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authorMax Filippov <jcmvbkbc@gmail.com>2018-12-20 06:48:37 +0300
committerMax Filippov <jcmvbkbc@gmail.com>2018-12-21 01:44:38 +0300
commit64711f9a47d4defa90417f5e8db8ed0060bc3275 (patch)
tree78a9fbb468c6b667ea99b57e6563689792b285d3 /arch/xtensa/kernel
parentaf5395c214c15c18de3decf2229373a8c88c4fde (diff)
downloadlinux-64711f9a47d4defa90417f5e8db8ed0060bc3275.tar.xz
xtensa: implement jump_label support
Use 3-byte 'nop' and 'j' instructions that are always present. Don't let assembler mark a spot right after patchable 'j' instruction as unreachable and later put literals or padding bytes there. Add separate implementations of patch_text for SMP and UP cases, avoiding use of atomics on UP. Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Diffstat (limited to 'arch/xtensa/kernel')
-rw-r--r--arch/xtensa/kernel/Makefile1
-rw-r--r--arch/xtensa/kernel/jump_label.c99
2 files changed, 100 insertions, 0 deletions
diff --git a/arch/xtensa/kernel/Makefile b/arch/xtensa/kernel/Makefile
index 8dff506caf07..6f629027ac7d 100644
--- a/arch/xtensa/kernel/Makefile
+++ b/arch/xtensa/kernel/Makefile
@@ -16,6 +16,7 @@ obj-$(CONFIG_SMP) += smp.o mxhead.o
obj-$(CONFIG_XTENSA_VARIANT_HAVE_PERF_EVENTS) += perf_event.o
obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
obj-$(CONFIG_S32C1I_SELFTEST) += s32c1i_selftest.o
+obj-$(CONFIG_JUMP_LABEL) += jump_label.o
# In the Xtensa architecture, assembly generates literals which must always
# precede the L32R instruction with a relative offset less than 256 kB.
diff --git a/arch/xtensa/kernel/jump_label.c b/arch/xtensa/kernel/jump_label.c
new file mode 100644
index 000000000000..d108f721c116
--- /dev/null
+++ b/arch/xtensa/kernel/jump_label.c
@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2018 Cadence Design Systems Inc.
+
+#include <linux/cpu.h>
+#include <linux/jump_label.h>
+#include <linux/kernel.h>
+#include <linux/memory.h>
+#include <linux/stop_machine.h>
+#include <linux/types.h>
+
+#include <asm/cacheflush.h>
+
+#ifdef HAVE_JUMP_LABEL
+
+#define J_OFFSET_MASK 0x0003ffff
+#define J_SIGN_MASK (~(J_OFFSET_MASK >> 1))
+
+#if defined(__XTENSA_EL__)
+#define J_INSN 0x6
+#define NOP_INSN 0x0020f0
+#elif defined(__XTENSA_EB__)
+#define J_INSN 0x60000000
+#define NOP_INSN 0x0f020000
+#else
+#error Unsupported endianness.
+#endif
+
+struct patch {
+ atomic_t cpu_count;
+ unsigned long addr;
+ size_t sz;
+ const void *data;
+};
+
+static void local_patch_text(unsigned long addr, const void *data, size_t sz)
+{
+ memcpy((void *)addr, data, sz);
+ local_flush_icache_range(addr, addr + sz);
+}
+
+static int patch_text_stop_machine(void *data)
+{
+ struct patch *patch = data;
+
+ if (atomic_inc_return(&patch->cpu_count) == 1) {
+ local_patch_text(patch->addr, patch->data, patch->sz);
+ atomic_inc(&patch->cpu_count);
+ } else {
+ while (atomic_read(&patch->cpu_count) <= num_online_cpus())
+ cpu_relax();
+ __invalidate_icache_range(patch->addr, patch->sz);
+ }
+ return 0;
+}
+
+static void patch_text(unsigned long addr, const void *data, size_t sz)
+{
+ if (IS_ENABLED(CONFIG_SMP)) {
+ struct patch patch = {
+ .cpu_count = ATOMIC_INIT(0),
+ .addr = addr,
+ .sz = sz,
+ .data = data,
+ };
+ stop_machine_cpuslocked(patch_text_stop_machine,
+ &patch, NULL);
+ } else {
+ unsigned long flags;
+
+ local_irq_save(flags);
+ local_patch_text(addr, data, sz);
+ local_irq_restore(flags);
+ }
+}
+
+void arch_jump_label_transform(struct jump_entry *e,
+ enum jump_label_type type)
+{
+ u32 d = (jump_entry_target(e) - (jump_entry_code(e) + 4));
+ u32 insn;
+
+ /* Jump only works within 128K of the J instruction. */
+ BUG_ON(!((d & J_SIGN_MASK) == 0 ||
+ (d & J_SIGN_MASK) == J_SIGN_MASK));
+
+ if (type == JUMP_LABEL_JMP) {
+#if defined(__XTENSA_EL__)
+ insn = ((d & J_OFFSET_MASK) << 6) | J_INSN;
+#elif defined(__XTENSA_EB__)
+ insn = ((d & J_OFFSET_MASK) << 8) | J_INSN;
+#endif
+ } else {
+ insn = NOP_INSN;
+ }
+
+ patch_text(jump_entry_code(e), &insn, JUMP_LABEL_NOP_SIZE);
+}
+
+#endif /* HAVE_JUMP_LABEL */