[RFC PATCH] ptrace: add PTRACE_GET_SYSCALL_INFO request

Elvira Khabirova
2018-11-07T03:51:34Z

PTRACE_GET_SYSCALL_INFO lets ptracer obtain details of the syscall
the tracee is blocked in. The request returns meaningful data only
when the tracee is in a syscall-enter-stop or a syscall-exit-stop.

There are two reasons for a special syscall-related ptrace request.

Firstly, with the current ptrace API there are cases when ptracer cannot
retrieve necessary information about syscalls. Some examples include:
* The notorious int-0x80-from-64-bit-task issue. See [1] for details.
In short, if a 64-bit task performs a syscall through int 0x80, its tracer
has no reliable means to find out that the syscall was, in fact,
a compat syscall, and misidentifies it.
* Syscall-enter-stop and syscall-exit-stop look the same for the tracer.
Common practice is to keep track of the sequence of ptrace-stops in order
not to mix the two syscall-stops up. But it is not as simple as it looks;
for example, strace had a (just recently fixed) long-standing bug where
attaching strace to a tracee that is performing the execve system call
led to the tracer identifying the following syscall-exit-stop as
syscall-enter-stop, which messed up all the state tracking.
* Since the introduction of commit 84d77d3f06e7e8dea057d10e8ec77ad71f721be3
("ptrace: Don't allow accessing an undumpable mm"), both PTRACE_PEEKDATA
and process_vm_readv become unavailable when the process dumpable flag
is cleared. On ia64 this results in all syscall arguments being unavailable.

Secondly, ptracers also have to support a lot of arch-specific code for
obtaining information about the tracee. For some architectures, this
requires a ptrace(PTRACE_PEEKUSER, ...) invocation for every syscall
argument and return value.

PTRACE_GET_SYSCALL_INFO returns the following structure:

struct ptrace_syscall_info {
__u8 op; /* 0 for entry, 1 for exit */
__u8 __pad0[7];
union {
struct {
__u64 nr;
__u64 ip;
__u64 args[6];
__u8 is_compat;
__u8 __pad1[7];
} entry_info;
struct {
__s64 rval;
__u8 is_error;
__u8 __pad2[7];
} exit_info;
};
};

The structure was chosen according to [2], except for two changes.
First: instead of an arch field with a value of AUDIT_ARCH_*, a boolean
is_compat value is returned, because a) not all arches have an AUDIT_ARCH_*
defined for them, b) the tracer already knows what *arch* it is running on,
but it does not know whether the tracee/syscall is in compat mode or not.
Second: a boolean is_error value is added to rval. This way the tracer can
more reliably distinguish a return value from an error value.

[1] https://lkml.kernel.org/r/CA+55aFzcSVmdDj9Lh_gdbz1OzHyEm6ZrGPBDAJnywm2LF_eVyg@mail.gmail.com
[2] http://lkml.kernel.org/r/CAObL_7GM0n80N7J_DFw_eQyfLyzq+sf4y2AvsCCV88Tb3AwEHA@mail.gmail.com

Signed-off-by: Elvira Khabirova <lineprinter@altlinux.org>
---
arch/alpha/kernel/ptrace.c | 2 +-
arch/arc/kernel/ptrace.c | 2 +-
arch/arm/kernel/ptrace.c | 2 +-
arch/arm64/kernel/ptrace.c | 2 +-
arch/c6x/kernel/ptrace.c | 2 +-
arch/h8300/kernel/ptrace.c | 2 +-
arch/hexagon/kernel/traps.c | 2 +-
arch/ia64/kernel/ptrace.c | 2 +-
arch/m68k/kernel/ptrace.c | 3 ++-
arch/microblaze/kernel/ptrace.c | 2 +-
arch/mips/kernel/ptrace.c | 2 +-
arch/nds32/kernel/ptrace.c | 2 +-
arch/nios2/kernel/ptrace.c | 3 ++-
arch/openrisc/kernel/ptrace.c | 2 +-
arch/parisc/kernel/ptrace.c | 2 +-
arch/powerpc/kernel/ptrace.c | 2 +-
arch/riscv/kernel/ptrace.c | 2 +-
arch/s390/kernel/ptrace.c | 2 +-
arch/sh/kernel/ptrace_32.c | 2 +-
arch/sh/kernel/ptrace_64.c | 2 +-
arch/sparc/kernel/ptrace_32.c | 2 +-
arch/sparc/kernel/ptrace_64.c | 2 +-
arch/um/kernel/ptrace.c | 2 +-
arch/x86/entry/common.c | 2 +-
arch/xtensa/kernel/ptrace.c | 2 +-
include/linux/ptrace.h | 16 ++++++++++---
include/linux/tracehook.h | 13 ++++++----
include/uapi/linux/ptrace.h | 22 +++++++++++++++++
kernel/ptrace.c | 42 +++++++++++++++++++++++++++++++++
29 files changed, 113 insertions(+), 32 deletions(-)

