Thread (9 messages) flat view 9 messages, 3 authors, 2016-02-16

[PATCH 1/2] ARM: mm: DEBUG_RODATA makes no sense with XIP_KERNEL

From: Kees Cook <hidden>
Date: 2016-02-16 18:41:14
Also in: lkml

On Tue, Feb 16, 2016 at 8:03 AM, Arnd Bergmann [off-list ref] wrote:
When CONFIG_DEBUG_ALIGN_RODATA is set, we get a link error:

arch/arm/mm/built-in.o:(.data+0x4bc): undefined reference to `__start_rodata_section_aligned'

However, this combination is useless, as XIP_KERNEL implies that all the
RODATA is already marked readonly, so both CONFIG_DEBUG_RODATA and
CONFIG_DEBUG_ALIGN_RODATA (which depends on the other) are not
needed with XIP_KERNEL, and this patches enforces that using a Kconfig
dependency.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 25362dc496ed ("ARM: 8501/1: mm: flip priority of CONFIG_DEBUG_RODATA")
Oh, hm, I didn't see this before sending my fix for the rodata start issue.
quoted hunk ↗ jump to hunk
---
 arch/arm/mm/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index fbf2296388ce..8894045caba9 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -1039,7 +1039,7 @@ config ARCH_SUPPORTS_BIG_ENDIAN

 config DEBUG_RODATA
        bool "Make kernel text and rodata read-only"
-       depends on MMU
+       depends on MMU && !XIP_KERNEL
If we do this, we need to probably clean up the xip linker script to
remove all the references to DEBUG_*RODATA too.

-Kees
        default y if CPU_V7
        help
          If this is set, kernel text and rodata memory will be made
--
2.7.0


-- 
Kees Cook
Chrome OS & Brillo Security
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