This patch set includes the building blocks of dynamic ftrace features
for RISC-V machines.
Changes in v2:
- Fix the return value as writing to kernel text goes wrong (2/6)
- Replace manual comparisons by calling memcmp (2/6)
- Simplify the conditional assignment in the Makefile (1/6)
Alan Kao (6):
riscv/ftrace: Add RECORD_MCOUNT support
riscv/ftrace: Add dynamic function tracer support
riscv/ftrace: Add dynamic function graph tracer support
riscv/ftrace: Add ARCH_SUPPORTS_FTRACE_OPS support
riscv/ftrace: Add DYNAMIC_FTRACE_WITH_REGS support
riscv/ftrace: Add HAVE_FUNCTION_GRAPH_RET_ADDR_PTR support
arch/riscv/Kconfig | 3 +
arch/riscv/Makefile | 3 +
arch/riscv/include/asm/ftrace.h | 47 ++++++++
arch/riscv/kernel/Makefile | 5 +-
arch/riscv/kernel/ftrace.c | 142 ++++++++++++++++++++++-
arch/riscv/kernel/mcount-dyn.S | 244 ++++++++++++++++++++++++++++++++++++++++
arch/riscv/kernel/mcount.S | 22 ++--
arch/riscv/kernel/stacktrace.c | 6 +
scripts/recordmcount.pl | 5 +
9 files changed, 464 insertions(+), 13 deletions(-)
create mode 100644 arch/riscv/kernel/mcount-dyn.S
--
2.15.1
Now recordmcount.pl recognizes RISC-V object files. For the mechanism to
work, we have to disable the linker relaxation.
Cc: Greentime Hu <[email protected]>
Signed-off-by: Alan Kao <[email protected]>
---
arch/riscv/Kconfig | 1 +
arch/riscv/Makefile | 3 +++
scripts/recordmcount.pl | 5 +++++
3 files changed, 9 insertions(+)
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 40a67fc12328..1f45a76f412e 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -117,6 +117,7 @@ config ARCH_RV64I
select 64BIT
select HAVE_FUNCTION_TRACER
select HAVE_FUNCTION_GRAPH_TRACER
+ select HAVE_FTRACE_MCOUNT_RECORD
endchoice
diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index 6719dd30ec5b..899226e0da7d 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -11,6 +11,9 @@
LDFLAGS :=
OBJCOPYFLAGS := -O binary
LDFLAGS_vmlinux :=
+ifeq ($(CONFIG_DYNAMIC_FTRACE),y)
+ LDFLAGS_vmlinux := --no-relax
+endif
KBUILD_AFLAGS_MODULE += -fPIC
KBUILD_CFLAGS_MODULE += -fPIC
diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl
index 2033af758173..d44d55db7c06 100755
--- a/scripts/recordmcount.pl
+++ b/scripts/recordmcount.pl
@@ -376,6 +376,11 @@ if ($arch eq "x86_64") {
$mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s__mcount\$";
$type = ".quad";
$alignment = 8;
+} elsif ($arch eq "riscv") {
+ $function_regex = "^([0-9a-fA-F]+)\\s+<([^.0-9][0-9a-zA-Z_\\.]+)>:";
+ $mcount_regex = "^\\s*([0-9a-fA-F]+):\\sR_RISCV_CALL\\s_mcount\$";
+ $type = ".quad";
+ $alignment = 2;
} else {
die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
}
--
2.15.1
We now have dynamic ftrace with the following added items:
* ftrace_make_call, ftrace_make_nop (in kernel/ftrace.c)
The two functions turns any recorded call site of filtered functions
into a call to ftrace_caller or nops
* ftracce_update_ftrace_func (in kernel/ftrace.c)
turns the nops at ftrace_call into a call to a generic entry for
function tracers.
* ftrace_caller (in kernel/mcount-dyn.S)
The entry where each _mcount call sites calls to once they are
filtered to be traced.
Also, this patch fixes the semantic problems in mcount.S, which will be
treated as only a reference implementation once we have the dynamic
ftrace.
