[Libunwind-devel] [PATCH 2/3] Add module for parsing ARM-specific unwind tables

[Ken Werner]

From: Zachary T Welch <address@hidden>

Handles lookup, extracting unwind entries, and decoding the entry.

Signed-off-by: Ken Werner <address@hidden>
---
 include/tdep-arm/ex_tables.h   |   75 +++++++
 include/tdep-arm/libunwind_i.h |    1 +
 src/Makefile.am                |    3 +-
 src/arm/ex_tables.c            |  432 ++++++++++++++++++++++++++++++++++++++++
 src/elfxx.h                    |    4 +-
 5 files changed, 512 insertions(+), 3 deletions(-)
 create mode 100644 include/tdep-arm/ex_tables.h
 create mode 100644 src/arm/ex_tables.c

diff --git a/include/tdep-arm/ex_tables.h b/include/tdep-arm/ex_tables.h
new file mode 100644
index 0000000..17de86b
--- /dev/null
+++ b/include/tdep-arm/ex_tables.h
@@ -0,0 +1,75 @@
+/* libunwind - a platform-independent unwind library
+   Copyright 2011 Linaro Limited
+
+This file is part of libunwind.
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
+
+#ifndef ARM_EX_TABLES_H
+#define ARM_EX_TABLES_H
+
+struct arm_exidx_entry
+{
+  uint32_t addr;
+  uint32_t data;
+};
+
+struct arm_exidx_table
+{
+  const char *name;
+  struct arm_exidx_entry *start;
+  struct arm_exidx_entry *end;
+  void *start_addr;
+  void *end_addr;
+};
+
+typedef enum arm_exbuf_cmd
+{
+  ARM_EXIDX_CMD_FINISH,
+  ARM_EXIDX_CMD_DATA_PUSH,
+  ARM_EXIDX_CMD_DATA_POP,
+  ARM_EXIDX_CMD_REG_POP,
+  ARM_EXIDX_CMD_REG_TO_SP,
+  ARM_EXIDX_CMD_VFP_POP,
+  ARM_EXIDX_CMD_WREG_POP,
+  ARM_EXIDX_CMD_WCGR_POP,
+  ARM_EXIDX_CMD_RESERVED,
+  ARM_EXIDX_CMD_REFUSED,
+} arm_exbuf_cmd_t;
+
+struct arm_exbuf_data
+{
+  arm_exbuf_cmd_t cmd;
+  uint32_t data;
+};
+
+void arm_exidx_init_local (void);
+void arm_exidx_table_add (const char *name,
+                        struct arm_exidx_entry *start,
+                        struct arm_exidx_entry *end);
+struct arm_exidx_table *arm_exidx_table_find (void *pc);
+struct arm_exidx_entry *arm_exidx_table_lookup (struct arm_exidx_table *table,
+                                               void *pc);
+int arm_exidx_extract (struct arm_exidx_entry *entry, uint8_t * buf);
+int arm_exidx_decode (const uint8_t * buf, uint8_t len,
+                     struct dwarf_cursor *c);
+int arm_exidx_apply_cmd (struct arm_exbuf_data *edata, struct dwarf_cursor *c);
+
+#endif /* ARM_EX_TABLES_H */
diff --git a/include/tdep-arm/libunwind_i.h b/include/tdep-arm/libunwind_i.h
index 5f02ed0..21628cf 100644
--- a/include/tdep-arm/libunwind_i.h
+++ b/include/tdep-arm/libunwind_i.h
@@ -34,6 +34,7 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 
SOFTWARE.  */
 #include "elf32.h"
 #include "mempool.h"
 #include "dwarf.h"
+#include "ex_tables.h"
 
 struct unw_addr_space
   {
diff --git a/src/Makefile.am b/src/Makefile.am
index b87cbab..7c1505a 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -137,7 +137,8 @@ libunwind_la_LIBADD += $(LIBUNWIND_ELF)
 # The list of files that go into libunwind and libunwind-arm:
 noinst_HEADERS += arm/init.h arm/offsets.h arm/unwind_i.h
 libunwind_la_SOURCES_arm_common = $(libunwind_la_SOURCES_common)           \
-       arm/is_fpreg.c arm/regname.c
+       arm/is_fpreg.c arm/regname.c                                        \
+       arm/ex_tables.c arm/ex_tables.h
 
