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signal: Simplify tracehook_report_syscall_exit

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Replace user_single_step_siginfo with user_single_step_report
that allocates siginfo structure on the stack and sends it.

This allows tracehook_report_syscall_exit to become a simple
if statement that calls user_single_step_report or ptrace_report_syscall
depending on the value of step.

Update the default helper function now called user_single_step_report
to explicitly set si_code to SI_USER and to set si_uid and si_pid to 0.
The default helper has always been doing this (using memset) but it
was far from obvious.

The powerpc helper can now just call force_sig_fault.
The x86 helper can now just call send_sigtrap.

Unfortunately the default implementation of user_single_step_report
can not use force_sig_fault as it does not use a SIGTRAP si_code.
So it has to carefully setup the siginfo and use use force_sig_info.

The net result is code that is easier to understand and simpler
to maintain.

Ref: 85ec7fd9f8 ("ptrace: introduce user_single_step_siginfo() helper")
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2018-04-16 14:18:26 -05:00
parent fb50f5a401
commit efc463adbc
6 changed files with 24 additions and 28 deletions
Download patch file Download diff file Expand all files Collapse all files

2
arch/powerpc/include/asm/ptrace.h
View file

@ -149,7 +149,7 @@ do { \
#define arch_has_single_step() (1) #define arch_has_single_step() (1)
#define arch_has_block_step() (!cpu_has_feature(CPU_FTR_601)) #define arch_has_block_step() (!cpu_has_feature(CPU_FTR_601))
#define ARCH_HAS_USER_SINGLE_STEP_INFO #define ARCH_HAS_USER_SINGLE_STEP_REPORT
/* /*
* kprobe-based event tracer support * kprobe-based event tracer support

7
arch/powerpc/kernel/traps.c
View file

@ -307,12 +307,9 @@ void die(const char *str, struct pt_regs *regs, long err)
} }
NOKPROBE_SYMBOL(die); NOKPROBE_SYMBOL(die);
void user_single_step_siginfo(struct task_struct *tsk, void user_single_step_report(struct pt_regs *regs)
struct pt_regs *regs, siginfo_t *info)
{ {
info->si_signo = SIGTRAP; force_sig_fault(SIGTRAP, TRAP_TRACE, (void __user *)regs->nip, current);
info->si_code = TRAP_TRACE;
info->si_addr = (void __user *)regs->nip;
} }
static void show_signal_msg(int signr, struct pt_regs *regs, int code, static void show_signal_msg(int signr, struct pt_regs *regs, int code,

2
arch/x86/include/asm/ptrace.h
View file

@ -263,7 +263,7 @@ static inline unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs,
#define arch_has_block_step() (boot_cpu_data.x86 >= 6) #define arch_has_block_step() (boot_cpu_data.x86 >= 6)
#endif #endif
#define ARCH_HAS_USER_SINGLE_STEP_INFO #define ARCH_HAS_USER_SINGLE_STEP_REPORT
/* /*
* When hitting ptrace_stop(), we cannot return using SYSRET because * When hitting ptrace_stop(), we cannot return using SYSRET because

11
arch/x86/kernel/ptrace.c
View file

@ -1382,12 +1382,6 @@ static void fill_sigtrap_info(struct task_struct *tsk,
info->si_addr = user_mode(regs) ? (void __user *)regs->ip : NULL; info->si_addr = user_mode(regs) ? (void __user *)regs->ip : NULL;
} }
void user_single_step_siginfo(struct task_struct *tsk,
struct pt_regs *regs,
struct siginfo *info)
{
fill_sigtrap_info(tsk, regs, 0, TRAP_BRKPT, info);
}
void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs, void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs,
int error_code, int si_code) int error_code, int si_code)
@ -1399,3 +1393,8 @@ void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs,
/* Send us the fake SIGTRAP */ /* Send us the fake SIGTRAP */
force_sig_info(SIGTRAP, &info, tsk); force_sig_info(SIGTRAP, &info, tsk);
} }
void user_single_step_report(struct pt_regs *regs)
{
send_sigtrap(current, regs, 0, TRAP_BRKPT);
}

17
include/linux/ptrace.h
View file

@ -336,14 +336,19 @@ static inline void user_enable_block_step(struct task_struct *task)
extern void user_enable_block_step(struct task_struct *); extern void user_enable_block_step(struct task_struct *);
#endif /* arch_has_block_step */ #endif /* arch_has_block_step */
#ifdef ARCH_HAS_USER_SINGLE_STEP_INFO #ifdef ARCH_HAS_USER_SINGLE_STEP_REPORT
extern void user_single_step_siginfo(struct task_struct *tsk, extern void user_single_step_report(struct pt_regs *regs);
struct pt_regs *regs, siginfo_t *info);
#else #else
static inline void user_single_step_siginfo(struct task_struct *tsk, static inline void user_single_step_report(struct pt_regs *regs)
struct pt_regs *regs, siginfo_t *info)
{ {
info->si_signo = SIGTRAP; siginfo_t info;
clear_siginfo(&info);
info.si_signo = SIGTRAP;
info.si_errno = 0;
info.si_code = SI_USER;
info.si_pid = 0;
info.si_uid = 0;
force_sig_info(info.si_signo, &info, current);
} }
#endif #endif

13
include/linux/tracehook.h
View file

@ -123,15 +123,10 @@ static inline __must_check int tracehook_report_syscall_entry(
*/ */
static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step) static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step)
{ {
if (step) { if (step)
siginfo_t info; user_single_step_report(regs);
clear_siginfo(&info); else
user_single_step_siginfo(current, regs, &info); ptrace_report_syscall(regs);
force_sig_info(SIGTRAP, &info, current);
return;
}
ptrace_report_syscall(regs);
} }
/** /**