| Message ID | 20191021163426.9408-2-mark.rutland@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: ftrace cleanup + FTRACE_WITH_REGS | expand |
On Mon, 21 Oct 2019 17:34:19 +0100 Mark Rutland <mark.rutland@arm.com> wrote: > Architectures may need to perform special initialization of ftrace > callsites, and today they do so by special-casing ftrace_make_nop() when > the expected branch address is MCOUNT_ADDR. In some cases (e.g. for > patchable-function-entry), we don't have an mcount-like symbol and don't > want a synthetic MCOUNT_ADDR, but we may need to perform some > initialization of callsites. > > To make it possible to separate initialization from runtime > modification, and to handle cases without an mcount-like symbol, this > patch adds an optional ftrace_init_nop() function that architectures can > implement, which does not pass a branch address. > > Where an architecture does not provide ftrace_init_nop(), we will fall > back to the existing behaviour of calling ftrace_make_nop() with > MCOUNT_ADDR. > > At the same time, ftrace_code_disable() is renamed to > ftrace_code_init_disabled() to make it clearer that it is intended to > intialize a callsite into a disabled state, and is not for disabling a > callsite that has been runtime enabled. To make the name even better, let's just rename it to: ftrace_nop_initialization() I think that may be the best description for it. > > Signed-off-by: Mark Rutland <mark.rutland@arm.com> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: Steven Rostedt <rostedt@goodmis.org> > Cc: Torsten Duwe <duwe@suse.de> > --- > kernel/trace/ftrace.c | 13 ++++++++++--- > 1 file changed, 10 insertions(+), 3 deletions(-) > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > index f296d89be757..afd7e210e595 100644 > --- a/kernel/trace/ftrace.c > +++ b/kernel/trace/ftrace.c > @@ -2493,15 +2493,22 @@ struct dyn_ftrace *ftrace_rec_iter_record(struct ftrace_rec_iter *iter) > return &iter->pg->records[iter->index]; > } > > +#ifndef ftrace_init_nop > +static int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) > +{ > + return ftrace_make_nop(mod, rec, MCOUNT_ADDR); > +} > +#endif Can you place the above in the ftrace.h header. That's where that would belong. #ifndef ftrace_init_nop struct module; static inline int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) { return ftrace_make_nop(mod, rec, MCOUNT_ADDR); } #endif -- Steve > + > static int > -ftrace_code_disable(struct module *mod, struct dyn_ftrace *rec) > +ftrace_code_init_disabled(struct module *mod, struct dyn_ftrace *rec) > { > int ret; > > if (unlikely(ftrace_disabled)) > return 0; > > - ret = ftrace_make_nop(mod, rec, MCOUNT_ADDR); > + ret = ftrace_init_nop(mod, rec); > if (ret) { > ftrace_bug_type = FTRACE_BUG_INIT; > ftrace_bug(ret, rec); > @@ -2943,7 +2950,7 @@ static int ftrace_update_code(struct module *mod, struct ftrace_page *new_pgs) > * to the NOP instructions. > */ > if (!__is_defined(CC_USING_NOP_MCOUNT) && > - !ftrace_code_disable(mod, p)) > + !ftrace_code_init_disabled(mod, p)) > break; > > update_cnt++;
On Mon, Oct 21, 2019 at 02:07:56PM -0400, Steven Rostedt wrote: > On Mon, 21 Oct 2019 17:34:19 +0100 > Mark Rutland <mark.rutland@arm.com> wrote: > > > Architectures may need to perform special initialization of ftrace > > callsites, and today they do so by special-casing ftrace_make_nop() when > > the expected branch address is MCOUNT_ADDR. In some cases (e.g. for > > patchable-function-entry), we don't have an mcount-like symbol and don't > > want a synthetic MCOUNT_ADDR, but we may need to perform some > > initialization of callsites. > > > > To make it possible to separate initialization from runtime > > modification, and to handle cases without an mcount-like symbol, this > > patch adds an optional ftrace_init_nop() function that architectures can > > implement, which does not pass a branch address. > > > > Where an architecture does not provide ftrace_init_nop(), we will fall > > back to the existing behaviour of calling ftrace_make_nop() with > > MCOUNT_ADDR. > > > > At the same time, ftrace_code_disable() is renamed to > > ftrace_code_init_disabled() to make it clearer that it is intended to > > intialize a callsite into a disabled state, and is not for disabling a > > callsite that has been runtime enabled. > > To make the name even better, let's just rename it to: > > ftrace_nop_initialization() > > I think that may be the best description for it. Perhaps ftrace_nop_initialize(), so that it's not a noun? I've made it ftrace_nop_initialization() in