guest process switching from using PTRACE_SYSEMU to PTRACE_SYSCALL crashes. The problem is in arch/i386/kernel/entry.S. The current SYSEMU patch inhibits the syscall-handler to be called, but does not prevent do_syscall_trace() to be called after this for syscall completion interception. The appended patch fixes this. It reuses the flag TIF_SYSCALL_EMU to remember "we come from PTRACE_SYSEMU and now are in PTRACE_SYSCALL", since the flag is unused in the depicted situation. * Fix behaviour when changing interception kind #3: avoid intercepting syscall on return when using SINGLESTEP. When testing 2.6.9 and the skas3.v6 patch, with my latest patch and had problems with singlestepping on UML in SKAS with SYSEMU. It looped receiving SIGTRAPs without moving forward. EIP of the traced process was the same for all SIGTRAPs. What's missing is to handle switching from PTRACE_SYSCALL_EMU to PTRACE_SINGLESTEP in a way very similar to what is done for the change from PTRACE_SYSCALL_EMU to PTRACE_SYSCALL_TRACE. I.e., after calling ptrace(PTRACE_SYSEMU), on the return path, the debugger is notified and then wake ups the process; the syscall is executed (or skipped, when do_syscall_trace() returns 0, i.e. when using PTRACE_SYSEMU), and do_syscall_trace() is called again. Since we are on the return path of a SYSEMU'd syscall, if the wake up is performed through ptrace(PTRACE_SYSCALL), we must still avoid notifying the parent of the syscall exit. Now, this behaviour is extended even to resuming with PTRACE_SINGLESTEP. Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> Cc: Jeff Dike <jdike@addtoit.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-09-03 22:57:18 +00:00
testw $(_TIF_SYSCALL_EMU|_TIF_SYSCALL_TRACE|_TIF_SECCOMP|_TIF_SYSCALL_AUDIT),TI_flags(%ebp)
jnz syscall_trace_entry
cmpl $(nr_syscalls), %eax
jae syscall_badsys
syscall_call:
call *sys_call_table(,%eax,4)
movl %eax,EAX(%esp) # store the return value
syscall_exit:
cli # make sure we don't miss an interrupt
# setting need_resched or sigpending
# between sampling and the iret
movl TI_flags(%ebp), %ecx
testw $_TIF_ALLWORK_MASK, %cx # current->work
jne syscall_exit_work
restore_all:
movl EFLAGS(%esp), %eax # mix EFLAGS, SS and CS
# Warning: OLDSS(%esp) contains the wrong/random values if we
# are returning to the kernel.
# See comments in process.c:copy_thread() for details.
movb OLDSS(%esp), %ah
movb CS(%esp), %al
andl $(VM_MASK | (4 << 8) | 3), %eax
cmpl $((4 << 8) | 3), %eax
je ldt_ss # returning to user-space with LDT SS
restore_nocheck:
RESTORE_REGS
addl $4, %esp
1: iret
.section .fixup,"ax"
iret_exc:
sti
pushl $0 # no error code
pushl $do_iret_error
jmp error_code
.previous
.section __ex_table,"a"
.align 4
.long 1b,iret_exc
.previous
ldt_ss:
larl OLDSS(%esp), %eax
jnz restore_nocheck
testl $0x00400000, %eax # returning to 32bit stack?
jnz restore_nocheck # allright, normal return
/* If returning to userspace with 16bit stack,
* try to fix the higher word of ESP, as the CPU
* won't restore it.
