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Subject[PATCH v3 1/3] ptrace: pass type of a syscall-stop in ptrace_message
Define two constants, PTRACE_EVENTMSG_SYSCALL_ENTRY and
PTRACE_EVENTMSG_SYSCALL_EXIT, and place them in ptrace_message
for the duration of syscall-stops.
This way ptracers can distinguish syscall-enter-stops
from syscall-exit-stops using PTRACE_GETEVENTMSG request.

Signed-off-by: Elvira Khabirova <lineprinter@altlinux.org>
Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
---
include/linux/tracehook.h | 9 ++++++---
include/uapi/linux/ptrace.h | 10 ++++++++++
2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
index 40b0b4c1bf7b..633a83fe7051 100644
--- a/include/linux/tracehook.h
+++ b/include/linux/tracehook.h
@@ -57,13 +57,15 @@ 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_message = message;
ptrace_notify(SIGTRAP | ((ptrace & PT_TRACESYSGOOD) ? 0x80 : 0));

/*
@@ -76,6 +78,7 @@ static inline int ptrace_report_syscall(struct pt_regs *regs)
current->exit_code = 0;
}

+ current->ptrace_message = 0;
return fatal_signal_pending(current);
}

@@ -101,7 +104,7 @@ static inline int ptrace_report_syscall(struct pt_regs *regs)
static inline __must_check int tracehook_report_syscall_entry(
struct pt_regs *regs)
{
- return ptrace_report_syscall(regs);
+ return ptrace_report_syscall(regs, PTRACE_EVENTMSG_SYSCALL_ENTRY);
}

/**
@@ -126,7 +129,7 @@ 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, PTRACE_EVENTMSG_SYSCALL_EXIT);
}

/**
diff --git a/include/uapi/linux/ptrace.h b/include/uapi/linux/ptrace.h
index d5a1b8a492b9..cb138902d042 100644
--- a/include/uapi/linux/ptrace.h
+++ b/include/uapi/linux/ptrace.h
@@ -104,6 +104,16 @@ struct seccomp_metadata {
#define PTRACE_O_MASK (\
0x000000ff | PTRACE_O_EXITKILL | PTRACE_O_SUSPEND_SECCOMP)

+/*
+ * These values are stored in task->ptrace_message by tracehook_report_syscall_*
+ * to describe current syscall-stop.
+ *
+ * Values for these constants are chosen so that they do not appear
+ * in task->ptrace_message by other means.
+ */
+#define PTRACE_EVENTMSG_SYSCALL_ENTRY 0x80000000U
+#define PTRACE_EVENTMSG_SYSCALL_EXIT 0x90000000U
+
#include <asm/ptrace.h>


--
2.19.1
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