/*
   * Post mortem Dwarf CFI based unwinding on top of regs and stack dumps.
   *
   * Lots of this code have been borrowed or heavily inspired from parts of
   * the libunwind 0.99 code which are (amongst other contributors I may have
   * forgotten):
   *
   * Copyright (C) 2002-2007 Hewlett-Packard Co
   *	Contributed by David Mosberger-Tang <davidm@hpl.hp.com>
   *
   * And the bugs have been added by:
   *
   * Copyright (C) 2010, Frederic Weisbecker <fweisbec@gmail.com>
   * Copyright (C) 2012, Jiri Olsa <jolsa@redhat.com>
   *
   */
  
  #include <elf.h>
  #include <gelf.h>
  #include <fcntl.h>
  #include <string.h>
  #include <unistd.h>
  #include <sys/mman.h>
  #include <linux/list.h>
  #include <libunwind.h>
  #include <libunwind-ptrace.h>
  #include "thread.h"
  #include "session.h"
  #include "perf_regs.h"
  #include "unwind.h"
  #include "symbol.h"
  #include "util.h"
  
  extern int
  UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as,
  				    unw_word_t ip,
  				    unw_dyn_info_t *di,
  				    unw_proc_info_t *pi,
  				    int need_unwind_info, void *arg);
  
  #define dwarf_search_unwind_table UNW_OBJ(dwarf_search_unwind_table)
  
  extern int
  UNW_OBJ(dwarf_find_debug_frame) (int found, unw_dyn_info_t *di_debug,
  				 unw_word_t ip,
  				 unw_word_t segbase,
  				 const char *obj_name, unw_word_t start,
  				 unw_word_t end);
  
  #define dwarf_find_debug_frame UNW_OBJ(dwarf_find_debug_frame)
  
  #define DW_EH_PE_FORMAT_MASK	0x0f	/* format of the encoded value */
  #define DW_EH_PE_APPL_MASK	0x70	/* how the value is to be applied */
  
  /* Pointer-encoding formats: */
  #define DW_EH_PE_omit		0xff
  #define DW_EH_PE_ptr		0x00	/* pointer-sized unsigned value */
  #define DW_EH_PE_udata4		0x03	/* unsigned 32-bit value */
  #define DW_EH_PE_udata8		0x04	/* unsigned 64-bit value */
  #define DW_EH_PE_sdata4		0x0b	/* signed 32-bit value */
  #define DW_EH_PE_sdata8		0x0c	/* signed 64-bit value */
  
  /* Pointer-encoding application: */
  #define DW_EH_PE_absptr		0x00	/* absolute value */
  #define DW_EH_PE_pcrel		0x10	/* rel. to addr. of encoded value */
  
  /*
   * The following are not documented by LSB v1.3, yet they are used by
   * GCC, presumably they aren't documented by LSB since they aren't
   * used on Linux:
   */
  #define DW_EH_PE_funcrel	0x40	/* start-of-procedure-relative */
  #define DW_EH_PE_aligned	0x50	/* aligned pointer */
  
  /* Flags intentionaly not handled, since they're not needed:
   * #define DW_EH_PE_indirect      0x80
   * #define DW_EH_PE_uleb128       0x01
   * #define DW_EH_PE_udata2        0x02
   * #define DW_EH_PE_sleb128       0x09
   * #define DW_EH_PE_sdata2        0x0a
   * #define DW_EH_PE_textrel       0x20
   * #define DW_EH_PE_datarel       0x30
   */
  
  struct unwind_info {
  	struct perf_sample	*sample;
  	struct machine		*machine;
  	struct thread		*thread;
  	u64			sample_uregs;
  };
  
