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2000-03-04 Mark Kettenis <kettenis@gnu.org>
Fix support for Linux/i386 signal trampolines. The old approach
didn't work for Linux 2.2 and beyond, and didn't work with recent
versions of the GNU C library.
* i386-tdep.c (LINUX_RT_SIGTRAMP_INSN0, LINUX_RT_SIGTRAMP_OFFSET0,
LINUX_RT_SIGTRAMP_INSN1, LINUX_RT_SIGTRAMP_OFFSET1): New defines.
(linux_rt_sigtramp_code): New variable.
(LINUX_RT_SIGTRAMP_LEN): New define.
(i386_linux_rt_sigtramp_start): New function. Detect start of
signal trampolines for RT signals.
(i386_linux_sigtramp): Removed.
(i386_linux_in_sigtramp): New function.
(i386_linux_sigcontext_addr): New function. Recognize the names
of the signal tranmpolines used by recent versions of the GNU C
library, and add support for RT signals.
(LINUX_SIGCONTEXT_PC_OFFSET, LINUX_SIGCONTEXT_SP_OFFSET): New
defines. Moved here from config/i386/tm-linux.h.
(i386_linux_sigtramp_saved_pc, i386_linux_sigtramp_saved_sp):
Reimplement in terms of i386_linux_sigcontext_addr.
* config/i386/tm-linux.h (LINUX_SIGCONTEXT_SIZE): Removed.
(LINUX_SIGCONTEXT_PC_OFFSET, LINUX_SIGCONTEXT_SP_OFFSET):
Moved to i386-tdep.c.
(IN_SIGTRAMP): Redefine to call i386_linux_in_sigtramp.
This commit is contained in:
Mark Kettenis
parent
8ae7f924f3
commit
45a816d93e
@ -1,3 +1,28 @@
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2000-03-04 Mark Kettenis <kettenis@gnu.org>
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Fix support for Linux/i386 signal trampolines. The old approach
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didn't work for Linux 2.2 and beyond, and didn't work with recent
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versions of the GNU C library.
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* i386-tdep.c (LINUX_RT_SIGTRAMP_INSN0, LINUX_RT_SIGTRAMP_OFFSET0,
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LINUX_RT_SIGTRAMP_INSN1, LINUX_RT_SIGTRAMP_OFFSET1): New defines.
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(linux_rt_sigtramp_code): New variable.
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(LINUX_RT_SIGTRAMP_LEN): New define.
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(i386_linux_rt_sigtramp_start): New function. Detect start of
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signal trampolines for RT signals.
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(i386_linux_sigtramp): Removed.
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(i386_linux_in_sigtramp): New function.
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(i386_linux_sigcontext_addr): New function. Recognize the names
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of the signal tranmpolines used by recent versions of the GNU C
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library, and add support for RT signals.
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(LINUX_SIGCONTEXT_PC_OFFSET, LINUX_SIGCONTEXT_SP_OFFSET): New
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defines. Moved here from config/i386/tm-linux.h.
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(i386_linux_sigtramp_saved_pc, i386_linux_sigtramp_saved_sp):
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Reimplement in terms of i386_linux_sigcontext_addr.
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* config/i386/tm-linux.h (LINUX_SIGCONTEXT_SIZE): Removed.
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(LINUX_SIGCONTEXT_PC_OFFSET, LINUX_SIGCONTEXT_SP_OFFSET):
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Moved to i386-tdep.c.
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(IN_SIGTRAMP): Redefine to call i386_linux_in_sigtramp.
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Sat Mar 4 19:38:11 2000 Andrew Cagney <cagney@b1.cygnus.com>
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By: Sat Mar 4 04:08:58 2000 Alexandre Oliva <oliva@lsd.ic.unicamp.br>
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@ -30,15 +30,6 @@
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#include "i386/tm-i386.h"
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#include "tm-linux.h"
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/* Size of sigcontext, from <asm/sigcontext.h>. */
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#define LINUX_SIGCONTEXT_SIZE (88)
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/* Offset to saved PC in sigcontext, from <asm/sigcontext.h>. */
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#define LINUX_SIGCONTEXT_PC_OFFSET (56)
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/* Offset to saved SP in sigcontext, from <asm/sigcontext.h>. */
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#define LINUX_SIGCONTEXT_SP_OFFSET (28)
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#define LOW_RETURN_REGNUM 0 /* holds low four bytes of result */
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#define HIGH_RETURN_REGNUM 2 /* holds high four bytes of result */
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@ -108,15 +99,14 @@ extern int i387_store_floating (PTR addr, int len, long double val);
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order to support backtracing through calls to signal handlers. */
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#define I386_LINUX_SIGTRAMP
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#define IN_SIGTRAMP(pc, name) ((name) == NULL && i386_linux_sigtramp (pc))
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extern int i386_linux_sigtramp PARAMS ((CORE_ADDR));
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#define IN_SIGTRAMP(pc, name) i386_linux_in_sigtramp (pc, name)
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extern int i386_linux_in_sigtramp (CORE_ADDR, char *);
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/* We need our own version of sigtramp_saved_pc to get the saved PC in
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a sigtramp routine. */
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#define sigtramp_saved_pc i386_linux_sigtramp_saved_pc
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extern CORE_ADDR i386_linux_sigtramp_saved_pc PARAMS ((struct frame_info *));
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extern CORE_ADDR i386_linux_sigtramp_saved_pc (struct frame_info *);
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/* Signal trampolines don't have a meaningful frame. As in tm-i386.h,
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the frame pointer value we use is actually the frame pointer of the
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@ -162,7 +152,7 @@ extern CORE_ADDR i386_linux_sigtramp_saved_pc PARAMS ((struct frame_info *));
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? read_memory_integer (i386_linux_sigtramp_saved_sp ((FRAME)->next), 4) \
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: read_memory_integer ((FRAME)->frame + 4, 4)))
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extern CORE_ADDR i386_linux_sigtramp_saved_sp PARAMS ((struct frame_info *));
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extern CORE_ADDR i386_linux_sigtramp_saved_sp (struct frame_info *);
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/* When we call a function in a shared library, and the PLT sends us
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into the dynamic linker to find the function's real address, we
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179
gdb/i386-tdep.c
179
gdb/i386-tdep.c
@ -781,11 +781,19 @@ i386v4_sigtramp_saved_pc (frame)
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#ifdef I386_LINUX_SIGTRAMP
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/* When the i386 Linux kernel calls a signal handler, the return
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address points to a bit of code on the stack. This function
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returns whether the PC appears to be within this bit of code.