Cc: Greentime Hu <[email protected]>
Signed-off-by: Alan Kao <[email protected]>
---
arch/riscv/Kconfig | 1 +
arch/riscv/include/asm/ftrace.h | 45 ++++++++++++++++++
arch/riscv/kernel/Makefile | 5 +-
arch/riscv/kernel/ftrace.c | 100 +++++++++++++++++++++++++++++++++++++++-
arch/riscv/kernel/mcount-dyn.S | 52 +++++++++++++++++++++
arch/riscv/kernel/mcount.S | 22 +++++----
6 files changed, 213 insertions(+), 12 deletions(-)
create mode 100644 arch/riscv/kernel/mcount-dyn.S
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 1f45a76f412e..a5c5c88700d4 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -118,6 +118,7 @@ config ARCH_RV64I
select HAVE_FUNCTION_TRACER
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FTRACE_MCOUNT_RECORD
+ select HAVE_DYNAMIC_FTRACE
endchoice
diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h
index 66d4175eb13e..acf0c7d001f3 100644
--- a/arch/riscv/include/asm/ftrace.h
+++ b/arch/riscv/include/asm/ftrace.h
@@ -8,3 +8,48 @@
#if defined(CONFIG_FUNCTION_GRAPH_TRACER) && defined(CONFIG_FRAME_POINTER)
#define HAVE_FUNCTION_GRAPH_FP_TEST
#endif
+
+#ifndef __ASSEMBLY__
+void _mcount(void);
+static inline unsigned long ftrace_call_adjust(unsigned long addr)
+{
+ return addr;
+}
+
+struct dyn_arch_ftrace {
+};
+#endif
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+/*
+ * A general call in RISC-V is a pair of insts:
+ * 1) auipc: setting high-20 pc-related bits to ra register
+ * 2) jalr: setting low-12 offset to ra, jump to ra, and set ra to
+ * return address (original pc + 4)
+ *
+ * Dynamic ftrace generates probes to call sites, so we must deal with
+ * both auipc and jalr at the same time.
+ */
+
+#define MCOUNT_ADDR ((unsigned long)_mcount)
+#define JALR_SIGN_MASK (0x00000800)
+#define JALR_OFFSET_MASK (0x00000fff)
+#define AUIPC_OFFSET_MASK (0xfffff000)
+#define AUIPC_PAD (0x00001000)
+#define JALR_SHIFT 20
+#define JALR_BASIC (0x000080e7)
+#define AUIPC_BASIC (0x00000097)
+#define NOP4 (0x00000013)
+
+#define to_jalr_insn(_offset) \
+ (((_offset & JALR_OFFSET_MASK) << JALR_SHIFT) | JALR_BASIC)
+
+#define to_auipc_insn(_offset) ((_offset & JALR_SIGN_MASK) ? \
+ (((_offset & AUIPC_OFFSET_MASK) + AUIPC_PAD) | AUIPC_BASIC) : \
+ ((_offset & AUIPC_OFFSET_MASK) | AUIPC_BASIC))
+
+/*
+ * Let auipc+jalr be the basic *mcount unit*, so we make it 8 bytes here.
