arch/x86/boot/setup.elf currently has an orphan section .text.startup,
and lld git as of ebf14d9b6d8b is breaking on 64-bit due to what seems
to be a change in behavior on orphan section placement (details in patch
commit message).
I'm not sure if this was an intentional change in lld, but it seems like
a good idea to explicitly include .text.startup anyway.
Arvind Sankar (1):
x86/boot: Add .text.startup to setup.ld
arch/x86/boot/setup.ld | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--
2.26.2
gcc puts the main function into .text.startup when compiled with -Os (or
-O2). This results in arch/x86/boot/main.c having a .text.startup
section which is currently not included explicitly in the linker script
setup.ld in the same directory.
The BFD linker places this orphan section immediately after .text, so
this still works. However, LLD git, on 64-bit only, is choosing to place
it immediately after the .bstext section instead (this is the first code
section). This plays havoc with the section layout that setup.elf
requires to create the setup header:
LD arch/x86/boot/setup.elf
ld.lld: error: section .text.startup file range overlaps with .header
>>> .text.startup range is [0x200040, 0x2001FE]
>>> .header range is [0x2001EF, 0x20026B]
ld.lld: error: section .header file range overlaps with .bsdata
>>> .header range is [0x2001EF, 0x20026B]
>>> .bsdata range is [0x2001FF, 0x200398]
ld.lld: error: section .bsdata file range overlaps with .entrytext
>>> .bsdata range is [0x2001FF, 0x200398]
>>> .entrytext range is [0x20026C, 0x2002D3]
ld.lld: error: section .text.startup virtual address range overlaps
with .header
>>> .text.startup range is [0x40, 0x1FE]
>>> .header range is [0x1EF, 0x26B]
ld.lld: error: section .header virtual address range overlaps with
.bsdata
>>> .header range is [0x1EF, 0x26B]
>>> .bsdata range is [0x1FF, 0x398]
ld.lld: error: section .bsdata virtual address range overlaps with
.entrytext
>>> .bsdata range is [0x1FF, 0x398]
>>> .entrytext range is [0x26C, 0x2D3]
ld.lld: error: section .text.startup load address range overlaps with
.header
>>> .text.startup range is [0x40, 0x1FE]
>>> .header range is [0x1EF, 0x26B]
ld.lld: error: section .header load address range overlaps with
.bsdata
>>> .header range is [0x1EF, 0x26B]
>>> .bsdata range is [0x1FF, 0x398]
ld.lld: error: section .bsdata load address range overlaps with
.entrytext
>>> .bsdata range is [0x1FF, 0x398]
>>> .entrytext range is [0x26C, 0x2D3]
Explicitly pull .text.startup into the .text output section to avoid
this.
Signed-off-by: Arvind Sankar <[email protected]>
---
arch/x86/boot/setup.ld | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/boot/setup.ld b/arch/x86/boot/setup.ld
index 24c95522f231..ed60abcdb089 100644
--- a/arch/x86/boot/setup.ld
+++ b/arch/x86/boot/setup.ld
@@ -20,7 +20,7 @@ SECTIONS
.initdata : { *(.initdata) }
__end_init = .;
- .text : { *(.text) }
+ .text : { *(.text.startup) *(.text) }
.text32 : { *(.text32) }
. = ALIGN(16);
--
2.26.2
On Wed, May 20, 2020 at 06:56:53PM -0400, Arvind Sankar wrote:
> arch/x86/boot/setup.elf currently has an orphan section .text.startup,
> and lld git as of ebf14d9b6d8b is breaking on 64-bit due to what seems
> to be a change in behavior on orphan section placement (details in patch
> commit message).
>
> I'm not sure if this was an intentional change in lld, but it seems like
> a good idea to explicitly include .text.startup anyway.
>
> Arvind Sankar (1):
> x86/boot: Add .text.startup to setup.ld
>
> arch/x86/boot/setup.ld | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> --
> 2.26.2
>
Actually I'm not sure this is a recent change. I updated to the git tip
because on my system (gentoo with gcc-10), lld-10.0.0 segfaults when
trying to link the compressed kernel, and updating to lld git fixed
that. So I previously probably didn't get to the stage where it links
setup.elf.
On 2020-05-20, Arvind Sankar wrote:
>On Wed, May 20, 2020 at 06:56:53PM -0400, Arvind Sankar wrote:
>> arch/x86/boot/setup.elf currently has an orphan section .text.startup,
>> and lld git as of ebf14d9b6d8b is breaking on 64-bit due to what seems
>> to be a change in behavior on orphan section placement (details in patch
>> commit message).
>>
>> I'm not sure if this was an intentional change in lld, but it seems like
>> a good idea to explicitly include .text.startup anyway.
>>
>> Arvind Sankar (1):
>> x86/boot: Add .text.startup to setup.ld
>>
>> arch/x86/boot/setup.ld | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> --
>> 2.26.2
>>
I found your PATCH 1/1 on https://lkml.org/lkml/2020/5/20/1491
- .text : { *(.text) }
+ .text : { *(.text.startup) *(.text) }
The LLD behavior change was introduced in
https://reviews.llvm.org/D75225 (will be included in 11.0.0)
It was intended to match GNU ld.
