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x86 ptrace: unify syscall tracing

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This unifies and cleans up the syscall tracing code on i386 and x86_64.

Using a single function for entry and exit tracing on 32-bit made the
do_syscall_trace() into some terrible spaghetti.  The logic is clear and
simple using separate syscall_trace_enter() and syscall_trace_leave()
functions as on 64-bit.

The unification adds PTRACE_SYSEMU and PTRACE_SYSEMU_SINGLESTEP support
on x86_64, for 32-bit ptrace() callers and for 64-bit ptrace() callers
tracing either 32-bit or 64-bit tasks.  It behaves just like 32-bit.

Changing syscall_trace_enter() to return the syscall number shortens
all the assembly paths, while adding the SYSEMU feature in a simple way.

Signed-off-by: Roland McGrath <roland@redhat.com>
This commit is contained in:
Roland McGrath 2008-07-09 02:38:07 -07:00
commit d4d6715016
7 changed files with 88 additions and 132 deletions
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17
arch/x86/ia32/ia32entry.S
View file

@ -37,6 +37,11 @@
movq %rax,R8(%rsp)
.endm
/*
* Reload arg registers from stack in case ptrace changed them.
* We don't reload %eax because syscall_trace_enter() returned
* the value it wants us to use in the table lookup.
*/
.macro LOAD_ARGS32 offset
movl \offset(%rsp),%r11d
movl \offset+8(%rsp),%r10d
@ -46,7 +51,6 @@
movl \offset+48(%rsp),%edx
movl \offset+56(%rsp),%esi
movl \offset+64(%rsp),%edi
movl \offset+72(%rsp),%eax
.endm
.macro CFI_STARTPROC32 simple
@ -137,13 +141,12 @@ ENTRY(ia32_sysenter_target)
.previous
GET_THREAD_INFO(%r10)
orl $TS_COMPAT,TI_status(%r10)
testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP), \
TI_flags(%r10)
testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%r10)
CFI_REMEMBER_STATE
jnz sysenter_tracesys
sysenter_do_call:
cmpl $(IA32_NR_syscalls-1),%eax
ja ia32_badsys
sysenter_do_call:
IA32_ARG_FIXUP 1
call *ia32_sys_call_table(,%rax,8)
movq %rax,RAX-ARGOFFSET(%rsp)
@ -242,8 +245,7 @@ ENTRY(ia32_cstar_target)
.previous
GET_THREAD_INFO(%r10)
orl $TS_COMPAT,TI_status(%r10)
testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP), \
TI_flags(%r10)
testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%r10)
CFI_REMEMBER_STATE
jnz cstar_tracesys
cstar_do_call:
@ -336,8 +338,7 @@ ENTRY(ia32_syscall)
SAVE_ARGS 0,0,1
GET_THREAD_INFO(%r10)
orl $TS_COMPAT,TI_status(%r10)
testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP), \
TI_flags(%r10)
testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%r10)
jnz ia32_tracesys
ia32_do_syscall:
cmpl $(IA32_NR_syscalls-1),%eax

