| Message ID | 20190926175602.33098-8-keescook@chromium.org (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | vmlinux.lds.h: Refactor EXCEPTION_TABLE and NOTES | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/apply_patch | success | Successfully applied on branch next (6edfc6487b474fe01857dc3f1a9cd701bb9b21c8) |
| snowpatch_ozlabs/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 10 lines checked |
On Thu, Sep 26, 2019 at 10:55:40AM -0700, Kees Cook wrote: > Instead of depending on markings in the section following NOTES to > restore the associated Program Header, use a dummy section, as done > in other architectures. This is very laconic and after some staring at ld.info, I think you mean this: " If you place a section in one or more segments using ':PHDR', then the linker will place all subsequent allocatable sections which do not specify ':PHDR' in the same segments." but I could be way off. Yes, no? IOW, please write in the commit messages first what the problem is you're addressing. > This is preparation for moving NOTES into the > RO_DATA macro. > > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > arch/x86/kernel/vmlinux.lds.S | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S > index e2feacf921a0..788e78978030 100644 > --- a/arch/x86/kernel/vmlinux.lds.S > +++ b/arch/x86/kernel/vmlinux.lds.S > @@ -147,8 +147,9 @@ SECTIONS > } :text = 0x9090 > > NOTES :text :note > + .dummy : { *(.dummy) } :text > > - EXCEPTION_TABLE(16) :text = 0x9090 > + EXCEPTION_TABLE(16) This is killing the filler byte but I have a suspicion that'll change eventually to INT3... :)
On Thu, Oct 10, 2019 at 12:33:05PM +0200, Borislav Petkov wrote: > On Thu, Sep 26, 2019 at 10:55:40AM -0700, Kees Cook wrote: > > Instead of depending on markings in the section following NOTES to > > restore the associated Program Header, use a dummy section, as done > > in other architectures. > > This is very laconic and after some staring at ld.info, I think you mean > this: > > " If you place a section in one or more segments using ':PHDR', then > the linker will place all subsequent allocatable sections which do not > specify ':PHDR' in the same segments." > > but I could be way off. Yes, no? > > IOW, please write in the commit messages first what the problem is > you're addressing. Yeah, that's much improved. I really struggled to describe this, given how weird the linker script logic is here. > > --- a/arch/x86/kernel/vmlinux.lds.S > > +++ b/arch/x86/kernel/vmlinux.lds.S > > @@ -147,8 +147,9 @@ SECTIONS > > } :text = 0x9090 > > > > NOTES :text :note > > + .dummy : { *(.dummy) } :text > > > > - EXCEPTION_TABLE(16) :text = 0x9090 > > + EXCEPTION_TABLE(16) > > This is killing the filler byte but I have a suspicion that'll change > eventually to INT3... :) Yes, though since the exception table isn't executable, filling with 0x90 has no meaning, and I think when I looked at the alignment there were actually no fill bytes from here on. But it doesn't matter; it all goes away in the end.
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index e2feacf921a0..788e78978030 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -147,8 +147,9 @@ SECTIONS } :text = 0x9090 NOTES :text :note + .dummy : { *(.dummy) } :text - EXCEPTION_TABLE(16) :text = 0x9090 + EXCEPTION_TABLE(16) /* .text should occupy whole number of pages */ . = ALIGN(PAGE_SIZE);
Instead of depending on markings in the section following NOTES to restore the associated Program Header, use a dummy section, as done in other architectures. This is preparation for moving NOTES into the RO_DATA macro. Signed-off-by: Kees Cook <keescook@chromium.org> --- arch/x86/kernel/vmlinux.lds.S | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)