+2000-03-16 Jim Blandy <jimb@redhat.com>
+
+ * i386-tdep.c (LINUX_SIGTRAMP_INSN0, LINUX_SIGTRAMP_OFFSET0,
+ LINUX_SIGTRAMP_INSN1, LINUX_SIGTRAMP_OFFSET1,
+ LINUX_SIGTRAMP_INSN2, LINUX_SIGTRAMP_OFFSET2, linux_sigtramp_code,
+ LINUX_SIGTRAMP_LEN, i386_linux_sigtramp_start,
+ LINUX_RT_SIGTRAMP_INSN0, LINUX_RT_SIGTRAMP_OFFSET0,
+ LINUX_RT_SIGTRAMP_INSN1, LINUX_RT_SIGTRAMP_OFFSET1,
+ linux_rt_sigtramp_code, LINUX_RT_SIGTRAMP_LEN,
+ i386_linux_rt_sigtramp_start, i386_linux_in_sigtramp,
+ i386_linux_sigcontext_addr, LINUX_SIGCONTEXT_PC_OFFSET,
+ i386_linux_sigtramp_saved_pc, LINUX_SIGCONTEXT_SP_OFFSET,
+ i386_linux_sigtramp_saved_sp): Deleted. These all implement
+ Linux-specific signal trampoline detection, and should be moved to...
+ * i386-linux-nat.c: ... here.
+ * config/i386/tm-linux.h (I386_LINUX_SIGTRAMP): No need to define
+ this any more, since we're not enabling OS-specific code in a
+ OS-independent file.
+
2000-03-16 Eli Zaretskii <eliz@is.elta.co.il>
* Makefile.in (go32-nat.o): Add prerequisites.
are used to identify this bit of code as a signal trampoline in
order to support backtracing through calls to signal handlers. */
-#define I386_LINUX_SIGTRAMP
#define IN_SIGTRAMP(pc, name) i386_linux_in_sigtramp (pc, name)
extern int i386_linux_in_sigtramp (CORE_ADDR, char *);
}
\f
+/* Recognizing signal handler frames. */
+
+/* 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 Linux will support SA_SIGINFO for
+ normal signals too. */
+
+/* When the i386 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
+ pop %eax
+ mov $0x77,%eax
+ int $0x80
+ or 0x58 0xb8 0x77 0x00 0x00 0x00 0xcd 0x80.
+
+ 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. The IN_SIGTRAMP macro in tm-linux.h arranges to
+ only call us if no function name could be identified, which should
+ be the case since the code is on the stack.
+
+ Detection of signal trampolines for handlers that set the
+ SA_RESTORER flag is in general not possible. Unfortunately this is
+ what the GNU C Library has been doing for quite some time now.
+ However, as of version 2.1.2, the GNU C Library uses signal
+ trampolines (named __restore and __restore_rt) that are identical
+ to the ones used by the kernel. Therefore, these trampolines are
+ supported too. */
+
+#define LINUX_SIGTRAMP_INSN0 (0x58) /* pop %eax */
+#define LINUX_SIGTRAMP_OFFSET0 (0)
+#define LINUX_SIGTRAMP_INSN1 (0xb8) /* mov $NNNN,%eax */
+#define LINUX_SIGTRAMP_OFFSET1 (1)
+#define LINUX_SIGTRAMP_INSN2 (0xcd) /* int */
+#define LINUX_SIGTRAMP_OFFSET2 (6)
+
+static const unsigned char linux_sigtramp_code[] =
+{
+ LINUX_SIGTRAMP_INSN0, /* pop %eax */
+ LINUX_SIGTRAMP_INSN1, 0x77, 0x00, 0x00, 0x00, /* mov $0x77,%eax */
+ LINUX_SIGTRAMP_INSN2, 0x80 /* int $0x80 */
+};
+
+#define LINUX_SIGTRAMP_LEN (sizeof linux_sigtramp_code)
+
+/* If PC is in a sigtramp routine, return the address of the start of
+ the routine. Otherwise, return 0. */
