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Rework signal frame probing for FreeBSD/x86

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- Use signal frame sniffers that look for the signal trampoline
  instruction sequence to detect most signal frames.

- FreeBSD kernels between 9.2 and 10.1 inclusive do not include the
  signal trampoline code in process core dumps.  To detect signal
  frames for core dumps under these kernels, use the
  kern.proc.sigtramp.<pid> sysctl to fetch the location of the signal
  trampoline in the gdb process and assume that PC values within this
  location are signal frames.  This depends on that location being
  identical for all binaries.

gdb/ChangeLog:
2015-02-25  John Baldwin  <jhb@FreeBSD.org>

	* amd64fbsd-nat.c: Include sys/user.h.
	(_initialize_amd64fbsd_nat): Use the KERN_PROC_SIGTRAMP sysctl
	instead of KERN_PS_STRINGS to locate the signal trampoline.
	* i386fbsd-nat.c: Include sys/user.h.
	(_initialize_i386fbsd_nat): Use the KERN_PROC_SIGTRAMP sysctl
	instead of KERN_PS_STRINGS to locate the signal trampoline.
	* amd64fbsd-tdep.c (amd64fbsd_sigtramp_code): New.
	(amd64fbsd_sigtramp_p): New.
	(amd64fbsd_sigtramp_start_addr, amd64fbsd_sigtramp_end_addr): No
	longer set default values.
	(amd64fbsd_init_abi): Set "sigtramp_p" to "amd64fbsd_sigtramp_p".
	* i386fbsd-tdep.c (i386fbsd_sigtramp_start)
	(i386fbsd_sigtramp_middle, i386fbsd_sigtramp_end)
	(i386fbsd_freebsd4_sigtramp_start)
	(i386fbsd_freebsd4_sigtramp_middle)
	(i386fbsd_freebsd4_sigtramp_end, i386fbsd_osigtramp_start)
	(i386fbsd_osigtramp_middle, i386fbsd_osigtramp_end): New.
	(i386fbsd_sigtramp_p): New.
	(i386fbsd_sigtramp_start_addr, i386fbsd_sigtramp_end_addr): No
	longer set default values.
	(i386fbsd_init_abi): Set "sigtramp_p" to "i386fbsd_sigtramp_p".
This commit is contained in:
John Baldwin 2015-02-25 09:51:42 -05:00 committed by Pedro Alves
parent c5cb74eeb3
commit cf424aef0a
5 changed files with 245 additions and 31 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

24
gdb/ChangeLog
View file

@ -1,3 +1,27 @@
2015-02-25 John Baldwin <jhb@FreeBSD.org>
* amd64fbsd-nat.c: Include sys/user.h.
(_initialize_amd64fbsd_nat): Use the KERN_PROC_SIGTRAMP sysctl
instead of KERN_PS_STRINGS to locate the signal trampoline.
* i386fbsd-nat.c: Include sys/user.h.
(_initialize_i386fbsd_nat): Use the KERN_PROC_SIGTRAMP sysctl
instead of KERN_PS_STRINGS to locate the signal trampoline.
* amd64fbsd-tdep.c (amd64fbsd_sigtramp_code): New.
(amd64fbsd_sigtramp_p): New.
(amd64fbsd_sigtramp_start_addr, amd64fbsd_sigtramp_end_addr): No
longer set default values.
(amd64fbsd_init_abi): Set "sigtramp_p" to "amd64fbsd_sigtramp_p".
* i386fbsd-tdep.c (i386fbsd_sigtramp_start)
(i386fbsd_sigtramp_middle, i386fbsd_sigtramp_end)
(i386fbsd_freebsd4_sigtramp_start)
(i386fbsd_freebsd4_sigtramp_middle)
(i386fbsd_freebsd4_sigtramp_end, i386fbsd_osigtramp_start)
(i386fbsd_osigtramp_middle, i386fbsd_osigtramp_end): New.
(i386fbsd_sigtramp_p): New.
(i386fbsd_sigtramp_start_addr, i386fbsd_sigtramp_end_addr): No
longer set default values.
(i386fbsd_init_abi): Set "sigtramp_p" to "i386fbsd_sigtramp_p".
2015-02-25 John Baldwin <jhb@freebsd.org>
* amd64fbsd-tdep.c (amd64fbsd_sigcontext_addr): Use

