Hi Cyrill, Just a couple of comments for the moment. On Thu, Mar 1, 2012 at 1:23 AM, Cyrill Gorcunov <gorcunov@xxxxxxxxxx> wrote: > Signed-off-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx> > CC: Tejun Heo <tj@xxxxxxxxxx> > CC: Pavel Emelyanov <xemul@xxxxxxxxxxxxx> > --- > man2/prctl.2 | 104 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 files changed, 104 insertions(+), 0 deletions(-) > > diff --git a/man2/prctl.2 b/man2/prctl.2 > index effad2a..4d6244f 100644 > --- a/man2/prctl.2 > +++ b/man2/prctl.2 > @@ -378,6 +378,110 @@ Return the current per-process machine check kill policy. > All unused > .BR prctl () > arguments must be zero. > +.TP > +.BR PR_SET_MM " (since Linux 3.3)" > +Allows a user to modify certain kernel memory map descriptor fields > +of the calling process. > +Usually these fields are set by the kernel and dynamic loader (see > +.BR ld.so (8) > +for more information) and a regular application should not use this feature. > +Still there are cases such as self-modifying programs, where a program might > +find it useful to change its own memory map. By the way, do you have a *simple* program that demonstrates some usage of R_SET_MM? > +The kernel must be built with > +.BR CONFIG_CHECKPOINT_RESTORE > +option turned on, otherwise this feature will not be accessible > +from a user space level. > +The calling process must have > +.BR CAP_SYS_ADMIN > +(see > +.BR capabilities (7) > +for details) capability granted. As we discussed earlier (offlist), there are probably better choices than the hugely overloaded CAP_SYS_ADMIN (see http://man7.org/linux/man-pages/man7/capabilities.7.html). And if the capability governing PR_SET_MM is to change, then it would be good to do so before 3.3 is released. What are the plans on this point? Cheers, Michael > +The value in > +.I arg2 > +is one of the options below, while > +.I arg3 > +provides a new value for this option. > + > +.BR PR_SET_MM_START_CODE > +to set the address above which program text can run. > +The corresponding memory area must be readable and executable, > +but not writable or shareable (see > +.BR mprotect (2) > +and > +.BR mmap (2) > +for more information). > + > +.BR PR_SET_MM_END_CODE > +to set the address below which program text can run. > +The corresponding memory area must be readable and executable, > +but not writable or shareable. > + > +.BR PR_SET_MM_START_DATA > +to set the address above which program data+bss is placed. > +The corresponding memory area must be readable and writable, > +but not executable or shareable. > + > +.B PR_SET_MM_END_DATA > +to set the address below which program data+bss is placed. > +The corresponding memory area must be readable and writable, > +but not executable or shareable. > + > +.BR PR_SET_MM_START_STACK > +to set the start address of the stack. > +The corresponding memory area must be readable and writable. > + > +.BR PR_SET_MM_START_BRK > +to set the address above which program heap can be expanded with > +.BR brk (2) > +call. > +The address must not be greater than ending address of > +the current program data segment, neither it may exceed > +resource limit for data (see > +.BR setrlimit (2) > +for more information). > + > +.BR PR_SET_MM_BRK > +to set the current > +.BR brk (2) > +value. > +The requirements for address are the same as for > +.BR PR_SET_MM_START_BRK > +option. > + > +.BR PR_SET_MM_ARG_START > +to set the address above which program command line is placed. > + > +.BR PR_SET_MM_ARG_END > +to set the address below which program command line is placed. > + > +.BR PR_SET_MM_ENV_START > +to set the address above which program environment is placed. > + > +.BR PR_SET_MM_ENV_END > +to set the address below which program environment is placed. > + > +The address passed with > +.BR PR_SET_MM_ARG_START , > +.BR PR_SET_MM_ARG_END , > +.BR PR_SET_MM_ENV_START , > +.BR PR_SET_MM_ENV_END , > +should belong to a process stack area, thus corresponding memory area > +must be readable, writable and (depending on the kernel > +configuration) has > +.BR MAP_GROWSDOWN > +attribute set (see > +.BR mmap (2) > +for details). > + > +.BR PR_SET_MM_AUXV > +to set a new auxiliary vector. > +The > +.I arg3 > +argument should provide the address of the vector. > +The > +.I arg4 > +is the size of the vector. > +.\" > .SH "RETURN VALUE" > On success, > .BR PR_GET_DUMPABLE , > -- > 1.7.7.6 > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Author of "The Linux Programming Interface"; http://man7.org/tlpi/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
