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commit8fd4ddda2fupstream. System.map shows that vmlinux contains several instances of __static_call_return0(): c0004fc0 t __static_call_return0 c0011518 t __static_call_return0 c00d8160 t __static_call_return0 arch_static_call_transform() uses the middle one to check whether we are setting a call to __static_call_return0 or not: c0011520 <arch_static_call_transform>: c0011520: 3d 20 c0 01 lis r9,-16383 <== r9 = 0xc001 << 16 c0011524: 39 29 15 18 addi r9,r9,5400 <== r9 += 0x1518 c0011528: 7c 05 48 00 cmpw r5,r9 <== r9 has value 0xc0011518 here So if static_call_update() is called with one of the other instances of __static_call_return0(), arch_static_call_transform() won't recognise it. In order to work properly, global single instance of __static_call_return0() is required. Fixes:3f2a8fc4b1("static_call/x86: Add __static_call_return0()") Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Link: https://lkml.kernel.org/r/30821468a0e7d28251954b578e5051dc09300d04.1647258493.git.christophe.leroy@csgroup.eu Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
8 lines
158 B
C
8 lines
158 B
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/static_call.h>
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long __static_call_return0(void)
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{
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return 0;
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}
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EXPORT_SYMBOL_GPL(__static_call_return0);
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