Like do_wp_page(), __replace_page() should do munlock_vma_page()
for the case when the old page still has other !VM_LOCKED
mappings. Unfortunately this needs mm/internal.h.
Also, move put_page() outside of ptl lock. This doesn't really
matter but looks a bit better.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar.vnet.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20120729182249.GA20372@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
1. vma_address() returns loff_t, this looks confusing and this
is unnecessary after the previous change. Make it return "ulong",
all callers truncate the result anyway.
2. Its name conflicts with mm/rmap.c:vma_address(), rename it to
offset_to_vaddr(), this matches vaddr_to_offset().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar.vnet.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20120729182247.GA20365@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
1. register_for_each_vma() checks that vma_address() == vaddr,
but this is not enough. We should also ensure that
vaddr >= vm_start, find_vma() guarantees "vaddr < vm_end" only.
2. After the prevous changes, register_for_each_vma() is the
only reason why vma_address() has to return loff_t, all other
users know that we have the valid mapping at this offset and
thus the overflow is not possible.
Change the code to use vaddr_to_offset() instead, imho this looks
more clean/understandable and now we can change vma_address().
3. While at it, remove the unnecessary type-cast.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar.vnet.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20120729182244.GA20362@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Add the new helper, vaddr_to_offset(vma, vaddr) which returns
the offset in vma->vm_file this vaddr is mapped at.
Change build_probe_list() and find_active_uprobe() to use the
new helper, the next patch adds another user.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar.vnet.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20120729182242.GA20355@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Currently build_probe_list() builds the list of all uprobes
attached to the given inode, and the caller should filter out
those who don't fall into the [start,end) range, this is
sub-optimal.
This patch turns find_least_offset_node() into
find_node_in_range() which returns the first node inside the
[min,max] range, and changes build_probe_list() to use this node
as a starting point for rb_prev() and rb_next() to find all
other nodes the caller needs. The resulting list is no longer
sorted but we do not care.
This can speed up both build_probe_list() and the callers, but
there is another reason to introduce find_node_in_range(). It
can be used to figure out whether the given vma has uprobes or
not, this will be needed soon.
While at it, shift INIT_LIST_HEAD(tmp_list) into
build_probe_list().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar.vnet.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20120729182240.GA20352@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
vma->vm_pgoff is "unsigned long", it should be promoted to
loff_t before the multiplication to avoid the overflow.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar.vnet.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20120729182233.GA20339@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
uprobe_munmap() does get_user_pages() and it is also called from
the final mmput()->exit_mmap() path. This slows down
exit/mmput() for no reason, and I think it is simply
dangerous/wrong to try to fault-in a page into the dying mm. If
nothing else, this happens after the last sync_mm_rss(), afaics
handle_mm_fault() can change the task->rss_stat and make the
subsequent check_mm() unhappy.
Change uprobe_munmap() to check mm->mm_users != 0.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar.vnet.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20120729182231.GA20336@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The bug was introduced by me in 449d0d7c ("uprobes: Simplify the
usage of uprobe->pending_list").
Yes, we do not care about uprobe->pending_list after return and
nobody can remove the current list entry, but put_uprobe(uprobe)
can actually free it and thus we need list_for_each_safe().
Reported-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar.vnet.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Link: http://lkml.kernel.org/r/20120729182229.GA20329@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The comment above write_opcode()->lock_page(old_page) tells
about the race with do_wp_page(). I don't really understand
which exactly race it means, but afaics this lock_page() was not
enough to close all races with do_wp_page().
Anyway, since:
77fc4af1b5 uprobes: Change register_for_each_vma() to take mm->mmap_sem for writing
this code is always called with ->mmap_sem held for writing,
so we can forget about do_wp_page().
However, we can't simply remove this lock_page(), and the only
(afaics) reason is __replace_page()->try_to_free_swap().