+
+static CORE_ADDR
+i386_linux_sigtramp_start (CORE_ADDR pc)
+{
+ unsigned char buf[LINUX_SIGTRAMP_LEN];
+
+ /* We only recognize a signal trampoline if PC is at the start of
+ one of the three instructions. We optimize for finding the PC at
+ the start, 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, (char *) buf, LINUX_SIGTRAMP_LEN) != 0)
+ return 0;
+
+ if (buf[0] != LINUX_SIGTRAMP_INSN0)
+ {
+ int adjust;
+
+ switch (buf[0])
+ {
+ case LINUX_SIGTRAMP_INSN1:
+ adjust = LINUX_SIGTRAMP_OFFSET1;
+ break;
+ case LINUX_SIGTRAMP_INSN2:
+ adjust = LINUX_SIGTRAMP_OFFSET2;
+ break;
+ default:
+ return 0;
+ }
+
+ pc -= adjust;
+
+ if (read_memory_nobpt (pc, (char *) buf, LINUX_SIGTRAMP_LEN) != 0)
+ return 0;
+ }
+
+ if (memcmp (buf, linux_sigtramp_code, LINUX_SIGTRAMP_LEN) != 0)
+ return 0;
+
+ return pc;
+}
+
+/* This function does the same for RT signals. Here the instruction
+ sequence is
+ mov $0xad,%eax
+ int $0x80
+ or 0xb8 0xad 0x00 0x00 0x00 0xcd 0x80.
+
+ The effect is to call the system call rt_sigreturn. */
+
+#define LINUX_RT_SIGTRAMP_INSN0 (0xb8) /* mov $NNNN,%eax */
+#define LINUX_RT_SIGTRAMP_OFFSET0 (0)
+#define LINUX_RT_SIGTRAMP_INSN1 (0xcd) /* int */
+#define LINUX_RT_SIGTRAMP_OFFSET1 (5)
+
+static const unsigned char linux_rt_sigtramp_code[] =
+{
+ LINUX_RT_SIGTRAMP_INSN0, 0xad, 0x00, 0x00, 0x00, /* mov $0xad,%eax */
+ LINUX_RT_SIGTRAMP_INSN1, 0x80 /* int $0x80 */
+};
+
+#define LINUX_RT_SIGTRAMP_LEN (sizeof linux_rt_sigtramp_code)
+
+/* If PC is in a RT sigtramp routine, return the address of the start
+ of the routine. Otherwise, return 0. */
+
+static CORE_ADDR
+i386_linux_rt_sigtramp_start (CORE_ADDR pc)
+{
+ unsigned char buf[LINUX_RT_SIGTRAMP_LEN];
+
+ /* We only recognize a signal trampoline if PC is at the start of
+ one of the two instructions. We optimize for finding the PC at
+ the start, 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, (char *) buf, LINUX_RT_SIGTRAMP_LEN) != 0)
+ return 0;
+
+ if (buf[0] != LINUX_RT_SIGTRAMP_INSN0)
+ {
+ if (buf[0] != LINUX_RT_SIGTRAMP_INSN1)
+ return 0;
+
+ pc -= LINUX_RT_SIGTRAMP_OFFSET1;
+
+ if (read_memory_nobpt (pc, (char *) buf, LINUX_RT_SIGTRAMP_LEN) != 0)
+ return 0;
+ }
+
+ if (memcmp (buf, linux_rt_sigtramp_code, LINUX_RT_SIGTRAMP_LEN) != 0)
+ return 0;
+
+ return pc;
+}
+
+/* Return whether PC is in a Linux sigtramp routine. */
+
+int
+i386_linux_in_sigtramp (CORE_ADDR pc, char *name)
+{
+ if (name)
+ return STREQ ("__restore", name) || STREQ ("__restore_rt", name);
+
+ return (i386_linux_sigtramp_start (pc) != 0
+ || i386_linux_rt_sigtramp_start (pc) != 0);
+}
+
+/* Assuming FRAME is for a Linux sigtramp routine, return the address
+ of the associated sigcontext structure. */
+
+CORE_ADDR
+i386_linux_sigcontext_addr (struct frame_info *frame)
+{
+ CORE_ADDR pc;
+
+ pc = i386_linux_sigtramp_start (frame->pc);
+ if (pc)
+ {
+ CORE_ADDR sp;
+
+ if (frame->next)
