On Wed, Oct 2, 2024 at 3:08 AM Ilya Leoshkevich <i...@linux.ibm.com> wrote: > > On Fri, 2024-08-30 at 15:36 -0700, Noah Goldstein wrote: > > 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. > > Another reason to have this is that one may not have root permissions > to configure binfmt-misc. > +1
> There was a similar patch posted to the mailing list some years back, > which I used to cherry-pick when I needed this. I'm not sure what > happened to that discussion though. Yes(ish): https://patchwork.ozlabs.org/project/qemu-devel/patch/1455515507-26877-1-git-send-email-petros...@resin.io/ > > > Signed-off-by: Noah Goldstein <goldstein....@gmail.com> > > --- > > linux-user/main.c | 22 ++++++++++++++++++++++ > > linux-user/syscall.c | 20 +++++++++++++++----- > > 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..dfb303a1f2 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; > > Style: ** belong to the variable name. > There are a couple other issues, please check the output of > > git format-patch -1 --stdout | ./scripts/checkpatch.pl - > Will Do. > > + > > /* > > * 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 +742,15 @@ int main(int argc, char **argv, char **envp) > > > > optind = parse_args(argc, argv); > > > > + if (qemu_dup_for_children) { > > + int i; > > I get the following build error: > > qemu/linux-user/main.c: In function ‘main’: > qemu/linux-user/main.c:746:13: error: declaration of ‘i’ shadows a > previous local [-Werror=shadow=compatible-local] > 746 | int i; > | ^ > qemu/linux-user/main.c:699:9: note: shadowed declaration is here > 699 | int i; > | ^ > > I don't think this variable is needed at all. > Bah sorry. > > + 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 9d5415674d..732ef89054 100644 > > --- a/linux-user/syscall.c > > +++ b/linux-user/syscall.c > > @@ -8459,13 +8459,14 @@ 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 = !is_execveat && qemu_dup_for_children; > > Wouldn't it be better to check for dirfd == AT_FDCWD? Yeah that works. Ill fix in V2. > > > argc = 0; > > > > @@ -8489,10 +8490,11 @@ 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; > > } > > @@ -8537,9 +8539,17 @@ 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); > > @@ -8553,7 +8563,7 @@ 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..0719e65ff4 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, >