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/* Linux has two flavors of signals. Normal signal handlers, and
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"realtime" (RT) signals. The RT signals can provide additional
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information to the signal handler if the SA_SIGINFO flag is set
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when establishing a signal handler using `sigaction'. It is not
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unlikely that future versions of Linux will support SA_SIGINFO for
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normal signals too. */
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The instruction sequence is
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/* When the i386 Linux kernel calls a signal handler and the
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SA_RESTORER flag isn't set, the return address points to a bit of
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code on the stack. This function returns whether the PC appears to
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be within this bit of code.
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The instruction sequence for normal signals is
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pop %eax
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mov $0x77,%eax
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int $0x80
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@ -799,7 +807,15 @@ i386v4_sigtramp_saved_pc (frame)
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order to identify a signal trampoline, but there doesn't seem to be
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any other way. The IN_SIGTRAMP macro in tm-linux.h arranges to
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only call us if no function name could be identified, which should
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be the case since the code is on the stack. */
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be the case since the code is on the stack.
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Detection of signal trampolines for handlers that set the
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SA_RESTORER flag is in general not possible. Unfortunately this is
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what the GNU C Library has been doing for quite some time now.
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However, as of version 2.1.2, the GNU C Library uses signal
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trampolines (named __restore and __restore_rt) that are identical
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to the ones used by the kernel. Therefore, these trampolines are
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supported too. */
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#define LINUX_SIGTRAMP_INSN0 (0x58) /* pop %eax */
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#define LINUX_SIGTRAMP_OFFSET0 (0)
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@ -821,8 +837,7 @@ static const unsigned char linux_sigtramp_code[] =
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the routine. Otherwise, return 0. */
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static CORE_ADDR
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i386_linux_sigtramp_start (pc)
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CORE_ADDR pc;
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i386_linux_sigtramp_start (CORE_ADDR pc)
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{
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unsigned char buf[LINUX_SIGTRAMP_LEN];
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@ -864,51 +879,149 @@ i386_linux_sigtramp_start (pc)
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return pc;
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}
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/* This function does the same for RT signals. Here the instruction
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sequence is
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mov $0xad,%eax
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int $0x80
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or 0xb8 0xad 0x00 0x00 0x00 0xcd 0x80.