+ */
+#define MCOUNT_INSN_SIZE 8
+#endif
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index 196f62ffc428..d7bdf888f1ca 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -34,7 +34,8 @@ CFLAGS_setup.o := -mcmodel=medany
obj-$(CONFIG_SMP) += smpboot.o
obj-$(CONFIG_SMP) += smp.o
obj-$(CONFIG_MODULES) += module.o
-obj-$(CONFIG_FUNCTION_TRACER) += mcount.o
-obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o
+
+obj-$(CONFIG_FUNCTION_TRACER) += mcount.o ftrace.o
+obj-$(CONFIG_DYNAMIC_FTRACE) += mcount-dyn.o
clean:
diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
index d0de68d144cb..311c287433c9 100644
--- a/arch/riscv/kernel/ftrace.c
+++ b/arch/riscv/kernel/ftrace.c
@@ -6,9 +6,107 @@
*/
#include <linux/ftrace.h>
+#include <linux/uaccess.h>
+#include <asm/cacheflush.h>
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+static int ftrace_check_current_call(unsigned long hook_pos,
+ unsigned int *expected)
+{
+ unsigned int replaced[2];
+ unsigned int nops[2] = {NOP4, NOP4};
+
+ /* we expect nops at the hook position */
+ if (!expected)
+ expected = nops;
+
+ /*
+ * Read the text we want to modify;
+ * return must be -EFAULT on read error
+ */
+ if (probe_kernel_read(replaced, (void *)hook_pos, MCOUNT_INSN_SIZE))
+ return -EFAULT;
+
+ /*
+ * Make sure it is what we expect it to be;
+ * return must be -EINVAL on failed comparison
+ */
+ if (memcmp(expected, replaced, sizeof(replaced))) {
+ pr_err("%p: expected (%08x %08x) but get (%08x %08x)",
+ (void *)hook_pos, expected[0], expected[1], replaced[0],
+ replaced[1]);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target,
+ bool enable)
+{
+ unsigned int offset = (unsigned int)(target - hook_pos);
+ unsigned int auipc_call = to_auipc_insn(offset);
+ unsigned int jalr_call = to_jalr_insn(offset);
+ unsigned int calls[2] = {auipc_call, jalr_call};
+ unsigned int nops[2] = {NOP4, NOP4};
+ int ret = 0;
+
+ /* when ftrace_make_nop is called */
+ if (!enable)
+ ret = ftrace_check_current_call(hook_pos, calls);
+
+ if (ret)
+ return ret;
+
+ /* replace the auipc-jalr pair at once */
+ ret = probe_kernel_write((void *)hook_pos, enable ? calls : nops,
+ MCOUNT_INSN_SIZE);
+ /* return must be -EPERM on write error */
+ if (ret)
+ return -EPERM;
+
+ smp_mb();
+ flush_icache_range((void *)hook_pos, (void *)hook_pos + MCOUNT_INSN_SIZE);
+
+ return 0;
+}
+
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+ int ret = ftrace_check_current_call(rec->ip, NULL);
+
+ if (ret)
+ return ret;
+
+ return __ftrace_modify_call(rec->ip, addr, true);
+}
+
+int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
+ unsigned long addr)
+{
+ return __ftrace_modify_call(rec->ip, addr, false);
+}
+
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+ int ret = __ftrace_modify_call((unsigned long)&ftrace_call,
+ (unsigned long)func, true);
+ if (!ret) {
+ ret = __ftrace_modify_call((unsigned long)&ftrace_regs_call,
+ (unsigned long)func, true);
+ }
+
+ return ret;
+}
+
+int __init ftrace_dyn_arch_init(void)
+{
+ return 0;
+}
+#endif
/*
- * Most of this file is copied from arm64.
+ * Most of this function is copied from arm64.
*/
void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
unsigned long frame_pointer)
diff --git a/arch/riscv/kernel/mcount-dyn.S b/arch/riscv/kernel/mcount-dyn.S
new file mode 100644
index 000000000000..57f80fe09cbd
--- /dev/null
+++ b/arch/riscv/kernel/mcount-dyn.S
@@ -0,0 +1,52 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2017 Andes Technology Corporation */
+
+#include <linux/init.h>
+#include <linux/linkage.h>
+#include <asm/asm.h>
+#include <asm/csr.h>
+#include <asm/unistd.h>
+#include <asm/thread_info.h>
+#include <asm/asm-offsets.h>
+#include <asm-generic/export.h>
+#include <asm/ftrace.h>
+
+ .text
+
+ .macro SAVE_ABI_STATE
+ addi sp, sp, -16
+ sd s0, 0(sp)
+ sd ra, 8(sp)
+ addi s0, sp, 16
+ .endm
+
+ .macro RESTORE_ABI_STATE
+ ld ra, 8(sp)
+ ld s0, 0(sp)
+ addi sp, sp, 16
+ .endm
+
+ENTRY(ftrace_caller)
+ /*
+ * a0: the address in the caller when calling ftrace_caller
+ * a1: the caller's return address
+ */
+ ld a1, -8(s0)
+ addi a0, ra, -MCOUNT_INSN_SIZE
+ SAVE_ABI_STATE
+ftrace_call:
+ .global ftrace_call
+ /*
+ * For the dynamic ftrace to work, here we should reserve at least
+ * 8 bytes for a functional auipc-jalr pair. Pseudo inst nop may be
+ * interpreted as different length in different models, so we manually
+ * *expand* two 4-byte nops here.