+ /* If this isn't the top frame, the next frame must be for the
+ signal handler itself. The sigcontext structure lives on
+ the stack, right after the signum argument. */
+ return frame->next->frame + 12;
+
+ /* This is the top frame. We'll have to find the address of the
+ sigcontext structure by looking at the stack pointer. Keep
+ in mind that the first instruction of the sigtramp code is
+ "pop %eax". If the PC is at this instruction, adjust the
+ returned value accordingly. */
+ sp = read_register (SP_REGNUM);
+ if (pc == frame->pc)
+ return sp + 4;
+ return sp;
+ }
+
+ pc = i386_linux_rt_sigtramp_start (frame->pc);
+ if (pc)
+ {
+ if (frame->next)
+ /* If this isn't the top frame, the next frame must be for the
+ signal handler itself. The sigcontext structure is part of
+ the user context. A pointer to the user context is passed
+ as the third argument to the signal handler. */
+ return read_memory_integer (frame->next->frame + 16, 4) + 20;
+
+ /* This is the top frame. Again, use the stack pointer to find
+ the address of the sigcontext structure. */
+ return read_memory_integer (read_register (SP_REGNUM) + 8, 4) + 20;
+ }
+
+ error ("Couldn't recognize signal trampoline.");
+ return 0;
+}
+
+/* Offset to saved PC in sigcontext, from <asm/sigcontext.h>. */
+#define LINUX_SIGCONTEXT_PC_OFFSET (56)
+
+/* Assuming FRAME is for a Linux sigtramp routine, return the saved
+ program counter. */
+
+CORE_ADDR
+i386_linux_sigtramp_saved_pc (struct frame_info *frame)
+{
+ CORE_ADDR addr;
+ addr = i386_linux_sigcontext_addr (frame);
+ return read_memory_integer (addr + LINUX_SIGCONTEXT_PC_OFFSET, 4);
+}
+
+/* Offset to saved SP in sigcontext, from <asm/sigcontext.h>. */
+#define LINUX_SIGCONTEXT_SP_OFFSET (28)
+
+/* Assuming FRAME is for a Linux sigtramp routine, return the saved
+ stack pointer. */
+
+CORE_ADDR
+i386_linux_sigtramp_saved_sp (struct frame_info *frame)
+{
+ CORE_ADDR addr;
+ addr = i386_linux_sigcontext_addr (frame);
+ return read_memory_integer (addr + LINUX_SIGCONTEXT_SP_OFFSET, 4);
+}
+
+\f
/* Register that we are able to handle Linux ELF core file formats. */
static struct core_fns linux_elf_core_fns =
}
#endif /* I386V4_SIGTRAMP_SAVED_PC */
-#ifdef I386_LINUX_SIGTRAMP
-
-/* 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 Linux will support SA_SIGINFO for
- normal signals too. */
-
-/* When the i386 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
- pop %eax
- mov $0x77,%eax
- int $0x80
- or 0x58 0xb8 0x77 0x00 0x00 0x00 0xcd 0x80.
-
- 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. The IN_SIGTRAMP macro in tm-linux.h arranges to
- only call us if no function name could be identified, which should
- be the case since the code is on the stack.
-
- Detection of signal trampolines for handlers that set the
- SA_RESTORER flag is in general not possible. Unfortunately this is
- what the GNU C Library has been doing for quite some time now.
