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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
commit2c3c1048746a4622d8c89a29670120dc8fab93c4 (patch)
tree848558de17fb3008cdf4d861b01ac7781903ce39 /arch/x86/include/asm/static_call.h
parentInitial commit. (diff)
downloadlinux-2c3c1048746a4622d8c89a29670120dc8fab93c4.tar.xz
linux-2c3c1048746a4622d8c89a29670120dc8fab93c4.zip
Adding upstream version 6.1.76.upstream/6.1.76
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'arch/x86/include/asm/static_call.h')
-rw-r--r--arch/x86/include/asm/static_call.h68
1 files changed, 68 insertions, 0 deletions
diff --git a/arch/x86/include/asm/static_call.h b/arch/x86/include/asm/static_call.h
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+++ b/arch/x86/include/asm/static_call.h
@@ -0,0 +1,68 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_STATIC_CALL_H
+#define _ASM_STATIC_CALL_H
+
+#include <asm/text-patching.h>
+
+/*
+ * For CONFIG_HAVE_STATIC_CALL_INLINE, this is a temporary trampoline which
+ * uses the current value of the key->func pointer to do an indirect jump to
+ * the function. This trampoline is only used during boot, before the call
+ * sites get patched by static_call_update(). The name of this trampoline has
+ * a magical aspect: objtool uses it to find static call sites so it can create
+ * the .static_call_sites section.
+ *
+ * For CONFIG_HAVE_STATIC_CALL, this is a permanent trampoline which
+ * does a direct jump to the function. The direct jump gets patched by
+ * static_call_update().
+ *
+ * Having the trampoline in a special section forces GCC to emit a JMP.d32 when
+ * it does tail-call optimization on the call; since you cannot compute the
+ * relative displacement across sections.
+ */
+
+/*
+ * The trampoline is 8 bytes and of the general form:
+ *
+ * jmp.d32 \func
+ * ud1 %esp, %ecx
+ *
+ * That trailing #UD provides both a speculation stop and serves as a unique
+ * 3 byte signature identifying static call trampolines. Also see tramp_ud[]
+ * and __static_call_fixup().
+ */
+#define __ARCH_DEFINE_STATIC_CALL_TRAMP(name, insns) \
+ asm(".pushsection .static_call.text, \"ax\" \n" \
+ ".align 4 \n" \
+ ".globl " STATIC_CALL_TRAMP_STR(name) " \n" \
+ STATIC_CALL_TRAMP_STR(name) ": \n" \
+ ANNOTATE_NOENDBR \
+ insns " \n" \
+ ".byte 0x0f, 0xb9, 0xcc \n" \
+ ".type " STATIC_CALL_TRAMP_STR(name) ", @function \n" \
+ ".size " STATIC_CALL_TRAMP_STR(name) ", . - " STATIC_CALL_TRAMP_STR(name) " \n" \
+ ".popsection \n")
+
+#define ARCH_DEFINE_STATIC_CALL_TRAMP(name, func) \
+ __ARCH_DEFINE_STATIC_CALL_TRAMP(name, ".byte 0xe9; .long " #func " - (. + 4)")
+
+#ifdef CONFIG_RETHUNK
+#define ARCH_DEFINE_STATIC_CALL_NULL_TRAMP(name) \
+ __ARCH_DEFINE_STATIC_CALL_TRAMP(name, "jmp __x86_return_thunk")
+#else
+#define ARCH_DEFINE_STATIC_CALL_NULL_TRAMP(name) \
+ __ARCH_DEFINE_STATIC_CALL_TRAMP(name, "ret; int3; nop; nop; nop")
+#endif
+
+#define ARCH_DEFINE_STATIC_CALL_RET0_TRAMP(name) \
+ ARCH_DEFINE_STATIC_CALL_TRAMP(name, __static_call_return0)
+
+#define ARCH_ADD_TRAMP_KEY(name) \
+ asm(".pushsection .static_call_tramp_key, \"a\" \n" \
+ ".long " STATIC_CALL_TRAMP_STR(name) " - . \n" \
+ ".long " STATIC_CALL_KEY_STR(name) " - . \n" \
+ ".popsection \n")
+
+extern bool __static_call_fixup(void *tramp, u8 op, void *dest);
+
+#endif /* _ASM_STATIC_CALL_H */