From: Peter Zijlstra <peterz@infradead.org>
To: x86@kernel.org
Cc: linux-kernel@vger.kernel.org, peterz@infradead.org,
jpoimboe@redhat.com, mark.rutland@arm.com, dvyukov@google.com,
seanjc@google.com, pbonzini@redhat.com, mbenes@suse.cz
Subject: [PATCH 20/22] x86,word-at-a-time: Remove .fixup usage
Date: Fri, 05 Nov 2021 18:10:43 +0100 [thread overview]
Message-ID: <20211105171821.654356149@infradead.org> (raw)
In-Reply-To: 20211105171023.989862879@infradead.org
Rewrite load_unaligned_zeropad() to not require .fixup text.
This is easiest done using asm_goto_output, where we can stick a C
label in the exception table entry. The fallback version isn't nearly
so nice but should work.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/include/asm/word-at-a-time.h | 67 ++++++++++++++++++++++++----------
1 file changed, 48 insertions(+), 19 deletions(-)
--- a/arch/x86/include/asm/word-at-a-time.h
+++ b/arch/x86/include/asm/word-at-a-time.h
@@ -77,30 +77,59 @@ static inline unsigned long find_zero(un
* and the next page not being mapped, take the exception and
* return zeroes in the non-existing part.
*/
+#ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
+
+static inline unsigned long load_unaligned_zeropad(const void *addr)
+{
+ unsigned long offset, data;
+ unsigned long ret;
+
+ asm_volatile_goto(
+ "1: mov %[mem], %[ret]\n"
+
+ _ASM_EXTABLE(1b, %l[do_exception])
+
+ : [ret] "=&r" (ret)
+ : [mem] "m" (*(unsigned long *)addr)
+ : : do_exception);
+
+out:
+ return ret;
+
+do_exception: __cold;
+
+ offset = (unsigned long)addr & (sizeof(long) - 1);
+ addr = (void *)((unsigned long)addr & ~(sizeof(long) - 1));
+ data = *(unsigned long *)addr;
+ ret = data >> offset * 8;
+ goto out;
+}
+
+#else /* !CONFIG_CC_HAS_ASM_GOTO_OUTPUT */
+
static inline unsigned long load_unaligned_zeropad(const void *addr)
{
- unsigned long ret, dummy;
+ unsigned long offset, data;
+ unsigned long ret, err = 0;
- asm(
- "1:\tmov %2,%0\n"
+ asm( "1: mov %[mem], %[ret]\n"
"2:\n"
- ".section .fixup,\"ax\"\n"
- "3:\t"
- "lea %2,%1\n\t"
- "and %3,%1\n\t"
- "mov (%1),%0\n\t"
- "leal %2,%%ecx\n\t"
- "andl %4,%%ecx\n\t"
- "shll $3,%%ecx\n\t"
- "shr %%cl,%0\n\t"
- "jmp 2b\n"
- ".previous\n"
- _ASM_EXTABLE(1b, 3b)
- :"=&r" (ret),"=&c" (dummy)
- :"m" (*(unsigned long *)addr),
- "i" (-sizeof(unsigned long)),
- "i" (sizeof(unsigned long)-1));
+
+ _ASM_EXTABLE_FAULT(1b, 2b)
+
+ : [ret] "=&r" (ret), "+a" (err)
+ : [mem] "m" (*(unsigned long *)addr));
+
+ if (unlikely(err)) {
+ offset = (unsigned long)addr & (sizeof(long) - 1);
+ addr = (void *)((unsigned long)addr & ~(sizeof(long) - 1));
+ data = *(unsigned long *)addr;
+ ret = data >> offset * 8;
+ }
+
return ret;
}
+#endif /* CONFIG_CC_HAS_ASM_GOTO_OUTPUT */
+
#endif /* _ASM_WORD_AT_A_TIME_H */