 # The list of files that go into libunwind:
 libunwind_la_SOURCES_arm = $(libunwind_la_SOURCES_arm_common)              \
diff --git a/src/arm/ex_tables.c b/src/arm/ex_tables.c
new file mode 100644
index 0000000..9a7baf3
--- /dev/null
+++ b/src/arm/ex_tables.c
@@ -0,0 +1,432 @@
+/* libunwind - a platform-independent unwind library
+   Copyright 2011 Linaro Limited
+
+This file is part of libunwind.
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
+
+#include "libunwind_i.h"
+
+#define ARM_EXBUF_START(x)     (((x) >> 4) & 0x0f)
+#define ARM_EXBUF_COUNT(x)     ((x) & 0x0f)
+#define ARM_EXBUF_END(x)       (ARM_EXBUF_START(x) + ARM_EXBUF_COUNT(x))
+
+#define ARM_EXIDX_CANT_UNWIND  0x00000001
+#define ARM_EXIDX_COMPACT      0x80000000
+
+#define ARM_EXTBL_OP_FINISH    0xb0
+
+#define ARM_EXIDX_TABLE_LIMIT  32
+
+enum arm_exbuf_cmd_flags
+{
+  ARM_EXIDX_VFP_SHIFT_16 = 1 << 16,
+  ARM_EXIDX_VFP_DOUBLE = 1 << 17,
+};
+
+static struct arm_exidx_table arm_exidx_tables[ARM_EXIDX_TABLE_LIMIT];
+static unsigned arm_exidx_table_count = 0;
+
+static inline void *
+prel31_to_addr (void *addr)
+{
+  uint32_t offset = ((long) *(uint32_t *) addr << 1) >> 1;
+  return (char *) addr + offset;
+}
+
+static inline uint32_t
+prel31_read (uint32_t prel31)
+{
+  return ((int32_t) prel31 << 1) >> 1;
+}
+
+static void
+arm_exidx_table_reset_all (void)
+{
+  arm_exidx_table_count = 0;
+}
+
+HIDDEN void
+arm_exidx_table_add (const char *name,
+                    struct arm_exidx_entry *start,
+                    struct arm_exidx_entry *end)
+{
+  if (arm_exidx_table_count >= ARM_EXIDX_TABLE_LIMIT)
+    return -1;
+  struct arm_exidx_table *table = &arm_exidx_tables[arm_exidx_table_count++];
+  table->name = name;
+  table->start = start;
+  table->end = end;
+  table->start_addr = prel31_to_addr (&start->addr);
+  table->end_addr = prel31_to_addr (&(end - 1)->addr);
+  Debug (2, "name=%s, range=%p-%p, addr=%p-%p\n",
+        name, start, end, table->start_addr, table->end_addr);
+}
+
+/**
+ * Locate the appropriate unwind table from the given PC.
+ */
+HIDDEN struct arm_exidx_table *
+arm_exidx_table_find (void *pc)
+{
+  struct arm_exidx_table *table;
+  unsigned i;
+  for (i = 0; i < arm_exidx_table_count; i++)
+    {
+      table = &arm_exidx_tables[i];
+      if (pc >= table->start_addr && pc < table->end_addr)
+       return table;
+    }
+  return NULL;
+}
+
+HIDDEN struct arm_exidx_entry *
+arm_exidx_table_lookup (struct arm_exidx_table *table, void *pc)
+{
+  struct arm_exidx_entry *first = table->start, *last = table->end - 1;
+  if (pc < prel31_to_addr (&first->addr))
+    return NULL;
+  else if (pc >= prel31_to_addr (&last->addr))
+    return last;
+  while (first < last - 1)
+    {
+      struct arm_exidx_entry *mid = first + ((last - first + 1) >> 1);
+      if (pc < prel31_to_addr (&mid->addr))
+       last = mid;
+      else
+       first = mid;
+    }
+  return first;
+}
+
+/**
+ * Applies the given command onto the new state to the given dwarf_cursor.
+ */
+HIDDEN int
+arm_exidx_apply_cmd (struct arm_exbuf_data *edata, struct dwarf_cursor *c)
+{
+  int ret = 0;
+  unsigned i;
+
+  switch (edata->cmd)
+    {
+    case ARM_EXIDX_CMD_FINISH:
