[PATCH/SPARC] Add 32-bit GNU/Linux signal frame unwinder

Mark Kettenis kettenis@chello.nl
Fri Nov 14 22:10:00 GMT 2003


Committed to the SPARC branch.

Mark

Index: ChangeLog
from  Mark Kettenis  <kettenis@gnu.org>
 
	* sparc-linux-tdep.c: Include "frame.h", "frame-base.h",
	"frame-unwind.h", "gdbcore.h", "regcache.h", "symtab.h",
	"trad-frame.h", "gdb_assert.h" and "gdb_string.h".
	(LINUX32_SIGTRAMP_INSN0, LINUX32_SIGTRAMP_INSN1,
	LINUX32_RT_SIGTRAMP_INSN0, LINUX32_RT_SIGTRAMP_INSN1): New
	defines.
	(sparc_linux_sigtramp_start): New function.
	(sparc32_linux_sigtramp_start): New function.
	(sparc32_linux_rt_sigtramp_start): New function.
	(sparc32_linux_pc_in_sigtramp): New function.
	(sparc32_linux_sigtramp_frame_cache): New function.
	(sparc32_linux_sigtramp_frame_this_id): New function.
	(sparc32_linux_sigtramp_frame_prev_register): New function.
	(sparc32_linux_sigtramp_frame_unwind): New variable.
	(sparc32_linux_sigtramp_frame_sniffer): New function.
	(sparc32_linux_init_abi): Set pc_in_sigtramp, Add
	sparc32_linux_sigtramp_frame_sniffer.

Index: sparc-linux-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/Attic/sparc-linux-tdep.c,v
retrieving revision 1.1.2.2
diff -u -p -r1.1.2.2 sparc-linux-tdep.c
--- sparc-linux-tdep.c 2 Nov 2003 17:05:07 -0000 1.1.2.2
+++ sparc-linux-tdep.c 14 Nov 2003 22:09:21 -0000
@@ -20,12 +20,220 @@
    Boston, MA 02111-1307, USA.  */
 
 #include "defs.h"
+#include "frame.h"
+#include "frame-base.h"
+#include "frame-unwind.h"
 #include "gdbarch.h"
+#include "gdbcore.h"
 #include "osabi.h"
+#include "regcache.h"
 #include "solib-svr4.h"
+#include "symtab.h"
+#include "trad-frame.h"
+
+#include "gdb_assert.h"
+#include "gdb_string.h"
 
 #include "sparc-tdep.h"
 
