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1e688dd2a3
Using asm goto in __WARN_FLAGS() and WARN_ON() allows more
flexibility to GCC.
For that add an entry to the exception table so that
program_check_exception() knowns where to resume execution
after a WARNING.
Here are two exemples. The first one is done on PPC32 (which
benefits from the previous patch), the second is on PPC64.
unsigned long test(struct pt_regs *regs)
{
int ret;
WARN_ON(regs->msr & MSR_PR);
return regs->gpr[3];
}
unsigned long test9w(unsigned long a, unsigned long b)
{
if (WARN_ON(!b))
return 0;
return a / b;
}
Before the patch:
000003a8 <test>:
3a8: 81 23 00 84 lwz r9,132(r3)
3ac: 71 29 40 00 andi. r9,r9,16384
3b0: 40 82 00 0c bne 3bc <test+0x14>
3b4: 80 63 00 0c lwz r3,12(r3)
3b8: 4e 80 00 20 blr
3bc: 0f e0 00 00 twui r0,0
3c0: 80 63 00 0c lwz r3,12(r3)
3c4: 4e 80 00 20 blr
0000000000000bf0 <.test9w>:
bf0: 7c 89 00 74 cntlzd r9,r4
bf4: 79 29 d1 82 rldicl r9,r9,58,6
bf8: 0b 09 00 00 tdnei r9,0
bfc: 2c 24 00 00 cmpdi r4,0
c00: 41 82 00 0c beq c0c <.test9w+0x1c>
c04: 7c 63 23 92 divdu r3,r3,r4
c08: 4e 80 00 20 blr
c0c: 38 60 00 00 li r3,0
c10: 4e 80 00 20 blr
After the patch:
000003a8 <test>:
3a8: 81 23 00 84 lwz r9,132(r3)
3ac: 71 29 40 00 andi. r9,r9,16384
3b0: 40 82 00 0c bne 3bc <test+0x14>
3b4: 80 63 00 0c lwz r3,12(r3)
3b8: 4e 80 00 20 blr
3bc: 0f e0 00 00 twui r0,0
0000000000000c50 <.test9w>:
c50: 7c 89 00 74 cntlzd r9,r4
c54: 79 29 d1 82 rldicl r9,r9,58,6
c58: 0b 09 00 00 tdnei r9,0
c5c: 7c 63 23 92 divdu r3,r3,r4
c60: 4e 80 00 20 blr
c70: 38 60 00 00 li r3,0
c74: 4e 80 00 20 blr
In the first exemple, we see GCC doesn't need to duplicate what
happens after the trap.
In the second exemple, we see that GCC doesn't need to emit a test
and a branch in the likely path in addition to the trap.
We've got some WARN_ON() in .softirqentry.text section so it needs
to be added in the OTHER_TEXT_SECTIONS in modpost.c
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/389962b1b702e3c78d169e59bcfac56282889173.1618331882.git.christophe.leroy@csgroup.eu
166 lines
4.0 KiB
C
166 lines
4.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_POWERPC_BUG_H
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#define _ASM_POWERPC_BUG_H
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#ifdef __KERNEL__
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#include <asm/asm-compat.h>
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#include <asm/extable.h>
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#ifdef CONFIG_BUG
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#ifdef __ASSEMBLY__
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#include <asm/asm-offsets.h>
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#ifdef CONFIG_DEBUG_BUGVERBOSE
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.macro EMIT_BUG_ENTRY addr,file,line,flags
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.section __bug_table,"aw"
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5001: .4byte \addr - 5001b, 5002f - 5001b
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.short \line, \flags
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.org 5001b+BUG_ENTRY_SIZE
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.previous
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.section .rodata,"a"
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5002: .asciz "\file"
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.previous
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.endm
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#else
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.macro EMIT_BUG_ENTRY addr,file,line,flags
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.section __bug_table,"aw"
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5001: .4byte \addr - 5001b
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.short \flags
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.org 5001b+BUG_ENTRY_SIZE
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.previous
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.endm
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#endif /* verbose */
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.macro EMIT_WARN_ENTRY addr,file,line,flags
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EX_TABLE(\addr,\addr+4)
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EMIT_BUG_ENTRY \addr,\file,\line,\flags
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.endm
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#else /* !__ASSEMBLY__ */
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/* _EMIT_BUG_ENTRY expects args %0,%1,%2,%3 to be FILE, LINE, flags and
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sizeof(struct bug_entry), respectively */
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#ifdef CONFIG_DEBUG_BUGVERBOSE
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#define _EMIT_BUG_ENTRY \
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".section __bug_table,\"aw\"\n" \
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"2:\t.4byte 1b - 2b, %0 - 2b\n" \
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"\t.short %1, %2\n" \
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".org 2b+%3\n" \
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".previous\n"
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#else
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#define _EMIT_BUG_ENTRY \
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".section __bug_table,\"aw\"\n" \
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"2:\t.4byte 1b - 2b\n" \
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"\t.short %2\n" \
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".org 2b+%3\n" \
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".previous\n"
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#endif
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#define BUG_ENTRY(insn, flags, ...) \
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__asm__ __volatile__( \
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"1: " insn "\n" \
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_EMIT_BUG_ENTRY \
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: : "i" (__FILE__), "i" (__LINE__), \
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"i" (flags), \
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"i" (sizeof(struct bug_entry)), \
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##__VA_ARGS__)
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#define WARN_ENTRY(insn, flags, label, ...) \
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asm_volatile_goto( \
