diff options
author | Max Filippov <jcmvbkbc@gmail.com> | 2018-12-20 06:48:37 +0300 |
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committer | Max Filippov <jcmvbkbc@gmail.com> | 2018-12-21 01:44:38 +0300 |
commit | 64711f9a47d4defa90417f5e8db8ed0060bc3275 (patch) | |
tree | 78a9fbb468c6b667ea99b57e6563689792b285d3 /arch/xtensa/kernel | |
parent | af5395c214c15c18de3decf2229373a8c88c4fde (diff) | |
download | linux-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/Makefile | 1 | ||||
-rw-r--r-- | arch/xtensa/kernel/jump_label.c | 99 |
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 */ |