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Date: Sun, 07 Jan 2018 00:10:24 +0000
From: David Woodhouse <dwmw2@...radead.org>
To: Andi Kleen <ak@...ux.intel.com>,
"Van De Ven, Arjan" <arjan.van.de.ven@...el.com>
Cc: Paul Turner <pjt@...gle.com>, LKML <linux-kernel@...r.kernel.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Greg Kroah-Hartman <gregkh@...ux-foundation.org>,
Tim Chen <tim.c.chen@...ux.intel.com>,
Dave Hansen <dave.hansen@...el.com>, tglx@...utronix.de,
Kees Cook <keescook@...gle.com>,
Rik van Riel <riel@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Andy Lutomirski <luto@...capital.net>,
Jiri Kosina <jikos@...nel.org>, gnomes@...rguk.ukuu.org.uk
Subject: [RFC PATCH 13/12] Retpoline vs. CONFIG_TRIM_UNUSED_SYMBOLS
Arjan pointed out that CONFIG_TRIM_UNUSED_SYMBOLS *really* doesn't like
the dot in the symbols that GCC uses for the thunks.
This seems to work, although my eyes are bleeding just a little bit.
Given this, and the hack we already needed for MODVERSIONS, I wonder if
a better approach might be to export the thunks using underscores in
place of the dots, which is a relatively simple abuse of
__EXPORT_SYMBOL(__x86_indirect_thunk_foo,__x86.indirect_thunk.foo,),
and then have a hack either when generating or loading modules to do
the same replacement.
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index ccb117a4588b..64d7a45ea954 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -8,7 +8,13 @@
#include <asm/export.h>
#include <asm/nospec-branch.h>
-.macro THUNK reg
+#ifdef CONFIG_TRIM_UNUSED_KSYMS
+#define EXPORT_REG(reg) __is_defined(__KSYM___x86_indirect_thunk_ ## reg)
+#else
+#define EXPORT_REG(reg) 1
+#endif
+
+.macro THUNK reg export
.section .text.__x86.indirect_thunk.\reg
ENTRY(__x86.indirect_thunk.\reg)
@@ -16,15 +22,33 @@ ENTRY(__x86.indirect_thunk.\reg)
NOSPEC_JMP %\reg
CFI_ENDPROC
ENDPROC(__x86.indirect_thunk.\reg)
-EXPORT_SYMBOL(__x86.indirect_thunk.\reg)
+
+.if \export
+ EXPORT_SYMBOL_FORCE(__x86.indirect_thunk.\reg)
+.endif
.endm
-#ifdef CONFIG_64BIT
-.irp reg rax rbx rcx rdx rsi rdi rbp r8 r9 r10 r11 r12 r13 r14 r15
- THUNK \reg
-.endr
+#ifdef __KSYM_DEPS__
+#define GENERATE_THUNK(reg) EXPORT_SYMBOL(__x86.indirect_thunk. ## reg)
#else
-.irp reg eax ebx ecx edx esi edi ebp
- THUNK \reg
-.endr
+#define GENERATE_THUNK(reg) THUNK reg EXPORT_REG(reg)
+#endif
+
+GENERATE_THUNK(_ASM_AX)
+GENERATE_THUNK(_ASM_BX)
+GENERATE_THUNK(_ASM_CX)
+GENERATE_THUNK(_ASM_DX)
+GENERATE_THUNK(_ASM_SI)
+GENERATE_THUNK(_ASM_DI)
+GENERATE_THUNK(_ASM_BP)
+GENERATE_THUNK(_ASM_SP)
+#ifdef CONFIG_64BIT
+GENERATE_THUNK(r8)
+GENERATE_THUNK(r9)
+GENERATE_THUNK(r10)
+GENERATE_THUNK(r11)
+GENERATE_THUNK(r12)
+GENERATE_THUNK(r13)
+GENERATE_THUNK(r14)
+GENERATE_THUNK(r15)
#endif
diff --git a/include/asm-generic/export.h b/include/asm-generic/export.h
index 719db1968d81..b13bb65e2530 100644
--- a/include/asm-generic/export.h
+++ b/include/asm-generic/export.h
@@ -63,33 +63,33 @@ KSYM(__kcrctab_\name):
#if defined(__KSYM_DEPS__)
-#define __EXPORT_SYMBOL(sym, val, sec) === __KSYM_##sym ===
+#define __EXPORT_SYMBOL(sym, val, sec, force) === __KSYM_##sym ===
#elif defined(CONFIG_TRIM_UNUSED_KSYMS)
#include <linux/kconfig.h>
#include <generated/autoksyms.h>
-#define __EXPORT_SYMBOL(sym, val, sec) \
- __cond_export_sym(sym, val, sec, __is_defined(__KSYM_##sym))
+#define __EXPORT_SYMBOL(sym, val, sec, force) \
+ __cond_export_sym(sym, val, sec, __or(force, __is_defined(__KSYM_##sym)))
#define __cond_export_sym(sym, val, sec, conf) \
___cond_export_sym(sym, val, sec, conf)
#define ___cond_export_sym(sym, val, sec, enabled) \
__cond_export_sym_##enabled(sym, val, sec)
#define __cond_export_sym_1(sym, val, sec) ___EXPORT_SYMBOL sym, val, sec
#define __cond_export_sym_0(sym, val, sec) /* nothing */
-
#else
-#define __EXPORT_SYMBOL(sym, val, sec) ___EXPORT_SYMBOL sym, val, sec
+#define __EXPORT_SYMBOL(sym, val, sec, force) ___EXPORT_SYMBOL sym, val, sec
#endif
#define EXPORT_SYMBOL(name) \
- __EXPORT_SYMBOL(name, KSYM_FUNC(KSYM(name)),)
+ __EXPORT_SYMBOL(name, KSYM_FUNC(KSYM(name)), , 0)
#define EXPORT_SYMBOL_GPL(name) \
- __EXPORT_SYMBOL(name, KSYM_FUNC(KSYM(name)), _gpl)
+ __EXPORT_SYMBOL(name, KSYM_FUNC(KSYM(name)), _gpl, 0)
#define EXPORT_DATA_SYMBOL(name) \
- __EXPORT_SYMBOL(name, KSYM(name),)
+ __EXPORT_SYMBOL(name, KSYM(name), , 0)
#define EXPORT_DATA_SYMBOL_GPL(name) \
- __EXPORT_SYMBOL(name, KSYM(name),_gpl)
-
+ __EXPORT_SYMBOL(name, KSYM(name), _gpl, 0)
+#define EXPORT_SYMBOL_FORCE(name) \
+ __EXPORT_SYMBOL(name, KSYM(name), , 1)
#endif
diff --git a/scripts/adjust_autoksyms.sh b/scripts/adjust_autoksyms.sh
index 513da1a4a2da..991cd136291b 100755
--- a/scripts/adjust_autoksyms.sh
+++ b/scripts/adjust_autoksyms.sh
@@ -60,7 +60,7 @@ cat > "$new_ksyms_file" << EOT
EOT
[ "$(ls -A "$MODVERDIR")" ] &&
-sed -ns -e '3{s/ /\n/g;/^$/!p;}' "$MODVERDIR"/*.mod | sort -u |
+sed -ns -e '3{s/ /\n/g;/^$/!p;}' "$MODVERDIR"/*.mod | sort -u | tr . _ |
while read sym; do
if [ -n "$CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX" ]; then
sym="${sym#_}"
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