| Message ID | 1453884573-12864-1-git-send-email-petrosagg@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Le 27/01/2016 09:49, Petros Angelatos a écrit : > From: Petros Angelatos <petrosagg@resin.io> > > In order for one to use QEMU user mode emulation under a chroot, it is > required to use binfmt_misc. This can be avoided by QEMU never doing a > raw execve() to the host system. > > Introduce a new option, -execve, that uses the current QEMU interpreter > to intercept execve(). > > qemu_execve() will prepend the interpreter path , similar to what > binfmt_misc would do, and then pass the modified execve() to the host. > > It is necessary to parse hashbang scripts in that function otherwise > the kernel will try to run the interpreter of a script without QEMU and > get an invalid exec format error. > > Signed-off-by: Petros Angelatos <petrosagg@resin.io> > --- You can put here the difference between v1 and v2. > linux-user/main.c | 36 ++++++++++++++++ > linux-user/qemu.h | 1 + > linux-user/syscall.c | 117 ++++++++++++++++++++++++++++++++++++++++++++++++++- > 3 files changed, 153 insertions(+), 1 deletion(-) > > diff --git a/linux-user/main.c b/linux-user/main.c > index ee12035..751eafa 100644 > --- a/linux-user/main.c > +++ b/linux-user/main.c > @@ -22,6 +22,7 @@ > #include <string.h> > #include <errno.h> > #include <unistd.h> > +#include <sys/auxv.h> This line needs to be rebased. Otherwise: Tested-by: Laurent Vivier <laurent@vivier.eu> Reviewed-by: Laurent Vivier <laurent@vivier.eu> > #include <sys/mman.h> > #include <sys/syscall.h> > #include <sys/resource.h> > @@ -79,6 +80,7 @@ static void usage(int exitcode); > > static const char *interp_prefix = CONFIG_QEMU_INTERP_PREFIX; > const char *qemu_uname_release; > +const char *qemu_execve_path; > > /* XXX: on x86 MAP_GROWSDOWN only works if ESP <= address + 32, so > we allocate a bigger stack. Need a better solution, for example > @@ -3828,6 +3830,38 @@ static void handle_arg_guest_base(const char *arg) > have_guest_base = 1; > } > > +static void handle_arg_execve(const char *arg) > +{ > + const char *execfn; > + char buf[PATH_MAX]; > + char *ret; > + int len; > + > + /* try getauxval() */ > + execfn = (const char *) getauxval(AT_EXECFN); > + > + if (execfn != 0) { > + ret = realpath(execfn, buf); > + > + if (ret != NULL) { > + qemu_execve_path = strdup(buf); > + return; > + } > + } > + > + /* try /proc/self/exe */ > + len = readlink("/proc/self/exe", buf, sizeof(buf) - 1); > + > + if (len != -1) { > + buf[len] = '\0'; > + qemu_execve_path = strdup(buf); > + return; > + } > + > + fprintf(stderr, "qemu_execve: unable to determine intepreter's path\n"); > + exit(EXIT_FAILURE); > +} > + > static void handle_arg_reserved_va(const char *arg) > { > char *p; > @@ -3913,6 +3947,8 @@ static const struct qemu_argument arg_table[] = { > "uname", "set qemu uname release string to 'uname'"}, > {"B", "QEMU_GUEST_BASE", true, handle_arg_guest_base, > "address", "set guest_base address to 'address'"}, > + {"execve", "QEMU_EXECVE", false, handle_arg_execve, > + "", "use this interpreter when a process calls execve()"}, > {"R", "QEMU_RESERVED_VA", true, handle_arg_reserved_va, > "size", "reserve 'size' bytes for guest virtual address space"}, > {"d", "QEMU_LOG", true, handle_arg_log, > diff --git a/linux-user/qemu.h b/linux-user/qemu.h > index bd90cc3..0d9b058 100644 > --- a/linux-user/qemu.h > +++ b/linux-user/qemu.h > @@ -140,6 +140,7 @@ void init_task_state(TaskState *ts); > void task_settid(TaskState *); > void stop_all_tasks(void); > extern const char *qemu_uname_release; > +extern const char *qemu_execve_path; > extern unsigned long mmap_min_addr; > > /* ??? See if we can avoid exposing so much of the loader internals. */ > diff --git a/linux-user/syscall.c b/linux-user/syscall.c > index 0cbace4..4755978 100644 > --- a/linux-user/syscall.c > +++ b/linux-user/syscall.c > @@ -111,6 +111,7 @@ int __clone2(int (*fn)(void *), void *child_stack_base, > #include <linux/route.h> > #include <linux/filter.h> > #include <linux/blkpg.h> > +#include <linux/binfmts.h> > #include "linux_loop.h" > #include "uname.h" > > @@ -5854,6 +5855,118 @@ static target_timer_t get_timer_id(abi_long arg) > return timerid; > } > > +/* qemu_execve() Must return target