Messages in this thread Patch in this message | | | From | jarmo.tiitto@gmail ... | Subject | Re: [RFC PATCH 3/5] pgo: Wire up the new more generic code for modules | Date | Mon, 14 Jun 2021 22:08:06 +0300 |
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Kees Cook wrote maanantaina 14. kesäkuuta 2021 18.55.23 EEST: > On Sat, Jun 12, 2021 at 06:24:24AM +0300, Jarmo Tiitto wrote: > > prf_open() now uses the inode->i_private to get > > the prf_object for the file. This can be either > > vmlinux.profraw or any module.profraw file. > > > > The prf_vmlinux object is now added into prf_list and > > allocate_node() scans the list and reserves vnodes > > from corresponding prf_object(s). > > > > Signed-off-by: Jarmo Tiitto <jarmo.tiitto@gmail.com> > > --- > > note: There is no module notifier code yet, > > so only vmlinux.profraw profile data > > is available with this commit. > > > > Another thing is that pgo/reset will only > > reset vmlinux.profraw. > > Profile data reset for modules may be added later: > > maybe writing module's name into pgo/reset would reset only > > the specified module's profile data? > > Then writing "all" or zero would atomically reset everything. > > Yeah, I think matching the internal naming is right. "vmlinux", > module::name, and "all"? > > > I'm bit unsure about the new allocate_node() code since > > it is the first place I had to put rcu_read_lock() > > and the code is likely to change from this. > > Comments below... > > > --- > > > > kernel/pgo/fs.c | 30 ++++++++++++++++++++----- > > kernel/pgo/instrument.c | 49 +++++++++++++++++++++++++++-------------- > > kernel/pgo/pgo.h | 2 ++ > > 3 files changed, 60 insertions(+), 21 deletions(-) > > > > diff --git a/kernel/pgo/fs.c b/kernel/pgo/fs.c > > index 7e269d69bcd7..84b36e61758b 100644 > > --- a/kernel/pgo/fs.c > > +++ b/kernel/pgo/fs.c > > @@ -32,8 +32,10 @@ static struct dentry *directory; > > > > struct prf_private_data { > > > > void *buffer; > > size_t size; > > > > + struct prf_object *core; > > > > }; > > > > +/* vmlinux's prf core */ > > > > static struct prf_object prf_vmlinux; > > > > /* > > > > @@ -281,7 +283,6 @@ static int prf_serialize(struct prf_object *po, struct > > prf_private_data *p, size> > > prf_serialize_values(po, &buffer); > > > > return 0; > > > > - > > > > } > > > > /* open() implementation for PGO. Creates a copy of the profiling data set. > > */> > > @@ -292,13 +293,21 @@ static int prf_open(struct inode *inode, struct file > > *file)> > > size_t buf_size; > > int err = -EINVAL; > > > > + if (WARN_ON(!inode->i_private)) { > > + /* bug: inode was not initialized by us */ > > + return err; > > + } > > + > > > > data = kzalloc(sizeof(*data), GFP_KERNEL); > > if (!data) > > > > return -ENOMEM; > > > > + /* Get prf_object of this inode */ > > + data->core = inode->i_private; > > + > > > > /* Get initial buffer size. */ > > flags = prf_lock(); > > > > - data->size = prf_buffer_size(&prf_vmlinux); > > + data->size = prf_buffer_size(data->core); > > > > prf_unlock(flags); > > > > do { > > > > @@ -318,12 +327,13 @@ static int prf_open(struct inode *inode, struct file > > *file)> > > * data length in data->size. > > */ > > > > flags = prf_lock(); > > > > - err = prf_serialize(&prf_vmlinux, data, buf_size); > > + err = prf_serialize(data->core, data, buf_size); > > > > prf_unlock(flags); > > /* In unlikely case, try again. */ > > > > } while (err == -EAGAIN); > > > > if (err < 0) { > > > > + > > > > if (data) > > > > vfree(data->buffer); > > > > kfree(data); > > > > @@ -412,6 +422,8 @@ static const struct file_operations prf_reset_fops = { > > > > /* Create debugfs entries. */ > > static int __init pgo_init(void) > > { > > > > + unsigned long flags; > > + > > > > /* Init profiler vmlinux core entry */ > > memset(&prf_vmlinux, 0, sizeof(prf_vmlinux)); > > prf_vmlinux.data = __llvm_prf_data_start; > > > > @@ -430,19 +442,27 @@ static int __init pgo_init(void) > > > > prf_vmlinux.vnds_num = prf_get_count(__llvm_prf_vnds_start, > > > > __llvm_prf_vnds_end, sizeof(__llvm_prf_vnds_start[0])); > > > > + /* enable profiling */ > > + flags = prf_list_lock(); > > + list_add_tail_rcu(&prf_vmlinux.link, &prf_list); > > + prf_list_unlock(flags); > > > > directory = debugfs_create_dir("pgo", NULL); > > if (!directory) > > > > goto err_remove; > > > > - if (!debugfs_create_file("vmlinux.profraw", 0600, directory, NULL, > > - &prf_fops)) > > + prf_vmlinux.file = debugfs_create_file("vmlinux.profraw", > > + 0600, directory, &prf_vmlinux, &prf_fops); > > + if (!prf_vmlinux.file) > > > > goto err_remove; > > > > if (!debugfs_create_file("reset", 0200, directory, NULL, > > > > &prf_reset_fops)) > > > > goto err_remove; > > > > + /* show notice why the system slower: */ > > + pr_notice("Clang PGO instrumentation is active."); > > + > > Please pull this change into a separate patch and make it pr_info() > ("notice" is, I think, not right here). >
All rightly then.