+      /* Set LR to PC if not set already.  */
+      if (DWARF_IS_NULL_LOC (c->loc[UNW_ARM_R15]))
+       c->loc[UNW_ARM_R15] = c->loc[UNW_ARM_R14];
+      /* Set IP.  */
+      dwarf_get (c, c->loc[UNW_ARM_R15], &c->ip);
+      break;
+    case ARM_EXIDX_CMD_DATA_PUSH:
+      Debug (2, "vsp = vsp - %d\n", edata->data);
+      c->cfa -= edata->data;
+      break;
+    case ARM_EXIDX_CMD_DATA_POP:
+      Debug (2, "vsp = vsp + %d\n", edata->data);
+      c->cfa += edata->data;
+      break;
+    case ARM_EXIDX_CMD_REG_POP:
+      for (i = 0; i < 16; i++)
+       if (edata->data & (1 << i))
+         {
+           Debug (2, "pop {r%d}\n", i);
+           c->loc[UNW_ARM_R0 + i] = DWARF_LOC (c->cfa, 0);
+           c->cfa += 4;
+         }
+      /* Set cfa in case the SP got popped. */
+      if (edata->data & (1 << 13))
+       dwarf_get (c, c->loc[UNW_ARM_R13], &c->cfa);
+      break;
+    case ARM_EXIDX_CMD_REG_TO_SP:
+      assert (edata->data < 16);
+      Debug (2, "vsp = r%d\n", edata->data);
+      c->loc[UNW_ARM_R13] = c->loc[UNW_ARM_R0 + edata->data];
+      dwarf_get (c, c->loc[UNW_ARM_R13], &c->cfa);
+      break;
+    case ARM_EXIDX_CMD_VFP_POP:
+      /* Skip VFP registers, but be sure to adjust stack */
+      for (i = ARM_EXBUF_START (edata->data); i < ARM_EXBUF_END (edata->data);
+          i++)
+       c->cfa += 8;
+      if (!(edata->data & ARM_EXIDX_VFP_DOUBLE))
+       c->cfa += 4;
+      break;
+    case ARM_EXIDX_CMD_WREG_POP:
+      for (i = ARM_EXBUF_START (edata->data); i < ARM_EXBUF_END (edata->data);
+          i++)
+       c->cfa += 8;
+      break;
+    case ARM_EXIDX_CMD_WCGR_POP:
+      for (i = 0; i < 4; i++)
+       if (edata->data & (1 << i))
+         c->cfa += 4;
+      break;
+    case ARM_EXIDX_CMD_REFUSED:
+    case ARM_EXIDX_CMD_RESERVED:
+      ret = -1;
+      break;
+    }
+  return ret;
+}
+
+/**
+ * Decodes the given unwind instructions into arm_exbuf_data and calls
+ * arm_exidx_apply_cmd that applies the command onto the dwarf_cursor.
+ */
+HIDDEN int
+arm_exidx_decode (const uint8_t *buf, uint8_t len, struct dwarf_cursor *c)
+{
+#define READ_OP() *buf++
+  const uint8_t *end = buf + len;
+  int ret;
+  struct arm_exbuf_data edata;
+
+  assert (buf != NULL);
+  assert (len > 0);
+
+  while (buf < end)
+    {
+      uint8_t op = READ_OP ();
+      if ((op & 0xc0) == 0x00)
+       {
+         edata.cmd = ARM_EXIDX_CMD_DATA_POP;
+         edata.data = (((int) op & 0x3f) << 2) + 4;
+       }
+      else if ((op & 0xc0) == 0x40)
+       {
+         edata.cmd = ARM_EXIDX_CMD_DATA_PUSH;
+         edata.data = (((int) op & 0x3f) << 2) + 4;
+       }
+      else if ((op & 0xf0) == 0x80)
+       {
+         uint8_t op2 = READ_OP ();
+         if (op == 0x80 && op2 == 0x00)
+           edata.cmd = ARM_EXIDX_CMD_REFUSED;
+         else
+           {
+             edata.cmd = ARM_EXIDX_CMD_REG_POP;
+             edata.data = ((op & 0xf) << 8) | op2;
+             edata.data = edata.data << 4;
+           }
+       }
+      else if ((op & 0xf0) == 0x90)
+       {
+         if (op == 0x9d || op == 0x9f)
+           edata.cmd = ARM_EXIDX_CMD_RESERVED;
+         else
+           {