* This is an "official" bug of all the x86-compatible
* CPUs, which we can try to work around to make
* dosemu and wine happy. */
subl $8, %esp # reserve space for switch16 pointer
cli
movl %esp, %eax
/* Set up the 16bit stack frame with switch32 pointer on top,
* and a switch16 pointer on top of the current frame. */
call setup_x86_bogus_stack
RESTORE_REGS
lss 20+4(%esp), %esp # switch to 16bit stack
1: iret
.section __ex_table,"a"
.align 4
.long 1b,iret_exc
.previous
# perform work that needs to be done immediately before resumption
ALIGN
work_pending:
testb $_TIF_NEED_RESCHED, %cl
jz work_notifysig
work_resched:
call schedule
cli # make sure we don't miss an interrupt
# setting need_resched or sigpending
# between sampling and the iret
movl TI_flags(%ebp), %ecx
andl $_TIF_WORK_MASK, %ecx # is there any work to be done other
# than syscall tracing?
jz restore_all
testb $_TIF_NEED_RESCHED, %cl
jnz work_resched
work_notifysig: # deal with pending signals and
# notify-resume requests
testl $VM_MASK, EFLAGS(%esp)
movl %esp, %eax
jne work_notifysig_v86 # returning to kernel-space or
# vm86-space
xorl %edx, %edx
call do_notify_resume
jmp resume_userspace
ALIGN
work_notifysig_v86:
#ifdef CONFIG_VM86
pushl %ecx # save ti_flags for do_notify_resume
call save_v86_state # %eax contains pt_regs pointer
popl %ecx
movl %eax, %esp
xorl %edx, %edx
call do_notify_resume
jmp resume_userspace
#endif
# perform syscall exit tracing
ALIGN
syscall_trace_entry:
movl $-ENOSYS,EAX(%esp)
movl %esp, %eax
xorl %edx,%edx
call do_syscall_trace
[PATCH] UML Support - Ptrace: adds the host SYSEMU support, for UML and general usage Jeff Dike <jdike@addtoit.com>, Paolo 'Blaisorblade' Giarrusso <blaisorblade_spam@yahoo.it>, Bodo Stroesser <bstroesser@fujitsu-siemens.com> Adds a new ptrace(2) mode, called PTRACE_SYSEMU, resembling PTRACE_SYSCALL except that the kernel does not execute the requested syscall; this is useful to improve performance for virtual environments, like UML, which want to run the syscall on their own. In fact, using PTRACE_SYSCALL means stopping child execution twice, on entry and on exit, and each time you also have two context switches; with SYSEMU you avoid the 2nd stop and so save two context switches per syscall. Also, some architectures don't have support in the host for changing the syscall number via ptrace(), which is currently needed to skip syscall execution (UML turns any syscall into getpid() to avoid it being executed on the host). Fixing that is hard, while SYSEMU is easier to implement. * This version of the patch includes some suggestions of Jeff Dike to avoid adding any instructions to the syscall fast path, plus some other little changes, by myself, to make it work even when the syscall is executed with SYSENTER (but I'm unsure about them). It has been widely tested for quite a lot of time. * Various fixed were included to handle the various switches between various states, i.e. when for instance a syscall entry is traced with one of PT_SYSCALL / _SYSEMU / _SINGLESTEP and another one is used on exit. Basically, this is done by remembering which one of them was used even after the call to ptrace_notify(). * We're combining TIF_SYSCALL_EMU with TIF_SYSCALL_TRACE or TIF_SINGLESTEP to make do_syscall_trace() notice that the current syscall was started with SYSEMU on entry, so that no notification ought to be done in the exit path; this is a bit of a hack, so this problem is solved in another way in next patches. * Also, the effects of the patch: "Ptrace - i386: fix Syscall Audit interaction with singlestep" are cancelled; they are restored back in the last patch of this series. Detailed descriptions of the patches doing this kind of processing follow (but I've already summed everything up). * Fix behaviour when changing interception kind #1. In do_syscall_trace(), we check the status of the TIF_SYSCALL_EMU