  #define dw_read(ptr, type, end) ({	\
  	type *__p = (type *) ptr;	\
  	type  __v;			\
  	if ((__p + 1) > (type *) end)	\
  		return -EINVAL;		\
  	__v = *__p++;			\
  	ptr = (typeof(ptr)) __p;	\
  	__v;				\
  	})
  
  static int __dw_read_encoded_value(u8 **p, u8 *end, u64 *val,
  				   u8 encoding)
  {
  	u8 *cur = *p;
  	*val = 0;
  
  	switch (encoding) {
  	case DW_EH_PE_omit:
  		*val = 0;
  		goto out;
  	case DW_EH_PE_ptr:
  		*val = dw_read(cur, unsigned long, end);
  		goto out;
  	default:
  		break;
  	}
  
  	switch (encoding & DW_EH_PE_APPL_MASK) {
  	case DW_EH_PE_absptr:
  		break;
  	case DW_EH_PE_pcrel:
  		*val = (unsigned long) cur;
  		break;
  	default:
  		return -EINVAL;
  	}
  
  	if ((encoding & 0x07) == 0x00)
  		encoding |= DW_EH_PE_udata4;
  
  	switch (encoding & DW_EH_PE_FORMAT_MASK) {
  	case DW_EH_PE_sdata4:
  		*val += dw_read(cur, s32, end);
  		break;
  	case DW_EH_PE_udata4:
  		*val += dw_read(cur, u32, end);
  		break;
  	case DW_EH_PE_sdata8:
  		*val += dw_read(cur, s64, end);
  		break;
  	case DW_EH_PE_udata8:
  		*val += dw_read(cur, u64, end);
  		break;
  	default:
  		return -EINVAL;
  	}
  
   out:
  	*p = cur;
  	return 0;
  }
  
  #define dw_read_encoded_value(ptr, end, enc) ({			\
  	u64 __v;						\
  	if (__dw_read_encoded_value(&ptr, end, &__v, enc)) {	\
  		return -EINVAL;                                 \
  	}                                                       \
  	__v;                                                    \
  	})
  
  static u64 elf_section_offset(int fd, const char *name)
  {
  	Elf *elf;
  	GElf_Ehdr ehdr;
  	GElf_Shdr shdr;
  	u64 offset = 0;
  
  	elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL);
  	if (elf == NULL)
  		return 0;
  
  	do {
  		if (gelf_getehdr(elf, &ehdr) == NULL)
  			break;
  
  		if (!elf_section_by_name(elf, &ehdr, &shdr, name, NULL))
  			break;
  
  		offset = shdr.sh_offset;
  	} while (0);
  
  	elf_end(elf);
  	return offset;
  }
  
  struct table_entry {
  	u32 start_ip_offset;
  	u32 fde_offset;
  };
  
  struct eh_frame_hdr {
  	unsigned char version;
  	unsigned char eh_frame_ptr_enc;
  	unsigned char fde_count_enc;
  	unsigned char table_enc;
  
  	/*
  	 * The rest of the header is variable-length and consists of the
  	 * following members:
  	 *
  	 *	encoded_t eh_frame_ptr;
  	 *	encoded_t fde_count;
  	 */
  
  	/* A single encoded pointer should not be more than 8 bytes. */
  	u64 enc[2];
  
  	/*
  	 * struct {
  	 *    encoded_t start_ip;
  	 *    encoded_t fde_addr;
  	 * } binary_search_table[fde_count];
  	 */
  	char data[0];
  } __packed;
  
  static int unwind_spec_ehframe(struct dso *dso, struct machine *machine,
  			       u64 offset, u64 *table_data, u64 *segbase,
  			       u64 *fde_count)
  {
  	struct eh_frame_hdr hdr;
  	u8 *enc = (u8 *) &hdr.enc;
  	u8 *end = (u8 *) &hdr.data;
  	ssize_t r;
  
  	r = dso__data_read_offset(dso, machine, offset,
  				  (u8 *) &hdr, sizeof(hdr));
  	if (r != sizeof(hdr))
  		return -EINVAL;
  
  	/* We dont need eh_frame_ptr, just skip it. */
  	dw_read_encoded_value(enc, end, hdr.eh_frame_ptr_enc);
  
