Add another ftrace implementation in parallel with mcount-based ftrace
+. Depend on GCC with -fpatchable-function-entry
+. Use 3 nops for stub in module and vmlinux, smaller than old one.
+. Simplify ftrace_regs_caller/ftrace_caller handling, especially
on MIPS O32
+. No adjustment on sp, so callee(the traced function) can get caller's
sp, very friendly to livepatch
Signed-off-by: Huang Pei <huangpei@xxxxxxxxxxx>
---
arch/mips/Kconfig | 2 +
arch/mips/Makefile | 16 ++-
arch/mips/include/asm/ftrace.h | 7 ++
arch/mips/kernel/Makefile | 5 +-
arch/mips/kernel/entry-ftrace.S | 182 +++++++++++++++++++++++++++
arch/mips/kernel/ftrace.c | 215 ++++++++++++++++++++++++++++++++
6 files changed, 422 insertions(+), 5 deletions(-)
create mode 100644 arch/mips/kernel/entry-ftrace.S
create mode 100644 arch/mips/kernel/ftrace.c
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 5741dae35b74..6b96a19a42c2 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -56,6 +56,8 @@ config MIPS
select HAVE_DEBUG_STACKOVERFLOW
select HAVE_DMA_CONTIGUOUS
select HAVE_DYNAMIC_FTRACE
+ select HAVE_DYNAMIC_FTRACE_WITH_REGS \
+ if $(cc-option, -fpatchable-function-entry=3)
select HAVE_EBPF_JIT if 64BIT && !CPU_MICROMIPS && TARGET_ISA_REV >= 2
select HAVE_EXIT_THREAD
select HAVE_FAST_GUP
diff --git a/arch/mips/Makefile b/arch/mips/Makefile
index 0d0f29d662c9..1d6553f0623e 100644
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -56,13 +56,16 @@ ifneq ($(SUBARCH),$(ARCH))
endif
endif
-ifdef CONFIG_FUNCTION_GRAPH_TRACER
- ifndef KBUILD_MCOUNT_RA_ADDRESS
- ifeq ($(call cc-option-yn,-mmcount-ra-address), y)
- cflags-y += -mmcount-ra-address -DKBUILD_MCOUNT_RA_ADDRESS
+ifndef CONFIG_DYNMAIC_FTRACE_WITH_REGS
+ ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ ifndef KBUILD_MCOUNT_RA_ADDRESS
+ ifeq ($(call cc-option-yn,-mmcount-ra-address), y)
+ cflags-y += -mmcount-ra-address -DKBUILD_MCOUNT_RA_ADDRESS
+ endif
endif
endif
endif
+
cflags-y += $(call cc-option, -mno-check-zero-division)
ifdef CONFIG_32BIT
@@ -293,6 +296,11 @@ ifdef CONFIG_64BIT
bootvars-y += ADDR_BITS=64
endif
+ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+ KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY
+ CC_FLAGS_FTRACE := -fpatchable-function-entry=3
+endif
+
# This is required to get dwarf unwinding tables into .debug_frame
# instead of .eh_frame so we don't discard them.
KBUILD_CFLAGS += -fno-asynchronous-unwind-tables
diff --git a/arch/mips/include/asm/ftrace.h b/arch/mips/include/asm/ftrace.h
index b463f2aa5a61..e3b0910486ab 100644
--- a/arch/mips/include/asm/ftrace.h
+++ b/arch/mips/include/asm/ftrace.h
@@ -87,4 +87,11 @@ struct dyn_arch_ftrace {
#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* __ASSEMBLY__ */
#endif /* CONFIG_FUNCTION_TRACER */
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+struct dyn_ftrace;
+int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
+#define ftrace_init_nop ftrace_init_nop
+#endif
+
#endif /* _ASM_MIPS_FTRACE_H */
diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
index 3e7b0ee54cfb..7b07d80aadd5 100644
--- a/arch/mips/kernel/Makefile
+++ b/arch/mips/kernel/Makefile
@@ -21,6 +21,7 @@ CFLAGS_REMOVE_ftrace-mcount.o = $(CC_FLAGS_FTRACE)
CFLAGS_REMOVE_early_printk.o = $(CC_FLAGS_FTRACE)
CFLAGS_REMOVE_perf_event.o = $(CC_FLAGS_FTRACE)
CFLAGS_REMOVE_perf_event_mipsxx.o = $(CC_FLAGS_FTRACE)
+CFLAGS_REMOVE_ftrace.o = $(CC_FLAGS_FTRACE)
endif
obj-$(CONFIG_CEVT_BCM1480) += cevt-bcm1480.o
@@ -39,7 +40,9 @@ obj-$(CONFIG_DEBUG_FS) += segment.o
obj-$(CONFIG_STACKTRACE) += stacktrace.o
obj-$(CONFIG_MODULES) += module.o
-obj-$(CONFIG_FUNCTION_TRACER) += mcount.o ftrace-mcount.o
+ft-$(CONFIG_FUNCTION_TRACER) += mcount.o ftrace-mcount.o
+ft-$(CONFIG_DYNAMIC_FTRACE_WITH_REGS) := entry-ftrace.o ftrace.o
+obj-y += $(ft-y)
sw-y := r4k_switch.o
sw-$(CONFIG_CPU_R3000) := r2300_switch.o
diff --git a/arch/mips/kernel/entry-ftrace.S b/arch/mips/kernel/entry-ftrace.S
new file mode 100644
index 000000000000..1e1eebc523ea
--- /dev/null
+++ b/arch/mips/kernel/entry-ftrace.S
@@ -0,0 +1,182 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * arch/mips/kernel/entry_ftrace.S
+ *
+ * Copyright (C) 2021 Loongson Corp
+ * Author: Huang Pei <huangpei@xxxxxxxxxxx>
+ */
+
+#include <asm/export.h>
+#include <asm/regdef.h>
+#include <asm/stackframe.h>
+
+/*
+ * ftrace_regs_caller() is the function that replaces _mcount() when ftrace
+ * is active.
+ *
+ * we arrive here after a function A calls function B, and B is what we
+ * are tracing for. When we enter, sp points to A's stack frame, B has not
+ * yet had a chance to allocate one yet. (This is different from -pg case
+ * , in which the B's stack is allocated))
+
+ * when ftrace initialized, it replace three nops from all function with
+ * "lui + nop + move"
+ * B:
+ * lui at, %hi(ftrace_regs_caller)
+ * nop
+ * li t0, 0
+ * # B's real start
+ *
+ * at B's entry, when tracing enabled, replace the 'nop' with 'jalr'
+ *
+ * # B's entry, three nop for both in vmlinux and in kernel modules
+ * B:
+ * lui at, %hi(ftrace_regs_caller)
+ * jalr at, at
+ * move t0, zero
+ * # B's real start
+ *
+ * if set t0 to 1, then calling ftrace_regs_caller with partial regs saved
+ *
+ * B:
+ * lui at, %hi(ftrace_regs_caller)