+ *
+ * Calling ftrace_update_ftrace_func would overwrite the nops below.
+ * Check ftrace_modify_all_code for details.
+ */
+ addi x0, x0, 0
+ addi x0, x0, 0
+ RESTORE_ABI_STATE
+ ret
+ENDPROC(ftrace_caller)
diff --git a/arch/riscv/kernel/mcount.S b/arch/riscv/kernel/mcount.S
index c46a778627be..ce9bdc57a2a1 100644
--- a/arch/riscv/kernel/mcount.S
+++ b/arch/riscv/kernel/mcount.S
@@ -32,13 +32,13 @@
addi s0, sp, 32
.endm
- .macro STORE_ABI_STATE
+ .macro RESTORE_ABI_STATE
ld ra, 8(sp)
ld s0, 0(sp)
addi sp, sp, 16
.endm
- .macro STORE_RET_ABI_STATE
+ .macro RESTORE_RET_ABI_STATE
ld ra, 24(sp)
ld s0, 16(sp)
ld a0, 8(sp)
@@ -46,6 +46,10 @@
.endm
ENTRY(ftrace_stub)
+#ifdef CONFIG_DYNAMIC_FTRACE
+ .global _mcount
+ .set _mcount, ftrace_stub
+#endif
ret
ENDPROC(ftrace_stub)
@@ -66,15 +70,15 @@ ENTRY(return_to_handler)
#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
mv a0, t6
#endif
- la t0, ftrace_return_to_handler
- jalr t0
+ call ftrace_return_to_handler
mv a1, a0
- STORE_RET_ABI_STATE
+ RESTORE_RET_ABI_STATE
jalr a1
ENDPROC(return_to_handler)
EXPORT_SYMBOL(return_to_handler)
#endif
+#ifndef CONFIG_DYNAMIC_FTRACE
ENTRY(_mcount)
la t4, ftrace_stub
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
@@ -104,9 +108,8 @@ do_ftrace_graph_caller:
ld a2, -16(s0)
#endif
SAVE_ABI_STATE
- la t0, prepare_ftrace_return
- jalr t0
- STORE_ABI_STATE
+ call prepare_ftrace_return
+ RESTORE_ABI_STATE
ret
#endif
@@ -120,7 +123,8 @@ do_trace:
SAVE_ABI_STATE
jalr t5
- STORE_ABI_STATE
+ RESTORE_ABI_STATE
ret
ENDPROC(_mcount)
EXPORT_SYMBOL(_mcount)
+#endif
--
2.15.1
Cc: Greentime Hu <[email protected]>
Signed-off-by: Alan Kao <[email protected]>
---
arch/riscv/include/asm/ftrace.h | 1 +
arch/riscv/kernel/mcount-dyn.S | 3 +++
2 files changed, 4 insertions(+)
diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h
index acf0c7d001f3..429a6a156645 100644
--- a/arch/riscv/include/asm/ftrace.h
+++ b/arch/riscv/include/asm/ftrace.h
@@ -9,6 +9,7 @@
#define HAVE_FUNCTION_GRAPH_FP_TEST
#endif
+#define ARCH_SUPPORTS_FTRACE_OPS 1
#ifndef __ASSEMBLY__
void _mcount(void);
static inline unsigned long ftrace_call_adjust(unsigned long addr)
diff --git a/arch/riscv/kernel/mcount-dyn.S b/arch/riscv/kernel/mcount-dyn.S
index 64e715d4e180..627478571c7a 100644
--- a/arch/riscv/kernel/mcount-dyn.S
+++ b/arch/riscv/kernel/mcount-dyn.S
@@ -75,9 +75,12 @@ ENTRY(ftrace_caller)
/*
* a0: the address in the caller when calling ftrace_caller
* a1: the caller's return address
+ * a2: the address of global variable function_trace_op
*/
ld a1, -8(s0)
addi a0, ra, -MCOUNT_INSN_SIZE
+ la t5, function_trace_op
+ ld a2, 0(t5)
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
/*
--
2.15.1
In walk_stackframe, the pc now receives the address from calling
ftrace_graph_ret_addr instead of manual calculation.
