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[rfc] Improve NetBSD/i386 signal trampoline detection
- From: Nick Hudson <nick dot hudson at dsl dot pipex dot com>
- To: gdb-patches at sourceware dot org
- Date: Tue, 2 Oct 2007 12:07:15 +0100
- Subject: [rfc] Improve NetBSD/i386 signal trampoline detection
Hi,
I put together this patch to improve NetBSD/i386 signal trampoline detection.
I believe tramp_frame is a better and preferred method.
I think I need to add the instructions for when the setcontext/sigreturn fails
as well. Is this correct?
Any/all comments appreciated.
Thanks,
Nick
Index: gdb/i386nbsd-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/i386nbsd-tdep.c,v
retrieving revision 1.33
diff -u -p -u -r1.33 i386nbsd-tdep.c
--- gdb/i386nbsd-tdep.c 23 Aug 2007 18:08:34 -0000 1.33
+++ gdb/i386nbsd-tdep.c 2 Oct 2007 10:39:21 -0000
@@ -26,6 +26,8 @@
#include "regset.h"
#include "osabi.h"
#include "symtab.h"
+#include "trad-frame.h"
+#include "tramp-frame.h"
#include "gdb_assert.h"
#include "gdb_string.h"
@@ -91,109 +93,6 @@ i386nbsd_aout_regset_from_core_section (
return NULL;
}
-/* Under NetBSD/i386, signal handler invocations can be identified by the
- designated code sequence that is used to return from a signal handler.
- In particular, the return address of a signal handler points to the
- following code sequence:
-
- leal 0x10(%esp), %eax
- pushl %eax
- pushl %eax
- movl $0x127, %eax # __sigreturn14
- int $0x80
-
- Each instruction has a unique encoding, so we simply attempt to match
- the instruction the PC is pointing to with any of the above instructions.
- If there is a hit, we know the offset to the start of the designated
- sequence and can then check whether we really are executing in the
- signal trampoline. If not, -1 is returned, otherwise the offset from the
- start of the return sequence is returned. */
-#define RETCODE_INSN1 0x8d
-#define RETCODE_INSN2 0x50
-#define RETCODE_INSN3 0x50
-#define RETCODE_INSN4 0xb8
-#define RETCODE_INSN5 0xcd
-
-#define RETCODE_INSN2_OFF 4
-#define RETCODE_INSN3_OFF 5
-#define RETCODE_INSN4_OFF 6
-#define RETCODE_INSN5_OFF 11
-
-static const unsigned char sigtramp_retcode[] =
-{
- RETCODE_INSN1, 0x44, 0x24, 0x10,
- RETCODE_INSN2,
- RETCODE_INSN3,
- RETCODE_INSN4, 0x27, 0x01, 0x00, 0x00,
- RETCODE_INSN5, 0x80,
-};
-
-static LONGEST
-i386nbsd_sigtramp_offset (struct frame_info *next_frame)
-{
- CORE_ADDR pc = frame_pc_unwind (next_frame);
- unsigned char ret[sizeof(sigtramp_retcode)], insn;
- LONGEST off;
- int i;
-
- if (!safe_frame_unwind_memory (next_frame, pc, &insn, 1))
- return -1;
-
- switch (insn)
- {
- case RETCODE_INSN1:
- off = 0;
- break;
-
- case RETCODE_INSN2:
- /* INSN2 and INSN3 are the same. Read at the location of PC+1
- to determine if we're actually looking at INSN2 or INSN3. */
- if (!safe_frame_unwind_memory (next_frame, pc + 1, &insn, 1))
- return -1;
-
- if (insn == RETCODE_INSN3)
- off = RETCODE_INSN2_OFF;
- else
- off = RETCODE_INSN3_OFF;
- break;
-
- case RETCODE_INSN4:
- off = RETCODE_INSN4_OFF;
- break;
-
- case RETCODE_INSN5:
- off = RETCODE_INSN5_OFF;
- break;
-
- default:
- return -1;
- }
-
- pc -= off;
-