34
gdb/amd64fbsd-nat.c
View file

@ -26,6 +26,7 @@
#include <sys/types.h>
#include <sys/ptrace.h>
#include <sys/sysctl.h>
#include <sys/user.h>
#include <machine/reg.h>
#include "fbsd-nat.h"
@ -244,24 +245,31 @@ Please report this to <bug-gdb@gnu.org>."),
SC_RBP_OFFSET = offset;
/* FreeBSD provides a kern.ps_strings sysctl that we can use to
locate the sigtramp. That way we can still recognize a sigtramp
if its location is changed in a new kernel. Of course this is
still based on the assumption that the sigtramp is placed
directly under the location where the program arguments and
environment can be found. */
#ifdef KERN_PROC_SIGTRAMP
/* Normally signal frames are detected via amd64fbsd_sigtramp_p.
However, FreeBSD 9.2 through 10.1 do not include the page holding
the signal code in core dumps. These releases do provide a
kern.proc.sigtramp.<pid> sysctl that returns the location of the
signal trampoline for a running process. We fetch the location
of the current (gdb) process and use this to identify signal
frames in core dumps from these releases. Note that this only
works for core dumps of 64-bit (FreeBSD/amd64) processes and does
not handle core dumps of 32-bit (FreeBSD/i386) processes. */
{
int mib[2];
long ps_strings;
int mib[4];
struct kinfo_sigtramp kst;
size_t len;
mib[0] = CTL_KERN;
mib[1] = KERN_PS_STRINGS;
len = sizeof (ps_strings);
if (sysctl (mib, 2, &ps_strings, &len, NULL, 0) == 0)
mib[1] = KERN_PROC;
mib[2] = KERN_PROC_SIGTRAMP;
mib[3] = getpid ();
len = sizeof (kst);
if (sysctl (mib, 4, &kst, &len, NULL, 0) == 0)
{
amd64fbsd_sigtramp_start_addr = ps_strings - 32;
amd64fbsd_sigtramp_end_addr = ps_strings;
amd64fbsd_sigtramp_start_addr = (uintptr_t) kst.ksigtramp_start;
amd64fbsd_sigtramp_end_addr = (uintptr_t) kst.ksigtramp_end;
}
}
#endif
}

32
gdb/amd64fbsd-tdep.c
View file

@ -31,6 +31,33 @@
/* Support for signal handlers. */
/* Return whether THIS_FRAME corresponds to a FreeBSD sigtramp
routine. */
static const gdb_byte amd64fbsd_sigtramp_code[] =
{
0x48, 0x8d, 0x7c, 0x24, 0x10, /* lea SIGF_UC(%rsp),%rdi */
0x6a, 0x00, /* pushq $0 */
0x48, 0xc7, 0xc0, 0xa1, 0x01, 0x00, 0x00,
/* movq $SYS_sigreturn,%rax */
0x0f, 0x05 /* syscall */
};
static int
amd64fbsd_sigtramp_p (struct frame_info *this_frame)
{
CORE_ADDR pc = get_frame_pc (this_frame);
gdb_byte buf[sizeof amd64fbsd_sigtramp_code];
if (!safe_frame_unwind_memory (this_frame, pc, buf, sizeof buf))
return 0;
if (memcmp (buf, amd64fbsd_sigtramp_code, sizeof amd64fbsd_sigtramp_code) !=
0)
return 0;
return 1;
}
/* Assuming THIS_FRAME is for a BSD sigtramp routine, return the
address of the associated sigcontext structure. */
@ -88,8 +115,8 @@ static int amd64fbsd_r_reg_offset[] =
};
/* Location of the signal trampoline. */
CORE_ADDR amd64fbsd_sigtramp_start_addr = 0x7fffffffffc0ULL;
CORE_ADDR amd64fbsd_sigtramp_end_addr = 0x7fffffffffe0ULL;
CORE_ADDR amd64fbsd_sigtramp_start_addr;
CORE_ADDR amd64fbsd_sigtramp_end_addr;
/* From <machine/signal.h>. */
int amd64fbsd_sc_reg_offset[] =
@ -199,6 +226,7 @@ amd64fbsd_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
amd64_init_abi (info, gdbarch);
tdep->sigtramp_p = amd64fbsd_sigtramp_p;
tdep->sigtramp_start = amd64fbsd_sigtramp_start_addr;
tdep->sigtramp_end = amd64fbsd_sigtramp_end_addr;
tdep->sigcontext_addr = amd64fbsd_sigcontext_addr;

