From: Daniel Kalmar <kalmard@xxxxxxxxxxxxx>
Stack unwinding is done by code examination. For kernelspace, the
already existing unwind function is utilized that uses kallsyms to
quickly find the beginning of functions. For userspace a new function
was added that examines code at and before the pc.
Signed-off-by: Daniel Kalmar <kalmard@xxxxxxxxxxxxx>
Signed-off-by: Gergely Kis <gergely@xxxxxxxxxxxxx>
---
arch/mips/oprofile/Makefile | 2 +-
arch/mips/oprofile/backtrace.c | 173 ++++++++++++++++++++++++++++++++++++++++
arch/mips/oprofile/common.c | 1 +
arch/mips/oprofile/op_impl.h | 2 +
4 files changed, 177 insertions(+), 1 deletions(-)
create mode 100644 arch/mips/oprofile/backtrace.c
diff --git a/arch/mips/oprofile/Makefile b/arch/mips/oprofile/Makefile
index 4b9d704..29f2f13 100644
--- a/arch/mips/oprofile/Makefile
+++ b/arch/mips/oprofile/Makefile
@@ -8,7 +8,7 @@ DRIVER_OBJS = $(addprefix ../../../drivers/oprofile/, \
oprofilefs.o oprofile_stats.o \
timer_int.o )
-oprofile-y := $(DRIVER_OBJS) common.o
+oprofile-y := $(DRIVER_OBJS) common.o backtrace.o
oprofile-$(CONFIG_CPU_MIPS32) += op_model_mipsxx.o
oprofile-$(CONFIG_CPU_MIPS64) += op_model_mipsxx.o
diff --git a/arch/mips/oprofile/backtrace.c b/arch/mips/oprofile/backtrace.c
new file mode 100644
index 0000000..d508e9e
--- /dev/null
+++ b/arch/mips/oprofile/backtrace.c
@@ -0,0 +1,173 @@
+#include <linux/oprofile.h>
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <linux/uaccess.h>
+#include <asm/ptrace.h>
+#include <asm/stacktrace.h>
+#include <linux/stacktrace.h>
+#include <linux/kernel.h>
+#include <asm/sections.h>
+#include <asm/inst.h>
+
+struct stackframe {
+ unsigned long sp;
+ unsigned long pc;
+ unsigned long ra;
+};
+
+static inline int get_mem(unsigned long addr, unsigned long *result)
+{
+ unsigned long *address = (unsigned long *) addr;
+ if (!access_ok(VERIFY_READ, addr, sizeof(unsigned long)))
+ return -1;
+ if (__copy_from_user_inatomic(result, address, sizeof(unsigned long)))
+ return -3;
+ return 0;
+}
+
+/*
+ * These two instruction helpers were taken from process.c
+ */
+static inline int is_ra_save_ins(union mips_instruction *ip)
+{
+ /* sw / sd $ra, offset($sp) */
+ return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op)
+ && ip->i_format.rs == 29 && ip->i_format.rt == 31;
+}
+
+static inline int is_sp_move_ins(union mips_instruction *ip)
+{
+ /* addiu/daddiu sp,sp,-imm */
+ if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
+ return 0;
+ if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
+ return 1;
+ return 0;
+}
+
+/*
+ * Looks for specific instructions that mark the end of a function.
+ * This usually means we ran into the code area of the previous function.
