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s390/alternatives: Convert runtime sanity check into compile time check

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__apply_alternatives() contains a runtime check which verifies that the
size of the to be patched code area is even. Convert this to a compile time
check using a similar ".org" trick, which is already used to verify that
old and new code areas have the same size.

Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2024-05-13 12:16:20 +02:00 committed by Alexander Gordeev
parent effb835726
commit 207ddb9189
3 changed files with 2 additions and 7 deletions
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1
arch/s390/include/asm/alternative-asm.h
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@ -15,6 +15,7 @@
.long \alt_start - .
.word \feature
.byte \orig_end - \orig_start
.org . - ( \orig_end - \orig_start ) & 1
.org . - ( \orig_end - \orig_start ) + ( \alt_end - \alt_start )
.org . - ( \alt_end - \alt_start ) + ( \orig_end - \orig_start )
.endm

1
arch/s390/include/asm/alternative.h
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@ -53,6 +53,7 @@ void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
"\t.long " b_altinstr(num)"b - .\n" /* alt instruction */ \
"\t.word " __stringify(facility) "\n" /* facility bit */ \
"\t.byte " oldinstr_len "\n" /* instruction len */ \
"\t.org . - (" oldinstr_len ") & 1\n" \
"\t.org . - (" oldinstr_len ") + (" altinstr_len(num) ")\n" \
"\t.org . - (" altinstr_len(num) ") + (" oldinstr_len ")\n"

7
arch/s390/kernel/alternative.c
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@ -33,13 +33,6 @@ static void __init_or_module __apply_alternatives(struct alt_instr *start,
if (!__test_facility(a->facility, alt_stfle_fac_list))
continue;
if (unlikely(a->instrlen % 2)) {
WARN_ONCE(1, "cpu alternatives instructions length is "
"odd, skipping patching\n");
continue;
}
s390_kernel_write(instr, replacement, a->instrlen);
}
}