32
gdb/i386fbsd-nat.c
View file

@ -25,6 +25,7 @@
#include <sys/types.h>
#include <sys/ptrace.h>
#include <sys/sysctl.h>
#include <sys/user.h>
#include "fbsd-nat.h"
#include "i386-tdep.h"
@ -148,25 +149,28 @@ _initialize_i386fbsd_nat (void)
/* Support debugging kernel virtual memory images. */
bsd_kvm_add_target (i386fbsd_supply_pcb);
/* FreeBSD provides a kern.ps_strings sysctl that we can use to
locate the sigtramp. That way we can still recognize a sigtramp
if its location is changed in a new kernel. Of course this is
still based on the assumption that the sigtramp is placed
directly under the location where the program arguments and
environment can be found. */
#ifdef KERN_PS_STRINGS
#ifdef KERN_PROC_SIGTRAMP
/* Normally signal frames are detected via i386fbsd_sigtramp_p.
However, FreeBSD 9.2 through 10.1 do not include the page holding
the signal code in core dumps. These releases do provide a
kern.proc.sigtramp.<pid> sysctl that returns the location of the
signal trampoline for a running process. We fetch the location
of the current (gdb) process and use this to identify signal
frames in core dumps from these releases. */
{
int mib[2];
u_long ps_strings;
int mib[4];
struct kinfo_sigtramp kst;
size_t len;
mib[0] = CTL_KERN;
mib[1] = KERN_PS_STRINGS;
len = sizeof (ps_strings);
if (sysctl (mib, 2, &ps_strings, &len, NULL, 0) == 0)
mib[1] = KERN_PROC;
mib[2] = KERN_PROC_SIGTRAMP;
mib[3] = getpid ();
len = sizeof (kst);
if (sysctl (mib, 4, &kst, &len, NULL, 0) == 0)
{
i386fbsd_sigtramp_start_addr = ps_strings - 128;
i386fbsd_sigtramp_end_addr = ps_strings;
i386fbsd_sigtramp_start_addr = (uintptr_t) kst.ksigtramp_start;
i386fbsd_sigtramp_end_addr = (uintptr_t) kst.ksigtramp_end;
}
}
#endif