- However, as of version 2.1.2, the GNU C Library uses signal
- trampolines (named __restore and __restore_rt) that are identical
- to the ones used by the kernel. Therefore, these trampolines are
- supported too. */
-
-#define LINUX_SIGTRAMP_INSN0 (0x58) /* pop %eax */
-#define LINUX_SIGTRAMP_OFFSET0 (0)
-#define LINUX_SIGTRAMP_INSN1 (0xb8) /* mov $NNNN,%eax */
-#define LINUX_SIGTRAMP_OFFSET1 (1)
-#define LINUX_SIGTRAMP_INSN2 (0xcd) /* int */
-#define LINUX_SIGTRAMP_OFFSET2 (6)
-
-static const unsigned char linux_sigtramp_code[] =
-{
- LINUX_SIGTRAMP_INSN0, /* pop %eax */
- LINUX_SIGTRAMP_INSN1, 0x77, 0x00, 0x00, 0x00, /* mov $0x77,%eax */
- LINUX_SIGTRAMP_INSN2, 0x80 /* int $0x80 */
-};
-
-#define LINUX_SIGTRAMP_LEN (sizeof linux_sigtramp_code)
-
-/* If PC is in a sigtramp routine, return the address of the start of
- the routine. Otherwise, return 0. */
-
-static CORE_ADDR
-i386_linux_sigtramp_start (CORE_ADDR pc)
-{
- unsigned char buf[LINUX_SIGTRAMP_LEN];
-
- /* We only recognize a signal trampoline if PC is at the start of
- one of the three instructions. We optimize for finding the PC at
- the start, 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, (char *) buf, LINUX_SIGTRAMP_LEN) != 0)
- return 0;
-
- if (buf[0] != LINUX_SIGTRAMP_INSN0)
- {
- int adjust;
-
- switch (buf[0])
- {
- case LINUX_SIGTRAMP_INSN1:
- adjust = LINUX_SIGTRAMP_OFFSET1;
- break;
- case LINUX_SIGTRAMP_INSN2:
- adjust = LINUX_SIGTRAMP_OFFSET2;
- break;
- default:
- return 0;
- }
-
- pc -= adjust;
-
- if (read_memory_nobpt (pc, (char *) buf, LINUX_SIGTRAMP_LEN) != 0)
- return 0;
- }
-
- if (memcmp (buf, linux_sigtramp_code, LINUX_SIGTRAMP_LEN) != 0)
- return 0;
-
- return pc;
-}
-
-/* This function does the same for RT signals. Here the instruction
- sequence is
- mov $0xad,%eax
- int $0x80
- or 0xb8 0xad 0x00 0x00 0x00 0xcd 0x80.
-
- The effect is to call the system call rt_sigreturn. */
-
-#define LINUX_RT_SIGTRAMP_INSN0 (0xb8) /* mov $NNNN,%eax */
-#define LINUX_RT_SIGTRAMP_OFFSET0 (0)
-#define LINUX_RT_SIGTRAMP_INSN1 (0xcd) /* int */
-#define LINUX_RT_SIGTRAMP_OFFSET1 (5)
-
-static const unsigned char linux_rt_sigtramp_code[] =
-{
- LINUX_RT_SIGTRAMP_INSN0, 0xad, 0x00, 0x00, 0x00, /* mov $0xad,%eax */
- LINUX_RT_SIGTRAMP_INSN1, 0x80 /* int $0x80 */
-};
-
-#define LINUX_RT_SIGTRAMP_LEN (sizeof linux_rt_sigtramp_code)
-
-/* If PC is in a RT sigtramp routine, return the address of the start
- of the routine. Otherwise, return 0. */
-
-static CORE_ADDR
-i386_linux_rt_sigtramp_start (CORE_ADDR pc)
-{
- unsigned char buf[LINUX_RT_SIGTRAMP_LEN];
-
- /* We only recognize a signal trampoline if PC is at the start of
- one of the two instructions. We optimize for finding the PC at
- the start, 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, (char *) buf, LINUX_RT_SIGTRAMP_LEN) != 0)
- return 0;
-
- if (buf[0] != LINUX_RT_SIGTRAMP_INSN0)
- {
- if (buf[0] != LINUX_RT_SIGTRAMP_INSN1)
- return 0;
-
- pc -= LINUX_RT_SIGTRAMP_OFFSET1;
-
- if (read_memory_nobpt (pc, (char *) buf, LINUX_RT_SIGTRAMP_LEN) != 0)
- return 0;
- }
-
- if (memcmp (buf, linux_rt_sigtramp_code, LINUX_RT_SIGTRAMP_LEN) != 0)
- return 0;