flag only after doing the debugger notification; but the debugger might have changed the status of this flag because he continued execution with PTRACE_SYSCALL, so this is wrong. This patch fixes it by saving the flag status before calling ptrace_notify(). * Fix behaviour when changing interception kind #2: avoid intercepting syscall on return when using SYSCALL again. A guest process switching from using PTRACE_SYSEMU to PTRACE_SYSCALL crashes. The problem is in arch/i386/kernel/entry.S. The current SYSEMU patch inhibits the syscall-handler to be called, but does not prevent do_syscall_trace() to be called after this for syscall completion interception. The appended patch fixes this. It reuses the flag TIF_SYSCALL_EMU to remember "we come from PTRACE_SYSEMU and now are in PTRACE_SYSCALL", since the flag is unused in the depicted situation. * Fix behaviour when changing interception kind #3: avoid intercepting syscall on return when using SINGLESTEP. When testing 2.6.9 and the skas3.v6 patch, with my latest patch and had problems with singlestepping on UML in SKAS with SYSEMU. It looped receiving SIGTRAPs without moving forward. EIP of the traced process was the same for all SIGTRAPs. What's missing is to handle switching from PTRACE_SYSCALL_EMU to PTRACE_SINGLESTEP in a way very similar to what is done for the change from PTRACE_SYSCALL_EMU to PTRACE_SYSCALL_TRACE. I.e., after calling ptrace(PTRACE_SYSEMU), on the return path, the debugger is notified and then wake ups the process; the syscall is executed (or skipped, when do_syscall_trace() returns 0, i.e. when using PTRACE_SYSEMU), and do_syscall_trace() is called again. Since we are on the return path of a SYSEMU'd syscall, if the wake up is performed through ptrace(PTRACE_SYSCALL), we must still avoid notifying the parent of the syscall exit. Now, this behaviour is extended even to resuming with PTRACE_SINGLESTEP. Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> Cc: Jeff Dike <jdike@addtoit.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-09-03 22:57:18 +00:00
cmpl $0, %eax
jne resume_userspace # ret != 0 -> running under PTRACE_SYSEMU,
[PATCH] UML Support - Ptrace: adds the host SYSEMU support, for UML and general usage Jeff Dike <jdike@addtoit.com>, Paolo 'Blaisorblade' Giarrusso <blaisorblade_spam@yahoo.it>, Bodo Stroesser <bstroesser@fujitsu-siemens.com> Adds a new ptrace(2) mode, called PTRACE_SYSEMU, resembling PTRACE_SYSCALL except that the kernel does not execute the requested syscall; this is useful to improve performance for virtual environments, like UML, which want to run the syscall on their own. In fact, using PTRACE_SYSCALL means stopping child execution twice, on entry and on exit, and each time you also have two context switches; with SYSEMU you avoid the 2nd stop and so save two context switches per syscall. Also, some architectures don't have support in the host for changing the syscall number via ptrace(), which is currently needed to skip syscall execution (UML turns any syscall into getpid() to avoid it being executed on the host). Fixing that is hard, while SYSEMU is easier to implement. * This version of the patch includes some suggestions of Jeff Dike to avoid adding any instructions to the syscall fast path, plus some other little changes, by myself, to make it work even when the syscall is executed with SYSENTER (but I'm unsure about them). It has been widely tested for quite a lot of time. * Various fixed were included to handle the various switches between various states, i.e. when for instance a syscall entry is traced with one of PT_SYSCALL / _SYSEMU / _SINGLESTEP and another one is used on exit. Basically, this is done by remembering which one of them was used even after the call to ptrace_notify(). * We're combining TIF_SYSCALL_EMU with TIF_SYSCALL_TRACE or TIF_SINGLESTEP to make do_syscall_trace() notice that