  	*fde_count  = dw_read_encoded_value(enc, end, hdr.fde_count_enc);
  	*segbase    = offset;
  	*table_data = (enc - (u8 *) &hdr) + offset;
  	return 0;
  }
  
  static int read_unwind_spec_eh_frame(struct dso *dso, struct machine *machine,
  				     u64 *table_data, u64 *segbase,
  				     u64 *fde_count)
  {
  	int ret = -EINVAL, fd;
  	u64 offset;
  
  	fd = dso__data_fd(dso, machine);
  	if (fd < 0)
  		return -EINVAL;
  
  	/* Check the .eh_frame section for unwinding info */
  	offset = elf_section_offset(fd, ".eh_frame_hdr");
  	close(fd);
  
  	if (offset)
  		ret = unwind_spec_ehframe(dso, machine, offset,
  					  table_data, segbase,
  					  fde_count);
  
  	return ret;
  }
  
  #ifndef NO_LIBUNWIND_DEBUG_FRAME
  static int read_unwind_spec_debug_frame(struct dso *dso,
  					struct machine *machine, u64 *offset)
  {
  	int fd = dso__data_fd(dso, machine);
  
  	if (fd < 0)
  		return -EINVAL;
  
  	/* Check the .debug_frame section for unwinding info */
  	*offset = elf_section_offset(fd, ".debug_frame");
  	close(fd);
  
  	if (*offset)
  		return 0;
  
  	return -EINVAL;
  }
  #endif
  
  static struct map *find_map(unw_word_t ip, struct unwind_info *ui)
  {
  	struct addr_location al;
  
  	thread__find_addr_map(ui->thread, ui->machine, PERF_RECORD_MISC_USER,
  			      MAP__FUNCTION, ip, &al);
  	return al.map;
  }
  
  static int
  find_proc_info(unw_addr_space_t as, unw_word_t ip, unw_proc_info_t *pi,
  	       int need_unwind_info, void *arg)
  {
  	struct unwind_info *ui = arg;
  	struct map *map;
  	unw_dyn_info_t di;
  	u64 table_data, segbase, fde_count;
  
  	map = find_map(ip, ui);
  	if (!map || !map->dso)
  		return -EINVAL;
  
  	pr_debug("unwind: find_proc_info dso %s
  ", map->dso->name);
  
  	/* Check the .eh_frame section for unwinding info */
  	if (!read_unwind_spec_eh_frame(map->dso, ui->machine,
  				       &table_data, &segbase, &fde_count)) {
  		memset(&di, 0, sizeof(di));
  		di.format   = UNW_INFO_FORMAT_REMOTE_TABLE;
  		di.start_ip = map->start;
  		di.end_ip   = map->end;
  		di.u.rti.segbase    = map->start + segbase;
  		di.u.rti.table_data = map->start + table_data;
  		di.u.rti.table_len  = fde_count * sizeof(struct table_entry)
  				      / sizeof(unw_word_t);
  		return dwarf_search_unwind_table(as, ip, &di, pi,
  						 need_unwind_info, arg);
  	}
  
  #ifndef NO_LIBUNWIND_DEBUG_FRAME
  	/* Check the .debug_frame section for unwinding info */
  	if (!read_unwind_spec_debug_frame(map->dso, ui->machine, &segbase)) {
  		memset(&di, 0, sizeof(di));
  		if (dwarf_find_debug_frame(0, &di, ip, 0, map->dso->name,
  					   map->start, map->end))
  			return dwarf_search_unwind_table(as, ip, &di, pi,
  							 need_unwind_info, arg);
  	}
  #endif
  
  	return -EINVAL;
  }
  
  static int access_fpreg(unw_addr_space_t __maybe_unused as,
  			unw_regnum_t __maybe_unused num,
  			unw_fpreg_t __maybe_unused *val,
  			int __maybe_unused __write,
  			void __maybe_unused *arg)
  {
  	pr_err("unwind: access_fpreg unsupported
  ");
  	return -UNW_EINVAL;
  }
  