+             edata.cmd = ARM_EXIDX_CMD_REG_TO_SP;
+             edata.data = op & 0x0f;
+           }
+       }
+      else if ((op & 0xf0) == 0xa0)
+       {
+         unsigned end = (op & 0x07);
+         edata.data = (1 << (end + 1)) - 1;
+         edata.data = edata.data << 4;
+         if (op & 0x08)
+           edata.data |= 1 << 14;
+         edata.cmd = ARM_EXIDX_CMD_REG_POP;
+       }
+      else if (op == ARM_EXTBL_OP_FINISH)
+       {
+         edata.cmd = ARM_EXIDX_CMD_FINISH;
+         buf = end;
+       }
+      else if (op == 0xb1)
+       {
+         uint8_t op2 = READ_OP ();
+         if (op2 == 0 || (op2 & 0xf0))
+           edata.cmd = ARM_EXIDX_CMD_RESERVED;
+         else
+           {
+             edata.cmd = ARM_EXIDX_CMD_REG_POP;
+             edata.data = op2 & 0x0f;
+           }
+       }
+      else if (op == 0xb2)
+       {
+         uint32_t offset = 0;
+         uint8_t byte, shift = 0;
+         do
+           {
+             byte = READ_OP ();
+             offset |= (byte & 0x7f) << shift;
+             shift += 7;
+           }
+         while (byte & 0x80);
+         edata.data = (offset << 2) + 0x204;
+         edata.cmd = ARM_EXIDX_CMD_DATA_POP;
+       }
+      else if (op == 0xb3 || op == 0xc8 || op == 0xc9)
+       {
+         edata.cmd = ARM_EXIDX_CMD_VFP_POP;
+         edata.data = READ_OP ();
+         if (op == 0xc8)
+           edata.data |= ARM_EXIDX_VFP_SHIFT_16;
+         if (op != 0xb3)
+           edata.data |= ARM_EXIDX_VFP_DOUBLE;
+       }
+      else if ((op & 0xf8) == 0xb8 || (op & 0xf8) == 0xd0)
+       {
+         edata.cmd = ARM_EXIDX_CMD_VFP_POP;
+         edata.data = 0x80 | (op & 0x07);
+         if ((op & 0xf8) == 0xd0)
+           edata.data |= ARM_EXIDX_VFP_DOUBLE;
+       }
+      else if (op >= 0xc0 && op <= 0xc5)
+       {
+         edata.cmd = ARM_EXIDX_CMD_WREG_POP;
+         edata.data = 0xa0 | (op & 0x07);
+       }
+      else if (op == 0xc6)
+       {
+         edata.cmd = ARM_EXIDX_CMD_WREG_POP;
+         edata.data = READ_OP ();
+       }
+      else if (op == 0xc7)
+       {
+         uint8_t op2 = READ_OP ();
+         if (op2 == 0 || (op2 & 0xf0))
+           edata.cmd = ARM_EXIDX_CMD_RESERVED;
+         else
+           {
+             edata.cmd = ARM_EXIDX_CMD_WCGR_POP;
+             edata.data = op2 & 0x0f;
+           }
+       }
+      else
+       edata.cmd = ARM_EXIDX_CMD_RESERVED;
+
+      ret = arm_exidx_apply_cmd (&edata, c);
+      if (ret < 0)
+       return ret;
+    }
+  return 0;
+}
+
+/**
+ * Reads the given entry and extracts the unwind instructions into buf.
+ * Returns the number of the extracted unwind insns or -UNW_ESTOPUNWIND
+ * if the special bit pattern ARM_EXIDX_CANT_UNWIND (0x1) was found.
+ */
+HIDDEN int
+arm_exidx_extract (struct arm_exidx_entry *entry, uint8_t *buf)
+{
+  int nbuf = 0;
+  uint32_t *addr = prel31_to_addr (&entry->addr);
+
+  uint32_t data = entry->data;
+  if (data == ARM_EXIDX_CANT_UNWIND)
+    {
+      Debug (2, "0x1 [can't unwind]\n");
+      nbuf = -UNW_ESTOPUNWIND;
+    }
+  else if (data & ARM_EXIDX_COMPACT)
+    {
+      Debug (2, "%p compact model %d [%8.8x]\n", addr, (data >> 24) & 0x7f,
