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The newer gcc toolchain won't link due to a missing builtin: __sync_fetch_and_add. Xen is built with -fno-builtin, so add a patch to implement the one required function. Signed-off-by: Christopher Clark <christopher.w.clark@gmail.com> Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
51 lines
1.9 KiB
Diff
51 lines
1.9 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Christopher Clark <christopher.w.clark@gmail.com>
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Date: Fri, 26 June 2020 16:34:00 -0800
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Subject: [PATCH] xen: implement atomic op to fix arm64 compilation
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Xen's ARM implementation of arch_fetch_and_add since f9cc3cd9
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uses a builtin, despite the build being performed with -fno-builtin.
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With gcc 10.1.0, this now breaks prelinking spinlock.c, so
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implement the one atomic operation that is required with logic
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derived from Linux's atomic_ll_sc.h: ATOMIC_FETCH_OP and comparison with
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the binary produced with and without the patch with gcc 9.2.0.
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Signed-off-by: Christopher Clark <christopher.w.clark@gmail.com>
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diff --git a/xen/include/asm-arm/system.h b/xen/include/asm-arm/system.h
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index e5d062667d..c46dd3ac71 100644
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--- a/xen/include/asm-arm/system.h
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+++ b/xen/include/asm-arm/system.h
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@@ -55,7 +55,32 @@ static inline int local_abort_is_enabled(void)
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return !(flags & PSR_ABT_MASK);
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}
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+#ifdef CONFIG_ARM_64
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+
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+/* see atomic_ll_sc.h: ATOMIC_FETCH_OP(name, mb, acq, rel, cl, op, asm_op, constraint) */
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+static inline int arch_fetch_and_add(unsigned int *ptr, unsigned long i)
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+{
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+ int register lptr asm("x0");
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+ int register result asm("w1");
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+ int register newval asm("w2");
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+ int register status asm("w3");
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+
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+ asm volatile(
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+ " mov %[lptr], %[ptr]\n"
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+ "1: ldxr %w[result], [%[lptr]]\n"
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+ " add %w[newval], %w[result], %w[i]\n"
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+ " stlxr %w[status], %w[newval], [%[lptr]]\n"
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+ " cbnz %w[status], 1b\n"
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+ " dmb ish\n"
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+ : [result] "=&r" (result), [lptr] "=&r" (lptr), [newval] "=&r" (newval), [status] "=&r" (status), [i] "+r" (i), "+Q" (*ptr)
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+ : [ptr] "r" (ptr), "r" (i)
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+ : "memory");
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+
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+ return result;
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+}
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+#else
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#define arch_fetch_and_add(x, v) __sync_fetch_and_add(x, v)
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+#endif
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extern struct vcpu *__context_switch(struct vcpu *prev, struct vcpu *next);
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