* [PATCH] arm64: move elf notes into readonly segment @ 2013-08-23 15:16 Mark Salter 2013-08-27 10:49 ` Catalin Marinas 0 siblings, 1 reply; 4+ messages in thread From: Mark Salter @ 2013-08-23 15:16 UTC (permalink / raw) To: catalin.marinas, will.deacon; +Cc: linux-kernel The current vmlinux.lds.S places the notes sections between the end of rw data and start of bss. This means that _edata doesn't really point to the end of data. Since notes are read-only, this patch moves them to the read-only segment so that _edata does point to the end of initialized rw data. Signed-off-by: Mark Salter <msalter@redhat.com> --- arch/arm64/kernel/vmlinux.lds.S | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index f5e5574..f8ab9d8 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -71,6 +71,7 @@ SECTIONS RO_DATA(PAGE_SIZE) EXCEPTION_TABLE(8) + NOTES _etext = .; /* End of text and rodata section */ . = ALIGN(PAGE_SIZE); @@ -122,8 +123,6 @@ SECTIONS } _edata_loc = __data_loc + SIZEOF(.data); - NOTES - BSS_SECTION(0, 0, 0) _end = .; -- 1.8.3.1 ^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] arm64: move elf notes into readonly segment 2013-08-23 15:16 [PATCH] arm64: move elf notes into readonly segment Mark Salter @ 2013-08-27 10:49 ` Catalin Marinas 2013-08-27 13:01 ` Mark Salter 0 siblings, 1 reply; 4+ messages in thread From: Catalin Marinas @ 2013-08-27 10:49 UTC (permalink / raw) To: Mark Salter; +Cc: Will Deacon, linux-kernel On Fri, Aug 23, 2013 at 04:16:42PM +0100, Mark Salter wrote: > The current vmlinux.lds.S places the notes sections between the > end of rw data and start of bss. This means that _edata doesn't > really point to the end of data. Since notes are read-only, this > patch moves them to the read-only segment so that _edata does > point to the end of initialized rw data. > > Signed-off-by: Mark Salter <msalter@redhat.com> > --- > arch/arm64/kernel/vmlinux.lds.S | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S > index f5e5574..f8ab9d8 100644 > --- a/arch/arm64/kernel/vmlinux.lds.S > +++ b/arch/arm64/kernel/vmlinux.lds.S > @@ -71,6 +71,7 @@ SECTIONS > > RO_DATA(PAGE_SIZE) > EXCEPTION_TABLE(8) > + NOTES > _etext = .; /* End of text and rodata section */ > > . = ALIGN(PAGE_SIZE); > @@ -122,8 +123,6 @@ SECTIONS > } > _edata_loc = __data_loc + SIZEOF(.data); > > - NOTES > - > BSS_SECTION(0, 0, 0) > _end = .; The _edata is set before NOTES, so I don't fully understand where the problem is. -- Catalin ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] arm64: move elf notes into readonly segment 2013-08-27 10:49 ` Catalin Marinas @ 2013-08-27 13:01 ` Mark Salter 2013-08-27 14:27 ` Catalin Marinas 0 siblings, 1 reply; 4+ messages in thread From: Mark Salter @ 2013-08-27 13:01 UTC (permalink / raw) To: Catalin Marinas; +Cc: Will Deacon, linux-kernel On Tue, 2013-08-27 at 11:49 +0100, Catalin Marinas wrote: > On Fri, Aug 23, 2013 at 04:16:42PM +0100, Mark Salter wrote: > > The current vmlinux.lds.S places the notes sections between the > > end of rw data and start of bss. This means that _edata doesn't > > really point to the end of data. Since notes are read-only, this > > patch moves them to the read-only segment so that _edata does > > point to the end of initialized rw data. > > > > Signed-off-by: Mark Salter <msalter@redhat.com> > > --- > > arch/arm64/kernel/vmlinux.lds.S | 3 +-- > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S > > index f5e5574..f8ab9d8 100644 > > --- a/arch/arm64/kernel/vmlinux.lds.S > > +++ b/arch/arm64/kernel/vmlinux.lds.S > > @@ -71,6 +71,7 @@ SECTIONS > > > > RO_DATA(PAGE_SIZE) > > EXCEPTION_TABLE(8) > > + NOTES > > _etext = .; /* End of text and