Nothing in write_opcode() needs it, move it into
__replace_page() and fix the comment.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar.vnet.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20120729182220.GA20322@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
write_opcode() does lock_page(new_page) for no reason. Nobody
can see this page until __replace_page() exposes it under ptl
lock, and we do nothing with this page after pte_unmap_unlock().
If nothing else, the similar code in do_wp_page() doesn't lock
the new page for page_add_new_anon_rmap/set_pte_at_notify.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar.vnet.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20120729182218.GA20315@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
page_address_in_vma(old_page) in __replace_page() is ugly and
wrong. The caller already knows the correct virtual address,
this page was found by get_user_pages(vaddr).
However, page_address_in_vma() can actually fail if
page->mapping was cleared by __delete_from_page_cache() after
get_user_pages() returns. But this means the race with page
reclaim, write_opcode() should not fail, it should retry and
read this page again. Probably the race with remove_mapping() is
not possible due to page_freeze_refs() logic, but afaics at
least shmem_writepage()->shmem_delete_from_page_cache() can
clear ->mapping.
We could change __replace_page() to return -EAGAIN in this case,
but it would be better to simply use the caller's vaddr and rely
on page_check_address().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar.vnet.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20120729182216.GA20311@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
write_opcode() rechecks valid_vma() and ->f_mapping, this is
pointless. The caller, register_for_each_vma() or uprobe_mmap(),
has already done these checks under mmap_sem.
To clarify, uprobe_mmap() checks valid_vma() only, but we can
rely on build_probe_list(vm_file->f_mapping->host).
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar.vnet.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20120729182212.GA20304@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Originally from Peter Zijlstra. The helper migrates perf events
from one cpu to another cpu.
Signed-off-by: Zheng Yan <zheng.z.yan@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1339741902-8449-5-git-send-email-zheng.z.yan@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Allow the pmu->event_init callback to change event->cpu, so the PMU driver
can choose the CPU on which to install events.
Signed-off-by: Zheng Yan <zheng.z.yan@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1339741902-8449-4-git-send-email-zheng.z.yan@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
perf_event_open() requires the cpu on which to install event is online,
but the cpu can go offline after perf_event_open checks that. Add a
get_online_cpus()/put_online_cpus() pair to avoid the race.
Signed-off-by: Zheng Yan <zheng.z.yan@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1339741902-8449-3-git-send-email-zheng.z.yan@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
An rmdir pushes css's ref count to zero. However, if the associated
directory is open at the time, the dentry ref count is non-zero. If
the fd for this directory is then passed into perf_event_open, it
does a css_get(). This bounces the ref count back up from zero. This
is a problem by itself. But what makes it turn into a crash is the
fact that we end up doing an extra dput, since we perform a dput
when css_put sees the ref count go down to zero.
css_tryget() does not fall into that trap. So, we use that instead.
Reproduction test-case for the bug:
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <linux/unistd.h>
#include <linux/perf_event.h>
#include <string.h>
#include <errno.h>
#include <stdio.h>
#define PERF_FLAG_PID_CGROUP (1U << 2)
int perf_event_open(struct perf_event_attr *hw_event_uptr,
pid_t pid, int cpu, int group_fd, unsigned long flags) {
return syscall(__NR_perf_event_open,hw_event_uptr, pid, cpu,
group_fd, flags);
}
/*
* Directly poke at the perf_event bug, since it's proving hard to repro
* depending on where in the kernel tree. what moved?
*/
int main(int argc, char **argv)
{
int fd;
struct perf_event_attr attr;
memset(&attr, 0, sizeof(attr));
attr.exclude_kernel = 1;
attr.size = sizeof(attr);
mkdir("/dev/cgroup/perf_event/blah", 0777);
fd = open("/dev/cgroup/perf_event/blah", O_RDONLY);
perror("open");
rmdir("/dev/cgroup/perf_event/blah");
sleep(2);
perf_event_open(&attr, fd, 0, -1, PERF_FLAG_PID_CGROUP);
perror("perf_event_open");
close(fd);
return 0;
}
Signed-off-by: Salman Qazi <sqazi@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/20120614223108.1025.2503.stgit@dungbeetle.mtv.corp.google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
1. __copy_insn() needs "loff_t offset", not "unsigned long",
to read the file.
2. use pgoff_t for "idx" and remove the unnecessary typecast.
3. fix the typo, "&=" is not what we want
4. can't resist, rename off1 to off.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120615154359.GA9625@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
loff_t looks confusing when it is used for the virtual address.
Change map_info and install_breakpoint/remove_breakpoint paths
to use "unsigned long".
The patch doesn't change vma_address(), it can't return "long"
because it is used to verify the mapping. But probably this
needs some cleanups too.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Anton Arapov <anton@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120615154355.GA9622@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
uprobe->pending_list is only used to create the temporary list,
it has no meaning after we drop uprobes_mmap_hash(inode).
No need to initialize this node or remove it from tmp_list, and
we can use list_for_each_entry().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20120615154353.GA9614@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
write_opcode() ensures that UPROBE_SWBP_INSN doesn't cross the
page boundary. This looks a bit confusing, the check does not
depend on vaddr and it is enough to do it only once right after
install_breakpoint()->arch_uprobe_analyze_insn().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120615154350.GA9611@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
write_opcode() is called by register_for_each_vma() and
uprobe_mmap() paths. In both cases the caller has already
verified this vaddr under mmap_sem, no need to re-check.
Note also that this check is wrong anyway, we should not
truncate loff_t returned by vma_address() if we do not trust
this mapping.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120615154347.GA9604@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
copy_insn() returns -ENOMEM if the first __copy_insn() fails,
it should return the correct error code.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120615154344.GA9601@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
1. copy_insn() doesn't need "addr", it can use uprobe->offset.
Remove this argument.
2. Change copy_insn/__copy_insn to accept "struct file*" instead
of vma.
copy_insn() is called only once and mm/vma/vaddr are random, it
shouldn't depend on them.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120615154342.GA9598@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Because the mind is treacherous and makes us forget we need to
write stuff down.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20120615154339.GA9591@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
build_map_info() doesn't allocate the memory under i_mmap_mutex
to avoid the deadlock with page reclaim. But it can try
GFP_NOWAIT first, it should work in the likely case and thus we
almost never need the pre-alloc-and-retry path.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Link: http://lkml.kernel.org/r/20120615154336.GA9588@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Currently register_for_each_vma() is O(n ** 2) + O(n ** 3),
every time find_next_vma_info() "restarts" the
vma_prio_tree_foreach() loop and each iteration rechecks the
whole try_list. This also means that try_list can grow
"indefinitely" if register/unregister races with munmap/mmap
activity even if the number of mapping is bounded at any time.
With this patch register_for_each_vma() builds the list of
mm/vaddr structures only once and does install_breakpoint() for
each entry.
We do not care about the new mappings which can be created after
build_map_info() drops mapping->i_mmap_mutex, uprobe_mmap()
should do its work.
Note that we do not allocate map_info under i_mmap_mutex, this
can deadlock with page reclaim (but see the next patch). So we
use 2 lists, "curr" which we are going to return, and "prev"
which holds the already allocated memory. The main loop deques
the entry from "prev" (initially it is empty), and if "prev"
becomes empty again it counts the number of entries we need to
pre-allocate outside of i_mmap_mutex.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Link: http://lkml.kernel.org/r/20120615154333.GA9581@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
install_breakpoint() returns -EEXIST if is_swbp_insn(orig_insn)
== T, the caller treats this code as success.
This is doubly wrong. The successful return should set
UPROBE_COPY_INSN, but the real problem is that it shouldn't
succeed. If the probed insn is int3 the application should get
SIGTRAP, this won't happen with uprobe.
Probably we can fix this, we can add the UPROBE_SHARED_BP flag
and teach handle_swbp/set_orig_insn to handle this case
correctly. But this needs some complications and we have other
insns which can't be probed, lets make a simple fix for now.
