[PATCH 1/2] [ARM] Fixup PC in software single step
Yao Qi
qiyaoltc@gmail.com
Thu Feb 11 15:19:00 GMT 2016
When I exercise GDBserver software single step, I see the following
error, which has been already handled by GDB properly.
In GDBserver log, we can see, GDBserver tries to single step instruction
on 0xb6e0a6e4, and destination address is 0xffff0fe0,
stop pc is 0xb6e0a6e4
Writing f001f0e7 to 0xffff0fe0 in process 7132
Failed to insert breakpoint at 0xffff0fe0 (Input/output error).
Failed to insert breakpoint at 0xffff0fe0 (-1).
(gdb) disassemble __aeabi_read_tp,+8
Dump of assembler code from 0xb6e0a6e0 to 0xb6e0a6e8:
0xb6e0a6e0 <__aeabi_read_tp+0>: mvn r0, #61440 ; 0xf000
0xb6e0a6e4 <__aeabi_read_tp+4>: sub pc, r0, #31
however, it fails inserting breakpoint there. This problem has already
fixed by GDB, see comments in arm-linux-tdep.c:arm_linux_software_single_step
/* The Linux kernel offers some user-mode helpers in a high page. We can
not read this page (as of 2.6.23), and even if we could then we
couldn't set breakpoints in it, and even if we could then the atomic
operations would fail when interrupted. They are all called as
functions and return to the address in LR, so step to there
instead. */
so we need to do the same thing in GDB side as well. This patch adds
a new field fixup in arm_get_next_pcs_ops, so that we can fix up PC
for arm-linux target. In this way, both GDB and GDBserver can single
step instructions going to kernel helpers.
gdb:
2016-02-11 Yao Qi <yao.qi@linaro.org>
* arch/arm-get-next-pcs.c (arm_get_next_pcs): Call
self->ops->fixup if it isn't NULL.
* arch/arm-get-next-pcs.h: Include gdb_vecs.h.
(struct arm_get_next_pcs_ops) <fixup>: New field.
* arch/arm-linux.c: Include common-regcache.h and
arch/arm-get-next-pcs.h.
(arm_linux_get_next_pcs_fixup): New function.
* arch/arm-linux.h (arm_linux_get_next_pcs_fixup): Declare.
* arm-linux-tdep.c (arm_linux_get_next_pcs_ops): Initialize
it with arm_linux_get_next_pcs_fixup.
(arm_linux_software_single_step): Move code to
arm_linux_get_next_pcs_fixup.
* arm-tdep.c (arm_get_next_pcs_ops): Initialize it.
gdb/gdbserver:
2016-02-11 Yao Qi <yao.qi@linaro.org>
* linux-arm-low.c (get_next_pcs_ops): Initialize it with
arm_linux_get_next_pcs_fixup.
---
gdb/arch/arm-get-next-pcs.c | 11 +++++++++++
gdb/arch/arm-get-next-pcs.h | 4 ++++
gdb/arch/arm-linux.c | 20 ++++++++++++++++++++
gdb/arch/arm-linux.h | 4 ++++
gdb/arm-linux-tdep.c | 16 +++-------------
gdb/arm-tdep.c | 3 ++-
gdb/gdbserver/linux-arm-low.c | 3 ++-
7 files changed, 46 insertions(+), 15 deletions(-)
diff --git a/gdb/arch/arm-get-next-pcs.c b/gdb/arch/arm-get-next-pcs.c
index e840147..8404869 100644
--- a/gdb/arch/arm-get-next-pcs.c
+++ b/gdb/arch/arm-get-next-pcs.c
@@ -923,5 +923,16 @@ arm_get_next_pcs (struct arm_get_next_pcs *self)
next_pcs = arm_get_next_pcs_raw (self);
}
+ if (self->ops->fixup != NULL)
+ {
+ CORE_ADDR nextpc;
+ int i;
+
+ for (i = 0; VEC_iterate (CORE_ADDR, next_pcs, i, nextpc); i++)
+ {
+ nextpc = self->ops->fixup (self, nextpc);
+ VEC_replace (CORE_ADDR, next_pcs, i, nextpc);
+ }
+ }
return next_pcs;
}
diff --git a/gdb/arch/arm-get-next-pcs.h b/gdb/arch/arm-get-next-pcs.h
index 7cb0858..e038982 100644
--- a/gdb/arch/arm-get-next-pcs.h
+++ b/gdb/arch/arm-get-next-pcs.h
@@ -19,6 +19,7 @@
#ifndef ARM_GET_NEXT_PCS_H
#define ARM_GET_NEXT_PCS_H 1
+#include "gdb_vecs.h"
/* Forward declaration. */
struct arm_get_next_pcs;
@@ -30,6 +31,9 @@ struct arm_get_next_pcs_ops
CORE_ADDR (*syscall_next_pc) (struct arm_get_next_pcs *self, CORE_ADDR pc);
CORE_ADDR (*addr_bits_remove) (struct arm_get_next_pcs *self, CORE_ADDR val);
int (*is_thumb) (struct arm_get_next_pcs *self);
+
+ /* Fix up PC if needed. */
+ CORE_ADDR (*fixup) (struct arm_get_next_pcs *self, CORE_ADDR pc);
};
/* Context for a get_next_pcs call on ARM. */