values and target errnos. */ > +static abi_long qemu_execve(char *filename, char *argv[], > + char *envp[]) > +{ > + char *i_arg = NULL, *i_name = NULL; > + char **new_argp; > + int argc, fd, ret, i, offset = 3; > + char *cp; > + char buf[BINPRM_BUF_SIZE]; > + > + /* normal execve case */ > + if (qemu_execve_path == NULL || *qemu_execve_path == 0) { > + return get_errno(execve(filename, argv, envp)); > + } > + > + for (argc = 0; argv[argc] != NULL; argc++) { > + /* nothing */ ; > + } > + > + fd = open(filename, O_RDONLY); > + if (fd == -1) { > + return get_errno(fd); > + } > + > + ret = read(fd, buf, BINPRM_BUF_SIZE); > + if (ret == -1) { > + close(fd); > + return get_errno(ret); > + } > + > + /* if we have less than 2 bytes, we can guess it is not executable */ > + if (ret < 2) { > + close(fd); > + return -host_to_target_errno(ENOEXEC); > + } > + > + close(fd); > + > + /* adapted from the kernel > + * https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/fs/binfmt_script.c > + */ > + if ((buf[0] == '#') && (buf[1] == '!')) { > + /* > + * This section does the #! interpretation. > + * Sorta complicated, but hopefully it will work. -TYT > + */ > + > + buf[BINPRM_BUF_SIZE - 1] = '\0'; > + cp = strchr(buf, '\n'); > + if (cp == NULL) { > + cp = buf + BINPRM_BUF_SIZE - 1; > + } > + *cp = '\0'; > + while (cp > buf) { > + cp--; > + if ((*cp == ' ') || (*cp == '\t')) { > + *cp = '\0'; > + } else { > + break; > + } > + } > + for (cp = buf + 2; (*cp == ' ') || (*cp == '\t'); cp++) { > + /* nothing */ ; > + } > + if (*cp == '\0') { > + return -ENOEXEC; /* No interpreter name found */ > + } > + i_name = cp; > + i_arg = NULL; > + for ( ; *cp && (*cp != ' ') && (*cp != '\t'); cp++) { > + /* nothing */ ; > + } > + while ((*cp == ' ') || (*cp == '\t')) { > + *cp++ = '\0'; > + } > + if (*cp) { > + i_arg = cp; > + } > + > + if (i_arg) { > + offset = 5; > + } else { > + offset = 4; > + } > + } > + > + new_argp = alloca((argc + offset + 1) * sizeof(void *)); > + > + /* Copy the original arguments with offset */ > + for (i = 0; i < argc; i++) { > + new_argp[i + offset] = argv[i]; > + } > + > + new_argp[0] = strdup(qemu_execve_path); > + new_argp[1] = strdup("-0"); > + new_argp[offset] = filename; > + new_argp[argc + offset] = NULL; > + > + if (i_name) { > + new_argp[2] = i_name; > + new_argp[3] = i_name; > + > + if (i_arg) { > + new_argp[4] = i_arg; > + } > + } else { > + new_argp[2] = argv[0]; > + } > + > + return get_errno(execve(qemu_execve_path, new_argp, envp)); > +} > + > /* do_syscall() should always have a single exit point at the end so > that actions, such as logging of syscall results, can be performed. > All errnos that do_syscall() returns must be -TARGET_<errcode>. */ > @@ -6113,7 +6226,9 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, > > if (!(p = lock_user_string(arg1))) > goto execve_efault; > - ret = get_errno(execve(p, argp, envp)); > + > + ret = qemu_execve(p, argp, envp); > + > unlock_user(p, arg1, 0); > > goto execve_end; >
diff --git a/linux-user/main.c b/linux-user/main.c index ee12035..751eafa 100644 --- a/linux-user/main.c +++ b/linux-user/main.c @@ -22,6 +22,7 @@ #include <string.h> #include <errno.h> #include <unistd.h> +#include <sys/auxv.h> #include <sys/mman.h> #include <sys/syscall.h> #include <sys/resource.h> @@ -79,6 +80,7 @@ static void usage(int exitcode); static const char *interp_prefix = CONFIG_QEMU_INTERP_PREFIX; const char *qemu_uname_release; +const char *qemu_execve_path; /* XXX: on x86 MAP_GROWSDOWN only works if ESP <= address + 32, so we allocate a bigger stack. Need a better solution, for example @@ -3828,6 +3830,38 @@ static void handle_arg_guest_base(const char *arg) have_guest_base = 1; } +static void handle_arg_execve(const char *arg) +{ + const char *execfn; + char buf[PATH_MAX]; + char *ret; + int len; + + /* try getauxval() */ + execfn = (const char *) getauxval(AT_EXECFN); + + if (execfn != 0) { + ret = realpath(execfn, buf); + + if (ret != NULL) { + qemu_execve_path = strdup(buf); + return; + } + } + + /* try /proc/self/exe */ + len = readlink("/proc/self/exe", buf, sizeof(buf) - 1); + + if (len != -1) { + buf[len] = '\0'; + qemu_execve_path = strdup(buf); + return; + } + + fprintf(stderr, "qemu_execve: unable to determine