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"1: " insn "\n" \
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EX_TABLE(1b, %l[label]) \
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_EMIT_BUG_ENTRY \
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: : "i" (__FILE__), "i" (__LINE__), \
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"i" (flags), \
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"i" (sizeof(struct bug_entry)), \
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##__VA_ARGS__ : : label)
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/*
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* BUG_ON() and WARN_ON() do their best to cooperate with compile-time
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* optimisations. However depending on the complexity of the condition
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* some compiler versions may not produce optimal results.
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*/
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#define BUG() do { \
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BUG_ENTRY("twi 31, 0, 0", 0); \
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unreachable(); \
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} while (0)
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#define HAVE_ARCH_BUG
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#define __WARN_FLAGS(flags) do { \
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__label__ __label_warn_on; \
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\
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WARN_ENTRY("twi 31, 0, 0", BUGFLAG_WARNING | (flags), __label_warn_on); \
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unreachable(); \
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\
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__label_warn_on: \
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break; \
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} while (0)
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#ifdef CONFIG_PPC64
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#define BUG_ON(x) do { \
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if (__builtin_constant_p(x)) { \
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if (x) \
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BUG(); \
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} else { \
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BUG_ENTRY(PPC_TLNEI " %4, 0", 0, "r" ((__force long)(x))); \
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} \
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} while (0)
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#define WARN_ON(x) ({ \
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bool __ret_warn_on = false; \
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do { \
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if (__builtin_constant_p((x))) { \
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if (!(x)) \
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break; \
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__WARN(); \
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__ret_warn_on = true; \
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} else { \
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__label__ __label_warn_on; \
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\
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WARN_ENTRY(PPC_TLNEI " %4, 0", \
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BUGFLAG_WARNING | BUGFLAG_TAINT(TAINT_WARN), \
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__label_warn_on, "r" (x)); \
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break; \
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__label_warn_on: \
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__ret_warn_on = true; \
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} \
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} while (0); \
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unlikely(__ret_warn_on); \
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})
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#define HAVE_ARCH_BUG_ON
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#define HAVE_ARCH_WARN_ON
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#endif
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#endif /* __ASSEMBLY __ */
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#else
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#ifdef __ASSEMBLY__
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.macro EMIT_BUG_ENTRY addr,file,line,flags
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.endm
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.macro EMIT_WARN_ENTRY addr,file,line,flags
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.endm
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#else /* !__ASSEMBLY__ */
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#define _EMIT_BUG_ENTRY
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#define _EMIT_WARN_ENTRY
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#endif
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#endif /* CONFIG_BUG */
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#include <asm-generic/bug.h>
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#ifndef __ASSEMBLY__
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struct pt_regs;
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void hash__do_page_fault(struct pt_regs *);
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void bad_page_fault(struct pt_regs *, int);
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extern void _exception(int, struct pt_regs *, int, unsigned long);
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extern void _exception_pkey(struct pt_regs *, unsigned long, int);
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extern void die(const char *, struct pt_regs *, long);
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void die_mce(const char *str, struct pt_regs *regs, long err);
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extern bool die_will_crash(void);
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extern void panic_flush_kmsg_start(void);
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extern void panic_flush_kmsg_end(void);
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#endif /* !__ASSEMBLY__ */
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#endif /* __KERNEL__ */
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#endif /* _ASM_POWERPC_BUG_H */
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