From: Dmitry V. Levin <ldv@altlinux.org>
Date: Tue, 11 Apr 2017 04:04:37 +0000 (+0000)
Subject: Delay get_regs invocation
X-Git-Tag: v4.17~111
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=cb46fea4d5dbf3b4cf92cb8f6ce1e691cf28b171;p=strace

Delay get_regs invocation

strace used to call get_regs on every stop of a tracee, including cases
when the result is going to be discarded.  Prepare to change this lavish
practice by delaying get_regs invocation until its result is actually
needed.

* defs.h (get_regs): Remove.
* strace.c (trace): Do not call get_regs.
* syscall.c (get_regs): Add static qualifier.
(trace_syscall_exiting, print_pc, get_scno): Call get_regs.
---

diff --git a/defs.h b/defs.h
index 39d5693d..54f64174 100644
--- a/defs.h
+++ b/defs.h
@@ -412,7 +412,6 @@ extern void count_syscall(struct tcb *, const struct timeval *);
 extern void call_summary(FILE *);
 
 extern void clear_regs(void);
-extern void get_regs(pid_t pid);
 extern int get_scno(struct tcb *);
 extern kernel_ulong_t get_rt_sigframe_addr(struct tcb *);
 
diff --git a/strace.c b/strace.c
index 6adb2c9f..2933a780 100644
--- a/strace.c
+++ b/strace.c
@@ -2299,8 +2299,6 @@ trace(void)
 	}
 
 	clear_regs();
-	if (WIFSTOPPED(status))
-		get_regs(pid);
 
 	event = (unsigned int) status >> 16;
 
diff --git a/syscall.c b/syscall.c
index 8cfc3852..89491abb 100644
--- a/syscall.c
+++ b/syscall.c
@@ -559,6 +559,7 @@ clear_regs(void)
 	get_regs_error = -1;
 }
 
+static void get_regs(pid_t pid);
 static int get_syscall_args(struct tcb *);
 static int get_syscall_result(struct tcb *);
 static int arch_get_scno(struct tcb *tcp);
@@ -766,6 +767,7 @@ trace_syscall_exiting(struct tcb *tcp)
 	}
 #endif
 
+	get_regs(tcp->pid);
 #if SUPPORTED_PERSONALITIES > 1
 	update_personality(tcp, tcp->currpers);
 #endif
@@ -1065,6 +1067,7 @@ print_pc(struct tcb *tcp)
 #else
 # error Neither ARCH_PC_REG nor ARCH_PC_PEEK_ADDR is defined
 #endif
+	get_regs(tcp->pid);
 	if (get_regs_error || ARCH_GET_PC)
 		tprints(current_wordsize == 4 ? "[????????] "
 					      : "[????????????????] ");
@@ -1150,7 +1153,7 @@ ptrace_setregs(pid_t pid)
 
 #endif /* ARCH_REGS_FOR_GETREGSET || ARCH_REGS_FOR_GETREGS */
 
-void
+static void
 get_regs(pid_t pid)
 {
 #undef USE_GET_SYSCALL_RESULT_REGS
@@ -1225,6 +1228,8 @@ free_sysent_buf(void *ptr)
 int
 get_scno(struct tcb *tcp)
 {
+	get_regs(tcp->pid);
+
 	if (get_regs_error)
 		return -1;