19
arch/x86/kernel/entry_32.S
View file

@ -332,7 +332,7 @@ sysenter_past_esp:
GET_THREAD_INFO(%ebp)
/* Note, _TIF_SECCOMP is bit number 8, and so it needs testw and not testb */
testw $(_TIF_SYSCALL_EMU|_TIF_SYSCALL_TRACE|_TIF_SECCOMP|_TIF_SYSCALL_AUDIT),TI_flags(%ebp)
testw $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%ebp)
jnz syscall_trace_entry
cmpl $(nr_syscalls), %eax
jae syscall_badsys
@ -370,7 +370,7 @@ ENTRY(system_call)
GET_THREAD_INFO(%ebp)
# system call tracing in operation / emulation
/* Note, _TIF_SECCOMP is bit number 8, and so it needs testw and not testb */
testw $(_TIF_SYSCALL_EMU|_TIF_SYSCALL_TRACE|_TIF_SECCOMP|_TIF_SYSCALL_AUDIT),TI_flags(%ebp)
testw $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%ebp)
jnz syscall_trace_entry
cmpl $(nr_syscalls), %eax
jae syscall_badsys
@ -510,12 +510,8 @@ END(work_pending)
syscall_trace_entry:
movl $-ENOSYS,PT_EAX(%esp)
movl %esp, %eax
xorl %edx,%edx
call do_syscall_trace
cmpl $0, %eax
jne resume_userspace # ret != 0 -> running under PTRACE_SYSEMU,
# so must skip actual syscall
movl PT_ORIG_EAX(%esp), %eax
call syscall_trace_enter
/* What it returned is what we'll actually use. */
cmpl $(nr_syscalls), %eax
jnae syscall_call
jmp syscall_exit
@ -524,14 +520,13 @@ END(syscall_trace_entry)
# perform syscall exit tracing
ALIGN
syscall_exit_work:
testb $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SINGLESTEP), %cl
testb $_TIF_WORK_SYSCALL_EXIT, %cl
jz work_pending
TRACE_IRQS_ON
ENABLE_INTERRUPTS(CLBR_ANY) # could let do_syscall_trace() call
ENABLE_INTERRUPTS(CLBR_ANY) # could let syscall_trace_leave() call
# schedule() instead
movl %esp, %eax
movl $1, %edx
call do_syscall_trace
call syscall_trace_leave
jmp resume_userspace
END(syscall_exit_work)
CFI_ENDPROC

14
arch/x86/kernel/entry_64.S
View file

@ -349,8 +349,7 @@ ENTRY(system_call_after_swapgs)
movq %rcx,RIP-ARGOFFSET(%rsp)
CFI_REL_OFFSET rip,RIP-ARGOFFSET
GET_THREAD_INFO(%rcx)
testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SECCOMP), \
TI_flags(%rcx)
testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%rcx)
jnz tracesys
cmpq $__NR_syscall_max,%rax
ja badsys
@ -430,7 +429,12 @@ tracesys:
FIXUP_TOP_OF_STACK %rdi
movq %rsp,%rdi
call syscall_trace_enter
LOAD_ARGS ARGOFFSET /* reload args from stack in case ptrace changed it */
/*
* Reload arg registers from stack in case ptrace changed them.
* We don't reload %rax because syscall_trace_enter() returned
* the value it wants us to use in the table lookup.
*/
LOAD_ARGS ARGOFFSET, 1
RESTORE_REST
cmpq $__NR_syscall_max,%rax
ja int_ret_from_sys_call /* RAX(%rsp) set to -ENOSYS above */
@ -483,7 +487,7 @@ int_very_careful:
ENABLE_INTERRUPTS(CLBR_NONE)
SAVE_REST
/* Check for syscall exit trace */
testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SINGLESTEP),%edx
testl $_TIF_WORK_SYSCALL_EXIT,%edx
jz int_signal
pushq %rdi
CFI_ADJUST_CFA_OFFSET 8
@ -491,7 +495,7 @@ int_very_careful:
call syscall_trace_leave
popq %rdi
CFI_ADJUST_CFA_OFFSET -8
andl $~(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SINGLESTEP),%edi
andl $~(_TIF_WORK_SYSCALL_EXIT|_TIF_SYSCALL_EMU),%edi
jmp int_restore_rest
int_signal:

141
arch/x86/kernel/ptrace.c
View file

@ -1357,8 +1357,6 @@ const struct user_regset_view *task_user_regset_view(struct task_struct *task)
#endif
}
#ifdef CONFIG_X86_32
void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs, int error_code)
{
struct siginfo info;
@ -1377,89 +1375,10 @@ void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs, int error_code)
force_sig_info(SIGTRAP, &info, tsk);
}
/* notification of system call entry/exit
* - triggered by current->work.syscall_trace
*/
int do_syscall_trace(struct pt_regs *regs, int entryexit)
{
int is_sysemu = test_thread_flag(TIF_SYSCALL_EMU);
/*
* With TIF_SYSCALL_EMU set we want to ignore TIF_SINGLESTEP for syscall
* interception
*/
int is_singlestep = !is_sysemu && test_thread_flag(TIF_SINGLESTEP);
int ret = 0;
/* do the secure computing check first */
if (!entryexit)
secure_computing(regs->orig_ax);
if (unlikely(current->audit_context)) {
if (entryexit)
audit_syscall_exit(AUDITSC_RESULT(regs->ax),
regs->ax);
/* Debug traps, when using PTRACE_SINGLESTEP, must be sent only
* on the syscall exit path. Normally, when TIF_SYSCALL_AUDIT is
* not used, entry.S will call us only on syscall exit, not
* entry; so when TIF_SYSCALL_AUDIT is used we must avoid
* calling send_sigtrap() on syscall entry.
*
* Note that when PTRACE_SYSEMU_SINGLESTEP is used,
* is_singlestep is false, despite his name, so we will still do
* the correct thing.
*/
else if (is_singlestep)
goto out;
}
if (!(current->ptrace & PT_PTRACED))
goto out;
/* If a process stops on the 1st tracepoint with SYSCALL_TRACE
* and then is resumed with SYSEMU_SINGLESTEP, it will come in
* here. We have to check this and return */
if (is_sysemu && entryexit)
return 0;
/* Fake a debug trap */
if (is_singlestep)
send_sigtrap(current, regs, 0);
if (!test_thread_flag(TIF_SYSCALL_TRACE) && !is_sysemu)
goto out;
/* the 0x80 provides a way for the tracing parent to distinguish
between a syscall stop and SIGTRAP delivery */
/* Note that the debugger could change the result of test_thread_flag!*/
ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD) ? 0x80:0));
/*
* this isn't the same as continuing with a signal, but it will do
* for normal use. strace only continues with a signal if the
* stopping signal is not SIGTRAP. -brl
*/
if (current->exit_code) {
send_sig(current->exit_code, current, 1);
current->exit_code = 0;
}
ret = is_sysemu;
out:
if (unlikely(current->audit_context) && !entryexit)
audit_syscall_entry(AUDIT_ARCH_I386, regs->orig_ax,
regs->bx, regs->cx, regs->dx, regs->si);
if (ret == 0)
return 0;
regs->orig_ax = -1; /* force skip of syscall restarting */
if (unlikely(current->audit_context))
audit_syscall_exit(AUDITSC_RESULT(regs->ax), regs->ax);
return 1;
}
#else /* CONFIG_X86_64 */
static void syscall_trace(struct pt_regs *regs)
{
if (!(current->ptrace & PT_PTRACED))
return;
#if 0
printk("trace %s ip %lx sp %lx ax %d origrax %d caller %lx tiflags %x ptrace %x\n",
@ -1481,39 +1400,71 @@ static void syscall_trace(struct pt_regs *regs)
}
}
asmlinkage void syscall_trace_enter(struct pt_regs *regs)
#ifdef CONFIG_X86_32
# define IS_IA32 1
#elif defined CONFIG_IA32_EMULATION
# define IS_IA32 test_thread_flag(TIF_IA32)
#else
# define IS_IA32 0
#endif
/*
* We must return the syscall number to actually look up in the table.
* This can be -1L to skip running any syscall at all.
*/
asmregparm long syscall_trace_enter(struct pt_regs *regs)
{
long ret = 0;
/* do the secure computing check first */
secure_computing(regs->orig_ax);
if (test_thread_flag(TIF_SYSCALL_TRACE)
&& (current->ptrace & PT_PTRACED))
if (unlikely(test_thread_flag(TIF_SYSCALL_EMU)))
ret = -1L;
if (ret || test_thread_flag(TIF_SYSCALL_TRACE))
syscall_trace(regs);
if (unlikely(current->audit_context)) {
if (test_thread_flag(TIF_IA32)) {
if (IS_IA32)
audit_syscall_entry(AUDIT_ARCH_I386,
regs->orig_ax,
regs->bx, regs->cx,
regs->dx, regs->si);
} else {
#ifdef CONFIG_X86_64
else
audit_syscall_entry(AUDIT_ARCH_X86_64,
regs->orig_ax,
regs->di, regs->si,
regs->dx, regs->r10);
}
#endif
}
return ret ?: regs->orig_ax;
}
asmlinkage void syscall_trace_leave(struct pt_regs *regs)
asmregparm void syscall_trace_leave(struct pt_regs *regs)
{
if (unlikely(current->audit_context))
audit_syscall_exit(AUDITSC_RESULT(regs->ax), regs->ax);
if ((test_thread_flag(TIF_SYSCALL_TRACE)
|| test_thread_flag(TIF_SINGLESTEP))
&& (current->ptrace & PT_PTRACED))
if (test_thread_flag(TIF_SYSCALL_TRACE))
syscall_trace(regs);
}
#endif /* CONFIG_X86_32 */
/*
* If TIF_SYSCALL_EMU is set, we only get here because of
* TIF_SINGLESTEP (i.e. this is PTRACE_SYSEMU_SINGLESTEP).
* We already reported this syscall instruction in
* syscall_trace_enter(), so don't do any more now.
*/
if (unlikely(test_thread_flag(TIF_SYSCALL_EMU)))
return;
/*
* If we are single-stepping, synthesize a trap to follow the
* system call instruction.
*/
if (test_thread_flag(TIF_SINGLESTEP) &&
(current->ptrace & PT_PTRACED))
send_sigtrap(current, regs, 0);
}