- if (!safe_frame_unwind_memory (next_frame, pc, ret, sizeof (ret)))
- return -1;
-
- if (memcmp (ret, sigtramp_retcode, sizeof (ret)) == 0)
- return off;
-
- return -1;
-}
-
-/* Return whether the frame preceding NEXT_FRAME corresponds to a
- NetBSD sigtramp routine. */
-
-static int
-i386nbsd_sigtramp_p (struct frame_info *next_frame)
-{
- CORE_ADDR pc = frame_pc_unwind (next_frame);
- char *name;
-
- find_pc_partial_function (pc, &name, NULL, NULL);
- return (nbsd_pc_in_sigtramp (pc, name)
- || i386nbsd_sigtramp_offset (next_frame) >= 0);
-}
-
/* From <machine/signal.h>. */
int i386nbsd_sc_reg_offset[] =
{
@@ -215,31 +114,176 @@ int i386nbsd_sc_reg_offset[] =
0 * 4 /* %gs */
};
+/* From <machine/mcontext.h>. */
+int i386nbsd_mc_reg_offset[] =
+{
+ 11 * 4, /* %eax */
+ 10 * 4, /* %ecx */
+ 9 * 4, /* %edx */
+ 8 * 4, /* %ebx */
+ 7 * 4, /* %esp */
+ 6 * 4, /* %ebp */
+ 5 * 4, /* %esi */
+ 4 * 4, /* %edi */
+ 14 * 4, /* %eip */
+ 16 * 4, /* %eflags */
+ 15 * 4, /* %cs */
+ 18 * 4, /* %ss */
+ 3 * 4, /* %ds */
+ 2 * 4, /* %es */
+ 1 * 4, /* %fs */
+ 0 * 4 /* %gs */
+};
+
+
+static void
+i386nbsd_sigtramp_cache_init (const struct tramp_frame *,
+ struct frame_info *,
+ struct trad_frame_cache *,
+ CORE_ADDR);
+
+static const struct tramp_frame i386nbsd_sigtramp1 =
+{
+ SIGTRAMP_FRAME,
+ 1,
+ {
+ { 0x8d, -1 }, { 0x44, -1 }, { 0x24, -1 }, { 0x10, -1 },
+ /* leal 0x10(%esp), %eax */
+ { 0x50, -1 }, /* pushl %eax */
+ { 0x50, -1 }, /* pushl %eax */
+ { 0xb8, -1 }, { 0x27, -1 }, {0x01, -1 }, {0x00, -1 }, {0x00, -1 },
+ /* movl $0x127, %eax # __sigreturn14 */
+ { 0xcd, -1 }, { 0x80, -1},
+ /* int $0x80 */
+ { TRAMP_SENTINEL_INSN, -1 }
+ },
+ i386nbsd_sigtramp_cache_init
+};
+
+static const struct tramp_frame i386nbsd_sigtramp2 =
+{
+ SIGTRAMP_FRAME,
+ 1,
+ {
+ { 0x8d, -1 }, { 0x44, -1 }, { 0x24, -1 }, { 0x0c, -1 },
+ /* leal 0x0c(%esp), %eax */
+ { 0x89, -1 }, { 0x44, -1 }, { 0x24, -1 }, { 0x04, -1 },
+ /* movl %eax, 0x4(%esp) */
+ { 0xb8, -1 }, { 0x27, -1 }, {0x01, -1 }, {0x00, -1 }, {0x00, -1 },
+ /* movl $0x127, %eax # __sigreturn14 */
+ { 0xcd, -1 }, { 0x80, -1},
+ /* int $0x80 */
+ { TRAMP_SENTINEL_INSN, -1 }
+ },
+ i386nbsd_sigtramp_cache_init
+};
+
+static const struct tramp_frame i386nbsd_sigtramp3 =
+{
+ SIGTRAMP_FRAME,
+ 1,
+ {
+ { 0x8b, -1}, { 0x44, -1}, { 0x24, -1}, { 0x08, -1},
+ /* movl 8(%esp),%eax */
+ { 0x89, -1 }, { 0x44, -1 }, { 0x24, -1 }, { 0x04, -1 },
+ /* movl %eax, 0x4(%esp) */
+ { 0xb8, -1 }, { 0x34, -1 }, { 0x01, -1 }, { 0x00, -1 }, { 0x00, -1 },
+ /* movl $0x134, %eax # setcontext */
+ { 0xcd, -1 }, { 0x80, -1},
+ /* int $0x80 */
+ /* more... */
+ { TRAMP_SENTINEL_INSN, -1 }
+ },
+ i386nbsd_sigtramp_cache_init
+};
+
+
+static const struct tramp_frame i386nbsd_sigtramp4 =
+{
+ SIGTRAMP_FRAME,
+ 1,
+ {
+ { 0x8d, -1 }, { 0x84, -1 }, { 0x24, -1 },
+ { 0x8c, -1 }, { 0x00, -1 }, { 0x00, -1 }, { 0x00, -1 },
+ /* leal 0x8c(%esp), %eax */
+ { 0x89, -1 }, { 0x44, -1 }, { 0x24, -1 }, { 0x04, -1 },
+ /* movl %eax, 0x4(%esp) */
+ { 0xb8, -1 }, { 0x34, -1 }, { 0x01, -1 }, { 0x00, -1 }, { 0x00, -1 },
+ /* movl $0x134, %eax # setcontext */
+ { 0xcd, -1 }, { 0x80, -1},
+ /* int $0x80 */
+ /* more... */