diff --git a/arch/alpha/kernel/ptrace.c b/arch/alpha/kernel/ptrace.c
index cb8d599e72d6..970c0719b4d1 100644
--- a/arch/alpha/kernel/ptrace.c
+++ b/arch/alpha/kernel/ptrace.c
@@ -324,7 +324,7 @@ asmlinkage unsigned long syscall_trace_enter(void)
unsigned long ret = 0;
struct pt_regs *regs = current_pt_regs();
if (test_thread_flag(TIF_SYSCALL_TRACE) &&
- tracehook_report_syscall_entry(current_pt_regs()))
+ tracehook_report_syscall_entry(current_pt_regs(), false))
ret = -1UL;
audit_syscall_entry(regs->r0, regs->r16, regs->r17, regs->r18, regs->r19);
return ret ?: current_pt_regs()->r0;
diff --git a/arch/arc/kernel/ptrace.c b/arch/arc/kernel/ptrace.c
index 5ee4676f135d..d12c37c3da80 100644
--- a/arch/arc/kernel/ptrace.c
+++ b/arch/arc/kernel/ptrace.c
@@ -293,7 +293,7 @@ long arch_ptrace(struct task_struct *child, long request,

asmlinkage int syscall_trace_entry(struct pt_regs *regs)
{
- if (tracehook_report_syscall_entry(regs))
+ if (tracehook_report_syscall_entry(regs, false))
return ULONG_MAX;

return regs->r8;
diff --git a/arch/arm/kernel/ptrace.c b/arch/arm/kernel/ptrace.c
index 6fa5b6387556..686513749ac5 100644
--- a/arch/arm/kernel/ptrace.c
+++ b/arch/arm/kernel/ptrace.c
@@ -911,7 +911,7 @@ static void tracehook_report_syscall(struct pt_regs *regs,

if (dir == PTRACE_SYSCALL_EXIT)
tracehook_report_syscall_exit(regs, 0);
- else if (tracehook_report_syscall_entry(regs))
+ else if (tracehook_report_syscall_entry(regs, false))
current_thread_info()->syscall = -1;

regs->ARM_ip = ip;
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 1710a2d01669..667d7d96ae0a 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -1626,7 +1626,7 @@ static void tracehook_report_syscall(struct pt_regs *regs,

if (dir == PTRACE_SYSCALL_EXIT)
tracehook_report_syscall_exit(regs, 0);
- else if (tracehook_report_syscall_entry(regs))
+ else if (tracehook_report_syscall_entry(regs, is_compat_task()))
forget_syscall(regs);

regs->regs[regno] = saved_reg;
diff --git a/arch/c6x/kernel/ptrace.c b/arch/c6x/kernel/ptrace.c
index 8801dc98fd44..169b2bf4176d 100644
--- a/arch/c6x/kernel/ptrace.c
+++ b/arch/c6x/kernel/ptrace.c
@@ -127,7 +127,7 @@ long arch_ptrace(struct task_struct *child, long request,
*/
asmlinkage unsigned long syscall_trace_entry(struct pt_regs *regs)
{
- if (tracehook_report_syscall_entry(regs))
+ if (tracehook_report_syscall_entry(regs, false))
/* tracing decided this syscall should not happen, so
* We'll return a bogus call number to get an ENOSYS
* error, but leave the original number in
diff --git a/arch/h8300/kernel/ptrace.c b/arch/h8300/kernel/ptrace.c
index 0dc1c8f622bc..238918546603 100644
--- a/arch/h8300/kernel/ptrace.c
+++ b/arch/h8300/kernel/ptrace.c
@@ -179,7 +179,7 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
long ret = 0;

if (test_thread_flag(TIF_SYSCALL_TRACE) &&
- tracehook_report_syscall_entry(regs))
+ tracehook_report_syscall_entry(regs, false))
/*
* Tracing decided this syscall should not happen.
* We'll return a bogus call number to get an ENOSYS
diff --git a/arch/hexagon/kernel/traps.c b/arch/hexagon/kernel/traps.c
index 91ee04842c22..840f880760b7 100644
--- a/arch/hexagon/kernel/traps.c
+++ b/arch/hexagon/kernel/traps.c
@@ -368,7 +368,7 @@ void do_trap0(struct pt_regs *regs)

/* allow strace to catch syscall args */
if (unlikely(test_thread_flag(TIF_SYSCALL_TRACE) &&
- tracehook_report_syscall_entry(regs)))
+ tracehook_report_syscall_entry(regs, false)))
return; /* return -ENOSYS somewhere? */

/* Interrupts should be re-enabled for syscall processing */
diff --git a/arch/ia64/kernel/ptrace.c b/arch/ia64/kernel/ptrace.c
index 427cd565fd61..6c12265aed65 100644
--- a/arch/ia64/kernel/ptrace.c
+++ b/arch/ia64/kernel/ptrace.c
@@ -1218,7 +1218,7 @@ syscall_trace_enter (long arg0, long arg1, long arg2, long arg3,
struct pt_regs regs)
{
if (test_thread_flag(TIF_SYSCALL_TRACE))
- if (tracehook_report_syscall_entry(&regs))
+ if (tracehook_report_syscall_entry(&regs, false))
return -ENOSYS;

/* copy user rbs to kernel rbs */
diff --git a/arch/m68k/kernel/ptrace.c b/arch/m68k/kernel/ptrace.c
index 748c63bd0081..cdfd21325a62 100644
--- a/arch/m68k/kernel/ptrace.c
+++ b/arch/m68k/kernel/ptrace.c
@@ -293,7 +293,8 @@ asmlinkage int syscall_trace_enter(void)
int ret = 0;

if (test_thread_flag(TIF_SYSCALL_TRACE))
- ret = tracehook_report_syscall_entry(task_pt_regs(current));
+ ret = tracehook_report_syscall_entry(task_pt_regs(current),
+ false);
return ret;
}

diff --git a/arch/microblaze/kernel/ptrace.c b/arch/microblaze/kernel/ptrace.c
index badd286882ae..50b6bd6e2222 100644
--- a/arch/microblaze/kernel/ptrace.c
+++ b/arch/microblaze/kernel/ptrace.c
@@ -140,7 +140,7 @@ asmlinkage unsigned long do_syscall_trace_enter(struct pt_regs *regs)
secure_computing_strict(regs->r12);

if (test_thread_flag(TIF_SYSCALL_TRACE) &&
- tracehook_report_syscall_entry(regs))
+ tracehook_report_syscall_entry(regs, false))
/*
* Tracing decided this syscall should not happen.
* We'll return a bogus call number to get an ENOSYS
diff --git a/arch/mips/kernel/ptrace.c b/arch/mips/kernel/ptrace.c
index e5ba56c01ee0..633390fcca6a 100644
--- a/arch/mips/kernel/ptrace.c
+++ b/arch/mips/kernel/ptrace.c
@@ -1260,7 +1260,7 @@ asmlinkage long syscall_trace_enter(struct pt_regs *regs, long syscall)
current_thread_info()->syscall = syscall;

