[PATCH 4/5] unwind-libdw: introduce indirect data structure for storing unwinding context

[Masatake YAMATO]

unwind-libdw uses Dwfl as the data structure for storing unwinding
context.  It is raw data that come from libdw.

This commit introduces "struct ctx" file local data type for allowing
unwind-libdw to attach strace side data to the unwinding context.

* unwind-libdw.c (struct ctx): New struct definition.
(tcb_init, tcb_fin, tcb_walk, tcb_flush_cache): Use struct ctx instead
of Dwfl directly.

Signed-off-by: Masatake YAMATO <yamato at redhat.com>
---
 unwind-libdw.c | 29 +++++++++++++++++++----------
 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/unwind-libdw.c b/unwind-libdw.c
index a2d4e294..b20ba204 100644
--- a/unwind-libdw.c
+++ b/unwind-libdw.c
@@ -39,6 +39,10 @@
 #include "mmap_cache.h"
 #include <elfutils/libdwfl.h>
 
+struct ctx {
+	Dwfl *dwfl;
+};
+
 static void *
 tcb_init(struct tcb *tcp)
 {
@@ -68,14 +72,19 @@ tcb_init(struct tcb *tcp)
 		return NULL;
 	}
 
-	return dwfl;
+	struct ctx *ctx = xmalloc(sizeof(*ctx));
+	ctx->dwfl = dwfl;
+	return ctx;
 }
 
 static void
 tcb_fin(struct tcb *tcp)
 {
-	if (tcp->unwind_ctx)
-		dwfl_end(tcp->unwind_ctx);
+	struct ctx *ctx = tcp->unwind_ctx;
+	if (ctx) {
+		dwfl_end(ctx->dwfl);
+		free(ctx);
+	}
 }
 
 struct frame_user_data {
@@ -131,8 +140,8 @@ tcb_walk(struct tcb *tcp,
 	 unwind_error_action_fn error_action,
 	 void *data)
 {
-	Dwfl *dwfl = tcp->unwind_ctx;
-	if (!dwfl)
+	struct ctx *ctx = tcp->unwind_ctx;
+	if (!ctx)
 		return;
 
 	struct frame_user_data user_data = {
@@ -141,7 +150,7 @@ tcb_walk(struct tcb *tcp,
 		.data = data,
 		.stack_depth = 256,
 	};
-	int r = dwfl_getthread_frames(dwfl, tcp->pid, frame_callback,
+	int r = dwfl_getthread_frames(ctx->dwfl, tcp->pid, frame_callback,
 				      &user_data);
 	if (r)
 		error_action(data,
@@ -152,11 +161,11 @@ tcb_walk(struct tcb *tcp,
 static void
 tcb_flush_cache(struct tcb *tcp)
 {
-	Dwfl *dwfl = tcp->unwind_ctx;
-	if (!dwfl)
+	struct ctx *ctx = tcp->unwind_ctx;
+	if (!ctx)
 		return;
 
-	int r = dwfl_linux_proc_report(dwfl, tcp->pid);
+	int r = dwfl_linux_proc_report(ctx->dwfl, tcp->pid);
 
 	if (r < 0)
 		error_msg("dwfl_linux_proc_report returned an error"
@@ -164,7 +173,7 @@ tcb_flush_cache(struct tcb *tcp)
 	else if (r > 0)
 		error_msg("dwfl_linux_proc_report returned an error"
 			  " for pid %d", tcp->pid);
-	else if (dwfl_report_end(dwfl, NULL, NULL) != 0)
+	else if (dwfl_report_end(ctx->dwfl, NULL, NULL) != 0)
 		error_msg("dwfl_report_end returned an error"
 			  " for pid %d: %s", tcp->pid, dwfl_errmsg(-1));
 }
-- 
2.14.3