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The effect is to call the system call rt_sigreturn. */
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#define LINUX_RT_SIGTRAMP_INSN0 (0xb8) /* mov $NNNN,%eax */
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#define LINUX_RT_SIGTRAMP_OFFSET0 (0)
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#define LINUX_RT_SIGTRAMP_INSN1 (0xcd) /* int */
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#define LINUX_RT_SIGTRAMP_OFFSET1 (5)
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static const unsigned char linux_rt_sigtramp_code[] =
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{
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LINUX_RT_SIGTRAMP_INSN0, 0xad, 0x00, 0x00, 0x00, /* mov $0xad,%eax */
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LINUX_RT_SIGTRAMP_INSN1, 0x80 /* int $0x80 */
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};
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#define LINUX_RT_SIGTRAMP_LEN (sizeof linux_rt_sigtramp_code)
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/* If PC is in a RT sigtramp routine, return the address of the start
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of the routine. Otherwise, return 0. */
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static CORE_ADDR
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i386_linux_rt_sigtramp_start (CORE_ADDR pc)
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{
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unsigned char buf[LINUX_RT_SIGTRAMP_LEN];
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/* We only recognize a signal trampoline if PC is at the start of
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one of the two instructions. We optimize for finding the PC at
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the start, as will be the case when the trampoline is not the
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first frame on the stack. We assume that in the case where the
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PC is not at the start of the instruction sequence, there will be
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a few trailing readable bytes on the stack. */
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if (read_memory_nobpt (pc, (char *) buf, LINUX_RT_SIGTRAMP_LEN) != 0)
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return 0;
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if (buf[0] != LINUX_RT_SIGTRAMP_INSN0)
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{
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if (buf[0] != LINUX_RT_SIGTRAMP_INSN1)
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return 0;
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pc -= LINUX_RT_SIGTRAMP_OFFSET1;
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if (read_memory_nobpt (pc, (char *) buf, LINUX_RT_SIGTRAMP_LEN) != 0)
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return 0;
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}
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if (memcmp (buf, linux_rt_sigtramp_code, LINUX_RT_SIGTRAMP_LEN) != 0)
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return 0;
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return pc;
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}
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/* Return whether PC is in a Linux sigtramp routine. */
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int
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i386_linux_sigtramp (pc)
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CORE_ADDR pc;
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i386_linux_in_sigtramp (CORE_ADDR pc, char *name)
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{
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return i386_linux_sigtramp_start (pc) != 0;
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if (name)
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return STREQ ("__restore", name) || STREQ ("__restore_rt", name);
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return (i386_linux_sigtramp_start (pc) != 0
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|| i386_linux_rt_sigtramp_start (pc) != 0);
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}
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/* Assuming FRAME is for a Linux sigtramp routine, return the saved
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program counter. The Linux kernel will set up a sigcontext
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structure immediately before the sigtramp routine on the stack. */
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/* Assuming FRAME is for a Linux sigtramp routine, return the address
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of the associated sigcontext structure. */
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CORE_ADDR
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i386_linux_sigtramp_saved_pc (frame)
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struct frame_info *frame;
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i386_linux_sigcontext_addr (struct frame_info *frame)
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{
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CORE_ADDR pc;
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pc = i386_linux_sigtramp_start (frame->pc);
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if (pc == 0)
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error ("i386_linux_sigtramp_saved_pc called when no sigtramp");
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return read_memory_integer ((pc
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- LINUX_SIGCONTEXT_SIZE
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+ LINUX_SIGCONTEXT_PC_OFFSET),
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4);
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if (pc)
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{
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CORE_ADDR sp;
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if (frame->next)
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/* If this isn't the top frame, the next frame must be for the
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signal handler itself. The sigcontext structure lives on
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the stack, right after the signum argument. */
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return frame->next->frame + 12;
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/* This is the top frame. We'll have to find the address of the
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sigcontext structure by looking at the stack pointer. Keep
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in mind that the first instruction of the sigtramp code is
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"pop %eax". If the PC is at this instruction, adjust the
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returned value accordingly. */
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sp = read_register (SP_REGNUM);
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if (pc == frame->pc)
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return sp + 4;
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return sp;
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}
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pc = i386_linux_rt_sigtramp_start (frame->pc);
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if (pc)
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{
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if (frame->next)
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/* If this isn't the top frame, the next frame must be for the
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signal handler itself. The sigcontext structure is part of
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the user context. A pointer to the user context is passed
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as the third argument to the signal handler. */
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return read_memory_integer (frame->next->frame + 16, 4) + 20;
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/* This is the top frame. Again, use the stack pointer to find
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the address of the sigcontext structure. */
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return read_memory_integer (read_register (SP_REGNUM) + 8, 4) + 20;
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}
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error ("Couldn't recognize signal trampoline.");
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return 0;
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}
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/* Offset to saved PC in sigcontext, from <asm/sigcontext.h>. */
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#define LINUX_SIGCONTEXT_PC_OFFSET (56)
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/* Assuming FRAME is for a Linux sigtramp routine, return the saved
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stack pointer. The Linux kernel will set up a sigcontext structure
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immediately before the sigtramp routine on the stack. */
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program counter. */
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CORE_ADDR
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i386_linux_sigtramp_saved_sp (frame)
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struct frame_info *frame;
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i386_linux_sigtramp_saved_pc (struct frame_info *frame)
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{
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CORE_ADDR pc;
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CORE_ADDR addr;
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addr = i386_linux_sigcontext_addr (frame);
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return read_memory_integer (addr + LINUX_SIGCONTEXT_PC_OFFSET, 4);
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}
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pc = i386_linux_sigtramp_start (frame->pc);
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if (pc == 0)
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error ("i386_linux_sigtramp_saved_sp called when no sigtramp");
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return read_memory_integer ((pc
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- LINUX_SIGCONTEXT_SIZE
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+ LINUX_SIGCONTEXT_SP_OFFSET),
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4);
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/* Offset to saved SP in sigcontext, from <asm/sigcontext.h>. */
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#define LINUX_SIGCONTEXT_SP_OFFSET (28)
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/* Assuming FRAME is for a Linux sigtramp routine, return the saved
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stack pointer. */
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CORE_ADDR
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i386_linux_sigtramp_saved_sp (struct frame_info *frame)
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{
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CORE_ADDR addr;
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addr = i386_linux_sigcontext_addr (frame);
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return read_memory_integer (addr + LINUX_SIGCONTEXT_SP_OFFSET, 4);
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}
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#endif /* I386_LINUX_SIGTRAMP */
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