-
- return pc;
-}
-
-/* Return whether PC is in a Linux sigtramp routine. */
-
-int
-i386_linux_in_sigtramp (CORE_ADDR pc, char *name)
-{
- if (name)
- return STREQ ("__restore", name) || STREQ ("__restore_rt", name);
-
- return (i386_linux_sigtramp_start (pc) != 0
- || i386_linux_rt_sigtramp_start (pc) != 0);
-}
-
-/* Assuming FRAME is for a Linux sigtramp routine, return the address
- of the associated sigcontext structure. */
-
-CORE_ADDR
-i386_linux_sigcontext_addr (struct frame_info *frame)
-{
- CORE_ADDR pc;
-
- pc = i386_linux_sigtramp_start (frame->pc);
- if (pc)
- {
- CORE_ADDR sp;
-
- if (frame->next)
- /* If this isn't the top frame, the next frame must be for the
- signal handler itself. The sigcontext structure lives on
- the stack, right after the signum argument. */
- return frame->next->frame + 12;
-
- /* This is the top frame. We'll have to find the address of the
- sigcontext structure by looking at the stack pointer. Keep
- in mind that the first instruction of the sigtramp code is
- "pop %eax". If the PC is at this instruction, adjust the
- returned value accordingly. */
- sp = read_register (SP_REGNUM);
- if (pc == frame->pc)
- return sp + 4;
- return sp;
- }
-
- pc = i386_linux_rt_sigtramp_start (frame->pc);
- if (pc)
- {
- if (frame->next)
- /* If this isn't the top frame, the next frame must be for the
- signal handler itself. The sigcontext structure is part of
- the user context. A pointer to the user context is passed
- as the third argument to the signal handler. */
- return read_memory_integer (frame->next->frame + 16, 4) + 20;
-
- /* This is the top frame. Again, use the stack pointer to find
- the address of the sigcontext structure. */
- return read_memory_integer (read_register (SP_REGNUM) + 8, 4) + 20;
- }
-
- error ("Couldn't recognize signal trampoline.");
- return 0;
-}
-
-/* Offset to saved PC in sigcontext, from <asm/sigcontext.h>. */
-#define LINUX_SIGCONTEXT_PC_OFFSET (56)
-
-/* Assuming FRAME is for a Linux sigtramp routine, return the saved
- program counter. */
-
-CORE_ADDR
-i386_linux_sigtramp_saved_pc (struct frame_info *frame)
-{
- CORE_ADDR addr;
- addr = i386_linux_sigcontext_addr (frame);
- return read_memory_integer (addr + LINUX_SIGCONTEXT_PC_OFFSET, 4);
-}
-
-/* Offset to saved SP in sigcontext, from <asm/sigcontext.h>. */
-#define LINUX_SIGCONTEXT_SP_OFFSET (28)
-
-/* Assuming FRAME is for a Linux sigtramp routine, return the saved
- stack pointer. */
-
-CORE_ADDR
-i386_linux_sigtramp_saved_sp (struct frame_info *frame)
-{
- CORE_ADDR addr;
- addr = i386_linux_sigcontext_addr (frame);
- return read_memory_integer (addr + LINUX_SIGCONTEXT_SP_OFFSET, 4);
-}
-
-/* Immediately after a function call, return the saved pc. */
-
-CORE_ADDR
-i386_linux_saved_pc_after_call (struct frame_info *frame)
-{
- if (frame->signal_handler_caller)
- return i386_linux_sigtramp_saved_pc (frame);
-
- return read_memory_integer (read_register (SP_REGNUM), 4);
-}
-
-#endif /* I386_LINUX_SIGTRAMP */
#ifdef STATIC_TRANSFORM_NAME
/* SunPRO encodes the static variables. This is not related to C++ mangling,
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