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linux-user: add support of binfmt_misc 'O' flag

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The binfmt_misc module can calculate the credentials and security
token according to the binary instead of to the interpreter if the
'C' flag is enabled.

To be able to execute non-readable binaries, this flag implies 'O'
flag. When 'O' flag is enabled, bintfmt_misc opens the file for
reading and pass the file descriptor to the interpreter.

References:
linux/Documentation/binfmt_misc.txt          ['O' and 'C' description]
linux/fs/binfmt_misc.c linux/fs/binfmt_elf.c [ AT_EXECFD usage ]

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
This commit is contained in:
Laurent Vivier 2013-08-30 01:46:44 +02:00 • committed by Riku Voipio
parent 0d78b3b5b1
commit 03cfd8faa7
3 changed files with 34 additions and 8 deletions
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32
linux-user/main.c
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@ -3618,6 +3618,26 @@ static int parse_args(int argc, char **argv)
return optind;
}
static int get_execfd(char **envp)
{
typedef struct {
long a_type;
long a_val;
} auxv_t;
auxv_t *auxv;
while (*envp++ != NULL) {
;
}
for (auxv = (auxv_t *)envp; auxv->a_type != AT_NULL; auxv++) {
if (auxv->a_type == AT_EXECFD) {
return auxv->a_val;
}
}
return -1;
}
int main(int argc, char **argv, char **envp)
{
struct target_pt_regs regs1, *regs = &regs1;
@ -3632,6 +3652,7 @@ int main(int argc, char **argv, char **envp)
int target_argc;
int i;
int ret;
int execfd;
module_call_init(MODULE_INIT_QOM);
@ -3809,7 +3830,16 @@ int main(int argc, char **argv, char **envp)
env->opaque = ts;
task_settid(ts);
ret = loader_exec(filename, target_argv, target_environ, regs,
execfd = get_execfd(envp);
if (execfd < 0) {
execfd = open(filename, O_RDONLY);
}
if (execfd < 0) {
printf("Error while loading %s: %s\n", filename, strerror(-execfd));
_exit(1);
}
ret = loader_exec(execfd, filename, target_argv, target_environ, regs,
info, &bprm);
if (ret != 0) {
printf("Error while loading %s: %s\n", filename, strerror(-ret));