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SubjectRe: [PATCH] x86: clean up vdso-layout.lds.S
> > diff --git a/arch/x86/vdso/Makefile b/arch/x86/vdso/Makefile
> > index 16a9020..8c7f06a 100644
> > --- a/arch/x86/vdso/Makefile
> > +++ b/arch/x86/vdso/Makefile
> > @@ -23,7 +23,8 @@ $(obj)/vdso.o: $(obj)/vdso.so
> >
> > targets += vdso.so vdso.so.dbg vdso.lds $(vobjs-y)
> >
> > -export CPPFLAGS_vdso.lds += -P -C
> > +vdso-cppflags = -P -C
> > +export CPPFLAGS_vdso.lds += -m64 $(vdso-cppflags)

I am wondering why we need -P -C here - but we do not need it for lds.S files?
Seems like something we could let go.

> >
> > VDSO_LDFLAGS_vdso.lds = -m elf_x86_64 -Wl,-soname=linux-vdso.so.1 \
> > -Wl,-z,max-page-size=4096 -Wl,-z,common-page-size=4096
> > @@ -68,7 +69,7 @@ vdso32.so-$(VDSO32-y) += sysenter
> >
> > vdso32-images = $(vdso32.so-y:%=vdso32-%.so)
> >
> > -CPPFLAGS_vdso32.lds = $(CPPFLAGS_vdso.lds)
> > +CPPFLAGS_vdso32.lds = -m32 $(vdso-cppflags)
> > VDSO_LDFLAGS_vdso32.lds = -m elf_i386 -Wl,-soname=linux-gate.so.1
> >
> > # This makes sure the $(obj) subdirectory exists even though vdso32/
> > diff --git a/arch/x86/vdso/vdso-layout.lds.S b/arch/x86/vdso/vdso-layout.lds.S
> > index 634a2cf..1f4b215 100644
> > --- a/arch/x86/vdso/vdso-layout.lds.S
> > +++ b/arch/x86/vdso/vdso-layout.lds.S
> > @@ -22,16 +22,15 @@ SECTIONS
> > .eh_frame : { KEEP (*(.eh_frame)) } :text
> >
> > .dynamic : { *(.dynamic) } :text :dynamic
> > + .got : { *(.got.plt) *(.got) } :text

The style we try to introduce for .lds files in
arch/$ARCH/kernel/vmlinux.lds.S is much more C-like.
The above would have been:
.got : {
*(.got.plt)
*(.got)
} :text

Please use this all over so we have a consistent style in linker scripts.

> > .data : {
> > - *(.data*)
> > - *(.sdata*)
> > - *(.got.plt) *(.got)
> > - *(.gnu.linkonce.d.*)
> > - *(.bss*)
> > - *(.dynbss*)
> > - *(.gnu.linkonce.b.*)
> > + *(.data .data.* .gnu.linkonce.d.*)
> > + *(.bss .bss.* .gnu.linkonce.b.*)
> > + *(COMMON)
> > }
Where did *(.sdata*) go?
Why do we need *(.data .data.*) rather than *(.data*)?
*(.dynbss*)?

In your changelog you say:
"discard sections which are not useful to user-space" - but as you do not
list which one it is hard to tell what you removed on purpose
and what you removed by accident.

> >
> > .altinstructions : { *(.altinstructions) }
> > @@ -43,9 +42,49 @@ SECTIONS
> > */
> > . = ALIGN(0x100);

What is 0x100?

> >
> > - .text : { *(.text*) } :text =0x90909090
> > + .text : {
> > + *(.text .text.* .gnu.linkonce.t.*)
> > + } :text =0x90909090
> > +
> > + /* We would need a more sophisticated dynamic linker for the
> > + * vDSO to make the following sections work. Put them into
> > + * a special section and raise a link-time error if they get
> > + * used.
> > + */
> > + .broken : {
> > + /* Code in the Procedure Linkage Table will segfault */
> > + *(.plt)
> > +
> > + /* Relocation will not be done, so any pointers will
> > + * still point to the prelinked address, which is wrong
> > + */
> > + *(.data.rel.ro*)
> > + *(.gnu.linkonce.d.rel.ro.*)
> > +
> > + /* Initialization/termination won't work this way */
> > + *(.init) *(.fini)
> > + *(.preinit_array) *(.init_array*)
> > + *(.fini_array*)
> > +
> > + /* Thread-local data cannot be defined like this */
> > + *(.tdata .tdata.* .gnu.linkonce.td.*)
> > + *(.tbss .tbss.* .gnu.linkonce.tb.*)
> > + *(.tcommon)
> > + }
> > +
> > + /* These sections are not useful */
> > + /DISCARD/ : {
> > + *(.gnu.warning.*)
> > + *(.note.GNU-stack)
> > + }
> > }
> >
> > +ASSERT(!SIZEOF(.broken), "VDSO contains sections that don't work properly");
Can you give any better hints where to look and what to look for?
> > +
> > +/* Check that GOT has only the three entries defined by the ABI */
> > +ASSERT(SIZEOF(.got) == 3*__SIZEOF_POINTER__,
> > + "Found extra GOT entries. Check your use of external vars.");
Can you give any better hints where to look and what to look for?

Sam


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