6
include/asm-x86/calling.h
View file

@ -104,7 +104,7 @@
.endif
.endm
.macro LOAD_ARGS offset
.macro LOAD_ARGS offset, skiprax=0
movq \offset(%rsp), %r11
movq \offset+8(%rsp), %r10
movq \offset+16(%rsp), %r9
@ -113,7 +113,10 @@
movq \offset+48(%rsp), %rdx
movq \offset+56(%rsp), %rsi
movq \offset+64(%rsp), %rdi
.if \skiprax
.else
movq \offset+72(%rsp), %rax
.endif
.endm
#define REST_SKIP 6*8
@ -165,4 +168,3 @@
.macro icebp
.byte 0xf1
.endm

6
include/asm-x86/ptrace-abi.h
View file

@ -73,11 +73,11 @@
#ifdef __x86_64__
# define PTRACE_ARCH_PRCTL 30
#else
# define PTRACE_SYSEMU 31
# define PTRACE_SYSEMU_SINGLESTEP 32
#endif
#define PTRACE_SYSEMU 31
#define PTRACE_SYSEMU_SINGLESTEP 32
#define PTRACE_SINGLEBLOCK 33 /* resume execution until next branch */
#ifndef __ASSEMBLY__

17
include/asm-x86/thread_info.h
View file

@ -75,9 +75,7 @@ struct thread_info {
#define TIF_NEED_RESCHED 3 /* rescheduling necessary */
#define TIF_SINGLESTEP 4 /* reenable singlestep on user return*/
#define TIF_IRET 5 /* force IRET */
#ifdef CONFIG_X86_32
#define TIF_SYSCALL_EMU 6 /* syscall emulation active */
#endif
#define TIF_SYSCALL_AUDIT 7 /* syscall auditing active */
#define TIF_SECCOMP 8 /* secure computing */
#define TIF_MCE_NOTIFY 10 /* notify userspace of an MCE */
@ -100,11 +98,7 @@ struct thread_info {
#define _TIF_SINGLESTEP (1 << TIF_SINGLESTEP)
#define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED)
#define _TIF_IRET (1 << TIF_IRET)
#ifdef CONFIG_X86_32
#define _TIF_SYSCALL_EMU (1 << TIF_SYSCALL_EMU)
#else
#define _TIF_SYSCALL_EMU 0
#endif
#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
#define _TIF_SECCOMP (1 << TIF_SECCOMP)
#define _TIF_MCE_NOTIFY (1 << TIF_MCE_NOTIFY)
@ -121,11 +115,20 @@ struct thread_info {
#define _TIF_DS_AREA_MSR (1 << TIF_DS_AREA_MSR)
#define _TIF_BTS_TRACE_TS (1 << TIF_BTS_TRACE_TS)
/* work to do in syscall_trace_enter() */
#define _TIF_WORK_SYSCALL_ENTRY \
(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU | \
_TIF_SYSCALL_AUDIT | _TIF_SECCOMP)
/* work to do in syscall_trace_leave() */
#define _TIF_WORK_SYSCALL_EXIT \
(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SINGLESTEP)
/* work to do on interrupt/exception return */
#define _TIF_WORK_MASK \
(0x0000FFFF & \
~(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT| \
_TIF_SECCOMP|_TIF_SYSCALL_EMU))
_TIF_SINGLESTEP|_TIF_SECCOMP|_TIF_SYSCALL_EMU))
/* work to do on any return to user space */
#define _TIF_ALLWORK_MASK (0x0000FFFF & ~_TIF_SECCOMP)