FROMLIST: BACKPORT: kbuild: fix dynamic ftrace with clang LTO
With CONFIG_LTO_CLANG enabled, LLVM IR won't be compiled into object
files until modpost_link. This change postpones calls to recordmcount
until after this step.
In order to exclude ftrace_process_locs from inspection, we add a new
code section .text..ftrace, which we tell recordmcount to ignore, and
a __norecordmcount attribute for moving functions to this section.
Bug: 62093296
Bug: 67506682
Change-Id: Iba2c053968206acf533fadab1eb34a743b5088ee
(am from https://patchwork.kernel.org/patch/10060327/)
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index d1d7d5d..f2d0a7f 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -460,6 +460,7 @@
#define TEXT_TEXT \
ALIGN_FUNCTION(); \
*(.text.hot TEXT_MAIN .text.fixup .text.unlikely) \
+ *(.text..ftrace) \
*(.ref.text) \
MEM_KEEP(init.text) \
MEM_KEEP(exit.text) \
diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index de17999..fd29945 100644
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -15,3 +15,10 @@
* with any version that can compile the kernel
*/
#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
+
+#ifdef CONFIG_LTO_CLANG
+#ifdef CONFIG_FTRACE_MCOUNT_RECORD
+#define __norecordmcount \
+ __attribute__((__section__(".text..ftrace")))
+#endif
+#endif
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 5ce911d..40445d0 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -451,6 +451,10 @@
#define __visible
#endif
+#ifndef __norecordmcount
+#define __norecordmcount
+#endif
+
/*
* Assume alignment of return value.
*/