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: Roland McGrath <roland@redhat.com>
diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index 20371d0..8796d19 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -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 @@
.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 @@
.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 @@
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
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index 0ad987d..cadf73f 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -332,7 +332,7 @@
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 @@
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 @@
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 @@
# 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
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index ae63e58..63001c6 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -349,8 +349,7 @@
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 @@
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 @@
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 @@
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:
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 77040b6..34e77b1 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -1357,8 +1357,6 @@
#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 @@
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 @@
}
}
-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);
+}