+/* Recognizing signal handler frames.  */
+
+/* GNU/Linux has two flavors of signals.  Normal signal handlers, and
+   "realtime" (RT) signals.  The RT signals can provide additional
+   information to the signal handler if the SA_SIGINFO flag is set
+   when establishing a signal handler using `sigaction'.  It is not
+   unlikely that future versions of GNU/Linux will support SA_SIGINFO
+   for normal signals too.  */
+
+/* When the sparc Linux kernel calls a signal handler and the
+   SA_RESTORER flag isn't set, the return address points to a bit of
+   code on the stack.  This function returns whether the PC appears to
+   be within this bit of code.
+
+   The instruction sequence for normal signals is
+	mov __NR_sigreturn, %g1		! hex: 0x821020d8
+	ta  0x10			! hex: 0x91d02010
+
+   Checking for the code sequence should be somewhat reliable, because
+   the effect is to call the system call sigreturn.  This is unlikely
+   to occur anywhere other than a signal trampoline.
+
+   It kind of sucks that we have to read memory from the process in
+   order to identify a signal trampoline, but there doesn't seem to be
+   any other way.  However, sparc32_linux_pc_in_sigtramp arranges to
+   only call us if no function name could be identified, which should
+   be the case since the code is on the stack.  */
+
+#define LINUX32_SIGTRAMP_INSN0	0x821020d8	/* mov __NR_sigreturn, %g1 */
+#define LINUX32_SIGTRAMP_INSN1	0x91d02010	/* ta  0x10 */
+
+/* The instruction sequence for RT signals is
+       mov __NR_rt_sigreturn, %g1	! hex: 0x82102065
+       ta  {0x10,0x6d}			! hex: 0x91d02010 or 0x91d0206d
+
+   The effect is to call the system call rt_sigreturn.  The trap number
+   is variable based upon whether this is a 32-bit or 64-bit sparc binary.
+   Note that 64-bit binaries only use this RT signal return method.  */
+
+#define LINUX32_RT_SIGTRAMP_INSN0	0x82102065
+#define LINUX32_RT_SIGTRAMP_INSN1	0x91d02010
+
+/* If PC is in a sigtramp routine consisting of the instructions INSN0
+   and INSN1, return the address of the start of the routine.
+   Otherwise, return 0.  */
+
+CORE_ADDR
+sparc_linux_sigtramp_start (CORE_ADDR pc, ULONGEST insn0, ULONGEST insn1)
+{
+  ULONGEST word0, word1;
+  char buf[8];			/* Two instructions.  */
+
+  /* We only recognize a signal trampoline if PC is at the start of
+     one of the instructions.  We optimize for finding the PC at the
+     start of the instruction sequence, as will be the case when the
+     trampoline is not the first frame on the stack.  We assume that
+     in the case where the PC is not at the start of the instruction
+     sequence, there will be a few trailing readable bytes on the
+     stack.  */
+
+  if (read_memory_nobpt (pc, buf, sizeof buf) != 0)
+    return 0;
+
+  word0 = extract_unsigned_integer (buf, 4);
+  if (word0 != insn0)
+    {
+      if (word0 != insn1)
+	return 0;
+
+      pc -= 4;
+      if (read_memory_nobpt (pc, buf, sizeof buf) != 0)
+	return 0;
+
+      word0 = extract_unsigned_integer (buf, 4);
+    }
+
+  word1 = extract_unsigned_integer (buf + 4, 4);
+  if (word0 != insn0 || word1 != insn1)
+    return 0;
+
+  return pc;
+}
+
+static CORE_ADDR
+sparc32_linux_sigtramp_start (CORE_ADDR pc)
+{
+  return sparc_linux_sigtramp_start (pc, LINUX32_SIGTRAMP_INSN0,
+				     LINUX32_SIGTRAMP_INSN1);
+}
+
+static CORE_ADDR
+sparc32_linux_rt_sigtramp_start (CORE_ADDR pc)
+{
+  return sparc_linux_sigtramp_start (pc, LINUX32_RT_SIGTRAMP_INSN0,
+				     LINUX32_RT_SIGTRAMP_INSN1);
+}
+
+static int
+sparc32_linux_pc_in_sigtramp (CORE_ADDR pc, char *name)
+{
+  /* If we have NAME, we can optimize the search.  The trampolines are
+     named __restore and __restore_rt.  However, they aren't dynamically
