Messages in this thread | | | From | Florent Revest <> | Date | Wed, 9 Aug 2023 12:31:27 +0200 | Subject | Re: [RFC PATCH v2 5/6] ftrace: Add ftrace_partial_regs() for converting ftrace_regs to pt_regs |
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On Mon, Aug 7, 2023 at 8:49 AM Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote: > > From: Masami Hiramatsu (Google) <mhiramat@kernel.org> > > Add ftrace_partial_regs() which converts the ftrace_regas to pt_regs.
ftrace_regs*
> If the architecture defines its own ftrace_regs, this copies partial > registers to pt_regs and returns it. If not, ftrace_regs is the same as > pt_regs and ftrace_partial_regs() will return ftrace_regs::regs. > > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> > --- > arch/arm64/include/asm/ftrace.h | 11 +++++++++++ > include/linux/ftrace.h | 11 +++++++++++ > 2 files changed, 22 insertions(+) > > diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h > index ab158196480c..b108cd6718cf 100644 > --- a/arch/arm64/include/asm/ftrace.h > +++ b/arch/arm64/include/asm/ftrace.h > @@ -137,6 +137,17 @@ ftrace_override_function_with_return(struct ftrace_regs *fregs) > fregs->pc = fregs->lr; > } > > +static __always_inline struct pt_regs * > +ftrace_partial_regs(const struct ftrace_regs *fregs, struct pt_regs *regs) > +{ > + memcpy(regs->regs, fregs->regs, sizeof(u64) * 10);
Are you intentionally copying that tenth value (fregs.direct_tramp) into pt_regs.regs[9] ? This seems wrong and it looks like it will bite us back one day. Isn't it one of these cases where we can simply use sizeof(fregs->regs) ?
> + regs->sp = fregs->sp; > + regs->pc = fregs->pc; > + regs->x[29] = fregs->fp; > + regs->x[30] = fregs->lr; > + return regs; > +} > + > int ftrace_regs_query_register_offset(const char *name); > > int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec); > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h > index 3fb94a1a2461..7f45654441b7 100644 > --- a/include/linux/ftrace.h > +++ b/include/linux/ftrace.h > @@ -155,6 +155,17 @@ static __always_inline struct pt_regs *ftrace_get_regs(struct ftrace_regs *fregs > return arch_ftrace_get_regs(fregs); > } > > +#if !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) || \ > + defined(CONFIG_HAVE_PT_REGS_COMPAT_FTRACE_REGS) > + > +static __always_inline struct pt_regs * > +ftrace_partial_regs(const struct ftrace_regs *fregs, struct pt_regs *regs) > +{ > + return arch_ftrace_get_regs((struct ftrace_regs *)fregs); > +}
I don't think this works. Suppose you are on x86, WITH_ARGS, and with HAVE_PT_REGS_COMPAT_FTRACE_REGS. If you register to ftrace without FTRACE_OPS_FL_SAVE_REGS you will receive a ftrace_regs from the light ftrace pre-trampoline that has a CS register equal to 0 and arch_ftrace_get_regs will return NULL here, which should never happen.
Have you tested your series without registering as FTRACE_OPS_FL_SAVE_REGS ?
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