The new option '-qemu-children' makes it so that on `execve` the child
process will be launch by the same `qemu` executable that is currently
running along with its current commandline arguments.
The motivation for the change is to make it so that plugins running
through `qemu` can continue to run on children. Why not just
`binfmt`?: Plugins can be desirable regardless of system/architecture
emulation, and can sometimes be useful for elf files that can run
natively. Enabling `binfmt` for all natively runnable elf files may
not be desirable.
Signed-off-by: Noah Goldstein <goldstein....@gmail.com>
---
linux-user/main.c | 21 +++++++++++++++++++++
linux-user/syscall.c | 21 ++++++++++++++++-----
linux-user/user-internals.h | 4 ++++
3 files changed, 41 insertions(+), 5 deletions(-)
diff --git a/linux-user/main.c b/linux-user/main.c
index 8143a0d4b0..5e3d41dc2b 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -81,6 +81,10 @@ unsigned long mmap_min_addr;
uintptr_t guest_base;
bool have_guest_base;
+bool qemu_dup_for_children;
+int qemu_argc;
+char **qemu_argv;
+
/*
* Used to implement backwards-compatibility for the `-strace`, and
* QEMU_STRACE options. Without this, the QEMU_LOG can be overwritten by
@@ -451,6 +455,11 @@ static void handle_arg_jitdump(const char *arg)
perf_enable_jitdump();
}
+static void handle_arg_qemu_children(const char *arg)
+{
+ qemu_dup_for_children = true;
+}
+
static QemuPluginList plugins = QTAILQ_HEAD_INITIALIZER(plugins);
#ifdef CONFIG_PLUGIN
@@ -526,6 +535,10 @@ 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"},
+ {"qemu-children",
+ "QEMU_CHILDREN", false, handle_arg_qemu_children,
+ "", "Run child processes (created with execve) with qemu "
+ "(as instantiated for the parent)"},
{NULL, NULL, false, NULL, NULL, NULL}
};
@@ -729,6 +742,14 @@ int main(int argc, char **argv, char **envp)
optind = parse_args(argc, argv);
+ if (qemu_dup_for_children) {
+ qemu_argc = optind;
+ qemu_argv = g_new0(char *, qemu_argc);
+ for (i = 0; i < optind; ++i) {
+ qemu_argv[i] = strdup(argv[i]);
+ }
+ }
+
qemu_set_log_filename_flags(last_log_filename,
last_log_mask | (enable_strace * LOG_STRACE),
&error_fatal);
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index a666986189..79019c0db0 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -8457,13 +8457,14 @@ static int do_execv(CPUArchState *cpu_env, int dirfd,
abi_long pathname, abi_long guest_argp,
abi_long guest_envp, int flags, bool is_execveat)
{
- int ret;
+ int ret, argp_offset;
char **argp, **envp;
int argc, envc;
abi_ulong gp;
abi_ulong addr;
char **q;
void *p;
+ bool through_qemu = dirfd == AT_FDCWD && qemu_dup_for_children;
argc = 0;
@@ -8487,10 +8488,12 @@ static int do_execv(CPUArchState *cpu_env, int dirfd,
envc++;
}
- argp = g_new0(char *, argc + 1);
+ argp_offset = through_qemu ? qemu_argc : 0;
+ argp = g_new0(char *, argc + argp_offset + 1);
envp = g_new0(char *, envc + 1);
- for (gp = guest_argp, q = argp; gp; gp += sizeof(abi_ulong), q++) {
+ for (gp = guest_argp, q = argp + argp_offset;
+ gp; gp += sizeof(abi_ulong), q++) {
if (get_user_ual(addr, gp)) {
goto execve_efault;
}
@@ -8535,9 +8538,16 @@ static int do_execv(CPUArchState *cpu_env, int dirfd,
}
const char *exe = p;
- if (is_proc_myself(p, "exe")) {
+ if (through_qemu) {
+ int i;
+ for (i = 0; i < argp_offset; ++i) {
+ argp[i] = qemu_argv[i];
+ }
+ exe = qemu_argv[0];
+ } else if (is_proc_myself(p, "exe")) {
exe = exec_path;
}
+
ret = is_execveat
? safe_execveat(dirfd, exe, argp, envp, flags)
: safe_execve(exe, argp, envp);
@@ -8551,7 +8561,8 @@ execve_efault:
ret = -TARGET_EFAULT;
execve_end:
- for (gp = guest_argp, q = argp; *q; gp += sizeof(abi_ulong), q++) {
+ for (gp = guest_argp, q = argp + argp_offset;
+ *q; gp += sizeof(abi_ulong), q++) {
if (get_user_ual(addr, gp) || !addr) {
break;
}
diff --git a/linux-user/user-internals.h b/linux-user/user-internals.h
index 5c7f173ceb..a4615eee54 100644
--- a/linux-user/user-internals.h
+++ b/linux-user/user-internals.h
@@ -30,6 +30,10 @@ void stop_all_tasks(void);
extern const char *qemu_uname_release;
extern unsigned long mmap_min_addr;
+extern bool qemu_dup_for_children;
+extern int qemu_argc;
+extern char **qemu_argv;
+
typedef struct IOCTLEntry IOCTLEntry;
typedef abi_long do_ioctl_fn(const IOCTLEntry *ie, uint8_t *buf_temp,
--
2.43.0