+            data);
+      buf[nbuf++] = data >> 16;
+      buf[nbuf++] = data >> 8;
+      buf[nbuf++] = data;
+    }
+  else
+    {
+      uint32_t *extbl_data = prel31_to_addr (&entry->data);
+      data = extbl_data[0];
+      unsigned int n_table_words = 0;
+      if (data & ARM_EXIDX_COMPACT)
+       {
+         int pers = (data >> 24) & 0x0f;
+         Debug (2, "%p compact model %d [%8.8x]\n", addr, pers, data);
+         if (pers == 1 || pers == 2)
+           {
+             n_table_words = (data >> 16) & 0xff;
+             extbl_data += 1;
+           }
+         else
+           buf[nbuf++] = data >> 16;
+         buf[nbuf++] = data >> 8;
+         buf[nbuf++] = data;
+       }
+      else
+       {
+         void *pers = prel31_to_addr (extbl_data);
+         Debug (2, "%p Personality routine: %8p\n", addr, pers);
+         n_table_words = extbl_data[1] >> 24;
+         buf[nbuf++] = extbl_data[1] >> 16;
+         buf[nbuf++] = extbl_data[1] >> 8;
+         buf[nbuf++] = extbl_data[1];
+         extbl_data += 2;
+       }
+      assert (n_table_words <= 5);
+      unsigned j;
+      for (j = 0; j < n_table_words; j++)
+       {
+         data = *extbl_data++;
+         buf[nbuf++] = data >> 24;
+         buf[nbuf++] = data >> 16;
+         buf[nbuf++] = data >> 8;
+         buf[nbuf++] = data >> 0;
+       }
+    }
+
+  if (nbuf > 0 && buf[nbuf - 1] != ARM_EXTBL_OP_FINISH)
+    buf[nbuf++] = ARM_EXTBL_OP_FINISH;
+
+  return nbuf;
+}
+
+/**
+ * Callback to dl_iterate_phdr to find the unwind tables.
+ * If found, calls arm_exidx_table_add to remember it for later lookups.
+ */
+static int
+arm_exidx_init_local_cb (struct dl_phdr_info *info, size_t size, void *data)
+{
+  unsigned i;
+
+  for (i = 0; i < info->dlpi_phnum; i++)
+    {
+      const ElfW (Phdr) * phdr = info->dlpi_phdr + i;
+      if (phdr->p_type != PT_ARM_EXIDX)
+       continue;
+
+      ElfW (Addr) addr = info->dlpi_addr + phdr->p_vaddr;
+      ElfW (Word) size = phdr->p_filesz;
+
+      arm_exidx_table_add (info->dlpi_name,
+                          (struct arm_exidx_entry *) addr,
+                          (struct arm_exidx_entry *) (addr + size));
+      break;
+    }
+  return 0;
+}
+
+/**
+  * Traverse the program headers of the executable and its loaded
+  * shared objects to collect the unwind tables.
+ */
+HIDDEN void
+arm_exidx_init_local (void)
+{
+  arm_exidx_table_reset_all ();
+  dl_iterate_phdr (&arm_exidx_init_local_cb, NULL);
+}
diff --git a/src/elfxx.h b/src/elfxx.h
index e316970..a85cc68 100644
--- a/src/elfxx.h
+++ b/src/elfxx.h
@@ -31,8 +31,6 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 
SOFTWARE.  */
 #include <sys/mman.h>
 #include <sys/stat.h>
 
-#include "libunwind_i.h"
-
 #if ELF_CLASS == ELFCLASS32
 # define ELF_W(x)      ELF32_##x
 # define Elf_W(x)      Elf32_##x
@@ -43,6 +41,8 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 
SOFTWARE.  */
 # define elf_w(x)      _Uelf64_##x
 #endif
 
+#include "libunwind_i.h"
+
 extern int elf_w (valid_object) (struct elf_image *ei);
 extern int elf_w (get_proc_name) (unw_addr_space_t as,
                                  pid_t pid, unw_word_t ip,
-- 
1.7.4.1