my branch for now. > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > > index f296d89be757..afd7e210e595 100644 > > --- a/kernel/trace/ftrace.c > > +++ b/kernel/trace/ftrace.c > > @@ -2493,15 +2493,22 @@ struct dyn_ftrace *ftrace_rec_iter_record(struct ftrace_rec_iter *iter) > > return &iter->pg->records[iter->index]; > > } > > > > +#ifndef ftrace_init_nop > > +static int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) > > +{ > > + return ftrace_make_nop(mod, rec, MCOUNT_ADDR); > > +} > > +#endif > > Can you place the above in the ftrace.h header. That's where that would > belong. > > #ifndef ftrace_init_nop > struct module; > static inline int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) > { > return ftrace_make_nop(mod, rec, MCOUNT_ADDR); > } > #endif True. I've put this immediately after ftrace_make_nop() in the header, and given it a kerneldoc comment. There's a declaration for struct module at the top of the header, so I've just relied on that That looks like: | /** | * ftrace_init_nop - initialize a nop call site | * @mod: module structure if called by module load initialization | * @rec: the mcount call site record | * | * This is a very sensitive operation and great care needs | * to be taken by the arch. The operation should carefully | * read the location, check to see if what is read is indeed | * what we expect it to be, and then on success of the compare, | * it should write to the location. | * | * The code segment at @rec->ip should be as initialized by the | * compiler | * | * Return must be: | * 0 on success | * -EFAULT on error reading the location | * -EINVAL on a failed compare of the contents | * -EPERM on error writing to the location | * Any other value will be considered a failure. | */ | #ifndef ftrace_init_nop | static int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) | { | return ftrace_make_nop(mod, rec, MCOUNT_ADDR); | } | #endif Thanks, Mark.
On Tue, 22 Oct 2019 12:28:11 +0100 Mark Rutland <mark.rutland@arm.com> wrote: > > To make the name even better, let's just rename it to: > > > > ftrace_nop_initialization() > > > > I think that may be the best description for it. > > Perhaps ftrace_nop_initialize(), so that it's not a noun? > > I've made it ftrace_nop_initialization() in my branch for now. I'm fine with ftrace_nop_initialize(). > > > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > > > index f296d89be757..afd7e210e595 100644 > > > --- a/kernel/trace/ftrace.c > > > +++ b/kernel/trace/ftrace.c > > > @@ -2493,15 +2493,22 @@ struct dyn_ftrace *ftrace_rec_iter_record(struct ftrace_rec_iter *iter) > > > return &iter->pg->records[iter->index]; > > > } > > > > > > +#ifndef ftrace_init_nop > > > +static int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) > > > +{ > > > + return ftrace_make_nop(mod, rec, MCOUNT_ADDR); > > > +} > > > +#endif > > > > Can you place the above in the ftrace.h header. That's where that would > > belong. > > > > #ifndef ftrace_init_nop > > struct module; > > static inline int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) > > { > > return ftrace_make_nop(mod, rec, MCOUNT_ADDR); > > } > > #endif > > True. > > I've put this immediately after ftrace_make_nop() in the header, and > given it a kerneldoc comment. There's a declaration for struct module at > the top of the header, so I've just relied on that > > That looks like: > > | /** > | * ftrace_init_nop - initialize a nop call site > | * @mod: module structure if called by module load initialization > | * @rec: the mcount call site record Perhaps say "mcount/fentry" > | * > | * This is a very sensitive operation and great care needs > | * to be taken by the arch. The operation should carefully > | * read the location, check to see if what is read is indeed > | * what we expect it to be, and then on success of the compare, > | * it should write to the location. > | * > | * The code segment at @rec->ip should be as initialized by the "should be as" is a bit confusing. What about? "The code segment at @rec->ip should contain the contents created by the compiler". -- Steve > | * compiler > | * > | * Return must be: > | * 0 on success > | * -EFAULT on error reading the location > | * -EINVAL on a failed compare of the contents > | * -EPERM on error writing to the location > | * Any other value will be considered a failure. > | */ > | #ifndef ftrace_init_nop > | static int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) > | { > | return ftrace_make_nop(mod, rec, MCOUNT_ADDR); > | } > | #endif > > Thanks, > Mark.