next prev parent reply other threads:[~2021-11-05 17:20 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-05 17:10 [PATCH 00/22] x86: Remove anonymous out-of-line fixups Peter Zijlstra
2021-11-05 17:10 ` [PATCH 01/22] bitfield.h: Fix "type of reg too small for mask" test Peter Zijlstra
2021-11-05 17:10 ` [PATCH 02/22] x86,mmx_32: Remove .fixup usage Peter Zijlstra
2021-11-05 17:10 ` [PATCH 03/22] x86,copy_user_64: " Peter Zijlstra
2021-11-05 17:10 ` [PATCH 04/22] x86,copy_mc_64: " Peter Zijlstra
2021-11-05 17:10 ` [PATCH 05/22] x86,entry_64: " Peter Zijlstra
2021-11-05 17:10 ` [PATCH 06/22] x86,entry_32: " Peter Zijlstra
2021-11-05 17:10 ` [PATCH 07/22] x86,extable: Extend extable functionality Peter Zijlstra
2021-11-05 17:10 ` [PATCH 08/22] x86,msr: Remove .fixup usage Peter Zijlstra
2021-11-05 17:10 ` [PATCH 09/22] x86,futex: " Peter Zijlstra
2021-11-05 17:10 ` [PATCH 10/22] x86,uaccess: " Peter Zijlstra
2021-11-05 17:10 ` [PATCH 11/22] x86,xen: " Peter Zijlstra
2021-11-05 17:10 ` [PATCH 12/22] x86,fpu: " Peter Zijlstra
2021-11-05 17:10 ` [PATCH 13/22] x86,segment: " Peter Zijlstra
2021-11-05 17:10 ` [PATCH 14/22] x86,vmx: " Peter Zijlstra
2021-11-05 17:10 ` [PATCH 15/22] x86,checksum_32: " Peter Zijlstra
2021-11-05 17:10 ` [PATCH 16/22] x86,sgx: " Peter Zijlstra
2021-11-05 17:10 ` [PATCH 17/22] x86,kvm: " Peter Zijlstra
2021-11-05 17:10 ` [PATCH 18/22] x86,usercopy_32: Simplify __copy_user_intel_nocache() Peter Zijlstra
2021-11-05 17:10 ` [PATCH 19/22] x86,usercopy: Remove .fixup usage Peter Zijlstra
2021-11-05 17:10 ` Peter Zijlstra [this message]
2021-11-05 18:01 ` [PATCH 20/22] x86,word-at-a-time: " Josh Poimboeuf
2021-11-05 18:07 ` Peter Zijlstra
2021-11-08 16:47 ` Josh Poimboeuf
2021-11-08 18:29 ` Peter Zijlstra
2021-11-08 18:53 ` Nick Desaulniers
2021-11-09 8:23 ` Peter Zijlstra
2021-11-09 19:22 ` Nick Desaulniers
2021-11-09 20:59 ` Bill Wendling
2021-11-09 21:21 ` Peter Zijlstra
2021-11-09 21:25 ` Nick Desaulniers
2021-11-09 22:11 ` Peter Zijlstra
2021-11-09 22:15 ` Nick Desaulniers
2021-11-09 21:07 ` Peter Zijlstra
2021-11-10 10:18 ` Peter Zijlstra
2021-11-10 10:46 ` David Laight
2021-11-10 11:09 ` Peter Zijlstra
2021-11-10 12:20 ` David Laight
2021-11-12 1:50 ` Josh Poimboeuf
2021-11-12 9:33 ` Peter Zijlstra
2021-11-13 5:35 ` Josh Poimboeuf
2021-11-15 12:36 ` Miroslav Benes
2021-11-15 13:01 ` Joe Lawrence
2021-11-15 23:40 ` Josh Poimboeuf
2021-11-16 7:25 ` Miroslav Benes
2021-11-15 12:59 ` Miroslav Benes
2021-11-16 21:27 ` Josh Poimboeuf
2021-11-18 7:15 ` Miroslav Benes
2021-11-22 17:46 ` Petr Mladek
2021-11-24 17:42 ` Josh Poimboeuf
2021-11-25 8:18 ` Petr Mladek
2021-11-10 12:14 ` Segher Boessenkool
2021-11-05 17:10 ` [PATCH 21/22] x86: Remove .fixup section Peter Zijlstra
2021-11-05 17:10 ` [PATCH 22/22] objtool: Remove .fixup handling Peter Zijlstra
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