Messages in this thread | | | Date | Sat, 10 Jul 2010 15:25:02 -0700 | Subject | Re: [PATCH] tracing: properly align linker defined symbols | From | Linus Torvalds <> |
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On Fri, Jul 9, 2010 at 11:35 PM, Sam Ravnborg <sam@ravnborg.org> wrote: > > We define a number of symbols in the linker scipt like this: > > __start_syscalls_metadata = .; > *(__syscalls_metadata) > > But we do not know the alignment of "." when we assign > the __start_syscalls_metadata symbol. > gcc started to uses bigger alignment for structs (32 bytes), > so we saw situations where the linker due to alignment > constraints increased the value of "." after the symbol assignment.
Ok, why not clean this up a bit more, and use a helper macro for this pattern. There's a fair number of users of that kind of pattern, so that actually removes a few lines.
Here's an example patch. Untested. Whatever. But just this part
1 files changed, 21 insertions(+), 31 deletions(-)
says to me that it's a good idea, and there are other cases that could use the new SYMBOL_SECTION() helper.
What do people think?
Linus > > This resulted in boot fails. > > Fix this by forcing a 32 byte alignment of "." before the > assignment. > > This patch introduces the forced alignment for > ftrace_events and syscalls_metadata. > It may be required in more places. > > Reported-by: Zeev Tarantov <zeev.tarantov@gmail.com> > Signed-off-by: Sam Ravnborg <sam@ravnborg.org> > Cc: Steven Rostedt <rostedt@goodmis.org> > Cc: Frederic Weisbecker <fweisbec@gmail.com> > --- > include/asm-generic/vmlinux.lds.h | 10 ++++++++++ > 1 files changed, 10 insertions(+), 0 deletions(-) > > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > index 48c5299..4b5902a 100644 > --- a/include/asm-generic/vmlinux.lds.h > +++ b/include/asm-generic/vmlinux.lds.h > @@ -63,6 +63,12 @@ > /* Align . to a 8 byte boundary equals to maximum function alignment. */ > #define ALIGN_FUNCTION() . = ALIGN(8) > > +/* > + * Align to a 32 byte boundary equal to the > + * alignment gcc 4.5 uses for a struct > + */ > +#define STRUCT_ALIGN() . = ALIGN(32) > + > /* The actual configuration determine if the init/exit sections > * are handled as text/data or they can be discarded (which > * often happens at runtime) > @@ -166,7 +172,11 @@ > LIKELY_PROFILE() \ > BRANCH_PROFILE() \ > TRACE_PRINTKS() \ > + \ > + STRUCT_ALIGN(); \ > FTRACE_EVENTS() \ > + \ > + STRUCT_ALIGN(); \ > TRACE_SYSCALLS() > > /* > -- > 1.6.0.6 > > [unhandled content-type:application/octet-stream] | |