Note that the original calculation,
pc = frame->ra - 4
is buggy when the instruction at the return address happened to be a
compressed inst. But since it is not a critical part of ftrace, it is
ignored for now to ease the review process.
Cc: Greentime Hu <[email protected]>
Signed-off-by: Alan Kao <[email protected]>
---
arch/riscv/include/asm/ftrace.h | 1 +
arch/riscv/kernel/ftrace.c | 2 +-
arch/riscv/kernel/stacktrace.c | 6 ++++++
3 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h
index 429a6a156645..6e4b4c96b63e 100644
--- a/arch/riscv/include/asm/ftrace.h
+++ b/arch/riscv/include/asm/ftrace.h
@@ -8,6 +8,7 @@
#if defined(CONFIG_FUNCTION_GRAPH_TRACER) && defined(CONFIG_FRAME_POINTER)
#define HAVE_FUNCTION_GRAPH_FP_TEST
#endif
+#define HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
#define ARCH_SUPPORTS_FTRACE_OPS 1
#ifndef __ASSEMBLY__
diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
index 3922b29c107b..ded8ab25f4ad 100644
--- a/arch/riscv/kernel/ftrace.c
+++ b/arch/riscv/kernel/ftrace.c
@@ -150,7 +150,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
return;
err = ftrace_push_return_trace(old, self_addr, &trace.depth,
- frame_pointer, NULL);
+ frame_pointer, parent);
if (err == -EBUSY)
return;
*parent = return_hooker;
diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c
index 559aae781154..a4b1d94371a0 100644
--- a/arch/riscv/kernel/stacktrace.c
+++ b/arch/riscv/kernel/stacktrace.c
@@ -18,6 +18,7 @@
#include <linux/sched/debug.h>
#include <linux/sched/task_stack.h>
#include <linux/stacktrace.h>
+#include <linux/ftrace.h>
#ifdef CONFIG_FRAME_POINTER
@@ -63,7 +64,12 @@ static void notrace walk_stackframe(struct task_struct *task,
frame = (struct stackframe *)fp - 1;
sp = fp;
fp = frame->fp;
+#ifdef HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
+ pc = ftrace_graph_ret_addr(current, NULL, frame->ra,
+ (unsigned long *)(fp - 8));
+#else
pc = frame->ra - 0x4;
+#endif
}
}
--
2.15.1
Cc: Greentime Hu <[email protected]>
Signed-off-by: Alan Kao <[email protected]>
---
arch/riscv/Kconfig | 1 +
arch/riscv/kernel/ftrace.c | 17 ++++++
arch/riscv/kernel/mcount-dyn.S | 124 +++++++++++++++++++++++++++++++++++++++++
3 files changed, 142 insertions(+)
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index a5c5c88700d4..bb2c64976583 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -119,6 +119,7 @@ config ARCH_RV64I
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_DYNAMIC_FTRACE
+ select HAVE_DYNAMIC_FTRACE_WITH_REGS
endchoice
diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
index dce1286af9b0..3922b29c107b 100644
--- a/arch/riscv/kernel/ftrace.c
+++ b/arch/riscv/kernel/ftrace.c
@@ -105,6 +105,23 @@ int __init ftrace_dyn_arch_init(void)
}
#endif
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
+ unsigned long addr)
+{
+ unsigned int offset = (unsigned int)(old_addr - rec->ip);
+ unsigned int auipc_call = to_auipc_insn(offset);
+ unsigned int jalr_call = to_jalr_insn(offset);
+ unsigned int calls[2] = {auipc_call, jalr_call};
+ int ret = ftrace_check_current_call(rec->ip, calls);
+
+ if (ret)
+ return ret;
+
+ return __ftrace_modify_call(rec->ip, addr, true);
+}
+#endif
+
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
/*
* Most of this function is copied from arm64.