I think this needs a cleanup. UPROBE_COPY_INSN should die,
copy_insn() should be called by alloc_uprobe().
arch_uprobe_analyze_insn() depends on ->mm (ia32_compat) but it
is called only once.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120615154331.GA9578@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
write_opcode() gets old_page via get_user_pages() and then calls
__replace_page() which assumes that this old_page is still
mapped after pte_offset_map_lock().
This is not true if this old_page was already try_to_unmap()'ed,
and in this case everything __replace_page() does with old_page
is wrong. Just for example, put_page() is not balanced.
I think it is possible to teach __replace_page() to handle this
unlikely case correctly, but this patch simply changes it to use
page_check_address() and return -EAGAIN if it fails. The caller
should notice this error code and retry.
Note: write_opcode() asks for the cleanups, I'll try to do this
in a separate patch.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120615154328.GA9571@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
__copy_insn() blindly calls read_mapping_page(), this will crash
the kernel if ->readpage == NULL, add the necessary check. For
example, hugetlbfs_aops->readpage is NULL. Perhaps we should
change read_mapping_page() instead.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120615154325.GA9568@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
__replace_page() obviously can't work with the hugetlbfs
mappings, uprobe_register() will likely crash the kernel. Change
valid_vma() to check VM_HUGETLB as well.
As for PageTransHuge() no need to worry, vma->vm_file != NULL.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120615154322.GA9561@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Kill the no longer needed uprobes_srcu/uprobe_srcu_id code.
It doesn't really work anyway. synchronize_srcu() can only
synchronize with the code "inside" the
srcu_read_lock/srcu_read_unlock section, while
uprobe_pre_sstep_notifier() does srcu_read_lock() _after_ we
already hit the breakpoint.
I guess this probably works "in practice". synchronize_srcu() is
slow and it implies synchronize_sched(), and the probed task
enters the non- preemptible section at the start of exception
handler. Still this is not right at least in theory, and
task->uprobe_srcu_id blows task_struct.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120529193008.GG8057@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Currently handle_swbp() assumes that it can't race with
unregister, so it roughly does:
if (find_uprobe(vaddr))
process_uprobe();
else
send_sig(SIGTRAP);
This relies on the not-really-working uprobes_srcu code we are
going to remove, see the next patch.
With this patch we rely on the result of
is_swbp_at_addr(bp_vaddr) if find_uprobe() fails.
If is_swbp == 1, then we hit the normal int3, we should send
SIGTRAP.
If is_swbp == 0, we raced with uprobe_unregister(), we simply
restart this insn again.
The "difficult" case is is_swbp == -EFAULT, when we can't read
this memory. In this case I think we should restart too, and
this is more correct compared to the current code which sends
SIGTRAP.
Ignoring ENOMEM/etc from get_user_pages(), this can only happen
if another thread unmaps this memory before find_active_uprobe()
takes mmap_sem. It would be better to pretend it was unmapped
before this insn was executed, restart, and get SIGSEGV.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120529192947.GF8057@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Change register_for_each_vma() to take mm->mmap_sem for writing.
This is a bit unfortunate but hopefully not too bad, this is the
slow path anyway.
This is needed to ensure that find_active_uprobe() can not race
with uprobe_register() which adds the new bp at the same
bp_vaddr, after find_uprobe() fails and before
is_swbp_at_addr_fast() checks the memory.
IOW, this is needed to ensure that if find_active_uprobe()
returns NULL but is_swbp == true, we can safely assume that it
was the "normal" int3 and we should send SIGTRAP.
There is another reason for this change. We are going to replace
uprobes_state->count with MMF_ flags set by register/unregister
and cleared by find_active_uprobe(), and set/clear shouldn't
race with each other.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120529192928.GE8057@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
A separate patch to simplify the review, and for the
documentation.
