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Commit d4d67150 authored by Roland McGrath's avatar Roland McGrath
Browse files

x86 ptrace: unify syscall tracing 



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: default avatarRoland McGrath <roland@redhat.com>
parent 64f09733

arch/x86/ia32/ia32entry.S

+9 −8
Original line number Diff line number Diff line
@@ -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

arch/x86/kernel/entry_32.S

+7 −12
Original line number Diff line number Diff line
@@ -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

arch/x86/kernel/entry_64.S

+9 −5
Original line number Diff line number Diff line
@@ -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:

arch/x86/kernel/ptrace.c

+46 −95
Original line number Diff line number Diff line
@@ -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);

}

include/asm-x86/calling.h

+4 −2
Original line number Diff line number Diff line
@@ -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