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
45 lines
1.2 KiB
C
45 lines
1.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
#ifndef _ARCH_POWERPC_EXTABLE_H
|
|
#define _ARCH_POWERPC_EXTABLE_H
|
|
|
|
/*
|
|
* The exception table consists of pairs of relative addresses: the first is
|
|
* the address of an instruction that is allowed to fault, and the second is
|
|
* the address at which the program should continue. No registers are
|
|
* modified, so it is entirely up to the continuation code to figure out what
|
|
* to do.
|
|
*
|
|
* All the routines below use bits of fixup code that are out of line with the
|
|
* main instruction path. This means when everything is well, we don't even
|
|
* have to jump over them. Further, they do not intrude on our cache or tlb
|
|
* entries.
|
|
*/
|
|
|
|
#define ARCH_HAS_RELATIVE_EXTABLE
|
|
|
|
#ifndef __ASSEMBLY__
|
|
|
|
struct exception_table_entry {
|
|
int insn;
|
|
int fixup;
|
|
};
|
|
|
|
static inline unsigned long extable_fixup(const struct exception_table_entry *x)
|
|
{
|
|
return (unsigned long)&x->fixup + x->fixup;
|
|
}
|
|
|
|
#endif
|
|
|
|
/*
|
|
* Helper macro for exception table entries
|
|
*/
|
|
#define EX_TABLE(_fault, _target) \
|
|
stringify_in_c(.section __ex_table,"a";)\
|
|
stringify_in_c(.balign 4;) \
|
|
stringify_in_c(.long (_fault) - . ;) \
|
|
stringify_in_c(.long (_target) - . ;) \
|
|
stringify_in_c(.previous)
|
|
|
|
#endif
|