This series hunts the problems discovered after manual enabling of
ARCH_WANT_LD_ORPHAN_WARN. Notably:
- adds the missing PAGE_ALIGNED_DATA() section affecting VDSO
placement (marked for stable);
- properly stops .eh_frame section generation.
Compile and runtime tested on MIPS32R2 CPS board with no issues
using two different toolkits:
- Binutils 2.35.1, GCC 10.2.0;
- LLVM stack 11.0.0.
Since v2 [1]:
- stop discarding .eh_frame and just prevent it from generating
(Kees);
- drop redundant sections assertions (Fangrui);
- place GOT table in .text instead of asserting as it's not empty
when building with LLVM (Nathan);
- catch compound literals in generic definitions when building with
LD_DEAD_CODE_DATA_ELIMINATION (Kees);
- collect two Reviewed-bys (Kees).
Since v1 [0]:
- catch .got entries too as LLD may produce it (Nathan);
- check for unwanted sections to be zero-sized instead of
discarding (Fangrui).
[0] https://lore.kernel.org/linux-mips/[email protected]
[1] https://lore.kernel.org/linux-mips/[email protected]
Alexander Lobakin (7):
MIPS: vmlinux.lds.S: add missing PAGE_ALIGNED_DATA() section
MIPS: vmlinux.lds.S: add ".gnu.attributes" to DISCARDS
MIPS: properly stop .eh_frame generation
MIPS: vmlinux.lds.S: catch bad .rel.dyn at link time
MIPS: vmlinux.lds.S: explicitly declare .got table
vmlinux.lds.h: catch compound literals into data and BSS
MIPS: select ARCH_WANT_LD_ORPHAN_WARN
arch/mips/Kconfig | 1 +
arch/mips/include/asm/asm.h | 18 ++++++++++++++++++
arch/mips/kernel/vmlinux.lds.S | 15 ++++++++++++++-
include/asm-generic/vmlinux.lds.h | 6 +++---
4 files changed, 36 insertions(+), 4 deletions(-)
--
2.30.0
MIPS uses its own declaration of rwdata, and thus it should be kept
in sync with the asm-generic one. Currently PAGE_ALIGNED_DATA() is
missing from the linker script, which emits the following ld
warnings:
mips-alpine-linux-musl-ld: warning: orphan section
`.data..page_aligned' from `arch/mips/kernel/vdso.o' being placed
in section `.data..page_aligned'
mips-alpine-linux-musl-ld: warning: orphan section
`.data..page_aligned' from `arch/mips/vdso/vdso-image.o' being placed
in section `.data..page_aligned'
Add the necessary declaration, so the mentioned structures will be
placed in vmlinux as intended:
ffffffff80630580 D __end_once
ffffffff80630580 D __start___dyndbg
ffffffff80630580 D __start_once
ffffffff80630580 D __stop___dyndbg
ffffffff80634000 d mips_vdso_data
ffffffff80638000 d vdso_data
ffffffff80638580 D _gp
ffffffff8063c000 T __init_begin
ffffffff8063c000 D _edata
ffffffff8063c000 T _sinittext
->
ffffffff805a4000 D __end_init_task
ffffffff805a4000 D __nosave_begin
ffffffff805a4000 D __nosave_end
ffffffff805a4000 d mips_vdso_data
ffffffff805a8000 d vdso_data
ffffffff805ac000 D mmlist_lock
ffffffff805ac080 D tasklist_lock
Fixes: ebb5e78cc634 ("MIPS: Initial implementation of a VDSO")
Cc: [email protected] # 4.4+
Signed-off-by: Alexander Lobakin <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
---
arch/mips/kernel/vmlinux.lds.S | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S
index 5e97e9d02f98..83e27a181206 100644
--- a/arch/mips/kernel/vmlinux.lds.S
+++ b/arch/mips/kernel/vmlinux.lds.S
@@ -90,6 +90,7 @@ SECTIONS
INIT_TASK_DATA(THREAD_SIZE)
NOSAVE_DATA
+ PAGE_ALIGNED_DATA(PAGE_SIZE)
CACHELINE_ALIGNED_DATA(1 << CONFIG_MIPS_L1_CACHE_SHIFT)
READ_MOSTLY_DATA(1 << CONFIG_MIPS_L1_CACHE_SHIFT)
DATA_DATA
--
2.30.0
When building kernel with LD_DEAD_CODE_DATA_ELIMINATION, LLVM stack
generates separate sections for compound literals, just like in case
with enabled LTO [0]:
ld.lld: warning: drivers/built-in.a(mtd/nand/spi/gigadevice.o):
(.data..compoundliteral.14) is being placed in
'.data..compoundliteral.14'
ld.lld: warning: drivers/built-in.a(mtd/nand/spi/gigadevice.o):
(.data..compoundliteral.15) is being placed in
'.data..compoundliteral.15'
ld.lld: warning: drivers/built-in.a(mtd/nand/spi/gigadevice.o):
(.data..compoundliteral.16) is being placed in
'.data..compoundliteral.16'
ld.lld: warning: drivers/built-in.a(mtd/nand/spi/gigadevice.o):
(.data..compoundliteral.17) is being placed in
'.data..compoundliteral.17'
[...]