the current syscall was started with SYSEMU on entry, so that no notification ought to be done in the exit path; this is a bit of a hack, so this problem is solved in another way in next patches. * Also, the effects of the patch: "Ptrace - i386: fix Syscall Audit interaction with singlestep" are cancelled; they are restored back in the last patch of this series. Detailed descriptions of the patches doing this kind of processing follow (but I've already summed everything up). * Fix behaviour when changing interception kind #1. In do_syscall_trace(), we check the status of the TIF_SYSCALL_EMU flag only after doing the debugger notification; but the debugger might have changed the status of this flag because he continued execution with PTRACE_SYSCALL, so this is wrong. This patch fixes it by saving the flag status before calling ptrace_notify(). * Fix behaviour when changing interception kind #2: avoid intercepting syscall on return when using SYSCALL again. A guest process switching from using PTRACE_SYSEMU to PTRACE_SYSCALL crashes. The problem is in arch/i386/kernel/entry.S. The current SYSEMU patch inhibits the syscall-handler to be called, but does not prevent do_syscall_trace() to be called after this for syscall completion interception. The appended patch fixes this. It reuses the flag TIF_SYSCALL_EMU to remember "we come from PTRACE_SYSEMU and now are in PTRACE_SYSCALL", since the flag is unused in the depicted situation. * Fix behaviour when changing interception kind #3: avoid intercepting syscall on return when using SINGLESTEP. When testing 2.6.9 and the skas3.v6 patch, with my latest patch and had problems with singlestepping on UML in SKAS with SYSEMU. It looped receiving SIGTRAPs without moving forward. EIP of the traced process was the same for all SIGTRAPs. What's missing is to handle switching from PTRACE_SYSCALL_EMU to PTRACE_SINGLESTEP in a way very similar to what is done for the change from PTRACE_SYSCALL_EMU to PTRACE_SYSCALL_TRACE. I.e., after calling ptrace(PTRACE_SYSEMU), on the return path, the debugger is notified and then wake ups the process; the syscall is executed (or skipped, when do_syscall_trace() returns 0, i.e. when using PTRACE_SYSEMU), and do_syscall_trace() is called again. Since we are on the return path of a SYSEMU'd syscall, if the wake up is performed through ptrace(PTRACE_SYSCALL), we must still avoid notifying the parent of the syscall exit. Now, this behaviour is extended even to resuming with PTRACE_SINGLESTEP. Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> Cc: Jeff Dike <jdike@addtoit.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-09-03 22:57:18 +00:00
# so must skip actual syscall
movl ORIG_EAX(%esp), %eax
cmpl $(nr_syscalls), %eax
jnae syscall_call
jmp syscall_exit
# perform syscall exit tracing
ALIGN
syscall_exit_work:
testb $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SINGLESTEP), %cl
jz work_pending
sti # could let do_syscall_trace() call
# schedule() instead
movl %esp, %eax
movl $1, %edx
call do_syscall_trace
jmp resume_userspace
ALIGN
syscall_fault:
pushl %eax # save orig_eax
SAVE_ALL
GET_THREAD_INFO(%ebp)
movl $-EFAULT,EAX(%esp)
jmp resume_userspace
ALIGN
syscall_badsys:
movl $-ENOSYS,EAX(%esp)
jmp resume_userspace
#define FIXUP_ESPFIX_STACK \
movl %esp, %eax; \
/* switch to 32bit stack using the pointer on top of 16bit stack */ \
lss %ss:CPU_16BIT_STACK_SIZE-8, %esp; \
/* copy data from 16bit stack to 32bit stack */ \
call fixup_x86_bogus_stack; \
/* put ESP to the proper location */ \
movl %eax, %esp;
#define UNWIND_ESPFIX_STACK \
pushl %eax; \
movl %ss, %eax; \
/* see if on 16bit stack */ \
cmpw $__ESPFIX_SS, %ax; \
jne 28f; \
movl $__KERNEL_DS, %edx; \
movl %edx, %ds; \
movl %edx, %es; \
/* switch to 32bit stack */ \
FIXUP_ESPFIX_STACK \
28: popl %eax;
/*
* Build the entry stubs and pointer table with
* some assembler magic.