But yes, orphan section placement is still different in the two linkers.
Placing .text.startup before .text seems good.
In GNU ld's internal linker script (ld --verbose),
.text.startup is placed before .text
Reviewed-by: Fangrui Song <[email protected]>
On Wed, May 20, 2020 at 07:12:17PM -0700, Fangrui Song wrote:
> On 2020-05-20, Arvind Sankar wrote:
> >On Wed, May 20, 2020 at 06:56:53PM -0400, Arvind Sankar wrote:
> >> arch/x86/boot/setup.elf currently has an orphan section .text.startup,
> >> and lld git as of ebf14d9b6d8b is breaking on 64-bit due to what seems
> >> to be a change in behavior on orphan section placement (details in patch
> >> commit message).
> >>
> >> I'm not sure if this was an intentional change in lld, but it seems like
> >> a good idea to explicitly include .text.startup anyway.
> >>
> >> Arvind Sankar (1):
> >> x86/boot: Add .text.startup to setup.ld
> >>
> >> arch/x86/boot/setup.ld | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> --
> >> 2.26.2
> >>
>
> I found your PATCH 1/1 on https://lkml.org/lkml/2020/5/20/1491
>
> - .text : { *(.text) }
> + .text : { *(.text.startup) *(.text) }
>
> The LLD behavior change was introduced in
> https://reviews.llvm.org/D75225 (will be included in 11.0.0)
> It was intended to match GNU ld.
>
> But yes, orphan section placement is still different in the two linkers.
>
> Placing .text.startup before .text seems good.
> In GNU ld's internal linker script (ld --verbose),
> .text.startup is placed before .text
>
> Reviewed-by: Fangrui Song <[email protected]>
Thanks. I'll reword the commit message to include a reference to that
change. It's also not just 64-bit, on 32-bit it currently fails before
it gets around to linking setup.elf due to the text relocs issues,
that's why this one doesn't show up, but they are in fact at least
consistent.
gcc puts the main function into .text.startup when compiled with -Os (or
-O2). This results in arch/x86/boot/main.c having a .text.startup
section which is currently not included explicitly in the linker script
setup.ld in the same directory.
The BFD linker places this orphan section immediately after .text, so
this still works. However, LLD git, since [1], is choosing to place it
immediately after the .bstext section instead (this is the first code
section). This plays havoc with the section layout that setup.elf
requires to create the setup header, for eg on 64-bit:
LD arch/x86/boot/setup.elf
ld.lld: error: section .text.startup file range overlaps with .header
>>> .text.startup range is [0x200040, 0x2001FE]
>>> .header range is [0x2001EF, 0x20026B]
ld.lld: error: section .header file range overlaps with .bsdata
>>> .header range is [0x2001EF, 0x20026B]
>>> .bsdata range is [0x2001FF, 0x200398]
ld.lld: error: section .bsdata file range overlaps with .entrytext
>>> .bsdata range is [0x2001FF, 0x200398]
>>> .entrytext range is [0x20026C, 0x2002D3]
ld.lld: error: section .text.startup virtual address range overlaps
with .header
>>> .text.startup range is [0x40, 0x1FE]
>>> .header range is [0x1EF, 0x26B]
ld.lld: error: section .header virtual address range overlaps with
.bsdata
>>> .header range is [0x1EF, 0x26B]
>>> .bsdata range is [0x1FF, 0x398]
ld.lld: error: section .bsdata virtual address range overlaps with
.entrytext
>>> .bsdata range is [0x1FF, 0x398]
>>> .entrytext range is [0x26C, 0x2D3]
ld.lld: error: section .text.startup load address range overlaps with
.header
>>> .text.startup range is [0x40, 0x1FE]
>>> .header range is [0x1EF, 0x26B]
ld.lld: error: section .header load address range overlaps with
.bsdata
>>> .header range is [0x1EF, 0x26B]
>>> .bsdata range is [0x1FF, 0x398]
ld.lld: error: section .bsdata load address range overlaps with
.entrytext
>>> .bsdata range is [0x1FF, 0x398]
>>> .entrytext range is [0x26C, 0x2D3]
Explicitly pull .text.startup into the .text output section to avoid
this.
[1] https://reviews.llvm.org/D75225
Signed-off-by: Arvind Sankar <[email protected]>
Reviewed-by: Fangrui Song <[email protected]>
---
arch/x86/boot/setup.ld | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/boot/setup.ld b/arch/x86/boot/setup.ld
index 24c95522f231..ed60abcdb089 100644
--- a/arch/x86/boot/setup.ld
+++ b/arch/x86/boot/setup.ld
@@ -20,7 +20,7 @@ SECTIONS
.initdata : { *(.initdata) }
__end_init = .;
- .text : { *(.text) }
+ .text : { *(.text.startup) *(.text) }
.text32 : { *(.text32) }
. = ALIGN(16);
--
2.26.2