if (test_thread_flag(TIF_SYSCALL_TRACE)) {
- if (tracehook_report_syscall_entry(regs))
+ if (tracehook_report_syscall_entry(regs, is_compat_task()))
return -1;
syscall = current_thread_info()->syscall;
}
diff --git a/arch/nds32/kernel/ptrace.c b/arch/nds32/kernel/ptrace.c
index eaaf7a999b20..fe5870aa88ba 100644
--- a/arch/nds32/kernel/ptrace.c
+++ b/arch/nds32/kernel/ptrace.c
@@ -104,7 +104,7 @@ void user_disable_single_step(struct task_struct *child)
asmlinkage int syscall_trace_enter(struct pt_regs *regs)
{
if (test_thread_flag(TIF_SYSCALL_TRACE)) {
- if (tracehook_report_syscall_entry(regs))
+ if (tracehook_report_syscall_entry(regs, false))
forget_syscall(regs);
}
return regs->syscallno;
diff --git a/arch/nios2/kernel/ptrace.c b/arch/nios2/kernel/ptrace.c
index de97bcb7dd44..900daf87c771 100644
--- a/arch/nios2/kernel/ptrace.c
+++ b/arch/nios2/kernel/ptrace.c
@@ -155,7 +155,8 @@ asmlinkage int do_syscall_trace_enter(void)
int ret = 0;

if (test_thread_flag(TIF_SYSCALL_TRACE))
- ret = tracehook_report_syscall_entry(task_pt_regs(current));
+ ret = tracehook_report_syscall_entry(task_pt_regs(current),
+ false);

return ret;
}
diff --git a/arch/openrisc/kernel/ptrace.c b/arch/openrisc/kernel/ptrace.c
index eb97a8e7c8aa..2c6bdff65fdb 100644
--- a/arch/openrisc/kernel/ptrace.c
+++ b/arch/openrisc/kernel/ptrace.c
@@ -179,7 +179,7 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
long ret = 0;

if (test_thread_flag(TIF_SYSCALL_TRACE) &&
- tracehook_report_syscall_entry(regs))
+ tracehook_report_syscall_entry(regs, false))
/*
* Tracing decided this syscall should not happen.
* We'll return a bogus call number to get an ENOSYS
diff --git a/arch/parisc/kernel/ptrace.c b/arch/parisc/kernel/ptrace.c
index 2582df1c529b..a074efef61f2 100644
--- a/arch/parisc/kernel/ptrace.c
+++ b/arch/parisc/kernel/ptrace.c
@@ -309,7 +309,7 @@ long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
long do_syscall_trace_enter(struct pt_regs *regs)
{
if (test_thread_flag(TIF_SYSCALL_TRACE) &&
- tracehook_report_syscall_entry(regs)) {
+ tracehook_report_syscall_entry(regs, is_compat_task())) {
/*
* Tracing decided this syscall should not happen or the
* debugger stored an invalid system call number. Skip
diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index afb819f4ca68..e38374716866 100644
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -3282,7 +3282,7 @@ long do_syscall_trace_enter(struct pt_regs *regs)
* below on the exit path.
*/
if (test_thread_flag(TIF_SYSCALL_TRACE) &&
- tracehook_report_syscall_entry(regs))
+ tracehook_report_syscall_entry(regs, is_compat_task()))
goto skip;

/* Run seccomp after ptrace; allow it to set gpr[3]. */
diff --git a/arch/riscv/kernel/ptrace.c b/arch/riscv/kernel/ptrace.c
index 60f1e02eed36..51fc4ba43e90 100644
--- a/arch/riscv/kernel/ptrace.c
+++ b/arch/riscv/kernel/ptrace.c
@@ -156,7 +156,7 @@ long arch_ptrace(struct task_struct *child, long request,
void do_syscall_trace_enter(struct pt_regs *regs)
{
if (test_thread_flag(TIF_SYSCALL_TRACE))
- if (tracehook_report_syscall_entry(regs))
+ if (tracehook_report_syscall_entry(regs, false))
syscall_set_nr(current, regs, -1);