*/
.data
ENTRY(interrupt)
.text
vector=0
ENTRY(irq_entries_start)
.rept NR_IRQS
ALIGN
1: pushl $vector-256
jmp common_interrupt
.data
.long 1b
.text
vector=vector+1
.endr
ALIGN
common_interrupt:
SAVE_ALL
movl %esp,%eax
call do_IRQ
jmp ret_from_intr
#define BUILD_INTERRUPT(name, nr) \
ENTRY(name) \
pushl $nr-256; \
SAVE_ALL \
movl %esp,%eax; \
call smp_/**/name; \
jmp ret_from_intr;
/* The include is where all of the SMP etc. interrupts come from */
#include "entry_arch.h"
ENTRY(divide_error)
pushl $0 # no error code
pushl $do_divide_error
ALIGN
error_code:
pushl %ds
pushl %eax
xorl %eax, %eax
pushl %ebp
pushl %edi
pushl %esi
pushl %edx
decl %eax # eax = -1
pushl %ecx
pushl %ebx
cld
pushl %es
UNWIND_ESPFIX_STACK
popl %ecx
movl ES(%esp), %edi # get the function address
movl ORIG_EAX(%esp), %edx # get the error code
movl %eax, ORIG_EAX(%esp)
movl %ecx, ES(%esp)
movl $(__USER_DS), %ecx
movl %ecx, %ds
movl %ecx, %es
movl %esp,%eax # pt_regs pointer
call *%edi
jmp ret_from_exception
ENTRY(coprocessor_error)
pushl $0
pushl $do_coprocessor_error
jmp error_code
ENTRY(simd_coprocessor_error)
pushl $0
pushl $do_simd_coprocessor_error
jmp error_code
ENTRY(device_not_available)
pushl $-1 # mark this as an int
SAVE_ALL
movl %cr0, %eax
testl $0x4, %eax # EM (math emulation bit)
jne device_not_available_emulate
preempt_stop
call math_state_restore
jmp ret_from_exception
device_not_available_emulate:
pushl $0 # temporary storage for ORIG_EIP
call math_emulate
addl $4, %esp
jmp ret_from_exception
/*
* Debug traps and NMI can happen at the one SYSENTER instruction
* that sets up the real kernel stack. Check here, since we can't
* allow the wrong stack to be used.
*
* "TSS_sysenter_esp0+12" is because the NMI/debug handler will have
* already pushed 3 words if it hits on the sysenter instruction:
* eflags, cs and eip.
*
* We just load the right stack, and push the three (known) values
* by hand onto the new stack - while updating the return eip past
* the instruction that would have done it for sysenter.
*/
#define FIX_STACK(offset, ok, label) \
cmpw $__KERNEL_CS,4(%esp); \
jne ok; \
label: \
movl TSS_sysenter_esp0+offset(%esp),%esp; \
pushfl; \
pushl $__KERNEL_CS; \
pushl $sysenter_past_esp
KPROBE_ENTRY(debug)
cmpl $sysenter_entry,(%esp)
jne debug_stack_correct
FIX_STACK(12, debug_stack_correct, debug_esp_fix_insn)
debug_stack_correct:
pushl $-1 # mark this as an int
SAVE_ALL
xorl %edx,%edx # error code 0
movl %esp,%eax # pt_regs pointer
call do_debug
jmp ret_from_exception
.previous .text
/*
* NMI is doubly nasty. It can happen _while_ we're handling
* a debug fault, and the debug fault hasn't yet been able to
* clear up the stack. So we first check whether we got an
* NMI on the sysenter entry path, but after that we need to
* check whether we got an NMI on the debug path where the debug
* fault happened on the sysenter path.
*/
ENTRY(nmi)
pushl %eax
movl %ss, %eax
cmpw $__ESPFIX_SS, %ax
popl %eax
je nmi_16bit_stack
cmpl $sysenter_entry,(%esp)
je nmi_stack_fixup
pushl %eax
movl %esp,%eax
/* Do not access memory above the end of our stack page,
* it might not exist.
