Merge tag 'gcc-plugins-v4.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git...

[cascardo/linux.git] / arch / Kconfig

diff --git a/arch/Kconfig b/arch/Kconfig
index ae80cd2..659bdd0 100644 (file)
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -468,6 +468,27 @@ config CC_STACKPROTECTOR_STRONG
 
 endchoice
 
+config THIN_ARCHIVES
+       bool
+       help
+         Select this if the architecture wants to use thin archives
+         instead of ld -r to create the built-in.o files.
+
+config LD_DEAD_CODE_DATA_ELIMINATION
+       bool
+       help
+         Select this if the architecture wants to do dead code and
+         data elimination with the linker by compiling with
+         -ffunction-sections -fdata-sections and linking with
+         --gc-sections.
+
+         This requires that the arch annotates or otherwise protects
+         its external entry points from being discarded. Linker scripts
+         must also merge .text.*, .data.*, and .bss.* correctly into
+         output sections. Care must be taken not to pull in unrelated
+         sections (e.g., '.text.init'). Typically '.' in section names
+         is used to distinguish them from label names / C identifiers.
+
 config HAVE_ARCH_WITHIN_STACK_FRAMES
        bool
        help
@@ -714,4 +735,38 @@ config ARCH_NO_COHERENT_DMA_MMAP
 config CPU_NO_EFFICIENT_FFS
        def_bool n
 
+config HAVE_ARCH_VMAP_STACK
+       def_bool n
+       help
+         An arch should select this symbol if it can support kernel stacks
+         in vmalloc space.  This means:
+
+         - vmalloc space must be large enough to hold many kernel stacks.
+           This may rule out many 32-bit architectures.
+
+         - Stacks in vmalloc space need to work reliably.  For example, if
+           vmap page tables are created on demand, either this mechanism
+           needs to work while the stack points to a virtual address with
+           unpopulated page tables or arch code (switch_to() and switch_mm(),
+           most likely) needs to ensure that the stack's page table entries
+           are populated before running on a possibly unpopulated stack.
+
+         - If the stack overflows into a guard page, something reasonable
+           should happen.  The definition of "reasonable" is flexible, but
+           instantly rebooting without logging anything would be unfriendly.
+
+config VMAP_STACK
+       default y
+       bool "Use a virtually-mapped stack"
+       depends on HAVE_ARCH_VMAP_STACK && !KASAN
+       ---help---
+         Enable this if you want the use virtually-mapped kernel stacks
+         with guard pages.  This causes kernel stack overflows to be
+         caught immediately rather than causing difficult-to-diagnose
+         corruption.
+
+         This is presently incompatible with KASAN because KASAN expects
+         the stack to map directly to the KASAN shadow map using a formula
+         that is incorrect if the stack is in vmalloc space.
+
 source "kernel/gcov/Kconfig"