Handle this by adding the related sections to generic definitions
as suggested by Sami [0].
[0] https://lore.kernel.org/lkml/[email protected]
Suggested-by: Kees Cook <[email protected]>
Signed-off-by: Alexander Lobakin <[email protected]>
---
include/asm-generic/vmlinux.lds.h | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index b2b3d81b1535..5f2f5b1db84f 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -95,10 +95,10 @@
*/
#ifdef CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
#define TEXT_MAIN .text .text.[0-9a-zA-Z_]*
-#define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..LPBX*
+#define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..L* .data..compoundliteral*
#define SDATA_MAIN .sdata .sdata.[0-9a-zA-Z_]*
-#define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]*
-#define BSS_MAIN .bss .bss.[0-9a-zA-Z_]*
+#define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]* .rodata..L*
+#define BSS_MAIN .bss .bss.[0-9a-zA-Z_]* .bss..compoundliteral*
#define SBSS_MAIN .sbss .sbss.[0-9a-zA-Z_]*
#else
#define TEXT_MAIN .text
--
2.30.0
LLVM stack generates GOT table when building the kernel:
ld.lld: warning: <internal>:(.got) is being placed in '.got'
According to the debug assertions, it's not zero-sized and thus
can't be handled the same way as .rel.dyn (like it's done for x86).
Use the ARM/ARM64 path here and place it at the end of .text section.
Reported-by: Nathan Chancellor <[email protected]>
Signed-off-by: Alexander Lobakin <[email protected]>
---
arch/mips/kernel/vmlinux.lds.S | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S
index 0f736d60d43e..4709959f6985 100644
--- a/arch/mips/kernel/vmlinux.lds.S
+++ b/arch/mips/kernel/vmlinux.lds.S
@@ -69,6 +69,7 @@ SECTIONS
*(.text.*)
*(.fixup)
*(.gnu.warning)
+ *(.got)
} :text = 0
_etext = .; /* End of text section */
--
2.30.0
Now, after that all the sections are explicitly described and
declared in vmlinux.lds.S, we can enable ld orphan warnings to
prevent from missing any new sections in future.
Signed-off-by: Alexander Lobakin <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
---
arch/mips/Kconfig | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index d68df1febd25..d3e64cc0932b 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -18,6 +18,7 @@ config MIPS
select ARCH_USE_QUEUED_SPINLOCKS
select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
select ARCH_WANT_IPC_PARSE_VERSION
+ select ARCH_WANT_LD_ORPHAN_WARN
select BUILDTIME_TABLE_SORT
select CLONE_BACKWARDS
select CPU_NO_EFFICIENT_FFS if (TARGET_ISA_REV < 1)
--
2.30.0
> This series hunts the problems discovered after manual enabling of
> ARCH_WANT_LD_ORPHAN_WARN. Notably:
> - adds the missing PAGE_ALIGNED_DATA() section affecting VDSO
> placement (marked for stable);
> - properly stops .eh_frame section generation.
>
> Compile and runtime tested on MIPS32R2 CPS board with no issues
> using two different toolkits:
> - Binutils 2.35.1, GCC 10.2.0;
> - LLVM stack 11.0.0.
>
> Since v2 [1]:
> - stop discarding .eh_frame and just prevent it from generating
> (Kees);
> - drop redundant sections assertions (Fangrui);
> - place GOT table in .text instead of asserting as it's not empty
> when building with LLVM (Nathan);
> - catch compound literals in generic definitions when building with
> LD_DEAD_CODE_DATA_ELIMINATION (Kees);
> - collect two Reviewed-bys (Kees).
>
> Since v1 [0]:
> - catch .got entries too as LLD may produce it (Nathan);
> - check for unwanted sections to be zero-sized instead of
> discarding (Fangrui).
>
> [0] https://lore.kernel.org/linux-mips/[email protected]
> [1] https://lore.kernel.org/linux-mips/[email protected]
>
> Alexander Lobakin (7):
> MIPS: vmlinux.lds.S: add missing PAGE_ALIGNED_DATA() section
> MIPS: vmlinux.lds.S: add ".gnu.attributes" to DISCARDS
> MIPS: properly stop .eh_frame generation
Well, GNU fails to build VDSO with this patch... Sorry, sending
v4 now.
> MIPS: vmlinux.lds.S: catch bad .rel.dyn at link time
> MIPS: vmlinux.lds.S: explicitly declare .got table
> vmlinux.lds.h: catch compound literals into data and BSS
> MIPS: select ARCH_WANT_LD_ORPHAN_WARN
>
> arch/mips/Kconfig | 1 +
> arch/mips/include/asm/asm.h | 18 ++++++++++++++++++
> arch/mips/kernel/vmlinux.lds.S | 15 ++++++++++++++-
> include/asm-generic/vmlinux.lds.h | 6 +++---
> 4 files changed, 36 insertions(+), 4 deletions(-)
>
> --
> 2.30.0
Al