+ */
+static inline int is_end_of_function_marker(union mips_instruction *ip)
+{
+ /* jr ra */
+ if (ip->r_format.func == jr_op && ip->r_format.rs == 31)
+ return 1;
+ /* lui gp */
+ if (ip->i_format.opcode == lui_op && ip->i_format.rt == 28)
+ return 1;
+ return 0;
+}
+
+/*
+ * TODO for userspace stack unwinding:
+ * - handle cases where the stack is adjusted inside a function
+ * (generally doesn't happen)
+ * - find optimal value for max_instr_check
+ * - try to find a way to handle leaf functions
+ */
+
+static inline int unwind_user_frame(struct stackframe *old_frame,
+ const unsigned int max_instr_check)
+{
+ struct stackframe new_frame = *old_frame;
+ off_t ra_offset = 0;
+ size_t stack_size = 0;
+ unsigned long addr;
+
+ if (old_frame->pc == 0 || old_frame->sp == 0 || old_frame->ra == 0)
+ return -9;
+
+ for (addr = new_frame.pc; (addr + max_instr_check > new_frame.pc)
+ && (!ra_offset || !stack_size); --addr) {
+ union mips_instruction ip;
+
+ if (get_mem(addr, (unsigned long *) &ip))
+ return -11;
+
+ if (is_sp_move_ins(&ip)) {
+ int stack_adjustment = ip.i_format.simmediate;
+ if (stack_adjustment > 0)
+ /* This marks the end of the previous function,
+ which means we overran. */
+ break;
+ stack_size = (unsigned) stack_adjustment;
+ } else if (is_ra_save_ins(&ip)) {
+ int ra_slot = ip.i_format.simmediate;
+ if (ra_slot < 0)
+ /* This shouldn't happen. */
+ break;
+ ra_offset = ra_slot;
+ } else if (is_end_of_function_marker(&ip))
+ break;
+ }
+
+ if (!ra_offset || !stack_size)
+ return -1;
+
+ if (ra_offset) {
+ new_frame.ra = old_frame->sp + ra_offset;
+ if (get_mem(new_frame.ra, &(new_frame.ra)))
+ return -13;
+ }
+
+ if (stack_size) {
+ new_frame.sp = old_frame->sp + stack_size;
+ if (get_mem(new_frame.sp, &(new_frame.sp)))
+ return -14;
+ }
+
+ if (new_frame.sp > old_frame->sp)
+ return -2;
+
+ new_frame.pc = old_frame->ra;
+ *old_frame = new_frame;
+
+ return 0;
+}
+
+static inline void do_user_backtrace(unsigned long low_addr,
+ struct stackframe *frame,
+ unsigned int depth) {
+ const unsigned int max_instr_check = 512;
+ const unsigned long high_addr = low_addr + THREAD_SIZE;
+
+ while (depth-- && !unwind_user_frame(frame, max_instr_check)) {
+ oprofile_add_trace(frame->ra);
+ if (frame->sp < low_addr || frame->sp > high_addr)
+ break;
+ }
+}
+
+#ifndef CONFIG_KALLSYMS
+static inline void do_kernel_backtrace(unsigned long low_addr,
+ struct stackframe *frame,
+ unsigned int depth) { }
+#else
+static inline void do_kernel_backtrace(unsigned long low_addr,
+ struct stackframe *frame,
+ unsigned int depth) {
+ while (depth-- && frame->pc) {
+ frame->pc = unwind_stack_by_address(low_addr,
+ &(frame->sp),
+ frame->pc,
+ &(frame->ra));
+ oprofile_add_trace(frame->ra);
+ }
+}
+#endif
+
+void notrace op_mips_backtrace(struct pt_regs *const regs, unsigned int depth)
+{
+ struct stackframe frame = { .sp = regs->regs[29],
+ .pc = regs->cp0_epc,
+ .ra = regs->regs[31] };
+ const int userspace = user_mode(regs);
+ const unsigned long low_addr = ALIGN(frame.sp, THREAD_SIZE);
+
+ if (userspace)
+ do_user_backtrace(low_addr, &frame, depth);
+ else
+ do_kernel_backtrace(low_addr, &frame, depth);
+}
diff --git a/arch/mips/oprofile/common.c b/arch/mips/oprofile/common.c
index f9eb1ab..d1f2d4c 100644
--- a/arch/mips/oprofile/common.c
+++ b/arch/mips/oprofile/common.c
@@ -115,6 +115,7 @@ int __init oprofile_arch_init(struct oprofile_operations *ops)
ops->start = op_mips_start;
ops->stop = op_mips_stop;
ops->cpu_type = lmodel->cpu_type;
+ ops->backtrace = op_mips_backtrace;
printk(KERN_INFO "oprofile: using %s performance monitoring.\n",
lmodel->cpu_type);
diff --git a/arch/mips/oprofile/op_impl.h b/arch/mips/oprofile/op_impl.h
index f04b54f..7c2da27 100644
--- a/arch/mips/oprofile/op_impl.h
+++ b/arch/mips/oprofile/op_impl.h
@@ -36,4 +36,6 @@ struct op_mips_model {
unsigned char num_counters;
};
+void op_mips_backtrace(struct pt_regs * const regs, unsigned int depth);
+
#endif
--
1.7.0.4