intepreter's path\n"); + exit(EXIT_FAILURE); +} + static void handle_arg_reserved_va(const char *arg) { char *p; @@ -3913,6 +3947,8 @@ static const struct qemu_argument arg_table[] = { "uname", "set qemu uname release string to 'uname'"}, {"B", "QEMU_GUEST_BASE", true, handle_arg_guest_base, "address", "set guest_base address to 'address'"}, + {"execve", "QEMU_EXECVE", false, handle_arg_execve, + "", "use this interpreter when a process calls execve()"}, {"R", "QEMU_RESERVED_VA", true, handle_arg_reserved_va, "size", "reserve 'size' bytes for guest virtual address space"}, {"d", "QEMU_LOG", true, handle_arg_log, diff --git a/linux-user/qemu.h b/linux-user/qemu.h index bd90cc3..0d9b058 100644 --- a/linux-user/qemu.h +++ b/linux-user/qemu.h @@ -140,6 +140,7 @@ void init_task_state(TaskState *ts); void task_settid(TaskState *); void stop_all_tasks(void); extern const char *qemu_uname_release; +extern const char *qemu_execve_path; extern unsigned long mmap_min_addr; /* ??? See if we can avoid exposing so much of the loader internals. */ diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 0cbace4..4755978 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -111,6 +111,7 @@ int __clone2(int (*fn)(void *), void *child_stack_base, #include <linux/route.h> #include <linux/filter.h> #include <linux/blkpg.h> +#include <linux/binfmts.h> #include "linux_loop.h" #include "uname.h" @@ -5854,6 +5855,118 @@ static target_timer_t get_timer_id(abi_long arg) return timerid; } +/* qemu_execve() Must return target values and target errnos. */ +static abi_long qemu_execve(char *filename, char *argv[], + char *envp[]) +{ + char *i_arg = NULL, *i_name = NULL; + char **new_argp; + int argc, fd, ret, i, offset = 3; + char *cp; + char buf[BINPRM_BUF_SIZE]; + + /* normal execve case */ + if (qemu_execve_path == NULL || *qemu_execve_path == 0) { + return get_errno(execve(filename, argv, envp)); + } + + for (argc = 0; argv[argc] != NULL; argc++) { + /* nothing */ ; + } + + fd = open(filename, O_RDONLY); + if (fd == -1) { + return get_errno(fd); + } + + ret = read(fd, buf, BINPRM_BUF_SIZE); + if (ret == -1) { + close(fd); + return get_errno(ret); + } + + /* if we have less than 2 bytes, we can guess it is not executable */ + if (ret < 2) { + close(fd); + return -host_to_target_errno(ENOEXEC); + } + + close(fd); + + /* adapted from the kernel + * https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/fs/binfmt_script.c + */ + if ((buf[0] == '#') && (buf[1] == '!')) { + /* + * This section does the #! interpretation. + * Sorta complicated, but hopefully it will work. -TYT + */ + + buf[BINPRM_BUF_SIZE - 1] = '\0'; + cp = strchr(buf, '\n'); + if (cp == NULL) { + cp = buf + BINPRM_BUF_SIZE - 1; + } + *cp = '\0'; + while (cp > buf) { + cp--; + if ((*cp == ' ') || (*cp == '\t')) { + *cp = '\0'; + } else { + break; + } + } + for (cp = buf + 2; (*cp == ' ') || (*cp == '\t'); cp++) { + /* nothing */ ; + } + if (*cp == '\0') { + return -ENOEXEC; /* No interpreter name found */ + } + i_name = cp; + i_arg = NULL; + for ( ; *cp && (*cp != ' ') && (*cp != '\t'); cp++) { + /* nothing */ ; + } + while ((*cp == ' ') || (*cp == '\t')) { + *cp++ = '\0'; + } + if (*cp) { + i_arg = cp; + } + + if (i_arg) { + offset = 5; + } else { + offset = 4; + } + } + + new_argp = alloca((argc + offset + 1) * sizeof(void *)); + + /* Copy the original arguments with offset */ + for (i = 0; i < argc; i++) { + new_argp[i + offset] = argv[i]; + } + + new_argp[0] = strdup(qemu_execve_path); + new_argp[1] = strdup("-0"); + new_argp[offset] = filename; + new_argp[argc + offset] = NULL; + + if (i_name) { + new_argp[2] = i_name; + new_argp[3] = i_name; + + if (i_arg) { + new_argp[4] = i_arg; + } + } else { + new_argp[2] = argv[0]; + } + + return get_errno(execve(qemu_execve_path, new_argp, envp)); +} + /* do_syscall() should always have a single exit point at the end so that actions, such as logging of syscall results, can be performed. All errnos that do_syscall() returns must be -TARGET_<errcode>. */ @@ -6113,7 +6226,9 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1, if (!(p = lock_user_string(arg1))) goto execve_efault; - ret = get_errno(execve(p, argp, envp)); + + ret = qemu_execve(p, argp, envp); + unlock_user(p, arg1, 0); goto execve_end;