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authorThomas Gleixner <tglx@linutronix.de>2020-03-10 00:47:17 +0300
committerThomas Gleixner <tglx@linutronix.de>2020-05-19 16:47:20 +0300
commit6553896666433e7efec589838b400a2a652b3ffa (patch)
treec9dfa95f4349ad1e6cbc42f5e9e824c63e8c3011 /include/asm-generic
parent2ef96a5bb12be62ef75b5828c0aab838ebb29cb8 (diff)
downloadlinux-6553896666433e7efec589838b400a2a652b3ffa.tar.xz
vmlinux.lds.h: Create section for protection against instrumentation
Some code pathes, especially the low level entry code, must be protected against instrumentation for various reasons: - Low level entry code can be a fragile beast, especially on x86. - With NO_HZ_FULL RCU state needs to be established before using it. Having a dedicated section for such code allows to validate with tooling that no unsafe functions are invoked. Add the .noinstr.text section and the noinstr attribute to mark functions. noinstr implies notrace. Kprobes will gain a section check later. Provide also a set of markers: instrumentation_begin()/end() These are used to mark code inside a noinstr function which calls into regular instrumentable text section as safe. The instrumentation markers are only active when CONFIG_DEBUG_ENTRY is enabled as the end marker emits a NOP to prevent the compiler from merging the annotation points. This means the objtool verification requires a kernel compiled with this option. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com> Acked-by: Peter Zijlstra <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200505134100.075416272@linutronix.de
Diffstat (limited to 'include/asm-generic')
-rw-r--r--include/asm-generic/sections.h3
-rw-r--r--include/asm-generic/vmlinux.lds.h10
2 files changed, 13 insertions, 0 deletions
diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
index d1779d442aa5..66397ed10acb 100644
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -53,6 +53,9 @@ extern char __ctors_start[], __ctors_end[];
/* Start and end of .opd section - used for function descriptors. */
extern char __start_opd[], __end_opd[];
+/* Start and end of instrumentation protected text section */
+extern char __noinstr_text_start[], __noinstr_text_end[];
+
extern __visible const void __nosave_begin, __nosave_end;
/* Function descriptor handling (if any). Override in asm/sections.h */
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 71e387a5fe90..db600ef218d7 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -541,6 +541,15 @@
__end_rodata = .;
/*
+ * Non-instrumentable text section
+ */
+#define NOINSTR_TEXT \
+ ALIGN_FUNCTION(); \
+ __noinstr_text_start = .; \
+ *(.noinstr.text) \
+ __noinstr_text_end = .;
+
+/*
* .text section. Map to function alignment to avoid address changes
* during second ld run in second ld pass when generating System.map
*
@@ -551,6 +560,7 @@
#define TEXT_TEXT \
ALIGN_FUNCTION(); \
*(.text.hot TEXT_MAIN .text.fixup .text.unlikely) \
+ NOINSTR_TEXT \
*(.text..refcount) \
*(.ref.text) \
MEM_KEEP(init.text*) \