This commit implements the -native-bypass support in linux-user. The
native_calls_enabled() function can be true only when the
'-native-bypass' option is given.
Signed-off-by: Yeqi Fu
---
include/native/native.h | 9 +
linux-user/main.c | 38 ++
linux-user/syscall.c| 21 +
3 files changed, 68 insertions(+)
create mode 100644 include/native/native.h
diff --git a/include/native/native.h b/include/native/native.h
new file mode 100644
index 00..7d1baadfcf
--- /dev/null
+++ b/include/native/native.h
@@ -0,0 +1,9 @@
+/*
+ * Check if the native bypass feature is enabled.
+ */
+#if defined(CONFIG_USER_ONLY) && defined(CONFIG_NATIVE_CALL)
+extern char *native_lib_path;
+#define native_bypass_enabled() (native_lib_path != NULL)
+#else
+#define native_bypass_enabled() false
+#endif
diff --git a/linux-user/main.c b/linux-user/main.c
index dba67ffa36..5cf02c071b 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -60,6 +60,11 @@
#include "semihosting/semihost.h"
#endif
+#if defined(CONFIG_NATIVE_CALL)
+#include "native/native.h"
+char *native_lib_path;
+#endif
+
#ifndef AT_FLAGS_PRESERVE_ARGV0
#define AT_FLAGS_PRESERVE_ARGV0_BIT 0
#define AT_FLAGS_PRESERVE_ARGV0 (1 << AT_FLAGS_PRESERVE_ARGV0_BIT)
@@ -293,6 +298,17 @@ static void handle_arg_set_env(const char *arg)
free(r);
}
+#if defined(CONFIG_NATIVE_CALL)
+static void handle_arg_native_bypass(const char *arg)
+{
+if (access(arg, F_OK) != 0) {
+fprintf(stderr, "native library %s does not exist\n", arg);
+exit(EXIT_FAILURE);
+}
+native_lib_path = g_strdup(arg);
+}
+#endif
+
static void handle_arg_unset_env(const char *arg)
{
char *r, *p, *token;
@@ -522,6 +538,10 @@ static const struct qemu_argument arg_table[] = {
"", "Generate a /tmp/perf-${pid}.map file for perf"},
{"jitdump","QEMU_JITDUMP", false, handle_arg_jitdump,
"", "Generate a jit-${pid}.dump file for perf"},
+#if defined(CONFIG_NATIVE_CALL)
+{"native-bypass", "QEMU_NATIVE_BYPASS", true, handle_arg_native_bypass,
+ "", "native bypass for library calls"},
+#endif
{NULL, NULL, false, NULL, NULL, NULL}
};
@@ -834,6 +854,24 @@ int main(int argc, char **argv, char **envp)
}
}
+#if defined(CONFIG_NATIVE_CALL)
+/* Set the library for native bypass */
+if (native_lib_path) {
+if (g_file_test(native_lib_path, G_FILE_TEST_IS_REGULAR)) {
+GString *lib = g_string_new(native_lib_path);
+lib = g_string_prepend(lib, "LD_PRELOAD=");
+if (envlist_appendenv(envlist, g_string_free(lib, false), ":")) {
+fprintf(stderr,
+"failed to append the native library to environment.\n");
+exit(EXIT_FAILURE);
+}
+} else {
+fprintf(stderr, "native library %s does not exist.\n",
+native_lib_path);
+exit(EXIT_FAILURE);
+}
+}
+#endif
target_environ = envlist_to_environ(envlist, NULL);
envlist_free(envlist);
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 08162cc966..bd4c3045ff 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -143,6 +143,7 @@
#include "fd-trans.h"
#include "tcg/tcg.h"
#include "cpu_loop-common.h"
+#include "native/native.h"
#ifndef CLONE_IO
#define CLONE_IO0x8000 /* Clone io context */
@@ -8626,6 +8627,7 @@ static int do_execveat(CPUArchState *cpu_env, int dirfd,
abi_ulong addr;
char **q;
void *p;
+unsigned int i;
argc = 0;
@@ -8696,6 +8698,25 @@ static int do_execveat(CPUArchState *cpu_env, int dirfd,
goto execve_efault;
}
+/*
+ * An error may occur when executing execv, stating that the
+ * shared library from LD_PRELOAD cannot be preloaded on a
+ * different arch. So, we find LD_PRELOAD and remove it from
+ * envp before executing the execv.
+ */
+if (native_bypass_enabled()) {
+i = 0;
+while (envp[i] != NULL) {
+if (strncmp(envp[i], "LD_PRELOAD=", 11) == 0) {
+for (int j = i; envp[j] != NULL; j++) {
+envp[j] = envp[j + 1];
+}
+} else {
+i++;
+}
+}
+}
+
if (is_proc_myself(p, "exe")) {
ret = get_errno(safe_execveat(dirfd, exec_path, argp, envp, flags));
} else {
--
2.34.1