diff --git a/arch/riscv/kernel/mcount-dyn.S b/arch/riscv/kernel/mcount-dyn.S
index 627478571c7a..3ec3ddbfb5e7 100644
--- a/arch/riscv/kernel/mcount-dyn.S
+++ b/arch/riscv/kernel/mcount-dyn.S
@@ -118,3 +118,127 @@ ftrace_call:
RESTORE_ABI_STATE
ret
ENDPROC(ftrace_caller)
+
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+ .macro SAVE_ALL
+ addi sp, sp, -(PT_SIZE_ON_STACK+16)
+ sd s0, (PT_SIZE_ON_STACK)(sp)
+ sd ra, (PT_SIZE_ON_STACK+8)(sp)
+ addi s0, sp, (PT_SIZE_ON_STACK+16)
+
+ sd x1, PT_RA(sp)
+ sd x2, PT_SP(sp)
+ sd x3, PT_GP(sp)
+ sd x4, PT_TP(sp)
+ sd x5, PT_T0(sp)
+ sd x6, PT_T1(sp)
+ sd x7, PT_T2(sp)
+ sd x8, PT_S0(sp)
+ sd x9, PT_S1(sp)
+ sd x10, PT_A0(sp)
+ sd x11, PT_A1(sp)
+ sd x12, PT_A2(sp)
+ sd x13, PT_A3(sp)
+ sd x14, PT_A4(sp)
+ sd x15, PT_A5(sp)
+ sd x16, PT_A6(sp)
+ sd x17, PT_A7(sp)
+ sd x18, PT_S2(sp)
+ sd x19, PT_S3(sp)
+ sd x20, PT_S4(sp)
+ sd x21, PT_S5(sp)
+ sd x22, PT_S6(sp)
+ sd x23, PT_S7(sp)
+ sd x24, PT_S8(sp)
+ sd x25, PT_S9(sp)
+ sd x26, PT_S10(sp)
+ sd x27, PT_S11(sp)
+ sd x28, PT_T3(sp)
+ sd x29, PT_T4(sp)
+ sd x30, PT_T5(sp)
+ sd x31, PT_T6(sp)
+ .endm
+
+ .macro RESTORE_ALL
+ ld x1, PT_RA(sp)
+ ld x2, PT_SP(sp)
+ ld x3, PT_GP(sp)
+ ld x4, PT_TP(sp)
+ ld x5, PT_T0(sp)
+ ld x6, PT_T1(sp)
+ ld x7, PT_T2(sp)
+ ld x8, PT_S0(sp)
+ ld x9, PT_S1(sp)
+ ld x10, PT_A0(sp)
+ ld x11, PT_A1(sp)
+ ld x12, PT_A2(sp)
+ ld x13, PT_A3(sp)
+ ld x14, PT_A4(sp)
+ ld x15, PT_A5(sp)
+ ld x16, PT_A6(sp)
+ ld x17, PT_A7(sp)
+ ld x18, PT_S2(sp)
+ ld x19, PT_S3(sp)
+ ld x20, PT_S4(sp)
+ ld x21, PT_S5(sp)
+ ld x22, PT_S6(sp)
+ ld x23, PT_S7(sp)
+ ld x24, PT_S8(sp)
+ ld x25, PT_S9(sp)
+ ld x26, PT_S10(sp)
+ ld x27, PT_S11(sp)
+ ld x28, PT_T3(sp)
+ ld x29, PT_T4(sp)
+ ld x30, PT_T5(sp)
+ ld x31, PT_T6(sp)
+
+ ld s0, (PT_SIZE_ON_STACK)(sp)
+ ld ra, (PT_SIZE_ON_STACK+8)(sp)
+ addi sp, sp, (PT_SIZE_ON_STACK+16)
+ .endm
+
+ .macro RESTORE_GRAPH_REG_ARGS
+ ld a0, PT_T0(sp)
+ ld a1, PT_T1(sp)
+#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
+ ld a2, PT_T2(sp)
+#endif
+ .endm
+
+/*
+ * Most of the contents are the same as ftrace_caller.