> > return 0; > > > > err_remove: > > diff --git a/kernel/pgo/instrument.c b/kernel/pgo/instrument.c > > index 24fdeb79b674..e214c9d7a113 100644 > > --- a/kernel/pgo/instrument.c > > +++ b/kernel/pgo/instrument.c > > @@ -24,6 +24,7 @@ > > > > #include <linux/export.h> > > #include <linux/spinlock.h> > > #include <linux/types.h> > > > > +#include <linux/rculist.h> > > > > #include "pgo.h" > > > > /* > > > > @@ -56,22 +57,38 @@ void prf_unlock(unsigned long flags) > > > > static struct llvm_prf_value_node *allocate_node(struct llvm_prf_data *p, > > > > u32 index, u64 value) > > > > { > > > > - const int max_vnds = prf_get_count(__llvm_prf_vnds_start, > > - __llvm_prf_vnds_end, sizeof(struct llvm_prf_value_node)); > > - > > - /* > > - * Check that p is within vmlinux __llvm_prf_data section. > > - * If not, don't allocate since we can't handle modules yet. > > - */ > > - if (!memory_contains(__llvm_prf_data_start, > > - __llvm_prf_data_end, p, sizeof(*p))) > > - return NULL; > > - > > - if (WARN_ON_ONCE(current_node >= max_vnds)) > > - return NULL; /* Out of nodes */ > > - > > - /* reserve vnode for vmlinux */ > > - return &__llvm_prf_vnds_start[current_node++]; > > + struct llvm_prf_value_node *vnode = NULL; > > + struct prf_object *po; > > + struct llvm_prf_data *data_end; > > + int max_vnds; > > + > > + rcu_read_lock(); > > AIUI, list readers are using rcu_read_lock(), and writers are using > prf_list_lock()? >
Yes, I intended the list readers to use rcu_read_lock() and writers to take the prf_list_lock().
Sadly after I sent this patch set I found during more testing that there are few problems that I need to work on:
There is an lockup that only occurs during bare metal run after +15min, so I haven't been able to catch it in VM. I suspect this is caused by the RCU locking I added such that it results in recursive calls into __llvm_profile_instrument_target()
I will try build with CONFIG_PROVE_LOCKING, but I have had problems with the kernel not getting past cgroup_init_early()... even without my patches applied. (stock -rc kernel) :-(
> > + > > + list_for_each_entry_rcu(po, &prf_list, link) { > > + /* get section limits */ > > + max_vnds = prf_vnds_count(po); > > + data_end = po->data + prf_data_count(po); > > + > > + /* > > + * Check that p is within: > > + * [po->data, po->data + prf_data_count(po)] section. > > + * If yes, allocate vnode from this prf_object. > > + */ > > + if (memory_contains(po->data, data_end, p, sizeof(*p))) { > > + > > + > > + if (WARN_ON_ONCE(po->current_node >= max_vnds)) > > + return NULL; /* Out of nodes */ > > + > > + /* reserve the vnode */ > > + vnode = &po->vnds[po->current_node++]; > > + goto out; > > + } > > + } > > + > > +out: > > + rcu_read_unlock(); > > + return vnode; > > > > } > > > > /* > > > > diff --git a/kernel/pgo/pgo.h b/kernel/pgo/pgo.h > > index 44d79e2861e1..59d0aa966fbe 100644 > > --- a/kernel/pgo/pgo.h > > +++ b/kernel/pgo/pgo.h > > @@ -19,6 +19,8 @@ > > > > #ifndef _PGO_H > > #define _PGO_H > > > > +#include <linux/rculist.h> > > + > > > > /* > > > > * Note: These internal LLVM definitions must match the compiler version. > > * See llvm/include/llvm/ProfileData/InstrProfData.inc in LLVM's source > > code. > > > > -- > > 2.32.0 > > -- > Kees Cook
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