+ * jalr at, at
+ * li t0, 1
+ * # B's real start
+ *
+ * we make ftrace_regs_caller 64KB aligned, when entring ftrace_regs_caller
+ * AT points to the return address to B, and ra points to return address
+ * to A,
+ *
+ * if patched to new funcition, then clobbered the first real instruction
+ *
+ * B:
+ * lui at, %hi(new_B)
+ * addiu at, at, %lo(new_B)
+ * jr at
+ * # B's real start, now clobbered with zero
+ * nop
+ *
+ */
+ .text
+ .set push
+ .set noreorder
+ .set noat
+ .align 16
+NESTED(ftrace_regs_caller, PT_SIZE, ra)
+ PTR_ADDIU sp, sp, -PT_SIZE
+ .globl ftrace_caller
+ftrace_caller:
+#ifdef CONFIG_64BIT
+ PTR_S a4, PT_R8(sp)
+ PTR_S a5, PT_R9(sp)
+ PTR_S a6, PT_R10(sp)
+ PTR_S a7, PT_R11(sp)
+#endif
+ PTR_S a0, PT_R4(sp)
+ PTR_S a1, PT_R5(sp)
+ PTR_S a2, PT_R6(sp)
+
+ bnez t0, 1f
+ PTR_S a3, PT_R7(sp)
+
+ PTR_S t0, PT_R12(sp)
+ PTR_S t1, PT_R13(sp)
+ PTR_S t2, PT_R14(sp)
+ PTR_S t3, PT_R15(sp)
+
+ PTR_S s0, PT_R16(sp)
+ PTR_S s1, PT_R17(sp)
+ PTR_S s2, PT_R18(sp)
+ PTR_S s3, PT_R19(sp)
+
+ PTR_S s4, PT_R20(sp)
+ PTR_S s5, PT_R21(sp)
+ PTR_S s6, PT_R22(sp)
+ PTR_S s7, PT_R23(sp)
+
+ PTR_S t8, PT_R24(sp)
+ PTR_S t9, PT_R25(sp)
+ PTR_S s8, PT_R30(sp)
+ PTR_S gp, PT_R28(sp)
+
+1:
+ PTR_S sp, PT_R29(sp)
+ PTR_S ra, PT_R1(sp)
+ PTR_S AT, PT_R31(sp)
+
+ END(ftrace_regs_caller)
+
+ftrace_common:
+ PTR_ADDIU a0, AT, -12 //a0 points to B's entry address
+ move a1, ra //a1 points to return address to A
+ PTR_L a2, function_trace_op //a2 points to function_trace op
+
+ .globl ftrace_call
+ftrace_call:
+ jal ftrace_stub
+ move a3, sp //a3 point to frame pointer
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ .globl ftrace_graph_call
+ftrace_graph_call:
+ nop
+ nop
+#endif
+
+ftrace_common_return:
+ PTR_L AT, PT_R1(sp)
+ftrace_graph_return:
+ PTR_L ra, PT_R31(sp)
+ PTR_L a0, PT_R4(sp)
+ PTR_L a1, PT_R5(sp)
+ PTR_L a2, PT_R6(sp)
+ PTR_L a3, PT_R7(sp)
+#ifdef CONFIG_64BIT
+ PTR_L a4, PT_R8(sp)
+ PTR_L a5, PT_R9(sp)
+ PTR_L a6, PT_R10(sp)
+ PTR_L a7, PT_R11(sp)
+#endif
+ PTR_ADDIU sp, sp, PT_SIZE //retore stack frame
+ jr ra
+ move ra, AT
+
+
+ .globl ftrace_stub
+ftrace_stub:
+ jr ra
+ nop
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ .globl ftrace_graph_caller
+ftrace_graph_caller:
+ PTR_L a0, PT_R1(sp)
+ PTR_L a1, PT_R31(sp)
+ jal prepare_ftrace_return
+ PTR_ADDIU a2, sp, PT_SIZE
+
+ b ftrace_graph_return
+ move AT, v0
+
+
+ .align 2
+ .globl return_to_handler
+return_to_handler:
+ PTR_SUBU sp, PT_SIZE
+ PTR_S v0, PT_R2(sp)
+
+ jal ftrace_return_to_handler
+ PTR_S v1, PT_R3(sp)
+
+ /* restore the real parent address: v0 -> ra */
+ move ra, v0
+
+ PTR_L v0, PT_R2(sp)
+ PTR_L v1, PT_R3(sp)
+ jr ra
+ PTR_ADDIU sp, PT_SIZE
+
+ .set at
+ .set reorder
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
new file mode 100644
index 000000000000..4c8bea1818cb
--- /dev/null
+++ b/arch/mips/kernel/ftrace.c
@@ -0,0 +1,215 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * arch/mips/kernel/ftrace.c
+ *
+ * Copyright (C) 2021 Loongson Limited Corp.