+ */
+ENTRY(ftrace_regs_caller)
+ /*
+ * a3: the address of all registers in the stack
+ */
+ ld a1, -8(s0)
+ addi a0, ra, -MCOUNT_INSN_SIZE
+ la t5, function_trace_op
+ ld a2, 0(t5)
+ addi a3, sp, -(PT_SIZE_ON_STACK+16)
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ addi t0, s0, -8
+ mv t1, a0
+#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
+ ld t2, -16(s0)
+#endif
+#endif
+ SAVE_ALL
+
+ftrace_regs_call:
+ .global ftrace_regs_call
+ addi x0, x0, 0
+ addi x0, x0, 0
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ RESTORE_GRAPH_REG_ARGS
+ call ftrace_graph_caller
+#endif
+
+ RESTORE_ALL
+ ret
+ENDPROC(ftrace_regs_caller)
+#endif /* CONFIG_DYNAMIC_FTRACE_WITH_REGS */
--
2.15.1
Once the function_graph tracer is enabled, a filtered function has the
following call sequence:
* ftracer_caller ==> on/off by ftrace_make_call/ftrace_make_nop
* ftrace_graph_caller
* ftrace_graph_call ==> on/off by ftrace_en/disable_ftrace_graph_caller
* prepare_ftrace_return
Considering the following DYNAMIC_FTRACE_WITH_REGS feature, it would be
more extendable to have a ftrace_graph_caller function, instead of
calling prepare_ftrace_return directly in ftrace_caller.
Cc: Greentime Hu <[email protected]>
Signed-off-by: Alan Kao <[email protected]>
---
arch/riscv/kernel/ftrace.c | 25 +++++++++++++++-
arch/riscv/kernel/mcount-dyn.S | 65 ++++++++++++++++++++++++++++++++++++++++++
2 files changed, 89 insertions(+), 1 deletion(-)
diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
index 311c287433c9..dce1286af9b0 100644
--- a/arch/riscv/kernel/ftrace.c
+++ b/arch/riscv/kernel/ftrace.c
@@ -51,7 +51,7 @@ static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target,
unsigned int nops[2] = {NOP4, NOP4};
int ret = 0;
- /* when ftrace_make_nop is called */
+ /* for ftrace_make_nop and ftrace_disable_ftrace_graph_caller */
if (!enable)
ret = ftrace_check_current_call(hook_pos, calls);
@@ -105,6 +105,7 @@ int __init ftrace_dyn_arch_init(void)
}
#endif
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
/*
* Most of this function is copied from arm64.
*/
@@ -137,3 +138,25 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
return;
*parent = return_hooker;
}
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+extern void ftrace_graph_call(void);
+int ftrace_enable_ftrace_graph_caller(void)
+{
+ int ret = ftrace_check_current_call((unsigned long)&ftrace_graph_call,
+ NULL);
+
+ if (ret)
+ return ret;
+
+ return __ftrace_modify_call((unsigned long)&ftrace_graph_call,
+ (unsigned long)&prepare_ftrace_return, true);
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+ return __ftrace_modify_call((unsigned long)&ftrace_graph_call,
+ (unsigned long)&prepare_ftrace_return, false);
+}
+#endif /* CONFIG_DYNAMIC_FTRACE */
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
diff --git a/arch/riscv/kernel/mcount-dyn.S b/arch/riscv/kernel/mcount-dyn.S
index 57f80fe09cbd..64e715d4e180 100644
--- a/arch/riscv/kernel/mcount-dyn.S
+++ b/arch/riscv/kernel/mcount-dyn.S
@@ -14,18 +14,63 @@
.text
.macro SAVE_ABI_STATE
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ addi sp, sp, -48
+ sd s0, 32(sp)
+ sd ra, 40(sp)
+ addi s0, sp, 48
+ sd t0, 24(sp)
+ sd t1, 16(sp)
+#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
+ sd t2, 8(sp)
+#endif
+#else
addi sp, sp, -16
sd s0, 0(sp)
sd ra, 8(sp)
addi s0, sp, 16
+#endif
.endm
.macro RESTORE_ABI_STATE
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ ld s0, 32(sp)
+ ld ra, 40(sp)
+ addi sp, sp, 48
+#else
ld ra, 8(sp)
ld s0, 0(sp)
addi sp, sp, 16
+#endif
.endm
+ .macro RESTORE_GRAPH_ARGS
+ ld a0, 24(sp)
+ ld a1, 16(sp)
+#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
+ ld a2, 8(sp)
+#endif
+ .endm
+
+ENTRY(ftrace_graph_caller)
+ addi sp, sp, -16
+ sd s0, 0(sp)
+ sd ra, 8(sp)
+ addi s0, sp, 16
+ftrace_graph_call:
+ .global ftrace_graph_call
+ /*
+ * Calling ftrace_enable/disable_ftrace_graph_caller would overwrite the
+ * nops below. Check ftrace_modify_all_code for details.