  static int get_dyn_info_list_addr(unw_addr_space_t __maybe_unused as,
  				  unw_word_t __maybe_unused *dil_addr,
  				  void __maybe_unused *arg)
  {
  	return -UNW_ENOINFO;
  }
  
  static int resume(unw_addr_space_t __maybe_unused as,
  		  unw_cursor_t __maybe_unused *cu,
  		  void __maybe_unused *arg)
  {
  	pr_err("unwind: resume unsupported
  ");
  	return -UNW_EINVAL;
  }
  
  static int
  get_proc_name(unw_addr_space_t __maybe_unused as,
  	      unw_word_t __maybe_unused addr,
  		char __maybe_unused *bufp, size_t __maybe_unused buf_len,
  		unw_word_t __maybe_unused *offp, void __maybe_unused *arg)
  {
  	pr_err("unwind: get_proc_name unsupported
  ");
  	return -UNW_EINVAL;
  }
  
  static int access_dso_mem(struct unwind_info *ui, unw_word_t addr,
  			  unw_word_t *data)
  {
  	struct addr_location al;
  	ssize_t size;
  
  	thread__find_addr_map(ui->thread, ui->machine, PERF_RECORD_MISC_USER,
  			      MAP__FUNCTION, addr, &al);
  	if (!al.map) {
  		pr_debug("unwind: no map for %lx
  ", (unsigned long)addr);
  		return -1;
  	}
  
  	if (!al.map->dso)
  		return -1;
  
  	size = dso__data_read_addr(al.map->dso, al.map, ui->machine,
  				   addr, (u8 *) data, sizeof(*data));
  
  	return !(size == sizeof(*data));
  }
  
  static int reg_value(unw_word_t *valp, struct regs_dump *regs, int id,
  		     u64 sample_regs)
  {
  	int i, idx = 0;
  
  	if (!(sample_regs & (1 << id)))
  		return -EINVAL;
  
  	for (i = 0; i < id; i++) {
  		if (sample_regs & (1 << i))
  			idx++;
  	}
  
  	*valp = regs->regs[idx];
  	return 0;
  }
  
  static int access_mem(unw_addr_space_t __maybe_unused as,
  		      unw_word_t addr, unw_word_t *valp,
  		      int __write, void *arg)
  {
  	struct unwind_info *ui = arg;
  	struct stack_dump *stack = &ui->sample->user_stack;
  	unw_word_t start, end;
  	int offset;
  	int ret;
  
  	/* Don't support write, probably not needed. */
  	if (__write || !stack || !ui->sample->user_regs.regs) {
  		*valp = 0;
  		return 0;
  	}
  
  	ret = reg_value(&start, &ui->sample->user_regs, PERF_REG_SP,
  			ui->sample_uregs);
  	if (ret)
  		return ret;
  
  	end = start + stack->size;
  
  	/* Check overflow. */
  	if (addr + sizeof(unw_word_t) < addr)
  		return -EINVAL;
  
  	if (addr < start || addr + sizeof(unw_word_t) >= end) {
  		ret = access_dso_mem(ui, addr, valp);
  		if (ret) {
  			pr_debug("unwind: access_mem %p not inside range %p-%p
  ",
  				(void *)addr, (void *)start, (void *)end);
  			*valp = 0;
  			return ret;
  		}
  		return 0;
  	}
  
  	offset = addr - start;
  	*valp  = *(unw_word_t *)&stack->data[offset];
  	pr_debug("unwind: access_mem addr %p, val %lx, offset %d
  ",
  		 (void *)addr, (unsigned long)*valp, offset);
  	return 0;
  }
  
  static int access_reg(unw_addr_space_t __maybe_unused as,
  		      unw_regnum_t regnum, unw_word_t *valp,
  		      int __write, void *arg)
  {
  	struct unwind_info *ui = arg;
  	int id, ret;
  
