diff mbox series

[v2,2/2] arm/boot: Warn on orphan section placement

Message ID 20200622204915.2987555-3-keescook@chromium.org (mailing list archive)
State New, archived
Headers show
Series arm: Warn on orphan section placement | expand

Commit Message

Kees Cook June 22, 2020, 8:49 p.m. UTC 
We don't want to depend on the linker's orphan section placement
heuristics as these can vary between linkers, and may change between
versions. All sections need to be explicitly named in the linker
script.

Use common macros for debug sections, discards, and text stubs. Add
discards for unwanted .note, and .rel sections. Finally, enable orphan
section warning.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 arch/arm/boot/compressed/Makefile      |  2 ++
 arch/arm/boot/compressed/vmlinux.lds.S | 17 +++++++----------
 2 files changed, 9 insertions(+), 10 deletions(-)

Comments

Nick Desaulniers June 24, 2020, 12:08 a.m. UTC | #1 
On Mon, Jun 22, 2020 at 1:49 PM Kees Cook <keescook@chromium.org> wrote:
>
> We don't want to depend on the linker's orphan section placement
> heuristics as these can vary between linkers, and may change between
> versions. All sections need to be explicitly named in the linker
> script.
>
> Use common macros for debug sections, discards, and text stubs. Add
> discards for unwanted .note, and .rel sections. Finally, enable orphan
> section warning.
>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  arch/arm/boot/compressed/Makefile      |  2 ++
>  arch/arm/boot/compressed/vmlinux.lds.S | 17 +++++++----------
>  2 files changed, 9 insertions(+), 10 deletions(-)
>
> diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
> index 00602a6fba04..b8a97d81662d 100644
> --- a/arch/arm/boot/compressed/Makefile
> +++ b/arch/arm/boot/compressed/Makefile
> @@ -128,6 +128,8 @@ endif
>  LDFLAGS_vmlinux += --no-undefined
>  # Delete all temporary local symbols
>  LDFLAGS_vmlinux += -X
> +# Report orphan sections
> +LDFLAGS_vmlinux += --orphan-handling=warn
>  # Next argument is a linker script
>  LDFLAGS_vmlinux += -T
>
> diff --git a/arch/arm/boot/compressed/vmlinux.lds.S b/arch/arm/boot/compressed/vmlinux.lds.S
> index 09ac33f52814..c2a8509f876f 100644
> --- a/arch/arm/boot/compressed/vmlinux.lds.S
> +++ b/arch/arm/boot/compressed/vmlinux.lds.S
> @@ -2,6 +2,7 @@
>  /*
>   *  Copyright (C) 2000 Russell King
>   */
> +#include <asm/vmlinux.lds.h>
>
>  #ifdef CONFIG_CPU_ENDIAN_BE8
>  #define ZIMAGE_MAGIC(x) ( (((x) >> 24) & 0x000000ff) | \
> @@ -17,8 +18,11 @@ ENTRY(_start)
>  SECTIONS
>  {
>    /DISCARD/ : {
> +    ARM_COMMON_DISCARD
>      *(.ARM.exidx*)
>      *(.ARM.extab*)
> +    *(.note.*)
> +    *(.rel.*)

.rel.* is the only case I'm curious about.  Why do we want it in
vmlinux, but not the compressed image?  Should `.rel.*` just be part
of ARM_COMMON_DISCARD from the previous patch?

>      /*
>       * Discard any r/w data - this produces a link error if we have any,
>       * which is required for PIC decompression.  Local data generates
> @@ -36,9 +40,7 @@ SECTIONS
>      *(.start)
>      *(.text)
>      *(.text.*)
> -    *(.gnu.warning)
> -    *(.glue_7t)
> -    *(.glue_7)
> +    ARM_STUBS_TEXT
>    }
>    .table : ALIGN(4) {
>      _table_start = .;
> @@ -128,12 +130,7 @@ SECTIONS
>    PROVIDE(__pecoff_data_size = ALIGN(512) - ADDR(.data));
>    PROVIDE(__pecoff_end = ALIGN(512));
>
> -  .stab 0              : { *(.stab) }
> -  .stabstr 0           : { *(.stabstr) }
> -  .stab.excl 0         : { *(.stab.excl) }
> -  .stab.exclstr 0      : { *(.stab.exclstr) }
> -  .stab.index 0                : { *(.stab.index) }
> -  .stab.indexstr 0     : { *(.stab.indexstr) }
> -  .comment 0           : { *(.comment) }
> +  STABS_DEBUG
> +  DWARF_DEBUG
>  }
>  ASSERT(_edata_real == _edata, "error: zImage file size is incorrect");
> --
> 2.25.1
>
diff mbox series

Patch

diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
index 00602a6fba04..b8a97d81662d 100644
--- a/arch/arm/boot/compressed/Makefile
+++ b/arch/arm/boot/compressed/Makefile
@@ -128,6 +128,8 @@  endif
 LDFLAGS_vmlinux += --no-undefined
 # Delete all temporary local symbols
 LDFLAGS_vmlinux += -X
+# Report orphan sections
+LDFLAGS_vmlinux += --orphan-handling=warn
 # Next argument is a linker script
 LDFLAGS_vmlinux += -T
 
diff --git a/arch/arm/boot/compressed/vmlinux.lds.S b/arch/arm/boot/compressed/vmlinux.lds.S
index 09ac33f52814..c2a8509f876f 100644
--- a/arch/arm/boot/compressed/vmlinux.lds.S
+++ b/arch/arm/boot/compressed/vmlinux.lds.S
@@ -2,6 +2,7 @@ 
 /*
  *  Copyright (C) 2000 Russell King
  */
+#include <asm/vmlinux.lds.h>
 
 #ifdef CONFIG_CPU_ENDIAN_BE8
 #define ZIMAGE_MAGIC(x) ( (((x) >> 24) & 0x000000ff) | \
@@ -17,8 +18,11 @@  ENTRY(_start)
 SECTIONS
 {
   /DISCARD/ : {
+    ARM_COMMON_DISCARD
     *(.ARM.exidx*)
     *(.ARM.extab*)
+    *(.note.*)
+    *(.rel.*)
     /*
      * Discard any r/w data - this produces a link error if we have any,
      * which is required for PIC decompression.  Local data generates
@@ -36,9 +40,7 @@  SECTIONS
     *(.start)
     *(.text)
     *(.text.*)
-    *(.gnu.warning)
-    *(.glue_7t)
-    *(.glue_7)
+    ARM_STUBS_TEXT
   }
   .table : ALIGN(4) {
     _table_start = .;
@@ -128,12 +130,7 @@  SECTIONS
   PROVIDE(__pecoff_data_size = ALIGN(512) - ADDR(.data));
   PROVIDE(__pecoff_end = ALIGN(512));
 
-  .stab 0		: { *(.stab) }
-  .stabstr 0		: { *(.stabstr) }
-  .stab.excl 0		: { *(.stab.excl) }
-  .stab.exclstr 0	: { *(.stab.exclstr) }
-  .stab.index 0		: { *(.stab.index) }
-  .stab.indexstr 0	: { *(.stab.indexstr) }
-  .comment 0		: { *(.comment) }
+  STABS_DEBUG
+  DWARF_DEBUG
 }
 ASSERT(_edata_real == _edata, "error: zImage file size is incorrect");