Merge branch 'libmcount-update'

Two small updates in libmcount during debug #1835: * update debug message for clear PLT index understanding * ignore unpaired __cyg_profile_func_exit() Signed-off-by: Namhyung Kim <namhyung@gmail.com>
namhyung · Oct 30, 2023 · d36ff37 · d36ff37
2 parents f962a2c + a9e8782
commit d36ff37
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Showing 3 changed files with 19 additions and 4 deletions.
diff --git a/libmcount/mcount.c b/libmcount/mcount.c
@@ -1539,11 +1539,11 @@ static int __cygprof_entry(unsigned long parent, unsigned long child)
 
 	if (filtered == FILTER_IN) {
 		rstack->start_time = mcount_gettime();
-		rstack->flags = 0;
+		rstack->flags = MCOUNT_FL_CYGPROF;
 	}
 	else {
 		rstack->start_time = 0;
-		rstack->flags = MCOUNT_FL_NORECORD;
+		rstack->flags = MCOUNT_FL_CYGPROF | MCOUNT_FL_NORECORD;
 	}
 
 	mcount_entry_filter_record(mtdp, rstack, &tr, NULL);
@@ -1560,6 +1560,11 @@ static int cygprof_entry(unsigned long parent, unsigned long child)
 	return ret;
 }
 
+static void warn_unpaired_cygprof(void)
+{
+	pr_warn("unpaired cygprof exit: dropping...\n");
+}
+
 static void __cygprof_exit(unsigned long parent, unsigned long child)
 {
 	struct mcount_thread_data *mtdp;
@@ -1582,6 +1587,15 @@ static void __cygprof_exit(unsigned long parent, unsigned long child)
 
 	rstack = &mtdp->rstack[mtdp->idx - 1];
 
+	/* discard unpaired cygprof exit (due to compiler bug?) */
+	if (unlikely(!(rstack->flags & MCOUNT_FL_CYGPROF))) {
+		static pthread_once_t warn_once = PTHREAD_ONCE_INIT;
+
+		pthread_once(&warn_once, warn_unpaired_cygprof);
+		mcount_unguard_recursion(mtdp);
+		return;
+	}
+
 	if (!(rstack->flags & MCOUNT_FL_NORECORD))
 		rstack->end_time = mcount_gettime();
 

diff --git a/libmcount/mcount.h b/libmcount/mcount.h
@@ -38,6 +38,7 @@ enum mcount_rstack_flag {
 	MCOUNT_FL_ARGUMENT = (1U << 11),
 	MCOUNT_FL_READ = (1U << 12),
 	MCOUNT_FL_CALLER = (1U << 13),
+	MCOUNT_FL_CYGPROF = (1U << 14),
 };
 
 struct plthook_data;

diff --git a/libmcount/plthook.c b/libmcount/plthook.c
@@ -149,7 +149,7 @@ static void restore_plt_functions(struct plthook_data *pd)
 				continue;
 
 			overwrite_pltgot(pd, got_idx, skip_sym->addr);
-			pr_dbg2("overwrite GOT[%d] to %p (%s)\n", got_idx, skip_sym->addr,
+			pr_dbg2("overwrite GOT[%d + 3] to %p (%s)\n", i, skip_sym->addr,
 				skip_sym->name);
 
 			skipped = true;
@@ -171,7 +171,7 @@ static void restore_plt_functions(struct plthook_data *pd)
 				continue;
 
 			symname = demangle(sym->name);
-			pr_dbg2("restore GOT[%d] from \"%s\"(%#lx) to PLT(base + %#lx)\n", got_idx,
+			pr_dbg2("restore GOT[%d + 3] from \"%s\"(%#lx) to PLT(base + %#lx)\n", i,
 				symname, resolved_addr, plthook_addr - pd->base_addr);
 			free(symname);
 		}