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 ++ tests/tcg/multiarch/Makefile.target | 8 +++ .../linux/linux-execve-qemu-children.c | 68 +++++++++++++++++++ 5 files changed, 117 insertions(+), 5 deletions(-) create mode 100644 tests/tcg/multiarch/linux/linux-execve-qemu-children.c 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 59b2080b98..96b105e9ce 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -8550,13 +8550,14 @@ 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; @@ -8580,10 +8581,12 @@ 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; } @@ -8628,9 +8631,16 @@ 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); @@ -8644,7 +8654,8 @@ 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 46ffc093f4..ed3ed666a0 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, diff --git a/tests/tcg/multiarch/Makefile.target b/tests/tcg/multiarch/Makefile.target index 78b83d5575..0e220953e7 100644 --- a/tests/tcg/multiarch/Makefile.target +++ b/tests/tcg/multiarch/Makefile.target @@ -30,6 +30,14 @@ run-float_%: float_% $(call conditional-diff-out,$<,$(SRC_PATH)/tests/tcg/$(TARGET_NAME)/$<.ref) +run-linux-execve-qemu-children: linux-execve-qemu-children + $(call run-test,$<, $(QEMU) $(QEMU_OPTS) -qemu-children $< $(QEMU) 0) + $(call run-test,$<, $(QEMU) $(QEMU_OPTS) $< linux-execve 0 skip) + +run-plugin-linux-execve-qemu-children-with-%: linux-execve-qemu-children + $(call run-test,$<, $(QEMU) $(QEMU_OPTS) -qemu-children $< $(QEMU) 0) + $(call run-test,$<, $(QEMU) $(QEMU_OPTS) $< linux-execve 0 skip) + testthread: LDFLAGS+=-lpthread threadcount: LDFLAGS+=-lpthread diff --git a/tests/tcg/multiarch/linux/linux-execve-qemu-children.c b/tests/tcg/multiarch/linux/linux-execve-qemu-children.c new file mode 100644 index 0000000000..60d6537666 --- /dev/null +++ b/tests/tcg/multiarch/linux/linux-execve-qemu-children.c @@ -0,0 +1,68 @@ +#include <assert.h> +#include <errno.h> +#include <fcntl.h> +#include <libgen.h> +#include <malloc.h> +#include <stdio.h> +#include <string.h> +#include <unistd.h> + +#define MAX_COMM_SIZE (4096) + +int +main(int argc, char ** argv, char ** envp) { + int fd; + char next_arg[2]; + char * buf; + ssize_t off; + const char * expec_comm; + assert(argc == 3 || argc == 4); + fd = open("/proc/self/comm", O_RDONLY); + assert(fd > 0); + + buf = calloc(MAX_COMM_SIZE + 1, 1); + assert(buf != NULL); + + off = 0; + for (;;) { + ssize_t res = read(fd, buf + off, 1); + if (res < 0 && errno != EAGAIN) { + perror("Failed to read comm"); + return -1; + } + if (res == 0) { + break; + } + + off += res; + + if (off >= MAX_COMM_SIZE) { + fprintf(stderr, "/proc/self/comm too large for test\n"); + return -1; + } + } + assert(off && buf[off] == '\0' && buf[off - 1] == '\n'); + buf[off - 1] = '\0'; + expec_comm = basename(argv[1]); + if (argc == 3 && strncmp(buf, expec_comm, strlen(expec_comm))) { + fprintf(stderr, + "Didn't propagate qemu settings\nComm: '%s'\nExpec: '%s'\n", + buf, expec_comm); + return -1; + } + free(buf); + next_arg[0] = argv[2][0]; + next_arg[1] = '\0'; + if (next_arg[0] == '9') { + return 0; + } + next_arg[0] += 1; + char * next_args[] = { argv[0], argv[1], next_arg, NULL }; + int eres = execve(argv[0], &next_args[0], envp); + if (eres != 0) { + fprintf(stderr, "Unable to execve: %d/%d -> %s\n", eres, errno, + strerror(errno)); + return -1; + } + return 0; +} -- 2.43.0