#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index cd3df5514552..567b6fdb389f 100644
--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -845,7 +845,7 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
* call number to gprs[2].
*/
if (test_thread_flag(TIF_SYSCALL_TRACE) &&
- (tracehook_report_syscall_entry(regs) ||
+ (tracehook_report_syscall_entry(regs, is_compat_task()) ||
regs->gprs[2] >= NR_syscalls)) {
/*
* Tracing decided this syscall should not happen or the
diff --git a/arch/sh/kernel/ptrace_32.c b/arch/sh/kernel/ptrace_32.c
index 5fc3ff606210..d521976a0817 100644
--- a/arch/sh/kernel/ptrace_32.c
+++ b/arch/sh/kernel/ptrace_32.c
@@ -492,7 +492,7 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
secure_computing_strict(regs->regs[0]);

if (test_thread_flag(TIF_SYSCALL_TRACE) &&
- tracehook_report_syscall_entry(regs))
+ tracehook_report_syscall_entry(regs, false))
/*
* Tracing decided this syscall should not happen.
* We'll return a bogus call number to get an ENOSYS
diff --git a/arch/sh/kernel/ptrace_64.c b/arch/sh/kernel/ptrace_64.c
index 1e0656d9e7af..11f3e22f13df 100644
--- a/arch/sh/kernel/ptrace_64.c
+++ b/arch/sh/kernel/ptrace_64.c
@@ -512,7 +512,7 @@ asmlinkage long long do_syscall_trace_enter(struct pt_regs *regs)
secure_computing_strict(regs->regs[9]);

if (test_thread_flag(TIF_SYSCALL_TRACE) &&
- tracehook_report_syscall_entry(regs))
+ tracehook_report_syscall_entry(regs, false))
/*
* Tracing decided this syscall should not happen.
* We'll return a bogus call number to get an ENOSYS
diff --git a/arch/sparc/kernel/ptrace_32.c b/arch/sparc/kernel/ptrace_32.c
index 16b50afe7b52..5ab2b55b3db6 100644
--- a/arch/sparc/kernel/ptrace_32.c
+++ b/arch/sparc/kernel/ptrace_32.c
@@ -452,7 +452,7 @@ asmlinkage int syscall_trace(struct pt_regs *regs, int syscall_exit_p)
if (syscall_exit_p)
tracehook_report_syscall_exit(regs, 0);
else
- ret = tracehook_report_syscall_entry(regs);
+ ret = tracehook_report_syscall_entry(regs, false);
}

return ret;
diff --git a/arch/sparc/kernel/ptrace_64.c b/arch/sparc/kernel/ptrace_64.c
index e1d965e90e16..8ad2b7183b88 100644
--- a/arch/sparc/kernel/ptrace_64.c
+++ b/arch/sparc/kernel/ptrace_64.c
@@ -1117,7 +1117,7 @@ asmlinkage int syscall_trace_enter(struct pt_regs *regs)
user_exit();

if (test_thread_flag(TIF_SYSCALL_TRACE))
- ret = tracehook_report_syscall_entry(regs);
+ ret = tracehook_report_syscall_entry(regs, is_compat_task());

if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
trace_sys_enter(regs, regs->u_regs[UREG_G1]);
diff --git a/arch/um/kernel/ptrace.c b/arch/um/kernel/ptrace.c
index 1a1d88a4d940..36b847b10814 100644
--- a/arch/um/kernel/ptrace.c
+++ b/arch/um/kernel/ptrace.c
@@ -136,7 +136,7 @@ int syscall_trace_enter(struct pt_regs *regs)
if (!test_thread_flag(TIF_SYSCALL_TRACE))
return 0;

