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Arnd reported some false positive warnings with GCC 7: drivers/hid/wacom_wac.o: warning: objtool: wacom_bpt3_touch()+0x2a5: stack state mismatch: cfa1=7+8 cfa2=6+16 drivers/iio/adc/vf610_adc.o: warning: objtool: vf610_adc_calculate_rates() falls through to next function vf610_adc_sample_set() drivers/pwm/pwm-hibvt.o: warning: objtool: hibvt_pwm_get_state() falls through to next function hibvt_pwm_remove() drivers/pwm/pwm-mediatek.o: warning: objtool: mtk_pwm_config() falls through to next function mtk_pwm_enable() drivers/spi/spi-bcm2835.o: warning: objtool: .text: unexpected end of section drivers/spi/spi-bcm2835aux.o: warning: objtool: .text: unexpected end of section drivers/watchdog/digicolor_wdt.o: warning: objtool: dc_wdt_get_timeleft() falls through to next function dc_wdt_restart() When GCC 7 detects a potential divide-by-zero condition, it sometimes inserts a UD2 instruction for the case where the divisor is zero, instead of letting the hardware trap on the divide instruction. Objtool doesn't consider UD2 to be fatal unless it's annotated with unreachable(). So it considers the GCC-generated UD2 to be non-fatal, and it tries to follow the control flow past the UD2 and gets confused. Previously, objtool *did* assume UD2 was always a dead end. That changed with the following commit:d1091c7fa3("objtool: Improve detection of BUG() and other dead ends") The motivation behind that change was that Peter was planning on using UD2 for __WARN(), which is *not* a dead end. However, it turns out that some emulators rely on UD2 being fatal, so he ended up using 'ud0' instead:9a93848fe7("x86/debug: Implement __WARN() using UD0") For GCC 4.5+, it should be safe to go back to the previous assumption that UD2 is fatal, even when it's not annotated with unreachable(). But for pre-4.5 versions of GCC, the unreachable() macro isn't supported, so such cases of UD2 need to be explicitly annotated as reachable. Reported-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes:d1091c7fa3("objtool: Improve detection of BUG() and other dead ends") Link: http://lkml.kernel.org/r/e57fa9dfede25f79487da8126ee9cdf7b856db65.1501188854.git.jpoimboe@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
83 lines
1.9 KiB
C
83 lines
1.9 KiB
C
/*
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* Copyright (C) 2015 Josh Poimboeuf <jpoimboe@redhat.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef _ARCH_H
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#define _ARCH_H
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#include <stdbool.h>
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#include <linux/list.h>
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#include "elf.h"
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#include "cfi.h"
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#define INSN_JUMP_CONDITIONAL 1
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#define INSN_JUMP_UNCONDITIONAL 2
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#define INSN_JUMP_DYNAMIC 3
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#define INSN_CALL 4
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#define INSN_CALL_DYNAMIC 5
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#define INSN_RETURN 6
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#define INSN_CONTEXT_SWITCH 7
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#define INSN_STACK 8
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#define INSN_BUG 9
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#define INSN_NOP 10
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#define INSN_OTHER 11
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#define INSN_LAST INSN_OTHER
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enum op_dest_type {
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OP_DEST_REG,
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OP_DEST_REG_INDIRECT,
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OP_DEST_MEM,
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OP_DEST_PUSH,
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OP_DEST_LEAVE,
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};
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struct op_dest {
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enum op_dest_type type;
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unsigned char reg;
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int offset;
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};
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enum op_src_type {
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OP_SRC_REG,
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OP_SRC_REG_INDIRECT,
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OP_SRC_CONST,
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OP_SRC_POP,
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OP_SRC_ADD,
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OP_SRC_AND,
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};
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struct op_src {
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enum op_src_type type;
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unsigned char reg;
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int offset;
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};
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struct stack_op {
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struct op_dest dest;
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struct op_src src;
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};
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void arch_initial_func_cfi_state(struct cfi_state *state);
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int arch_decode_instruction(struct elf *elf, struct section *sec,
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unsigned long offset, unsigned int maxlen,
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unsigned int *len, unsigned char *type,
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unsigned long *immediate, struct stack_op *op);
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bool arch_callee_saved_reg(unsigned char reg);
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#endif /* _ARCH_H */
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