The patch adds another "int *is_swbp" argument to
find_active_uprobe(), so far its only caller doesn't use this
info.
With this patch find_active_uprobe() additionally does:
- if find_vma() + ->vm_start check fails, *is_swbp = -EFAULT
- otherwise, if valid_vma() + find_uprobe() fails, it holds
the result of is_swbp_at_addr(), can be negative too. The
latter is only possible if we raced with another thread
which did munmap/etc after we hit this bp.
IOW. If find_active_uprobe(&is_swbp) returns NULL, the caller
can look at is_swbp to figure out whether the current insn is bp
or not, or detect the race with another thread if it is
negative.
Note: I think that performance-wise this change is fine. This
adds is_swbp_at_addr(), but only if we raced with
uprobe_unregister() or if we hit the "normal" int3 but this mm
has uprobes as well. And even in this case the slow
read_opcode() path is very unlikely, this insn recently
triggered do_int3(), __copy_from_user_inatomic() shouldn't fail
in the likely case.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120529192914.GD8057@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
No functional changes. Move the "find uprobe" code from
handle_swbp() to the new helper, find_active_uprobe().
Note: with or without this change, the find-active-uprobe logic
is not exactly right. We can race with another thread which
unmaps the memory with the valid uprobe before we take
mm->mmap_sem. We can't find this uprobe simply because
find_vma() fails. In this case we wrongly assume that this trap
was not caused by uprobe and send the erroneous SIGTRAP. See the
next changes.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120529192857.GC8057@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
set_orig_insn()->read_opcode() should not fail if the probed
task did mprotect() after uprobe_register(), change it to use
FOLL_FORCE. Without FOLL_WRITE this doesn't have any "side"
effect but allows to read the !VM_READ memory.
There is another reason for this change, we are going to use
is_swbp_at_addr() from handle_swbp() which can race with another
thread doing mprotect().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120529192759.GB8057@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Change is_swbp_at_addr() to try to avoid the costly
read_opcode() if mm == current->mm, __copy_from_user_inatomic()
should succeed in the likely case.
Currently this optimization is not important, but we are going
to add more is_swbp_at_addr(current->mm) callers.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120529192744.GA8057@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The @func callback was invoked twice for group leader when
perf_event_for_each() called. It seems the commit 75f937f24b
("perf_counter: Fix ctx->mutex vs counter ->mutex inversion") made the
mistake during the change.
Signed-off-by: Namhyung Kim <namhyung.kim@lge.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1338443506-25009-1-git-send-email-namhyung.kim@lge.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Pull user-space probe instrumentation from Ingo Molnar:
"The uprobes code originates from SystemTap and has been used for years
in Fedora and RHEL kernels. This version is much rewritten, reviews
from PeterZ, Oleg and myself shaped the end result.
This tree includes uprobes support in 'perf probe' - but SystemTap
(and other tools) can take advantage of user probe points as well.
Sample usage of uprobes via perf, for example to profile malloc()
calls without modifying user-space binaries.
First boot a new kernel with CONFIG_UPROBE_EVENT=y enabled.
If you don't know which function you want to probe you can pick one
from 'perf top' or can get a list all functions that can be probed
within libc (binaries can be specified as well):
$ perf probe -F -x /lib/libc.so.6
To probe libc's malloc():
$ perf probe -x /lib64/libc.so.6 malloc
Added new event:
probe_libc:malloc (on 0x7eac0)
You can now use it in all perf tools, such as:
perf record -e probe_libc:malloc -aR sleep 1
Make use of it to create a call graph (as the flat profile is going to
look very boring):
$ perf record -e probe_libc:malloc -gR make
[ perf record: Woken up 173 times to write data ]
[ perf record: Captured and wrote 44.190 MB perf.data (~1930712
$ perf report | less
32.03% git libc-2.15.so [.] malloc
|
--- malloc
29.49% cc1 libc-2.15.so [.] malloc
|
--- malloc
|
|--0.95%-- 0x208eb1000000000
|
|--0.63%-- htab_traverse_noresize
11.04% as libc-2.15.so [.] malloc
|
--- malloc
|
7.15% ld libc-2.15.so [.] malloc
|
--- malloc
|
5.07% sh libc-2.15.so [.] malloc
|
--- malloc
|
4.99% python-config libc-2.15.so [.] malloc
|
--- malloc
|
4.54% make libc-2.15.so [.] malloc
|
--- malloc
|
|--7.34%-- glob
| |
| |--93.18%-- 0x41588f
| |
| --6.82%-- glob
| 0x41588f
...
Or:
$ perf report -g flat | less
# Overhead Command Shared Object Symbol
# ........ ............. ............. ..........
#
32.03% git libc-2.15.so [.] malloc
27.19%
malloc
29.49% cc1 libc-2.15.so [.] malloc
24.77%
malloc
11.04% as libc-2.15.so [.] malloc
11.02%
malloc
7.15% ld libc-2.15.so [.] malloc
6.57%
malloc
...
The core uprobes design is fairly straightforward: uprobes probe
points register themselves at (inode:offset) addresses of
libraries/binaries, after which all existing (or new) vmas that map
that address will have a software breakpoint injected at that address.
vmas are COW-ed to preserve original content. The probe points are
kept in an rbtree.
If user-space executes the probed inode:offset instruction address
then an event is generated which can be recovered from the regular
perf event channels and mmap-ed ring-buffer.
Multiple probes at the same address are supported, they create a
dynamic callback list of event consumers.
The basic model is further complicated by the XOL speedup: the
original instruction that is probed is copied (in an architecture
specific fashion) and executed out of line when the probe triggers.
The XOL area is a single vma per process, with a fixed number of
entries (which limits probe execution parallelism).
The API: uprobes are installed/removed via
/sys/kernel/debug/tracing/uprobe_events, the API is integrated to
align with the kprobes interface as much as possible, but is separate
to it.
Injecting a probe point is privileged operation, which can be relaxed
by setting perf_paranoid to -1.
You can use multiple probes as well and mix them with kprobes and
regular PMU events or tracepoints, when instrumenting a task."
Fix up trivial conflicts in mm/memory.c due to previous cleanup of
unmap_single_vma().
* 'perf-uprobes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (21 commits)
perf probe: Detect probe target when m/x options are absent
perf probe: Provide perf interface for uprobes
tracing: Fix kconfig warning due to a typo
tracing: Provide trace events interface for uprobes
tracing: Extract out common code for kprobes/uprobes trace events
tracing: Modify is_delete, is_return from int to bool
uprobes/core: Decrement uprobe count before the pages are unmapped
uprobes/core: Make background page replacement logic account for rss_stat counters
uprobes/core: Optimize probe hits with the help of a counter
uprobes/core: Allocate XOL slots for uprobes use
uprobes/core: Handle breakpoint and singlestep exceptions
uprobes/core: Rename bkpt to swbp
uprobes/core: Make order of function parameters consistent across functions
uprobes/core: Make macro names consistent
uprobes: Update copyright notices
uprobes/core: Move insn to arch specific structure
uprobes/core: Remove uprobe_opcode_sz
uprobes/core: Make instruction tables volatile
uprobes: Move to kernel/events/
uprobes/core: Clean up, refactor and improve the code
...
This reverts commit cb04ff9ac4 ("sched, perf: Use a single
callback into the scheduler").
Before this change was introduced, the process switch worked
like this (wrt. to perf event schedule):
schedule (prev, next)
- schedule out all perf events for prev
- switch to next
- schedule in all perf events for current (next)
After the commit, the process switch looks like:
schedule (prev, next)
- schedule out all perf events for prev
- schedule in all perf events for (next)
- switch to next
The problem is, that after we schedule perf events in, the pmu
is enabled and we can receive events even before we make the
switch to next - so "current" still being prev process (event
SAMPLE data are filled based on the value of the "current"
process).
