[tip: core/entry] ptrace: Migrate to use SYSCALL_TRACE flag

tip-bot2 for Gabriel Krisman Bertazi
2020-11-16T21:12:00Z

The following commit has been merged into the core/entry branch of tip:

Commit-ID: 64c19ba29b66e98af9306b4a7525fb22c895d252
Gitweb: https://git.kernel.org/tip/64c19ba29b66e98af9306b4a7525fb22c895d252
Author: Gabriel Krisman Bertazi <krisman@collabora.com>
AuthorDate: Mon, 16 Nov 2020 12:42:02 -05:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Mon, 16 Nov 2020 21:53:16 +01:00

ptrace: Migrate to use SYSCALL_TRACE flag

On architectures using the generic syscall entry code the architecture
independent syscall work is moved to flags in thread_info::syscall_work.
This removes architecture dependencies and frees up TIF bits.

Define SYSCALL_WORK_SYSCALL_TRACE, use it in the generic entry code and
convert the code which uses the TIF specific helper functions to use the
new *_syscall_work() helpers which either resolve to the new mode for users
of the generic entry code or to the TIF based functions for the other
architectures.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20201116174206.2639648-7-krisman@collabora.com

---
include/asm-generic/syscall.h | 15 ++++++++-------
include/linux/entry-common.h | 10 ++++++----
include/linux/thread_info.h | 2 ++
include/linux/tracehook.h | 17 +++++++++--------
kernel/entry/common.c | 4 ++--
kernel/fork.c | 2 +-
kernel/ptrace.c | 6 +++---
7 files changed, 31 insertions(+), 25 deletions(-)

diff --git a/include/asm-generic/syscall.h b/include/asm-generic/syscall.h
index 524d8e6..ed94e56 100644
--- a/include/asm-generic/syscall.h
+++ b/include/asm-generic/syscall.h
@@ -43,7 +43,7 @@ int syscall_get_nr(struct task_struct *task, struct pt_regs *regs);
* @regs: task_pt_regs() of @task
*
* It's only valid to call this when @task is stopped for system
- * call exit tracing (due to TIF_SYSCALL_TRACE or TIF_SYSCALL_AUDIT),
+ * call exit tracing (due to %SYSCALL_WORK_SYSCALL_TRACE or TIF_SYSCALL_AUDIT),
* after tracehook_report_syscall_entry() returned nonzero to prevent
* the system call from taking place.
*
@@ -63,7 +63,7 @@ void syscall_rollback(struct task_struct *task, struct pt_regs *regs);
* Returns 0 if the system call succeeded, or -ERRORCODE if it failed.
*
* It's only valid to call this when @task is stopped for tracing on exit
- * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
+ * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
*/
long syscall_get_error(struct task_struct *task, struct pt_regs *regs);

@@ -76,7 +76,7 @@ long syscall_get_error(struct task_struct *task, struct pt_regs *regs);
* This value is meaningless if syscall_get_error() returned nonzero.
*
* It's only valid to call this when @task is stopped for tracing on exit
- * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
+ * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
*/
long syscall_get_return_value(struct task_struct *task, struct pt_regs *regs);

@@ -93,7 +93,7 @@ long syscall_get_return_value(struct task_struct *task, struct pt_regs *regs);
* code; the user sees a failed system call with this errno code.
*
* It's only valid to call this when @task is stopped for tracing on exit
- * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
+ * from a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
*/
void syscall_set_return_value(struct task_struct *task, struct pt_regs *regs,
int error, long val);
@@ -108,7 +108,7 @@ void syscall_set_return_value(struct task_struct *task, struct pt_regs *regs,
* @args[0], and so on.
*
* It's only valid to call this when @task is stopped for tracing on
- * entry to a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
+ * entry to a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
*/
void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
unsigned long *args);
@@ -123,7 +123,7 @@ void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,
* The first argument gets value @args[0], and so on.
*
* It's only valid to call this when @task is stopped for tracing on
- * entry to a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
+ * entry to a system call, due to %SYSCALL_WORK_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.
*/
void syscall_set_arguments(struct task_struct *task, struct pt_regs *regs,
const unsigned long *args);
@@ -135,7 +135,8 @@ void syscall_set_arguments(struct task_struct *task, struct pt_regs *regs,
* Returns the AUDIT_ARCH_* based on the system call convention in use.
*
* It's only valid to call this when @task is stopped on entry to a system
- * call, due to %TIF_SYSCALL_TRACE, %TIF_SYSCALL_AUDIT, or %SYSCALL_WORK_SECCOMP.
+ * call, due to %SYSCALL_WORK_SYSCALL_TRACE, %TIF_SYSCALL_AUDIT, or
+ * %SYSCALL_WORK_SECCOMP.
*
* Architectures which permit CONFIG_HAVE_ARCH_SECCOMP_FILTER must
* provide an implementation of this.
diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index 2a01eee..ae426ab 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -41,7 +41,7 @@
#endif

#define SYSCALL_ENTER_WORK \
- (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
+ (_TIF_SYSCALL_AUDIT | \
_TIF_SYSCALL_EMU | \
ARCH_SYSCALL_ENTER_WORK)

@@ -53,12 +53,14 @@
#endif

#define SYSCALL_EXIT_WORK \
- (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
+ (_TIF_SYSCALL_AUDIT | \
ARCH_SYSCALL_EXIT_WORK)