+ { TRAMP_SENTINEL_INSN, -1 }
+ },
+ i386nbsd_sigtramp_cache_init
+};
+
+static void
+i386nbsd_sigtramp_cache_init (const struct tramp_frame *self,
+ struct frame_info *next_frame,
+ struct trad_frame_cache *this_cache,
+ CORE_ADDR func)
+{
+ struct gdbarch *gdbarch = get_frame_arch (next_frame);
+ struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
+ CORE_ADDR sp = frame_unwind_register_unsigned (next_frame, I386_ESP_REGNUM);
+ CORE_ADDR base;
+ int *reg_offset;
+ int num_regs;
+ int i;
+
+ if (self == &i386nbsd_sigtramp1 || self == &i386nbsd_sigtramp2)
+ {
+ reg_offset = i386nbsd_sc_reg_offset;
+ num_regs = ARRAY_SIZE (i386nbsd_sc_reg_offset);
+
+ /* Read in the sigcontext address */
+ base = read_memory_unsigned_integer (sp + 8, 4);
+ }
+ else
+ {
+ reg_offset = i386nbsd_mc_reg_offset;
+ num_regs = ARRAY_SIZE (i386nbsd_mc_reg_offset);
+
+ /* Read in the ucontext address */
+ base = read_memory_unsigned_integer (sp + 8, 4);
+ /* offsetof(ucontext_t, uc_mcontext) == 36 */
+ base += 36;
+ }
+
+ for (i = 0; i < num_regs; i++)
+ if (reg_offset[i] != -1)
+ trad_frame_set_reg_addr (this_cache, i, base + reg_offset[i]);
+
+ /* Construct the frame ID using the function start. */
+ trad_frame_set_id (this_cache, frame_id_build (sp, func));
+}
+
static void
i386nbsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
{
struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
- /* Obviously NetBSD is BSD-based. */
- i386bsd_init_abi (info, gdbarch);
-
/* NetBSD has a different `struct reg'. */
tdep->gregset_reg_offset = i386nbsd_r_reg_offset;
tdep->gregset_num_regs = ARRAY_SIZE (i386nbsd_r_reg_offset);
tdep->sizeof_gregset = 16 * 4;
- /* NetBSD has different signal trampoline conventions. */
- tdep->sigtramp_start = 0;
- tdep->sigtramp_end = 0;
- tdep->sigtramp_p = i386nbsd_sigtramp_p;
-
/* NetBSD uses -freg-struct-return by default. */
tdep->struct_return = reg_struct_return;
- /* NetBSD has a `struct sigcontext' that's different from the
- original 4.3 BSD. */
- tdep->sc_reg_offset = i386nbsd_sc_reg_offset;
- tdep->sc_num_regs = ARRAY_SIZE (i386nbsd_sc_reg_offset);
+ /* NetBSD uses tramp_frame sniffers for signal trampolines. */
+ tdep->sigcontext_addr = 0;
+ tdep->sigtramp_start = 0;
+ tdep->sigtramp_end = 0;
+ tdep->sigtramp_p = 0;
+ tdep->sc_reg_offset = 0;
+ tdep->sc_num_regs = 0;
+
+ tramp_frame_prepend_unwinder (gdbarch, &i386nbsd_sigtramp1);
+ tramp_frame_prepend_unwinder (gdbarch, &i386nbsd_sigtramp2);
+ tramp_frame_prepend_unwinder (gdbarch, &i386nbsd_sigtramp3);
+ tramp_frame_prepend_unwinder (gdbarch, &i386nbsd_sigtramp4);
}
/* NetBSD a.out. */
Index: gdb/tramp-frame.h
===================================================================
RCS file: /cvs/src/src/gdb/tramp-frame.h,v
retrieving revision 1.9
diff -u -p -u -r1.9 tramp-frame.h
--- gdb/tramp-frame.h 23 Aug 2007 18:08:46 -0000 1.9
+++ gdb/tramp-frame.h 2 Oct 2007 10:39:23 -0000
@@ -62,7 +62,7 @@ struct tramp_frame
{
ULONGEST bytes;
ULONGEST mask;
- } insn[16];
+ } insn[32];
/* Initialize a trad-frame cache corresponding to the tramp-frame.
FUNC is the address of the instruction TRAMP[0] in memory. */
void (*init) (const struct tramp_frame *self,