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@@ -0,0 +1,175 @@
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+#include <linux/oprofile.h>
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+#include <linux/sched.h>
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+#include <linux/mm.h>
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+#include <linux/uaccess.h>
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+#include <asm/ptrace.h>
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+#include <asm/stacktrace.h>
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+#include <linux/stacktrace.h>
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+#include <linux/kernel.h>
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+#include <asm/sections.h>
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+#include <asm/inst.h>
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+
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+struct stackframe {
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+ unsigned long sp;
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+ unsigned long pc;
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+ unsigned long ra;
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+};
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+
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+static inline int get_mem(unsigned long addr, unsigned long *result)
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+{
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+ unsigned long *address = (unsigned long *) addr;
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+ if (!access_ok(VERIFY_READ, addr, sizeof(unsigned long)))
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+ return -1;
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+ if (__copy_from_user_inatomic(result, address, sizeof(unsigned long)))
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+ return -3;
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+ return 0;
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+}
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+
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+/*
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+ * These two instruction helpers were taken from process.c
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+ */
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+static inline int is_ra_save_ins(union mips_instruction *ip)
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+{
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+ /* sw / sd $ra, offset($sp) */
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+ return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op)
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+ && ip->i_format.rs == 29 && ip->i_format.rt == 31;
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+}
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+
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+static inline int is_sp_move_ins(union mips_instruction *ip)
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+{
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+ /* addiu/daddiu sp,sp,-imm */
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+ if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
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+ return 0;
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+ if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
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+ return 1;
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+ return 0;
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+}
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+
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+/*
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+ * Looks for specific instructions that mark the end of a function.
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+ * This usually means we ran into the code area of the previous function.
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+ */
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+static inline int is_end_of_function_marker(union mips_instruction *ip)
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+{
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+ /* jr ra */
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+ if (ip->r_format.func == jr_op && ip->r_format.rs == 31)
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+ return 1;
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+ /* lui gp */
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+ if (ip->i_format.opcode == lui_op && ip->i_format.rt == 28)
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+ return 1;
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+ return 0;
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+}
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+
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+/*
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+ * TODO for userspace stack unwinding:
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+ * - handle cases where the stack is adjusted inside a function
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+ * (generally doesn't happen)
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+ * - find optimal value for max_instr_check
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+ * - try to find a way to handle leaf functions
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+ */
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+
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+static inline int unwind_user_frame(struct stackframe *old_frame,
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+ const unsigned int max_instr_check)
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+{
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+ struct stackframe new_frame = *old_frame;
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+ off_t ra_offset = 0;
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+ size_t stack_size = 0;
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+ unsigned long addr;
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+
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+ if (old_frame->pc == 0 || old_frame->sp == 0 || old_frame->ra == 0)
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+ return -9;
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+
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+ for (addr = new_frame.pc; (addr + max_instr_check > new_frame.pc)
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+ && (!ra_offset || !stack_size); --addr) {
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+ union mips_instruction ip;
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+
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+ if (get_mem(addr, (unsigned long *) &ip))
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+ return -11;
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+
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+ if (is_sp_move_ins(&ip)) {
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+ int stack_adjustment = ip.i_format.simmediate;
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+ if (stack_adjustment > 0)
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+ /* This marks the end of the previous function,
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+ which means we overran. */
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+ break;
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+ stack_size = (unsigned) stack_adjustment;
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+ } else if (is_ra_save_ins(&ip)) {
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+ int ra_slot = ip.i_format.simmediate;
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+ if (ra_slot < 0)
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+ /* This shouldn't happen. */
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+ break;
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+ ra_offset = ra_slot;
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+ } else if (is_end_of_function_marker(&ip))
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+ break;
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+ }
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+
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+ if (!ra_offset || !stack_size)
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+ return -1;
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+
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+ if (ra_offset) {
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+ new_frame.ra = old_frame->sp + ra_offset;
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+ if (get_mem(new_frame.ra, &(new_frame.ra)))
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+ return -13;
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+ }
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+
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+ if (stack_size) {
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+ new_frame.sp = old_frame->sp + stack_size;
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+ if (get_mem(new_frame.sp, &(new_frame.sp)))
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+ return -14;
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+ }
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+
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+ if (new_frame.sp > old_frame->sp)
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+ return -2;
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+
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+ new_frame.pc = old_frame->ra;
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+ *old_frame = new_frame;
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+
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+ return 0;
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+}
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+
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+static inline void do_user_backtrace(unsigned long low_addr,
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+ struct stackframe *frame,
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+ unsigned int depth)
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+{
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+ const unsigned int max_instr_check = 512;
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+ const unsigned long high_addr = low_addr + THREAD_SIZE;
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+
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+ while (depth-- && !unwind_user_frame(frame, max_instr_check)) {
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+ oprofile_add_trace(frame->ra);
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+ if (frame->sp < low_addr || frame->sp > high_addr)
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+ break;
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+ }
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+}
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+
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+#ifndef CONFIG_KALLSYMS
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+static inline void do_kernel_backtrace(unsigned long low_addr,
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+ struct stackframe *frame,
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+ unsigned int depth) { }
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+#else
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+static inline void do_kernel_backtrace(unsigned long low_addr,
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+ struct stackframe *frame,
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+ unsigned int depth)
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+{
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+ while (depth-- && frame->pc) {
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+ frame->pc = unwind_stack_by_address(low_addr,
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+ &(frame->sp),
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+ frame->pc,
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+ &(frame->ra));
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+ oprofile_add_trace(frame->ra);
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+ }
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+}
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+#endif
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+
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+void notrace op_mips_backtrace(struct pt_regs *const regs, unsigned int depth)
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+{
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+ struct stackframe frame = { .sp = regs->regs[29],
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+ .pc = regs->cp0_epc,
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+ .ra = regs->regs[31] };
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+ const int userspace = user_mode(regs);
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+ const unsigned long low_addr = ALIGN(frame.sp, THREAD_SIZE);
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+
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+ if (userspace)
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+ do_user_backtrace(low_addr, &frame, depth);
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+ else
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+ do_kernel_backtrace(low_addr, &frame, depth);
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+}
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