#define SYSCALL_WORK_ENTER (SYSCALL_WORK_SECCOMP | \
- SYSCALL_WORK_SYSCALL_TRACEPOINT)
-#define SYSCALL_WORK_EXIT (SYSCALL_WORK_SYSCALL_TRACEPOINT)
+ SYSCALL_WORK_SYSCALL_TRACEPOINT | \
+ SYSCALL_WORK_SYSCALL_TRACE)
+#define SYSCALL_WORK_EXIT (SYSCALL_WORK_SYSCALL_TRACEPOINT | \
+ SYSCALL_WORK_SYSCALL_TRACE)

/*
* TIF flags handled in exit_to_user_mode_loop()
diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index c232043..761a459 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -38,10 +38,12 @@ enum {
enum syscall_work_bit {
SYSCALL_WORK_BIT_SECCOMP,
SYSCALL_WORK_BIT_SYSCALL_TRACEPOINT,
+ SYSCALL_WORK_BIT_SYSCALL_TRACE,
};

#define SYSCALL_WORK_SECCOMP BIT(SYSCALL_WORK_BIT_SECCOMP)
#define SYSCALL_WORK_SYSCALL_TRACEPOINT BIT(SYSCALL_WORK_BIT_SYSCALL_TRACEPOINT)
+#define SYSCALL_WORK_SYSCALL_TRACE BIT(SYSCALL_WORK_BIT_SYSCALL_TRACE)

#include <asm/thread_info.h>

diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
index f7d82e4..3f20368 100644
--- a/include/linux/tracehook.h
+++ b/include/linux/tracehook.h
@@ -83,11 +83,12 @@ static inline int ptrace_report_syscall(struct pt_regs *regs,
* tracehook_report_syscall_entry - task is about to attempt a system call
* @regs: user register state of current task
*
- * This will be called if %TIF_SYSCALL_TRACE or %TIF_SYSCALL_EMU have been set,
- * when the current task has just entered the kernel for a system call.
- * Full user register state is available here. Changing the values
- * in @regs can affect the system call number and arguments to be tried.
- * It is safe to block here, preventing the system call from beginning.
+ * This will be called if %SYSCALL_WORK_SYSCALL_TRACE or
+ * %TIF_SYSCALL_EMU have been set, when the current task has just
+ * entered the kernel for a system call. Full user register state is
+ * available here. Changing the values in @regs can affect the system
+ * call number and arguments to be tried. It is safe to block here,
+ * preventing the system call from beginning.
*
* Returns zero normally, or nonzero if the calling arch code should abort
* the system call. That must prevent normal entry so no system call is
@@ -109,15 +110,15 @@ static inline __must_check int tracehook_report_syscall_entry(
* @regs: user register state of current task
* @step: nonzero if simulating single-step or block-step
*
- * This will be called if %TIF_SYSCALL_TRACE has been set, when the
- * current task has just finished an attempted system call. Full
+ * This will be called if %SYSCALL_WORK_SYSCALL_TRACE has been set, when
+ * the current task has just finished an attempted system call. Full
* user register state is available here. It is safe to block here,
* preventing signals from being processed.
*
* If @step is nonzero, this report is also in lieu of the normal
* trap that would follow the system call instruction because
* user_enable_block_step() or user_enable_single_step() was used.
- * In this case, %TIF_SYSCALL_TRACE might not be set.
+ * In this case, %SYSCALL_WORK_SYSCALL_TRACE might not be set.
*
* Called without locks, just before checking for pending signals.
*/
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index f651967..917328a 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -47,7 +47,7 @@ static long syscall_trace_enter(struct pt_regs *regs, long syscall,
long ret = 0;

/* Handle ptrace */
- if (ti_work & (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_EMU)) {
+ if (work & SYSCALL_WORK_SYSCALL_TRACE || ti_work & _TIF_SYSCALL_EMU) {
ret = arch_syscall_enter_tracehook(regs);
if (ret || (ti_work & _TIF_SYSCALL_EMU))
return -1L;
@@ -237,7 +237,7 @@ static void syscall_exit_work(struct pt_regs *regs, unsigned long ti_work,
trace_sys_exit(regs, syscall_get_return_value(current, regs));

step = report_single_step(ti_work);
- if (step || ti_work & _TIF_SYSCALL_TRACE)
+ if (step || work & SYSCALL_WORK_SYSCALL_TRACE)
arch_syscall_exit_tracehook(regs, step);
}

diff --git a/kernel/fork.c b/kernel/fork.c
index bc5b109..99f68c2 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2158,7 +2158,7 @@ static __latent_entropy struct task_struct *copy_process(
* child regardless of CLONE_PTRACE.
*/
user_disable_single_step(p);
- clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE);
+ clear_task_syscall_work(p, SYSCALL_TRACE);
#ifdef TIF_SYSCALL_EMU
clear_tsk_thread_flag(p, TIF_SYSCALL_EMU);
#endif
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 43d6179..55a2bc3 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -117,7 +117,7 @@ void __ptrace_unlink(struct task_struct *child)
const struct cred *old_cred;
BUG_ON(!child->ptrace);

- clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
+ clear_task_syscall_work(child, SYSCALL_TRACE);
#ifdef TIF_SYSCALL_EMU
clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
#endif
@@ -812,9 +812,9 @@ static int ptrace_resume(struct task_struct *child, long request,
return -EIO;

if (request == PTRACE_SYSCALL)
- set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
+ set_task_syscall_work(child, SYSCALL_TRACE);
else
- clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
+ clear_task_syscall_work(child, SYSCALL_TRACE);

#ifdef TIF_SYSCALL_EMU
if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP)