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* uprobes: Turn copy_opcode() into copy_from_page()Oleg Nesterov2013-04-041-4/+4
| | | | | | | | | | No functional changes. Rename copy_opcode() into copy_from_page() and add the new "int len" argument to make it more more generic for the new users. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Anton Arapov <anton@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: Add trap variant helperAnanth N Mavinakayanahalli2013-04-041-5/+29
| | | | | | | | | | | | | | | | | | | | | | Some architectures like powerpc have multiple variants of the trap instruction. Introduce an additional helper is_trap_insn() for run-time handling of non-uprobe traps on such architectures. While there, change is_swbp_at_addr() to is_trap_at_addr() for reading clarity. With this change, the uprobe registration path will supercede any trap instruction inserted at the requested location, while taking care of delivering the SIGTRAP for cases where the trap notification came in for an address without a uprobe. See [1] for a more detailed explanation. [1] https://lists.ozlabs.org/pipermail/linuxppc-dev/2013-March/104771.html This change was suggested by Oleg Nesterov. Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
* uprobes: Use file_inode()Oleg Nesterov2013-04-041-5/+5
| | | | | | | | | | | | | Cleanup. Now that we have f_inode/file_inode() we can use it instead of vm_file->f_mapping->host. This should not make any difference for uprobes, but in theory this change is more correct. We use this inode as a key, to compare it with uprobe->inode set by uprobe_register(inode), and the caller uses d_inode. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: Introduce uprobe_apply()Oleg Nesterov2013-02-081-4/+35
| | | | | | | | | | | | | | | | | | | | | | | | Currently it is not possible to change the filtering constraints after uprobe_register(), so a consumer can not, say, start to trace a task/mm which was previously filtered out, or remove the no longer needed bp's. Introduce uprobe_apply() which simply does register_for_each_vma() again to consult uprobe_consumer->filter() and install/remove the breakpoints. The only complication is that register_for_each_vma() can no longer assume that uprobe->consumers should be consulter if is_register == T, so we change it to accept "struct uprobe_consumer *new" instead. Unlike uprobe_register(), uprobe_apply(true) doesn't do "unregister" if register_for_each_vma() fails, it is up to caller to handle the error. Note: we probably need to cleanup the current interface, it is strange that uprobe_apply/unregister need inode/offset. We should either change uprobe_register() to return "struct uprobe *", or add a private ->uprobe member in uprobe_consumer. And in the long term uprobe_apply() should take a single argument, uprobe or consumer, even "bool add" should go away. Signed-off-by: Oleg Nesterov <oleg@redhat.com>
* uprobes: Add exports for module useJosh Stone2013-02-081-0/+3
| | | | | | | | | | | | | | | | The original pull message for uprobes (commit 654443e2) noted: This tree includes uprobes support in 'perf probe' - but SystemTap (and other tools) can take advantage of user probe points as well. In order to actually be usable in module-based tools like SystemTap, the interface needs to be exported. This patch first adds the obvious exports for uprobe_register and uprobe_unregister. Then it also adds one for task_user_regset_view, which is necessary to get the correct state of userspace registers. Signed-off-by: Josh Stone <jistone@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
* uprobes: Kill the bogus IS_ERR_VALUE(xol_vaddr) checkOleg Nesterov2013-02-081-2/+1
| | | | | | | | | utask->xol_vaddr is either zero or valid, remove the bogus IS_ERR_VALUE() check in xol_free_insn_slot(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Anton Arapov <anton@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: Do not allocate current->utask unnecessaryOleg Nesterov2013-02-081-10/+6
| | | | | | | | | | | | handle_swbp() does get_utask() before can_skip_sstep() for no reason, we do not need ->utask if can_skip_sstep() succeeds. Move get_utask() to pre_ssout() who actually starts to use it. Move the initialization of utask->active_uprobe/state as well. This way the whole initialization is consolidated in pre_ssout(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Anton Arapov <anton@redhat.com>
* uprobes: Fix utask->xol_vaddr leak in pre_ssout()Oleg Nesterov2013-02-081-1/+8
| | | | | | | | | pre_ssout() should do xol_free_insn_slot() if arch_uprobe_pre_xol() fails, otherwise nobody will free the allocated slot. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Anton Arapov <anton@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: Do not play with utask in xol_get_insn_slot()Oleg Nesterov2013-02-081-16/+21
| | | | | | | | | | | | pre_ssout()->xol_get_insn_slot() path is confusing and buggy. This patch cleanups the code, the next one fixes the bug. Change xol_get_insn_slot() to only allocate the slot and do nothing more, move the initialization of utask->xol_vaddr/vaddr into pre_ssout(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Anton Arapov <anton@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: Turn add_utask() into get_utask()Oleg Nesterov2013-02-081-18/+9
| | | | | | | | | | Rename add_utask() into get_utask() and change it to allocate on demand to simplify the caller. Like get_xol_area() it will have more users. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Anton Arapov <anton@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: Fold xol_alloc_area() into get_xol_area()Oleg Nesterov2013-02-081-22/+16
| | | | | | | | | | | Currently only xol_get_insn_slot() does get_xol_area() + xol_alloc_area(), but this will have more users and we do not want to copy-and-paste this code. This patch simply moves xol_alloc_area() into get_xol_area() to simplify the current and future code. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Anton Arapov <anton@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: Move alloc_page() from xol_add_vma() to xol_alloc_area()Oleg Nesterov2013-02-081-19/+13
| | | | | | | | | | Move alloc_page() from xol_add_vma() to xol_alloc_area() to cleanup the code. This separates the memory allocations and consolidates the -EALREADY cleanups and the error handling. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Anton Arapov <anton@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: Change handle_swbp() to expose bp_vaddr to handler_chain()Oleg Nesterov2013-02-081-8/+7
| | | | | | | | | | | | | Change handle_swbp() to set regs->ip = bp_vaddr in advance, this is what consumer->handler() needs but uprobe_get_swbp_addr() is not exported. This also simplifies the code and makes it more consistent across the supported architectures. handle_swbp() becomes the only caller of uprobe_get_swbp_addr(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
* uprobes: Teach handler_chain() to filter out the probed taskOleg Nesterov2013-02-081-10/+48
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currrently the are 2 problems with pre-filtering: 1. It is not possible to add/remove a task (mm) after uprobe_register() 2. A forked child inherits all breakpoints and uprobe_consumer can not control this. This patch does the first step to improve the filtering. handler_chain() removes the breakpoints installed by this uprobe from current->mm if all handlers return UPROBE_HANDLER_REMOVE. Note that handler_chain() relies on ->register_rwsem to avoid the race with uprobe_register/unregister which can add/del a consumer, or even remove and then insert the new uprobe at the same address. Perhaps we will add uprobe_apply_mm(uprobe, mm, is_register) and teach copy_mm() to do filter(UPROBE_FILTER_FORK), but I think this change makes sense anyway. Note: instead of checking the retcode from uc->handler, we could add uc->filter(UPROBE_FILTER_BPHIT). But I think this is not optimal to call 2 hooks in a row. This buys nothing, and if handler/filter do something nontrivial they will probably do the same work twice. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: Reintroduce uprobe_consumer->filter()Oleg Nesterov2013-02-081-7/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Finally add uprobe_consumer->filter() and change consumer_filter() to actually call this method. Note that ->filter() accepts mm_struct, not task_struct. Because: 1. We do not have for_each_mm_user(mm, task). 2. Even if we implement for_each_mm_user(), ->filter() can use it itself. 3. It is not clear who will actually need this interface to do the "nontrivial" filtering. Another argument is "enum uprobe_filter_ctx", consumer->filter() can use it to figure out why/where it was called. For example, perhaps we can add UPROBE_FILTER_PRE_REGISTER used by build_map_info() to quickly "nack" the unwanted mm's. In this case consumer should know that it is called under ->i_mmap_mutex. See the previous discussion at http://marc.info/?t=135214229700002 Perhaps we should pass more arguments, vma/vaddr? Note: this patch obviously can't help to filter out the child created by fork(), this will be addressed later. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: Rationalize the usage of filter_chain()Oleg Nesterov2013-02-081-23/+21
| | | | | | | | | | | | | | | | | | | | | | | | filter_chain() was added into install_breakpoint/remove_breakpoint to simplify the initial changes but this is sub-optimal. This patch shifts the callsite to the callers, register_for_each_vma() and uprobe_mmap(). This way: - It will be easier to add the new arguments. This is the main reason, we can do more optimizations later. - register_for_each_vma(is_register => true) can be optimized, we only need to consult the new consumer. The previous consumers were already asked when they called uprobe_register(). This patch also moves the MMF_HAS_UPROBES check from remove_breakpoint(), this allows to avoid the potentionally costly filter_chain(). Note that register_for_each_vma(is_register => false) doesn't really need to take ->consumer_rwsem, but I don't think it makes sense to optimize this and introduce filter_chain_lockless(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: Kill uprobes_mutex[], separate alloc_uprobe() and __uprobe_register()Oleg Nesterov2013-02-081-36/+15
| | | | | | | | | | | | | | | | | | | | | | | uprobe_register() and uprobe_unregister() are the only users of mutex_lock(uprobes_hash(inode)), and the only reason why we can't simply remove it is that we need to ensure that delete_uprobe() is not possible after alloc_uprobe() and before consumer_add(). IOW, we need to ensure that when we take uprobe->register_rwsem this uprobe is still valid and we didn't race with _unregister() which called delete_uprobe() in between. With this patch uprobe_register() simply checks uprobe_is_active() and retries if it hits this very unlikely race. uprobes_mutex[] is no longer needed and can be removed. There is another reason for this change, prepare_uprobe() should be folded into alloc_uprobe() and we do not want to hold the extra locks around read_mapping_page/etc. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Anton Arapov <anton@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: Introduce uprobe_is_active()Oleg Nesterov2013-02-081-0/+8
| | | | | | | | | | | | | | | | | The lifetime of uprobe->rb_node and uprobe->inode is not refcounted, delete_uprobe() is called when we detect that uprobe has no consumers, and it would be deadly wrong to do this twice. Change delete_uprobe() to WARN() if it was already called. We use RB_CLEAR_NODE() to mark uprobe "inactive", then RB_EMPTY_NODE() can be used to detect this case. RB_EMPTY_NODE() is not used directly, we add the trivial helper for the next change. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Anton Arapov <anton@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: Kill uprobe_events, use RB_EMPTY_ROOT() insteadOleg Nesterov2013-02-081-12/+7
| | | | | | | | | | | | uprobe_events counts the number of uprobes in uprobes_tree but it is used as a boolean. We can use RB_EMPTY_ROOT() instead. Probably no_uprobe_events() added by this patch can have more callers, say, mmf_recalc_uprobes(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Anton Arapov <anton@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: Kill uprobe->copy_mutexOleg Nesterov2013-02-081-4/+3
| | | | | | | | | | | Now that ->register_rwsem is safe under ->mmap_sem we can kill ->copy_mutex and abuse down_write(&uprobe->consumer_rwsem). This makes prepare_uprobe() even more ugly, but we should kill it anyway. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: Kill UPROBE_RUN_HANDLER flagOleg Nesterov2013-02-081-18/+5
| | | | | | | | | | | Simply remove UPROBE_RUN_HANDLER and the corresponding code. It can only help if uprobe has a single consumer, and in fact it is no longer needed after handler_chain() was changed to use ->register_rwsem, we simply can not race with uprobe_register(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: Change filter_chain() to iterate ->consumers listOleg Nesterov2013-02-081-8/+13
| | | | | | | | | | Now that it safe to use ->consumer_rwsem under ->mmap_sem we can almost finish the implementation of filter_chain(). It still lacks the actual uc->filter(...) call but othewrwise it is ready, just it pretends that ->filter() always returns true. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: Introduce uprobe->register_rwsemOleg Nesterov2013-02-081-2/+8
| | | | | | | | | | | | | | | | | | | | | | | | | Introduce uprobe->register_rwsem. It is taken for writing around __uprobe_register/unregister. Change handler_chain() to use this sem rather than consumer_rwsem. The main reason for this change is that we have the nasty problem with mmap_sem/consumer_rwsem dependency. filter_chain() needs to protect uprobe->consumers like handler_chain(), but they can not use the same lock. filter_chain() can be called under ->mmap_sem (currently this is always true), but we want to allow ->handler() to play with the probed task's memory, and this needs ->mmap_sem. Alternatively we could use srcu, but synchronize_srcu() is very slow and ->register_rwsem allows us to do more. In particular, we can teach handler_chain() to do remove_breakpoint() if this bp is "nacked" by all consumers, we know that we can't race with the new consumer which does uprobe_register(). See also the next patches. uprobes_mutex[] is almost ready to die. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: _register() should always do register_for_each_vma(true)Oleg Nesterov2013-02-081-18/+13
| | | | | | | | | | | | | | | | | | | | | | To support the filtering uprobe_register() should do register_for_each_vma(true) every time the new consumer comes, we need to install the previously nacked breakpoints. Note: - uprobes_mutex[] should die, what it actually protects is alloc_uprobe(). - UPROBE_RUN_HANDLER should die too, obviously it can't work unless uprobe has a single consumer. The consumer should serialize with _register/_unregister itself. Or this flag should live in uprobe_consumer->state. - Perhaps we can do some optimizations later. For example, if filter_chain() never returns false uprobe can record this fact and avoid the unnecessary register_for_each_vma(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: _unregister() should always do register_for_each_vma(false)Oleg Nesterov2013-02-081-14/+14
| | | | | | | | | | | | | uprobe_unregister() removes the breakpoints only if the last consumer goes away. To support the filtering it should do this every time, we want to remove the breakpoints which nobody else want to keep. Note: given that filter_chain() is not actually implemented, this patch itself doesn't change the behaviour yet, register_for_each_vma(false) is a heavy "nop" unless there are no more consumers. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: Introduce filter_chain()Oleg Nesterov2013-02-081-5/+19
| | | | | | | | | | | | | | | | | | | Add the new helper filter_chain(). Currently it is only placeholder, the comment explains what is should do. We will change it later to consult every consumer to decide whether we need to install the swbp. Until then it works as if any consumer returns true, this matches the current behavior. Change install_breakpoint() to call filter_chain() instead of checking uprobe->consumers != NULL. We obviously need this, and this equally closes the race with _unregister(). Change remove_breakpoint() to call this helper too. Currently this is pointless because remove_breakpoint() is only called when the last consumer goes away, but we will change this. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: Kill uprobe_consumer->filter()Oleg Nesterov2013-02-081-4/+2
| | | | | | | | | | | uprobe_consumer->filter() is pointless in its current form, kill it. We will add it back, but with the different signature/semantics. Perhaps we will even re-introduce the callsite in handler_chain(), but not to just skip uc->handler(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: Kill the pointless inode/uc checks in register/unregisterOleg Nesterov2013-02-081-6/+1
| | | | | | | | | | | | | | | | register/unregister verifies that inode/uc != NULL. For what? This really looks like "hide the potential problem", the caller should pass the valid data. register() also checks uc->next == NULL, probably to prevent the double-register but the caller can do other stupid/wrong things. If we do this check, then we should document that uc->next should be cleared before register() and add BUG_ON(). Also add the small comment about the i_size_read() check. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: Move __set_bit(UPROBE_SKIP_SSTEP) into alloc_uprobe()Oleg Nesterov2013-02-081-3/+2
| | | | | | | | Cosmetic. __set_bit(UPROBE_SKIP_SSTEP) is the part of initialization, it is not clear why it is set in insert_uprobe(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes: remove redundant checkSasha Levin2013-01-241-2/+1
| | | | | | | | | | | We checked for uprobe==NULL earlier, no need to redo that. Signed-off-by: Sasha Levin <sasha.levin@oracle.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1356030701-16284-22-git-send-email-sasha.levin@oracle.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
* uprobes: Use percpu_rw_semaphore to fix register/unregister vs dup_mmap() raceOleg Nesterov2012-11-161-3/+23
| | | | | | | | | | | | | | | | | | | | | | | | This was always racy, but 268720903f87e0b84b161626c4447b81671b5d18 "uprobes: Rework register_for_each_vma() to make it O(n)" should be blamed anyway, it made everything worse and I didn't notice. register/unregister call build_map_info() and then do install/remove breakpoint for every mm which mmaps inode/offset. This can obviously race with fork()->dup_mmap() in between and we can miss the child. uprobe_register() could be easily fixed but unregister is much worse, the new mm inherits "int3" from parent and there is no way to detect this if uprobe goes away. So this patch simply adds percpu_down_read/up_read around dup_mmap(), and percpu_down_write/up_write into register_for_each_vma(). This adds 2 new hooks into dup_mmap() but we can kill uprobe_dup_mmap() and fold it into uprobe_end_dup_mmap(). Reported-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
* uprobes: Flush cache after xol writeRabin Vincent2012-11-141-0/+5
| | | | | | | | | Flush the cache so that the instructions written to the XOL area are visible. Signed-off-by: Rabin Vincent <rabin@rab.in> Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
* uprobes: Kill arch_uprobe_enable/disable_step() hooksOleg Nesterov2012-11-031-10/+0
| | | | | | | | Kill arch_uprobe_enable/disable_step() hooks, they do nothing and nobody needs them. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* uprobes/powerpc: Do not use arch_uprobe_*_step() helpersOleg Nesterov2012-11-031-2/+0
| | | | | | | | | | | | | | | | | | No functional changes. powerpc is the only user of arch_uprobe_enable/disable_step() helpers, but they should die. They can not be used correctly, every arch needs its own implementation (like x86 does). And they do not really help even as initial-and-almost-working code, arch_uprobe_*_xol() hooks can easily use user_enable/disable_single_step() directly. Change arch_uprobe_*_step() to do nothing, and convert powerpc to use ptrace helpers. This is equally wrong, powerpc needs the arch-specific fixes. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
* Merge branch 'uprobes/core' of ↵Ingo Molnar2012-10-211-183/+162
|\ | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/oleg/misc into perf/urgent Pull various uprobes bugfixes from Oleg Nesterov - mostly race and failure path fixes. Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * uprobes: Fix the racy uprobe->flags manipulationOleg Nesterov2012-10-071-14/+14
| | | | | | | | | | | | | | | | | | | | | | | | Multiple threads can manipulate uprobe->flags, this is obviously unsafe. For example mmap can set UPROBE_COPY_INSN while register tries to set UPROBE_RUN_HANDLER, the latter can also race with can_skip_sstep() which clears UPROBE_SKIP_SSTEP. Change this code to use bitops. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
| * uprobes: Fix prepare_uprobe() race with itselfOleg Nesterov2012-10-071-0/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | install_breakpoint() is called under mm->mmap_sem, this protects set_swbp() but not prepare_uprobe(). Two or more different tasks can call install_breakpoint()->prepare_uprobe() at the same time, this leads to numerous problems if UPROBE_COPY_INSN is not set. Just for example, the second copy_insn() can corrupt the already analyzed/fixuped uprobe->arch.insn and race with handle_swbp(). This patch simply adds uprobe->copy_mutex to serialize this code. We could probably reuse ->consumer_rwsem, but this would mean that consumer->handler() can not use mm->mmap_sem, not good. Note: this is another temporary ugly hack until we move this logic into uprobe_register(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
| * uprobes: Introduce prepare_uprobe()Oleg Nesterov2012-10-071-19/+41
| | | | | | | | | | | | | | | | | | | | | | Preparation. Extract the copy_insn/arch_uprobe_analyze_insn code from install_breakpoint() into the new helper, prepare_uprobe(). And move uprobe->flags defines from uprobes.h to uprobes.c, nobody else can use them anyway. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
| * uprobes: Fix handle_swbp() vs unregister() + register() raceOleg Nesterov2012-10-071-0/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Strictly speaking this race was added by me in 56bb4cf6. However I think that this bug is just another indication that we should move copy_insn/uprobe_analyze_insn code from install_breakpoint() to uprobe_register(), there are a lot of other reasons for that. Until then, add a hack to close the race. A task can hit uprobe U1, but before it calls find_uprobe() this uprobe can be unregistered *AND* another uprobe U2 can be added to uprobes_tree at the same inode/offset. In this case handle_swbp() will use the not-fully-initialized U2, in particular its arch.insn for xol. Add the additional !UPROBE_COPY_INSN check into handle_swbp(), if this flag is not set we simply restart as if the new uprobe was not inserted yet. This is not very nice, we need barriers, but we will remove this hack when we change uprobe_register(). Note: with or without this patch install_breakpoint() can race with itself, yet another reson to kill UPROBE_COPY_INSN altogether. And even the usage of uprobe->flags is not safe. See the next patches. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
| * uprobes: Do not delete uprobe if uprobe_unregister() failsOleg Nesterov2012-10-071-6/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | delete_uprobe() must not be called if register_for_each_vma(false) fails to remove all breakpoints, __uprobe_unregister() is correct. The problem is that register_for_each_vma(false) always returns 0 and thus this logic does not work. 1. Change verify_opcode() to return 0 rather than -EINVAL when unregister detects the !is_swbp insn, we can treat this case as success and currently unregister paths ignore the error code anyway. 2. Change remove_breakpoint() to propagate the error code from write_opcode(). 3. Change register_for_each_vma(is_register => false) to remove as much breakpoints as possible but return non-zero if remove_breakpoint() fails at least once. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
| * uprobes: Don't return success if alloc_uprobe() failsOleg Nesterov2012-10-071-1/+3
| | | | | | | | | | | | | | If alloc_uprobe() fails uprobe_register() should return ENOMEM, not 0. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
| * uprobes: Simplify is_swbp_at_addr(), remove stale commentsOleg Nesterov2012-09-291-49/+24
| | | | | | | | | | | | | | | | | | | | | | After the previous change is_swbp_at_addr() is always called with current->mm. Remove this check and move it close to its single caller. Also, remove the obsolete comment about is_swbp_at_addr() and uprobe_state.count. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
| * uprobes: Kill set_orig_insn()->is_swbp_at_addr()Oleg Nesterov2012-09-291-9/+23
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Unlike set_swbp(), set_orig_insn()->is_swbp_at_addr() makes sense, although it can't prevent all confusions. But the usage of is_swbp_at_addr() is equally confusing, and it adds the extra get_user_pages() we can avoid. This patch removes set_orig_insn()->is_swbp_at_addr() but changes write_opcode() to do the necessary checks before replace_page(). Perhaps it also makes sense to ensure PAGE_MAPPING_ANON in unregister case. find_active_uprobe() becomes the only user of is_swbp_at_addr(), we can change its semantics. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
| * uprobes: Introduce copy_opcode(), kill read_opcode()Oleg Nesterov2012-09-291-44/+19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | No functional changes, preparations. 1. Extract the kmap-and-memcpy code from read_opcode() into the new trivial helper, copy_opcode(). The next patch will add another user. 2. read_opcode() becomes really trivial, fold it into its single caller, is_swbp_at_addr(). 3. Remove "auprobe" argument from write_opcode(), it is not used since f403072c6. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
| * uprobes: Kill set_swbp()->is_swbp_at_addr()Oleg Nesterov2012-09-291-11/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | A separate patch for better documentation. set_swbp()->is_swbp_at_addr() is not needed for correctness, it is harmless to do the unnecessary __replace_page(old_page, new_page) when these 2 pages are identical. And it can not be counted as optimization. mmap/register races are very unlikely, while in the likely case is_swbp_at_addr() adds the extra get_user_pages() even if the caller is uprobe_mmap(current->mm) and returns false. Note also that the semantics/usage of is_swbp_at_addr() in uprobe.c is confusing. set_swbp() uses it to detect the case when this insn was already modified by uprobes, that is why it should always compare the opcode with UPROBE_SWBP_INSN even if the hardware (like powerpc) has other trap insns. It doesn't matter if this breakpoint was in fact installed by gdb or application itself, we are going to "steal" this breakpoint anyway and execute the original insn from vm_file even if it no longer matches the memory. OTOH, handle_swbp()->find_active_uprobe() uses is_swbp_at_addr() to figure out whether we need to send SIGTRAP or not if we can not find uprobe, so in this case it should return true for all trap variants, not only for UPROBE_SWBP_INSN. This patch removes set_swbp()->is_swbp_at_addr(), the next patches will remove it from set_orig_insn() which is similar to set_swbp() in this respect. So the only caller will be handle_swbp() and we can make its semantics clear. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
| * uprobes: Restrict valid_vma(false) to skip VM_SHARED vmasOleg Nesterov2012-09-291-9/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | valid_vma(false) ignores ->vm_flags, this is not actually right. We should never try to write into MAP_SHARED mapping, this can confuse an apllication which actually writes to ->vm_file. With this patch valid_vma(false) ignores VM_WRITE only but checks other (immutable) bits checked by valid_vma(true). This can also speedup uprobe_munmap() and uprobe_unregister(). Note: even after this patch _unregister can confuse the probed application if it does mprotect(PROT_WRITE) after _register and installs "int3", but this is hardly possible to avoid and this doesn't differ from gdb case. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
| * uprobes: Change valid_vma() to demand VM_MAYEXEC rather than VM_EXECOleg Nesterov2012-09-291-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | uprobe_register() or uprobe_mmap() requires VM_READ | VM_EXEC, this is not right. An apllication can do mprotect(PROT_EXEC) later and execute this code. Change valid_vma(is_register => true) to check VM_MAYEXEC instead. No need to check VM_MAYREAD, it is always set. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
| * uprobes: Change write_opcode() to use FOLL_FORCEOleg Nesterov2012-09-291-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | write_opcode()->get_user_pages() needs FOLL_FORCE to ensure we can read the page even if the probed task did mprotect(PROT_NONE) after uprobe_register(). Without FOLL_WRITE, FOLL_FORCE doesn't have any side effect but allows to read the !VM_READ memory. Otherwiese the subsequent uprobe_unregister()->set_orig_insn() fails and we leak "int3". If that task does mprotect(PROT_READ | EXEC) and execute the probed insn later it will be killed. Note: in fact this is also needed for _register, see the next patch. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
| * uprobes: Move clear_thread_flag(TIF_UPROBE) to uprobe_notify_resume()Oleg Nesterov2012-09-291-0/+2
| | | | | | | | | | | | | | | | Move clear_thread_flag(TIF_UPROBE) from do_notify_resume() to uprobe_notify_resume() for !CONFIG_UPROBES case. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
| * uprobes: Kill UTASK_BP_HIT stateOleg Nesterov2012-09-291-20/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Kill UTASK_BP_HIT state, it buys nothing but complicates the code. It is only used in uprobe_notify_resume() to decide who should be called, we can check utask->active_uprobe != NULL instead. And this allows us to simplify handle_swbp(), no need to clear utask->state. Likewise we could kill UTASK_SSTEP, but UTASK_BP_HIT is worse and imho should die. The problem is, it creates the special case when task->utask is NULL, we can't distinguish RUNNING and BP_HIT. With this patch utask == NULL always means RUNNING. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
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