*/
andl $(THREAD_SIZE-1),%eax
cmpl $(THREAD_SIZE-20),%eax
popl %eax
jae nmi_stack_correct
cmpl $sysenter_entry,12(%esp)
je nmi_debug_stack_check
nmi_stack_correct:
pushl %eax
SAVE_ALL
xorl %edx,%edx # zero error code
movl %esp,%eax # pt_regs pointer
call do_nmi
jmp restore_all
nmi_stack_fixup:
FIX_STACK(12,nmi_stack_correct, 1)
jmp nmi_stack_correct
nmi_debug_stack_check:
cmpw $__KERNEL_CS,16(%esp)
jne nmi_stack_correct
cmpl $debug,(%esp)
jb nmi_stack_correct
cmpl $debug_esp_fix_insn,(%esp)
ja nmi_stack_correct
FIX_STACK(24,nmi_stack_correct, 1)
jmp nmi_stack_correct
nmi_16bit_stack:
/* create the pointer to lss back */
pushl %ss
pushl %esp
movzwl %sp, %esp
addw $4, (%esp)
/* copy the iret frame of 12 bytes */
.rept 3
pushl 16(%esp)
.endr
pushl %eax
SAVE_ALL
FIXUP_ESPFIX_STACK # %eax == %esp
xorl %edx,%edx # zero error code
call do_nmi
RESTORE_REGS
lss 12+4(%esp), %esp # back to 16bit stack
1: iret
.section __ex_table,"a"
.align 4
.long 1b,iret_exc
.previous
KPROBE_ENTRY(int3)
pushl $-1 # mark this as an int
SAVE_ALL
xorl %edx,%edx # zero error code
movl %esp,%eax # pt_regs pointer
call do_int3
jmp ret_from_exception
.previous .text
ENTRY(overflow)
pushl $0
pushl $do_overflow
jmp error_code
ENTRY(bounds)
pushl $0
pushl $do_bounds
jmp error_code
ENTRY(invalid_op)
pushl $0
pushl $do_invalid_op
jmp error_code
ENTRY(coprocessor_segment_overrun)
pushl $0
pushl $do_coprocessor_segment_overrun
jmp error_code
ENTRY(invalid_TSS)
pushl $do_invalid_TSS
jmp error_code
ENTRY(segment_not_present)
pushl $do_segment_not_present
jmp error_code
ENTRY(stack_segment)
pushl $do_stack_segment
jmp error_code
KPROBE_ENTRY(general_protection)
pushl $do_general_protection
jmp error_code
.previous .text
ENTRY(alignment_check)
pushl $do_alignment_check
jmp error_code
KPROBE_ENTRY(page_fault)
pushl $do_page_fault
jmp error_code
.previous .text
#ifdef CONFIG_X86_MCE
ENTRY(machine_check)
pushl $0
pushl machine_check_vector
jmp error_code
#endif
ENTRY(spurious_interrupt_bug)
pushl $0
pushl $do_spurious_interrupt_bug
jmp error_code
#ifdef CONFIG_STACK_UNWIND
ENTRY(arch_unwind_init_running)
movl 4(%esp), %edx
movl (%esp), %ecx
leal 4(%esp), %eax
movl %ebx, EBX(%edx)
xorl %ebx, %ebx
movl %ebx, ECX(%edx)
movl %ebx, EDX(%edx)
movl %esi, ESI(%edx)
movl %edi, EDI(%edx)
movl %ebp, EBP(%edx)
movl %ebx, EAX(%edx)
movl $__USER_DS, DS(%edx)
movl $__USER_DS, ES(%edx)
movl %ebx, ORIG_EAX(%edx)
movl %ecx, EIP(%edx)
movl 12(%esp), %ecx
movl $__KERNEL_CS, CS(%edx)
movl %ebx, EFLAGS(%edx)
movl %eax, OLDESP(%edx)
movl 8(%esp), %eax
movl %ecx, 8(%esp)
movl EBX(%edx), %ebx
movl $__KERNEL_DS, OLDSS(%edx)
jmpl *%eax
ENDPROC(arch_unwind_init_running)
#endif
.section .rodata,"a"
#include "syscall_table.S"
syscall_table_size=(.-sys_call_table)