- return tracehook_report_syscall_entry(regs);
+ return tracehook_report_syscall_entry(regs, false);
}

void syscall_trace_leave(struct pt_regs *regs)
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 3b2490b81918..f4593e17cc6f 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -82,7 +82,7 @@ static long syscall_trace_enter(struct pt_regs *regs)
emulated = true;

if ((emulated || (work & _TIF_SYSCALL_TRACE)) &&
- tracehook_report_syscall_entry(regs))
+ tracehook_report_syscall_entry(regs, in_ia32_syscall()))
return -1L;

if (emulated)
diff --git a/arch/xtensa/kernel/ptrace.c b/arch/xtensa/kernel/ptrace.c
index c0845cb1cbb9..4bd0babe5536 100644
--- a/arch/xtensa/kernel/ptrace.c
+++ b/arch/xtensa/kernel/ptrace.c
@@ -466,7 +466,7 @@ long arch_ptrace(struct task_struct *child, long request,
unsigned long do_syscall_trace_enter(struct pt_regs *regs)
{
if (test_thread_flag(TIF_SYSCALL_TRACE) &&
- tracehook_report_syscall_entry(regs))
+ tracehook_report_syscall_entry(regs, false))
return -1;

return regs->areg[2];
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index 6c2ffed907f5..8c95adccb64e 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -21,9 +21,10 @@ extern int ptrace_access_vm(struct task_struct *tsk, unsigned long addr,
* flags. When the a task is stopped the ptracer owns task->ptrace.
*/

-#define PT_SEIZED 0x00010000 /* SEIZE used, enable new behavior */
-#define PT_PTRACED 0x00000001
-#define PT_DTRACE 0x00000002 /* delayed trace (used on m68k, i386) */
+#define PT_SEIZED 0x00010000 /* SEIZE used, enable new behavior */
+#define PT_PTRACED 0x00000001
+#define PT_DTRACE 0x00000002 /* delayed trace (used on m68k, i386) */
+#define PT_IN_SYSCALL_STOP 0x00000004 /* task is in a syscall-stop */

#define PT_OPT_FLAG_SHIFT 3
/* PT_TRACE_* event enable flags */
@@ -46,6 +47,15 @@ extern int ptrace_access_vm(struct task_struct *tsk, unsigned long addr,
#define PT_BLOCKSTEP_BIT 30
#define PT_BLOCKSTEP (1<<PT_BLOCKSTEP_BIT)

+/*
+ * These flags are used in tracehook_report_syscall_* to store
+ * some information about current syscall-stop in task->ptrace_message.
+ * We can use ptrace_message because ptrace_message doesn't have to contain
+ * any specific value during syscall-stops.
+ */
+#define PT_SYSCALL_ISCOMPAT 0x00000001
+#define PT_SYSCALL_ISENTERING 0x00000002
+
extern long arch_ptrace(struct task_struct *child, long request,
unsigned long addr, unsigned long data);
extern int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len);
diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
index 40b0b4c1bf7b..e02ca656d2c9 100644
--- a/include/linux/tracehook.h
+++ b/include/linux/tracehook.h
@@ -57,13 +57,16 @@ struct linux_binprm;
/*
* ptrace report for syscall entry and exit looks identical.
*/
-static inline int ptrace_report_syscall(struct pt_regs *regs)
+static inline int ptrace_report_syscall(struct pt_regs *regs,
+ unsigned long message)
{
int ptrace = current->ptrace;

if (!(ptrace & PT_PTRACED))
return 0;
+ current->ptrace |= PT_IN_SYSCALL_STOP;

+ current->ptrace_message = message;
ptrace_notify(SIGTRAP | ((ptrace & PT_TRACESYSGOOD) ? 0x80 : 0));

/*
@@ -76,6 +79,7 @@ static inline int ptrace_report_syscall(struct pt_regs *regs)
current->exit_code = 0;
}

+ current->ptrace &= ~PT_IN_SYSCALL_STOP;
return fatal_signal_pending(current);
}

@@ -99,9 +103,10 @@ static inline int ptrace_report_syscall(struct pt_regs *regs)
* Called without locks, just after entering kernel mode.
*/
static inline __must_check int tracehook_report_syscall_entry(
- struct pt_regs *regs)
+ struct pt_regs *regs, bool is_compat)
{
- return ptrace_report_syscall(regs);
+ return ptrace_report_syscall(regs, PT_SYSCALL_ISENTERING |
+ (is_compat ? PT_SYSCALL_ISCOMPAT : 0));
}

