summaryrefslogtreecommitdiff
path: root/arch/riscv/kernel/mcount.S
diff options
context:
space:
mode:
authorAlan Kao <nonerkao@gmail.com>2017-12-18 17:52:48 +0800
committerPalmer Dabbelt <palmer@dabbelt.com>2018-01-30 19:10:54 -0800
commit10626c32e3827bca560217966f5bd586c4e91584 (patch)
treedb45aeec301859aa5885fba76298b9c272d5443e /arch/riscv/kernel/mcount.S
parent5d44bf2065e169dd857a4207505210fce25743e6 (diff)
riscv/ftrace: Add basic support
This patch contains basic ftrace support for RV64I platform. Specifically, function tracer (HAVE_FUNCTION_TRACER), function graph tracer (HAVE_FUNCTION_GRAPH_TRACER), and a frame pointer test (HAVE_FUNCTION_GRAPH_FP_TEST) are implemented following the instructions in Documentation/trace/ftrace-design.txt. Note that the functions in both ftrace.c and setup.c should not be hooked with the compiler's -pg option: to prevent infinite self- referencing for the former, and to ignore early setup stuff for the latter. Signed-off-by: Alan Kao <alankao@andestech.com> Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
Diffstat (limited to 'arch/riscv/kernel/mcount.S')
-rw-r--r--arch/riscv/kernel/mcount.S126
1 files changed, 126 insertions, 0 deletions
diff --git a/arch/riscv/kernel/mcount.S b/arch/riscv/kernel/mcount.S
new file mode 100644
index 000000000000..c46a778627be
--- /dev/null
+++ b/arch/riscv/kernel/mcount.S
@@ -0,0 +1,126 @@
+/* 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
+
+ /*
+ * The call to ftrace_return_to_handler would overwrite the return
+ * register if a0 was not saved.
+ */
+ .macro SAVE_RET_ABI_STATE
+ addi sp, sp, -32
+ sd s0, 16(sp)
+ sd ra, 24(sp)
+ sd a0, 8(sp)
+ addi s0, sp, 32
+ .endm
+
+ .macro STORE_ABI_STATE
+ ld ra, 8(sp)
+ ld s0, 0(sp)
+ addi sp, sp, 16
+ .endm
+
+ .macro STORE_RET_ABI_STATE
+ ld ra, 24(sp)
+ ld s0, 16(sp)
+ ld a0, 8(sp)
+ addi sp, sp, 32
+ .endm
+
+ENTRY(ftrace_stub)
+ ret
+ENDPROC(ftrace_stub)
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ENTRY(return_to_handler)
+/*
+ * On implementing the frame point test, the ideal way is to compare the
+ * s0 (frame pointer, if enabled) on entry and the sp (stack pointer) on return.
+ * However, the psABI of variable-length-argument functions does not allow this.
+ *
+ * So alternatively we check the *old* frame pointer position, that is, the
+ * value stored in -16(s0) on entry, and the s0 on return.
+ */
+#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
+ mv t6, s0
+#endif
+ SAVE_RET_ABI_STATE
+#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
+ mv a0, t6
+#endif
+ la t0, ftrace_return_to_handler
+ jalr t0
+ mv a1, a0
+ STORE_RET_ABI_STATE
+ jalr a1
+ENDPROC(return_to_handler)
+EXPORT_SYMBOL(return_to_handler)
+#endif
+
+ENTRY(_mcount)
+ la t4, ftrace_stub
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ la t0, ftrace_graph_return
+ ld t1, 0(t0)
+ bne t1, t4, do_ftrace_graph_caller
+
+ la t3, ftrace_graph_entry
+ ld t2, 0(t3)
+ la t6, ftrace_graph_entry_stub
+ bne t2, t6, do_ftrace_graph_caller
+#endif
+ la t3, ftrace_trace_function
+ ld t5, 0(t3)
+ bne t5, t4, do_trace
+ ret
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+/*
+ * A pseudo representation for the function graph tracer:
+ * prepare_to_return(&ra_to_caller_of_caller, ra_to_caller)
+ */
+do_ftrace_graph_caller:
+ addi a0, s0, -8
+ mv a1, ra
+#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
+ ld a2, -16(s0)
+#endif
+ SAVE_ABI_STATE
+ la t0, prepare_ftrace_return
+ jalr t0
+ STORE_ABI_STATE
+ ret
+#endif
+
+/*
+ * A pseudo representation for the function tracer:
+ * (*ftrace_trace_function)(ra_to_caller, ra_to_caller_of_caller)
+ */
+do_trace:
+ ld a1, -8(s0)
+ mv a0, ra
+
+ SAVE_ABI_STATE
+ jalr t5
+ STORE_ABI_STATE
+ ret
+ENDPROC(_mcount)
+EXPORT_SYMBOL(_mcount)