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authorJosh Poimboeuf <jpoimboe@redhat.com>2019-06-27 20:50:46 -0500
committerIngo Molnar <mingo@kernel.org>2019-07-09 13:55:46 +0200
commit87b512def792579641499d9bef1d640994ea9c18 (patch)
treebac6ea7c9a3a0822b358931ff7260eecfb9a1f59 /include/linux/compiler.h
parent222a21d29521d144f3dd7a0bc4d4020e448f0126 (diff)
objtool: Add support for C jump tables
Objtool doesn't know how to read C jump tables, so it has to whitelist functions which use them, causing missing ORC unwinder data for such functions, e.g. ___bpf_prog_run(). C jump tables are very similar to GCC switch jump tables, which objtool already knows how to read. So adding support for C jump tables is easy. It just needs to be able to find the tables and distinguish them from other data. To allow the jump tables to be found, create an __annotate_jump_table macro which can be used to annotate them. The annotation is done by placing the jump table in an .rodata..c_jump_table section. The '.rodata' prefix ensures that the data will be placed in the rodata section by the vmlinux linker script. The double periods are part of an existing convention which distinguishes kernel sections from GCC sections. Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Song Liu <songliubraving@fb.com> Cc: Kairui Song <kasong@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Daniel Borkmann <daniel@iogearbox.net> Link: https://lkml.kernel.org/r/0ba2ca30442b16b97165992381ce643dc27b3d1a.1561685471.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'include/linux/compiler.h')
-rw-r--r--include/linux/compiler.h5
1 files changed, 5 insertions, 0 deletions
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 8aaf7cd026b0..f0fd5636fddb 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -116,9 +116,14 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
".pushsection .discard.unreachable\n\t" \
".long 999b - .\n\t" \
".popsection\n\t"
+
+/* Annotate a C jump table to allow objtool to follow the code flow */
+#define __annotate_jump_table __section(".rodata..c_jump_table")
+
#else
#define annotate_reachable()
#define annotate_unreachable()
+#define __annotate_jump_table
#endif
#ifndef ASM_UNREACHABLE