+ * Author: Huang Pei <huangpei@xxxxxxxxxxx>
+ */
+
+#include <linux/ftrace.h>
+#include <linux/module.h>
+#include <linux/swab.h>
+#include <linux/uaccess.h>
+
+#include <asm/ftrace.h>
+#include <asm/asm.h>
+#include <asm/asm-offsets.h>
+#include <asm/cacheflush.h>
+#include <asm/uasm.h>
+
+
+#define INSN_NOP 0x00000000 /* nop */
+#define INSN_JALR_AT2 0x00200809 /* jalr at, at */
+#define INSN_LI_0 0x240c0000 /* li t0, 0 */
+#define INSN_LI_1 0x240c0001 /* li t0, 1 */
+#define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
+#define JAL 0x0c000000 /* jump & link: ip --> ra, jump to target */
+#define ADDR_MASK 0x03ffffff /* op_code|addr : 31...26|25 ....0 */
+#define INSN_JAL(addr) \
+ ((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))
+
+extern void ftrace_graph_call(void);
+
+static unsigned int insn_lui __read_mostly;
+
+/* Arch override because MIPS doesn't need to run this from stop_machine() */
+void arch_ftrace_update_code(int command)
+{
+ ftrace_modify_all_code(command);
+}
+
+static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
+{
+ int faulted;
+ mm_segment_t old_fs;
+
+ /* *(unsigned int *)ip = new_code; */
+ safe_store_code(new_code, ip, faulted);
+
+ if (unlikely(faulted))
+ return -EFAULT;
+
+ old_fs = get_fs();
+ set_fs(KERNEL_DS);
+ flush_icache_range(ip, ip + 8);
+ set_fs(old_fs);
+
+ return 0;
+}
+
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+ unsigned int new;
+
+ new = INSN_JAL((unsigned long)func);
+
+ return ftrace_modify_code(FTRACE_CALL_IP, new);
+}
+
+/*
+ * enable tracing by replacing the middle nop with jalr, like
+ *
+ * lui at, %hi(ftrace_regs_all)
+ * jalr at, at
+ * li t0, 0
+ */
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+ unsigned long ip = rec->ip;
+
+ ftrace_modify_code(ip + 4, INSN_JALR_AT2);
+ return 0;
+}
+
+/*
+ * disable recording regs by replacing
+ *
+ * li t0, 0
+ *
+ * with
+ *
+ * li, t0, 1
+ *
+ * or vesa
+ */
+int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
+ unsigned long addr)
+{
+ unsigned long ip = rec->ip;
+
+ if (abs(old_addr - addr) == 4) {
+ if (addr == (unsigned long)ftrace_regs_caller)
+ return ftrace_modify_code(ip + 4, INSN_LI_0);
+
+ if (addr == (unsigned long)ftrace_caller)
+ return ftrace_modify_code(ip + 4, INSN_LI_1);
+
+ }
+
+ /* we do not support direct call or trampoline now */
+
+ return -1;
+
+}
+
+/*
+ * replace all three nop at the entry with
+ *
+ * lui at, %hi(ftrace_regs_all)
+ * nop
+ * li t0, 1
+ */
+
+int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
+{
+ unsigned long ip = rec->ip;
+
+ ftrace_modify_code(ip, insn_lui);
+
+ ftrace_modify_code(ip + 8, INSN_LI_1);
+ return 0;
+}
+
+
+
+/*
+ * disable tracing by replacing
+ *
+ * jalr at, at
+ *
+ * with
+ *
+ * nop
+ *
+ */
+
+int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
+ unsigned long addr)
+
+{
+ unsigned int new = INSN_NOP;
+ unsigned long ip = rec->ip + 4;
+
+ return ftrace_modify_code(ip, new);
+}
+
+int __init ftrace_dyn_arch_init(void)
+{
+ u32 *buf;
+ int reg;
+
+ reg = 1;
+ /* lui at, %hi(ftrace_regs_all) */
+ buf = (u32*)&insn_lui;
+ uasm_i_lui(&buf, reg, uasm_rel_hi((long)ftrace_regs_caller));
+
+ return 0;
+}
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+unsigned long prepare_ftrace_return(unsigned long parent, unsigned long self_ra,
+ unsigned long fp)
+{
+ unsigned long return_hooker = (unsigned long)&return_to_handler;
+
+ if (unlikely(ftrace_graph_is_dead()))
+ goto out;
+
+ if (unlikely(atomic_read(¤t->tracing_graph_pause)))
+ goto out;
+
+ self_ra -= 8;
+ if (!function_graph_enter(parent, self_ra, fp, NULL))
+ parent = return_hooker;
+out:
+ return parent;
+}
+
+/*
+ * Turn on/off the call to ftrace_graph_caller() in ftrace_caller()
+ * depending on @enable.
+ */
+static int ftrace_modify_graph_caller(bool enable)
+{
+ unsigned long pc = (unsigned long)ftrace_graph_call;
+ unsigned new;
+
+ if (enable)
+ new = INSN_JAL((unsigned long)ftrace_graph_caller);
+ else
+ new = INSN_NOP;
+
+ return ftrace_modify_code(pc, new);
+}
+
+int ftrace_enable_ftrace_graph_caller(void)
+{
+ return ftrace_modify_graph_caller(true);
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+ return ftrace_modify_graph_caller(false);
+}
+
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
--
2.17.1