rodata section */ > > > > . = ALIGN(PAGE_SIZE); > > @@ -122,8 +123,6 @@ SECTIONS > > } > > _edata_loc = __data_loc + SIZEOF(.data); > > > > - NOTES > > - > > BSS_SECTION(0, 0, 0) > > _end = .; > > The _edata is set before NOTES, so I don't fully understand where the > problem is. > The problem *is* _edata before the NOTES. We need a symbol to mark the end of initialized data. This should be _edata but _edata doesn't currently account for NOTES. In the EFI stub I'm working on, the PE/COFF header needs to know the end of the image. If we use _edata, we wouldn't include NOTES, so we're left with __bss_start. But _bss_start may not be exactly right because of alignment rounding and it is ugly to use for that purpose. So we either need a new symbol following NOTES, or move _edata past NOTES, or move NOTES. I chose the latter because NOTES are readonly and don't really need to be part of the RW segment. --Mark ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] arm64: move elf notes into readonly segment 2013-08-27 13:01 ` Mark Salter @ 2013-08-27 14:27 ` Catalin Marinas 0 siblings, 0 replies; 4+ messages in thread From: Catalin Marinas @ 2013-08-27 14:27 UTC (permalink / raw) To: Mark Salter; +Cc: Will Deacon, linux-kernel On Tue, Aug 27, 2013 at 02:01:01PM +0100, Mark Salter wrote: > On Tue, 2013-08-27 at 11:49 +0100, Catalin Marinas wrote: > > On Fri, Aug 23, 2013 at 04:16:42PM +0100, Mark Salter wrote: > > > The current vmlinux.lds.S places the notes sections between the > > > end of rw data and start of bss. This means that _edata doesn't > > > really point to the end of data. Since notes are read-only, this > > > patch moves them to the read-only segment so that _edata does > > > point to the end of initialized rw data. > > > > > > Signed-off-by: Mark Salter <msalter@redhat.com> > > > --- > > > arch/arm64/kernel/vmlinux.lds.S | 3 +-- > > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > > > diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S > > > index f5e5574..f8ab9d8 100644 > > > --- a/arch/arm64/kernel/vmlinux.lds.S > > > +++ b/arch/arm64/kernel/vmlinux.lds.S > > > @@ -71,6 +71,7 @@ SECTIONS > > > > > > RO_DATA(PAGE_SIZE) > > > EXCEPTION_TABLE(8) > > > + NOTES > > > _etext = .; /* End of text and rodata section */ > > > > > > . = ALIGN(PAGE_SIZE); > > > @@ -122,8 +123,6 @@ SECTIONS > > > } > > > _edata_loc = __data_loc + SIZEOF(.data); > > > > > > - NOTES > > > - > > > BSS_SECTION(0, 0, 0) > > > _end = .; > > > > The _edata is set before NOTES, so I don't fully understand where the > > problem is. > > > The problem *is* _edata before the NOTES. We need a symbol to mark the > end of initialized data. This should be _edata but _edata doesn't > currently account for NOTES. In the EFI stub I'm working on, the PE/COFF > header needs to know the end of the image. If we use _edata, we wouldn't > include NOTES, so we're left with __bss_start. But _bss_start may not be > exactly right because of alignment rounding and it is ugly to use for > that purpose. So we either need a new symbol following NOTES, or move > _edata past NOTES, or move NOTES. I chose the latter because NOTES are > readonly and don't really need to be part of the RW segment. OK, I got it now. I'll queue the patch for 3.12. Thanks. -- Catalin ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2013-08-27 14:27 UTC | newest] Thread overview: 4+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2013-08-23 15:16 [PATCH] arm64: move elf notes into readonly segment Mark Salter 2013-08-27 10:49 ` Catalin Marinas 2013-08-27 13:01 ` Mark Salter 2013-08-27 14:27 ` Catalin Marinas
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