On Tue, Oct 22, 2019 at 08:54:28AM -0400, Steven Rostedt wrote: > On Tue, 22 Oct 2019 12:28:11 +0100 > Mark Rutland <mark.rutland@arm.com> wrote: > > > To make the name even better, let's just rename it to: > > > > > > ftrace_nop_initialization() > > > > > > I think that may be the best description for it. > > > > Perhaps ftrace_nop_initialize(), so that it's not a noun? > > > > I've made it ftrace_nop_initialization() in my branch for now. > > I'm fine with ftrace_nop_initialize(). It's settled, then. :) [...] > > | /** > > | * ftrace_init_nop - initialize a nop call site > > | * @mod: module structure if called by module load initialization > > | * @rec: the mcount call site record > > Perhaps say "mcount/fentry" This is the exact wording that ftrace_make_nop and ftrace_modify_call have. For consistency, I think those should all match. I can add " (e.g. mcount/fentry)" to all of those if you'd like? ... or leave them all as-is? > > | * > > | * This is a very sensitive operation and great care needs > > | * to be taken by the arch. The operation should carefully > > | * read the location, check to see if what is read is indeed > > | * what we expect it to be, and then on success of the compare, > > | * it should write to the location. > > | * > > | * The code segment at @rec->ip should be as initialized by the > > "should be as" is a bit confusing. What about? > > "The code segment at @rec->ip should contain the contents created by > the compiler". Works for me. Mark.
On Tue, Oct 22, 2019 at 04:30:35PM +0100, Mark Rutland wrote: > On Tue, Oct 22, 2019 at 08:54:28AM -0400, Steven Rostedt wrote: > > On Tue, 22 Oct 2019 12:28:11 +0100 > > Mark Rutland <mark.rutland@arm.com> wrote: > > > | /** > > > | * ftrace_init_nop - initialize a nop call site > > > | * @mod: module structure if called by module load initialization > > > | * @rec: the mcount call site record > > > > Perhaps say "mcount/fentry" > > This is the exact wording that ftrace_make_nop and ftrace_modify_call > have. For consistency, I think those should all match. Now that I read this again, I see what you meant. If it's ok, I'll change those to: | @rec: the call site record (e.g. mcount/fentry) Thanks, Mark.
On Tue, 22 Oct 2019 16:33:35 +0100 Mark Rutland <mark.rutland@arm.com> wrote: > On Tue, Oct 22, 2019 at 04:30:35PM +0100, Mark Rutland wrote: > > On Tue, Oct 22, 2019 at 08:54:28AM -0400, Steven Rostedt wrote: > > > On Tue, 22 Oct 2019 12:28:11 +0100 > > > Mark Rutland <mark.rutland@arm.com> wrote: > > > > | /** > > > > | * ftrace_init_nop - initialize a nop call site > > > > | * @mod: module structure if called by module load initialization > > > > | * @rec: the mcount call site record > > > > > > Perhaps say "mcount/fentry" > > > > This is the exact wording that ftrace_make_nop and ftrace_modify_call > > have. For consistency, I think those should all match. > > Now that I read this again, I see what you meant. > > If it's ok, I'll change those to: > > | @rec: the call site record (e.g. mcount/fentry) > Ack -- Steve
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index f296d89be757..afd7e210e595 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -2493,15 +2493,22 @@ struct dyn_ftrace *ftrace_rec_iter_record(struct ftrace_rec_iter *iter) return &iter->pg->records[iter->index]; } +#ifndef ftrace_init_nop +static int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) +{ + return ftrace_make_nop(mod, rec, MCOUNT_ADDR); +} +#endif + static int -ftrace_code_disable(struct module *mod, struct dyn_ftrace *rec) +ftrace_code_init_disabled(struct module *mod, struct dyn_ftrace *rec) { int ret; if (unlikely(ftrace_disabled)) return 0; - ret = ftrace_make_nop(mod, rec, MCOUNT_ADDR); + ret = ftrace_init_nop(mod, rec); if (ret) { ftrace_bug_type = FTRACE_BUG_INIT; ftrace_bug(ret, rec); @@ -2943,7 +2950,7 @@ static int ftrace_update_code(struct module *mod, struct ftrace_page *new_pgs) * to the NOP instructions. */ if (!__is_defined(CC_USING_NOP_MCOUNT) && - !ftrace_code_disable(mod, p)) + !ftrace_code_init_disabled(mod, p)) break; update_cnt++;
Architectures may need to perform special initialization of ftrace callsites, and today they do so by special-casing ftrace_make_nop() when the expected branch address is MCOUNT_ADDR. In some cases (e.g. for patchable-function-entry), we don't have an mcount-like symbol and don't want a synthetic MCOUNT_ADDR, but we may need to perform some initialization of callsites. To make it possible to separate initialization from runtime modification, and to handle cases without an mcount-like symbol, this patch adds an optional ftrace_init_nop() function that architectures can implement, which does not pass a branch address. Where an architecture does not provide ftrace_init_nop(), we will fall back to the existing behaviour of calling ftrace_make_nop() with MCOUNT_ADDR. At the same time, ftrace_code_disable() is renamed to ftrace_code_init_disabled() to make it clearer that it is intended to intialize a callsite into a disabled state, and is not for disabling a callsite that has been runtime enabled. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Torsten Duwe <duwe@suse.de> --- kernel/trace/ftrace.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-)