diff --git a/gdb/arch/arm-linux.c b/gdb/arch/arm-linux.c
index b43e484..457080c 100644
--- a/gdb/arch/arm-linux.c
+++ b/gdb/arch/arm-linux.c
@@ -18,8 +18,10 @@
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include "common-defs.h"
+#include "common-regcache.h"
#include "arch/arm.h"
#include "arm-linux.h"
+#include "arch/arm-get-next-pcs.h"
/* Calculate the offset from stack pointer of the pc register on the stack
in the case of a sigreturn or sigreturn_rt syscall. */
@@ -55,3 +57,21 @@ arm_linux_sigreturn_next_pc_offset (unsigned long sp,
return pc_offset;
}
+
+/* Implementation of "fixup" method of struct arm_get_next_pcs_ops
+ for arm-linux. */
+
+CORE_ADDR
+arm_linux_get_next_pcs_fixup (struct arm_get_next_pcs *self,
+ CORE_ADDR nextpc)
+{
+ /* The Linux kernel offers some user-mode helpers in a high page. We can
+ not read this page (as of 2.6.23), and even if we could then we
+ couldn't set breakpoints in it, and even if we could then the atomic
+ operations would fail when interrupted. They are all called as
+ functions and return to the address in LR, so step to there
+ instead. */
+ if (nextpc > 0xffff0000)
+ nextpc = regcache_raw_get_unsigned (self->regcache, ARM_LR_REGNUM);
+ return nextpc;
+}
diff --git a/gdb/arch/arm-linux.h b/gdb/arch/arm-linux.h
index 31cb351..dfd634c 100644
--- a/gdb/arch/arm-linux.h
+++ b/gdb/arch/arm-linux.h
@@ -71,4 +71,8 @@ arm_linux_sigreturn_next_pc_offset (unsigned long sp,
unsigned long svc_number,
int is_sigreturn);
+struct arm_get_next_pcs;
+
+CORE_ADDR arm_linux_get_next_pcs_fixup (struct arm_get_next_pcs *self,
+ CORE_ADDR pc);
#endif /* ARM_LINUX_H */
diff --git a/gdb/arm-linux-tdep.c b/gdb/arm-linux-tdep.c
index 3421f3b..3dbf649 100644
--- a/gdb/arm-linux-tdep.c
+++ b/gdb/arm-linux-tdep.c
@@ -274,7 +274,8 @@ static struct arm_get_next_pcs_ops arm_linux_get_next_pcs_ops = {
arm_get_next_pcs_read_memory_unsigned_integer,
arm_linux_get_next_pcs_syscall_next_pc,
arm_get_next_pcs_addr_bits_remove,
- arm_get_next_pcs_is_thumb
+ arm_get_next_pcs_is_thumb,
+ arm_linux_get_next_pcs_fixup,
};
static void
@@ -950,18 +951,7 @@ arm_linux_software_single_step (struct frame_info *frame)
next_pcs = arm_get_next_pcs (&next_pcs_ctx);
for (i = 0; VEC_iterate (CORE_ADDR, next_pcs, i, pc); i++)
- {
- /* The Linux kernel offers some user-mode helpers in a high page. We can
- not read this page (as of 2.6.23), and even if we could then we
- couldn't set breakpoints in it, and even if we could then the atomic
- operations would fail when interrupted. They are all called as
- functions and return to the address in LR, so step to there
- instead. */
- if (pc > 0xffff0000)
- pc = get_frame_register_unsigned (frame, ARM_LR_REGNUM);
-
- arm_insert_single_step_breakpoint (gdbarch, aspace, pc);
- }
+ arm_insert_single_step_breakpoint (gdbarch, aspace, pc);
do_cleanups (old_chain);
diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
index 6ac05f0..bf59ea7 100644
--- a/gdb/arm-tdep.c
+++ b/gdb/arm-tdep.c
@@ -247,7 +247,8 @@ static struct arm_get_next_pcs_ops arm_get_next_pcs_ops = {
arm_get_next_pcs_read_memory_unsigned_integer,
arm_get_next_pcs_syscall_next_pc,
arm_get_next_pcs_addr_bits_remove,
- arm_get_next_pcs_is_thumb
+ arm_get_next_pcs_is_thumb,
+ NULL,
};
struct arm_prologue_cache
diff --git a/gdb/gdbserver/linux-arm-low.c b/gdb/gdbserver/linux-arm-low.c
index 0f62706..365f1c9 100644
--- a/gdb/gdbserver/linux-arm-low.c
+++ b/gdb/gdbserver/linux-arm-low.c
@@ -157,7 +157,8 @@ static struct arm_get_next_pcs_ops get_next_pcs_ops = {
get_next_pcs_read_memory_unsigned_integer,
get_next_pcs_syscall_next_pc,
get_next_pcs_addr_bits_remove,
- get_next_pcs_is_thumb
+ get_next_pcs_is_thumb,
+ arm_linux_get_next_pcs_fixup,
};
static int
--
1.9.1
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