  	/* Don't support write, I suspect we don't need it. */
  	if (__write) {
  		pr_err("unwind: access_reg w %d
  ", regnum);
  		return 0;
  	}
  
  	if (!ui->sample->user_regs.regs) {
  		*valp = 0;
  		return 0;
  	}
  
  	id = unwind__arch_reg_id(regnum);
  	if (id < 0)
  		return -EINVAL;
  
  	ret = reg_value(valp, &ui->sample->user_regs, id, ui->sample_uregs);
  	if (ret) {
  		pr_err("unwind: can't read reg %d
  ", regnum);
  		return ret;
  	}
  
  	pr_debug("unwind: reg %d, val %lx
  ", regnum, (unsigned long)*valp);
  	return 0;
  }
  
  static void put_unwind_info(unw_addr_space_t __maybe_unused as,
  			    unw_proc_info_t *pi __maybe_unused,
  			    void *arg __maybe_unused)
  {
  	pr_debug("unwind: put_unwind_info called
  ");
  }
  
  static int entry(u64 ip, struct thread *thread, struct machine *machine,
  		 unwind_entry_cb_t cb, void *arg)
  {
  	struct unwind_entry e;
  	struct addr_location al;
  
  	thread__find_addr_location(thread, machine,
  				   PERF_RECORD_MISC_USER,
  				   MAP__FUNCTION, ip, &al);
  
  	e.ip = ip;
  	e.map = al.map;
  	e.sym = al.sym;
  
  	pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")
  ",
  		 al.sym ? al.sym->name : "''",
  		 ip,
  		 al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
  
  	return cb(&e, arg);
  }
  
  static void display_error(int err)
  {
  	switch (err) {
  	case UNW_EINVAL:
  		pr_err("unwind: Only supports local.
  ");
  		break;
  	case UNW_EUNSPEC:
  		pr_err("unwind: Unspecified error.
  ");
  		break;
  	case UNW_EBADREG:
  		pr_err("unwind: Register unavailable.
  ");
  		break;
  	default:
  		break;
  	}
  }
  
  static unw_accessors_t accessors = {
  	.find_proc_info		= find_proc_info,
  	.put_unwind_info	= put_unwind_info,
  	.get_dyn_info_list_addr	= get_dyn_info_list_addr,
  	.access_mem		= access_mem,
  	.access_reg		= access_reg,
  	.access_fpreg		= access_fpreg,
  	.resume			= resume,
  	.get_proc_name		= get_proc_name,
  };
  
  static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
  		       void *arg, int max_stack)
  {
  	unw_addr_space_t addr_space;
  	unw_cursor_t c;
  	int ret;
  
  	addr_space = unw_create_addr_space(&accessors, 0);
  	if (!addr_space) {
  		pr_err("unwind: Can't create unwind address space.
  ");
  		return -ENOMEM;
  	}
  
  	ret = unw_init_remote(&c, addr_space, ui);
  	if (ret)
  		display_error(ret);
  
  	while (!ret && (unw_step(&c) > 0) && max_stack--) {
  		unw_word_t ip;
  
  		unw_get_reg(&c, UNW_REG_IP, &ip);
  		ret = entry(ip, ui->thread, ui->machine, cb, arg);
  	}
  
  	unw_destroy_addr_space(addr_space);
  	return ret;
  }
  
  int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
  			struct machine *machine, struct thread *thread,
  			u64 sample_uregs, struct perf_sample *data,
  			int max_stack)
  {
  	unw_word_t ip;
  	struct unwind_info ui = {
  		.sample       = data,
  		.sample_uregs = sample_uregs,
  		.thread       = thread,
  		.machine      = machine,
  	};
  	int ret;
  
  	if (!data->user_regs.regs)
  		return -EINVAL;
  
  	ret = reg_value(&ip, &data->user_regs, PERF_REG_IP, sample_uregs);
  	if (ret)
  		return ret;
  
  	ret = entry(ip, thread, machine, cb, arg);
  	if (ret)
  		return -ENOMEM;
  
  	return get_entries(&ui, cb, arg, max_stack);
  }