+ */
+ addi x0, x0, 0
+ addi x0, x0, 0
+ ld ra, 8(sp)
+ ld s0, 0(sp)
+ addi sp, sp, 16
+ ret
+ENDPROC(ftrace_graph_caller)
+
ENTRY(ftrace_caller)
/*
* a0: the address in the caller when calling ftrace_caller
@@ -33,6 +78,20 @@ ENTRY(ftrace_caller)
*/
ld a1, -8(s0)
addi a0, ra, -MCOUNT_INSN_SIZE
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ /*
+ * the graph tracer (specifically, prepare_ftrace_return) needs these
+ * arguments but for now the function tracer occupies the regs, so we
+ * save them in temporary regs to recover later.
+ */
+ addi t0, s0, -8
+ mv t1, a0
+#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
+ ld t2, -16(s0)
+#endif
+#endif
+
SAVE_ABI_STATE
ftrace_call:
.global ftrace_call
@@ -47,6 +106,12 @@ ftrace_call:
*/
addi x0, x0, 0
addi x0, x0, 0
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ RESTORE_GRAPH_ARGS
+ call ftrace_graph_caller
+#endif
+
RESTORE_ABI_STATE
ret
ENDPROC(ftrace_caller)
--
2.15.1
On Sun, Jan 14, 2018 at 10:47 PM, Alan Kao <[email protected]> wrote:
> + /*
> + * For the dynamic ftrace to work, here we should reserve at least
> + * 8 bytes for a functional auipc-jalr pair. Pseudo inst nop may be
> + * interpreted as different length in different models, so we manually
> + * *expand* two 4-byte nops here.
> + *
> + * Calling ftrace_update_ftrace_func would overwrite the nops below.
> + * Check ftrace_modify_all_code for details.
> + */
> + addi x0, x0, 0
> + addi x0, x0, 0
This relies on behavior of the assembler which is undocumented and, if
my reading of the specification is correct, a bug.
The documented way to assemble an sequence of 2 4-byte NOPs regardless
of subtarget is as follows:
.option push
.option norvc
nop
nop
.option pop
I have filed https://github.com/riscv/riscv-binutils-gdb/issues/135 to
get clarity on the assembler behavior; the explicit approach may be
preferable even if the assembler behavior turns out to be correct.
-s
On Sun, Jan 14, 2018 at 11:24:53PM -0800, Stefan O'Rear wrote:
> On Sun, Jan 14, 2018 at 10:47 PM, Alan Kao <[email protected]> wrote:
> > + /*
> > + * For the dynamic ftrace to work, here we should reserve at least
> > + * 8 bytes for a functional auipc-jalr pair. Pseudo inst nop may be
> > + * interpreted as different length in different models, so we manually
> > + * *expand* two 4-byte nops here.
> > + *
> > + * Calling ftrace_update_ftrace_func would overwrite the nops below.
> > + * Check ftrace_modify_all_code for details.
> > + */
> > + addi x0, x0, 0
> > + addi x0, x0, 0
>
> This relies on behavior of the assembler which is undocumented and, if
> my reading of the specification is correct, a bug.
>
> The documented way to assemble an sequence of 2 4-byte NOPs regardless
> of subtarget is as follows:
>
> .option push
> .option norvc
> nop
> nop
> .option pop
>
> I have filed https://github.com/riscv/riscv-binutils-gdb/issues/135 to
> get clarity on the assembler behavior; the explicit approach may be
> preferable even if the assembler behavior turns out to be correct.
>
> -s
>
Thanks for pointing this out.
After checking the way other architectures have done this, I think we can
just put a
call ftrace_stub
here. Currently we don't support linker relaxing with ftrace, so this
macro will be expand to 8-byte inst-pair.
Alan
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