+     exported from the shared C library, so the trampoline may appear to
+     be part of the preceding function.  This should always be sigaction,
+     __sigaction, or __libc_sigaction (all aliases to the same function).  */
+  if (name == NULL || strstr (name, "sigaction") != NULL)
+    return (sparc32_linux_sigtramp_start (pc) != 0
+	    || sparc32_linux_rt_sigtramp_start (pc) != 0);
+
+  return (strcmp ("__restore", name) == 0
+	  || strcmp ("__restore_rt", name) == 0);
+}
+
+static struct sparc32_frame_cache *
+sparc32_linux_sigtramp_frame_cache (struct frame_info *next_frame,
+				    void **this_cache)
+{
+  struct sparc32_frame_cache *cache;
+  CORE_ADDR sigcontext_addr, addr;
+  int regnum;
+
+  if (*this_cache)
+    return *this_cache;
+
+  cache = sparc32_frame_cache (next_frame, this_cache);
+  gdb_assert (cache == *this_cache);
+
+  cache->saved_regs = trad_frame_alloc_saved_regs (next_frame);
+
+  regnum = SPARC_O1_REGNUM;
+  sigcontext_addr = frame_unwind_register_unsigned (next_frame, regnum);
+  if (sparc32_linux_rt_sigtramp_start (cache->pc) != 0)
+    sigcontext_addr += 128;
+
+  cache->saved_regs[SPARC32_PSR_REGNUM].addr = sigcontext_addr + 0;
+  cache->saved_regs[SPARC32_PC_REGNUM].addr = sigcontext_addr + 4;
+  cache->saved_regs[SPARC32_NPC_REGNUM].addr = sigcontext_addr + 8;
+  cache->saved_regs[SPARC32_Y_REGNUM].addr = sigcontext_addr + 12;
+
+  /* Since %g0 is always zero, keep the identity encoding.  */
+  for (regnum = SPARC_G1_REGNUM, addr = sigcontext_addr + 16;
+       regnum <= SPARC_O7_REGNUM; regnum++, addr += 4)
+    cache->saved_regs[regnum].addr = addr;
+
+  for (regnum = SPARC_L0_REGNUM, addr = cache->base;
+       regnum <= SPARC_I7_REGNUM; regnum++, addr += 4)
+    cache->saved_regs[regnum].addr = addr;
+
+  return cache;
+}
+
+static void
+sparc32_linux_sigtramp_frame_this_id (struct frame_info *next_frame,
+				      void **this_cache,
+				      struct frame_id *this_id)
+{
+  struct sparc32_frame_cache *cache =
+    sparc32_linux_sigtramp_frame_cache (next_frame, this_cache);
+
+  (*this_id) = frame_id_build (cache->base, cache->pc);
+}
+
+static void
+sparc32_linux_sigtramp_frame_prev_register (struct frame_info *next_frame,
+					    void **this_cache,
+					    int regnum, int *optimizedp,
+					    enum lval_type *lvalp,
+					    CORE_ADDR *addrp,
+					    int *realnump, void *valuep)
+{
+  struct sparc32_frame_cache *cache =
+    sparc32_linux_sigtramp_frame_cache (next_frame, this_cache);
+
+  trad_frame_prev_register (next_frame, cache->saved_regs, regnum,
+			    optimizedp, lvalp, addrp, realnump, valuep);
+}
+
+static const struct frame_unwind sparc32_linux_sigtramp_frame_unwind =
+{
+  SIGTRAMP_FRAME,
+  sparc32_linux_sigtramp_frame_this_id,
+  sparc32_linux_sigtramp_frame_prev_register
+};
+
+static const struct frame_unwind *
+sparc32_linux_sigtramp_frame_sniffer (struct frame_info *next_frame)
+{
+  CORE_ADDR pc = frame_pc_unwind (next_frame);
+  char *name;
+
+  find_pc_partial_function (pc, &name, NULL, NULL);
+  if (sparc32_linux_pc_in_sigtramp (pc, name))
+    return &sparc32_linux_sigtramp_frame_unwind;
+
+  return NULL;
+}
+
+
 static struct link_map_offsets *
 sparc32_linux_svr4_fetch_link_map_offsets (void)
 {
@@ -64,6 +272,9 @@ sparc32_linux_init_abi (struct gdbarch_i
 
   /* ... but doesn't have kernel-assisted single-stepping support.  */
   set_gdbarch_software_single_step (gdbarch, sparc_software_single_step);
+
+  set_gdbarch_pc_in_sigtramp (gdbarch, sparc32_linux_pc_in_sigtramp);
+  frame_unwind_append_sniffer (gdbarch, sparc32_linux_sigtramp_frame_sniffer);
 
   set_solib_svr4_fetch_link_map_offsets
     (gdbarch, sparc32_linux_svr4_fetch_link_map_offsets);



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