Thats exactly what we see for test__PERF_RECORD test. We receive
SAMPLES with PID of the process that our tracee is scheduled
from.
Discussed with Peter Zijlstra:
> Bah!, yeah I guess reverting is the right thing for now. Sad
> though.
>
> So by having the two hooks we have a black-spot between them
> where we receive no events at all, this black-spot covers the
> hand-over of current and we thus don't receive the 'wrong'
> events.
>
> I rather liked we could do away with both that black-spot and
> clean up the code a little, but apparently people rely on it.
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: acme@redhat.com
Cc: paulus@samba.org
Cc: cjashfor@linux.vnet.ibm.com
Cc: fweisbec@gmail.com
Cc: eranian@google.com
Link: http://lkml.kernel.org/r/20120523111302.GC1638@m.brq.redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Merge reason: We are going to queue up a dependent patch:
"perf tools: Move parse event automated tests to separated object"
That depends on:
commit e7c72d8
perf tools: Add 'G' and 'H' modifiers to event parsing
Conflicts:
tools/perf/builtin-stat.c
Conflicted with the recent 'perf_target' patches when checking the
result of perf_evsel open routines to see if a retry is needed to cope
with older kernels where the exclude guest/host perf_event_attr bits
were not used.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
We can easily use a single callback for both sched-in and sched-out. This
reduces the code footprint in the scheduler path as well as removes
the PMU black spot otherwise present between the out and in callback.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-o56ajxp1edwqg6x9d31wb805@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
We always need to pass the last sample period to
perf_sample_data_init(), otherwise the event distribution will be
wrong. Thus, modifiyng the function interface with the required period
as argument. So basically a pattern like this:
perf_sample_data_init(&data, ~0ULL);
data.period = event->hw.last_period;
will now be like that:
perf_sample_data_init(&data, ~0ULL, event->hw.last_period);
Avoids unininitialized data.period and simplifies code.
Signed-off-by: Robert Richter <robert.richter@amd.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1333390758-10893-3-git-send-email-robert.richter@amd.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
In perf_event_for_each() we call a function on an event, and then
iterate over the siblings of the event.
However we don't call the function on the siblings, we call it
repeatedly on the original event - it seems "obvious" that we should
be calling it with sibling as the argument.
It looks like this broke in commit 75f937f24b ("Fix ctx->mutex
vs counter->mutex inversion").
The only effect of the bug is that the PERF_IOC_FLAG_GROUP parameter
to the ioctls doesn't work.
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1334109253-31329-1-git-send-email-michael@ellerman.id.au
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Uprobes has a callback (uprobe_munmap()) in the unmap path to
maintain the uprobes count.
In the exit path this callback gets called in unlink_file_vma().
However by the time unlink_file_vma() is called, the pages would
have been unmapped (in unmap_vmas()) and the task->rss_stat counts
accounted (in zap_pte_range()).
If the exiting process has probepoints, uprobe_munmap() checks if
the breakpoint instruction was around before decrementing the probe
count.
This results in a file backed page being reread by uprobe_munmap()
and hence it does not find the breakpoint.
This patch fixes this problem by moving the callback to
unmap_single_vma(). Since unmap_single_vma() may not unmap the
complete vma, add start and end parameters to uprobe_munmap().
This bug became apparent courtesy of commit c3f0327f8e
("mm: add rss counters consistency check").
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Jim Keniston <jkenisto@linux.vnet.ibm.com>
Cc: Linux-mm <linux-mm@kvack.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Anton Arapov <anton@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20120411103527.23245.9835.sendpatchset@srdronam.in.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Oleg Nesterov
Yan, Zheng
Ingo Molnar
Salman Qazi
Peter Zijlstra
Ananth N Mavinakayanahalli
Namhyung Kim
Linus Torvalds
Jiri Olsa
Arnaldo Carvalho de Melo
Robert Richter
Michael Ellerman
Srikar Dronamraju