Fix the initialization of bindings that point to "/proc/self".

The problem was due to the new module that emulates symlinks in
"/proc": it is used to initialize bindings that point to "/proc/self",
when no tracee can be associated to "self".  In this case "self" must
be PRoot.

Reported-by: Alkino (proot-me/proot#3)

src/execve/execve.c

@@ -208,6 +208,8 @@ int translate_execve(struct tracee_info *tracee)
 	int size = 0;
 	int status;
 
+	assert(tracee != NULL);
+
 	status = get_sysarg_path(tracee, u_path, SYSARG_1);
 	if (status < 0)
 		return status;

src/path/proc.c

@@ -25,6 +25,7 @@
 #include <stdlib.h>  /* atoi(3), strtol(3), */
 #include <errno.h>   /* E*, */
 #include <assert.h>  /* assert(3), */
+#include <unistd.h>  /* getpid(2), */
 
 #include "path/proc.h"
 #include "tracee/info.h"
@@ -39,25 +40,27 @@
  * Unlike readlink(), this function includes the nul terminating byte
  * to @result.
  */
-enum action readlink_proc(struct tracee_info *tracee, char result[PATH_MAX],
+enum action readlink_proc(const struct tracee_info *tracee, char result[PATH_MAX],
 			const char base[PATH_MAX], const char component[NAME_MAX],
 			enum path_comparison comparison)
 {
-	struct tracee_info *known_tracee;
+	const struct tracee_info *known_tracee;
 	char proc_path[64]; /* 64 > sizeof("/proc//fd/") + 2 * sizeof(#ULONG_MAX) */
 	int status;
 	pid_t pid;
 
 	assert(comparison == compare_paths("/proc", base));
 
+	pid = (tracee != NULL ? tracee->pid : getpid());
+
 	/* Remember: comparison = compare_paths("/proc", base)  */
 	switch (comparison) {
 	case PATHS_ARE_EQUAL:
 		/* Substitute "/proc/self" with "/proc/<PID>".  */
 		if (strcmp(component, "self") != 0)
 			return DEFAULT;
 
-		status = snprintf(result, PATH_MAX, "/proc/%d", tracee->pid);
+		status = snprintf(result, PATH_MAX, "/proc/%d", pid);
 		if (status < 0 || status >= PATH_MAX)
 			return -EPERM;
 
@@ -163,7 +166,7 @@ enum action readlink_proc(struct tracee_info *tracee, char result[PATH_MAX],
  * Unlike readlink(), this function includes the nul terminating byte
  * to @result (but this byte is not counted in the returned value).
  */
-size_t readlink_proc2(struct tracee_info *tracee, char result[PATH_MAX], const char referer[PATH_MAX])
+size_t readlink_proc2(const struct tracee_info *tracee, char result[PATH_MAX], const char referer[PATH_MAX])
 {
 	enum action action;
 	char base[PATH_MAX];

src/path/proc.h

@@ -36,10 +36,10 @@ enum action {
 };
 
 
-extern enum action readlink_proc(struct tracee_info *tracee, char result[PATH_MAX],
+extern enum action readlink_proc(const struct tracee_info *tracee, char result[PATH_MAX],
 				const char path[PATH_MAX], const char component[NAME_MAX],
 				enum path_comparison comparison);
 
-extern size_t readlink_proc2(struct tracee_info *tracee, char result[PATH_MAX], const char path[PATH_MAX]);
+extern size_t readlink_proc2(const struct tracee_info *tracee, char result[PATH_MAX], const char path[PATH_MAX]);
 
 #endif /* PROC_H */

src/tracee/info.c

@@ -46,6 +46,8 @@ static struct pool *first_pool = NULL;
  */
 void delete_tracee(struct tracee_info *tracee)
 {
+	assert(tracee != NULL);
+
 	if (tracee->exe != NULL)
 		free(tracee->exe);
 

tests/test-305ae31d.sh

@@ -0,0 +1,9 @@
+if [ -z `which mcookie` ] || [ -z `which ln` ] ||  [ -z `which true` ] ||  [ -z `which rm` ]; then
+    exit 125;
+fi
+
+TMP=$(mcookie)
+ln -s  /proc/self/mounts ${TMP}
+${PROOT} -b ${TMP} true
+rm ${TMP}
+