154
gdb/i386fbsd-tdep.c
View file

@ -29,6 +29,154 @@
#include "fbsd-tdep.h"
#include "solib-svr4.h"
/* Support for signal handlers. */
/* Return whether THIS_FRAME corresponds to a FreeBSD sigtramp
routine. */
/* FreeBSD/i386 supports three different signal trampolines, one for
versions before 4.0, a second for 4.x, and a third for 5.0 and
later. To complicate matters, FreeBSD/i386 binaries running under
an amd64 kernel use a different set of trampolines. These
trampolines differ from the i386 kernel trampolines in that they
omit a middle section that conditionally restores %gs. */
static const gdb_byte i386fbsd_sigtramp_start[] =
{
0x8d, 0x44, 0x24, 0x20, /* lea SIGF_UC(%esp),%eax */
0x50 /* pushl %eax */
};
static const gdb_byte i386fbsd_sigtramp_middle[] =
{
0xf7, 0x40, 0x54, 0x00, 0x00, 0x02, 0x00,
/* testl $PSL_VM,UC_EFLAGS(%eax) */
0x75, 0x03, /* jne +3 */
0x8e, 0x68, 0x14 /* mov UC_GS(%eax),%gs */
};
static const gdb_byte i386fbsd_sigtramp_end[] =
{
0xb8, 0xa1, 0x01, 0x00, 0x00, /* movl $SYS_sigreturn,%eax */
0x50, /* pushl %eax */
0xcd, 0x80 /* int $0x80 */
};
static const gdb_byte i386fbsd_freebsd4_sigtramp_start[] =
{
0x8d, 0x44, 0x24, 0x14, /* lea SIGF_UC4(%esp),%eax */
0x50 /* pushl %eax */
};
static const gdb_byte i386fbsd_freebsd4_sigtramp_middle[] =
{
0xf7, 0x40, 0x54, 0x00, 0x00, 0x02, 0x00,
/* testl $PSL_VM,UC4_EFLAGS(%eax) */
0x75, 0x03, /* jne +3 */
0x8e, 0x68, 0x14 /* mov UC4_GS(%eax),%gs */
};
static const gdb_byte i386fbsd_freebsd4_sigtramp_end[] =
{
0xb8, 0x58, 0x01, 0x00, 0x00, /* movl $344,%eax */
0x50, /* pushl %eax */
0xcd, 0x80 /* int $0x80 */
};
static const gdb_byte i386fbsd_osigtramp_start[] =
{
0x8d, 0x44, 0x24, 0x14, /* lea SIGF_SC(%esp),%eax */
0x50 /* pushl %eax */
};
static const gdb_byte i386fbsd_osigtramp_middle[] =
{
0xf7, 0x40, 0x18, 0x00, 0x00, 0x02, 0x00,
/* testl $PSL_VM,SC_PS(%eax) */
0x75, 0x03, /* jne +3 */
0x8e, 0x68, 0x44 /* mov SC_GS(%eax),%gs */
};
static const gdb_byte i386fbsd_osigtramp_end[] =
{
0xb8, 0x67, 0x00, 0x00, 0x00, /* movl $103,%eax */
0x50, /* pushl %eax */
0xcd, 0x80 /* int $0x80 */
};
/* The three different trampolines are all the same size. */
gdb_static_assert (sizeof i386fbsd_sigtramp_start ==
sizeof i386fbsd_freebsd4_sigtramp_start);
gdb_static_assert (sizeof i386fbsd_sigtramp_start ==
sizeof i386fbsd_osigtramp_start);
gdb_static_assert (sizeof i386fbsd_sigtramp_middle ==
sizeof i386fbsd_freebsd4_sigtramp_middle);
gdb_static_assert (sizeof i386fbsd_sigtramp_middle ==
sizeof i386fbsd_osigtramp_middle);
gdb_static_assert (sizeof i386fbsd_sigtramp_end ==
sizeof i386fbsd_freebsd4_sigtramp_end);
gdb_static_assert (sizeof i386fbsd_sigtramp_end ==
sizeof i386fbsd_osigtramp_end);
/* We assume that the middle is the largest chunk below. */
gdb_static_assert (sizeof i386fbsd_sigtramp_middle >
sizeof i386fbsd_sigtramp_start);
gdb_static_assert (sizeof i386fbsd_sigtramp_middle >
sizeof i386fbsd_sigtramp_end);
static int
i386fbsd_sigtramp_p (struct frame_info *this_frame)
{
CORE_ADDR pc = get_frame_pc (this_frame);
gdb_byte buf[sizeof i386fbsd_sigtramp_middle];
const gdb_byte *middle, *end;
/* Look for a matching start. */
if (!safe_frame_unwind_memory (this_frame, pc, buf,
sizeof i386fbsd_sigtramp_start))
return 0;
if (memcmp (buf, i386fbsd_sigtramp_start, sizeof i386fbsd_sigtramp_start) ==
0) {
middle = i386fbsd_sigtramp_middle;
end = i386fbsd_sigtramp_end;
} else if (memcmp (buf, i386fbsd_freebsd4_sigtramp_start,
sizeof i386fbsd_freebsd4_sigtramp_start) == 0) {
middle = i386fbsd_freebsd4_sigtramp_middle;
end = i386fbsd_freebsd4_sigtramp_end;
} else if (memcmp (buf, i386fbsd_osigtramp_start,
sizeof i386fbsd_osigtramp_start) == 0) {
middle = i386fbsd_osigtramp_middle;
end = i386fbsd_osigtramp_end;
} else
return 0;
/* Since the end is shorter than the middle, check for a matching end
next. */
pc += sizeof i386fbsd_sigtramp_start;
if (!safe_frame_unwind_memory (this_frame, pc, buf,
sizeof i386fbsd_sigtramp_end))
return 0;
if (memcmp (buf, end, sizeof i386fbsd_sigtramp_end) == 0)
return 1;
/* If the end didn't match, check for a matching middle. */
if (!safe_frame_unwind_memory (this_frame, pc, buf,
sizeof i386fbsd_sigtramp_middle))
return 0;
if (memcmp (buf, middle, sizeof i386fbsd_sigtramp_middle) != 0)
return 0;
/* The middle matched, check for a matching end. */
pc += sizeof i386fbsd_sigtramp_middle;
if (!safe_frame_unwind_memory (this_frame, pc, buf,
sizeof i386fbsd_sigtramp_end))
return 0;
if (memcmp (buf, end, sizeof i386fbsd_sigtramp_end) != 0)
return 0;
return 1;
}
/* FreeBSD 3.0-RELEASE or later. */
/* From <machine/reg.h>. */
@ -43,8 +191,8 @@ static int i386fbsd_r_reg_offset[] =
};
/* Sigtramp routine location. */
CORE_ADDR i386fbsd_sigtramp_start_addr = 0xbfbfdf20;
CORE_ADDR i386fbsd_sigtramp_end_addr = 0xbfbfdff0;
CORE_ADDR i386fbsd_sigtramp_start_addr;
CORE_ADDR i386fbsd_sigtramp_end_addr;
/* From <machine/signal.h>. */
int i386fbsd_sc_reg_offset[] =
@ -139,6 +287,8 @@ i386fbsdaout_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
/* FreeBSD uses -freg-struct-return by default. */
tdep->struct_return = reg_struct_return;
tdep->sigtramp_p = i386fbsd_sigtramp_p;
/* FreeBSD uses a different memory layout. */
tdep->sigtramp_start = i386fbsd_sigtramp_start_addr;
tdep->sigtramp_end = i386fbsd_sigtramp_end_addr;