/**
@@ -126,7 +131,7 @@ static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step)
if (step)
user_single_step_report(regs);
else
- ptrace_report_syscall(regs);
+ ptrace_report_syscall(regs, 0);
}

/**
diff --git a/include/uapi/linux/ptrace.h b/include/uapi/linux/ptrace.h
index d5a1b8a492b9..c2d30ae74de6 100644
--- a/include/uapi/linux/ptrace.h
+++ b/include/uapi/linux/ptrace.h
@@ -73,6 +73,28 @@ struct seccomp_metadata {
__u64 flags; /* Output: filter's flags */
};

+#define PTRACE_GET_SYSCALL_INFO 0x420f
+
+struct ptrace_syscall_info {
+ __u8 op; /* 0 for entry, 1 for exit */
+ __u8 __pad0[7];
+ union {
+ struct {
+ __u64 nr;
+ __u64 ip;
+ __u64 args[6];
+ __u8 is_compat;
+ __u8 __pad1[7];
+ } entry_info;
+ struct {
+ __s64 rval;
+ __u8 is_error;
+ __u8 __pad2[7];
+ } exit_info;
+ };
+};
+
+
/* Read signals from a shared (process wide) queue */
#define PTRACE_PEEKSIGINFO_SHARED (1 << 0)

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 80b34dffdfb9..05fa5977bed3 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -30,6 +30,10 @@
#include <linux/cn_proc.h>
#include <linux/compat.h>

+#ifdef CONFIG_HAVE_ARCH_TRACEHOOK
+#include <asm/syscall.h> /* For syscall_get_* */
+#endif
+
/*
* Access another process' address space via ptrace.
* Source/target buffer must be kernel space,
@@ -890,6 +894,37 @@ static int ptrace_regset(struct task_struct *task, int req, unsigned int type,
EXPORT_SYMBOL_GPL(task_user_regset_view);
#endif

+#ifdef CONFIG_HAVE_ARCH_TRACEHOOK
+static int ptrace_get_syscall(struct task_struct *child, void __user *datavp)
+{
+ struct ptrace_syscall_info info;
+ struct pt_regs *regs = task_pt_regs(child);
+ unsigned long args[ARRAY_SIZE(info.entry_info.args)];
+ int i;
+
+ if (child->ptrace_message & PT_SYSCALL_ISENTERING) {
+ info.op = 0;
+ info.entry_info.nr = syscall_get_nr(child, regs);
+ info.entry_info.ip = instruction_pointer(task_pt_regs(child));
+ syscall_get_arguments(child, regs, 0, ARRAY_SIZE(args), args);
+ for (i = 0; i < ARRAY_SIZE(args); i++)
+ info.entry_info.args[i] = args[i];
+ info.entry_info.is_compat =
+ !!(child->ptrace_message & PT_SYSCALL_ISCOMPAT);
+ } else {
+ info.op = 1;
+ info.exit_info.rval = syscall_get_error(child, regs);
+ info.exit_info.is_error = !!info.exit_info.rval;
+ if (!info.exit_info.is_error) {
+ info.exit_info.rval =
+ syscall_get_return_value(child, regs);
+ }
+ }
+
+ return copy_to_user(datavp, &info, sizeof(info)) ? -EFAULT : 0;
+}
+#endif
+
int ptrace_request(struct task_struct *child, long request,
unsigned long addr, unsigned long data)
{
@@ -1105,6 +1140,13 @@ int ptrace_request(struct task_struct *child, long request,
ret = seccomp_get_metadata(child, addr, datavp);
break;

+#ifdef CONFIG_HAVE_ARCH_TRACEHOOK
+ case PTRACE_GET_SYSCALL_INFO:
+ if (child->ptrace & PT_IN_SYSCALL_STOP)
+ ret = ptrace_get_syscall(child, datavp);
+ break;
+#endif
+
default:
break;
}
--
2.19.1