From ed443b61e1f6e4eb7919fe9122dd947d1e87e767 Mon Sep 17 00:00:00 2001 From: Yao Qi Date: Mon, 8 Feb 2016 16:05:31 +0000 Subject: [PATCH] [ARM] Fixup PC in software single step 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: 2016-02-12 Yao Qi * 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) : 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: 2016-02-12 Yao Qi * linux-arm-low.c (get_next_pcs_ops): Initialize it with arm_linux_get_next_pcs_fixup. --- gdb/ChangeLog | 16 ++++++++++++++++ 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/ChangeLog | 5 +++++ gdb/gdbserver/linux-arm-low.c | 3 ++- 9 files changed, 67 insertions(+), 15 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 4e8dfb54f6c..15d81577cfb 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,19 @@ +2016-02-12 Yao Qi + + * 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) : 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. + 2016-02-12 Marcin Kościelnicki * xml-tdesc.c (target_fetch_description_xml) [!HAVE_LIBEXPAT]: Warn diff --git a/gdb/arch/arm-get-next-pcs.c b/gdb/arch/arm-get-next-pcs.c index e84014742eb..84048697987 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 7cb0858cc70..e038982c514 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 b43e4845d5e..457080c27ff 100644 --- a/gdb/arch/arm-linux.c +++ b/gdb/arch/arm-linux.c @@ -18,8 +18,10 @@ along with this program. If not, see . */ #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 31cb35150e7..dfd634c5ffa 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 53169633b56..e416e28fefa 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 7308a40795a..048406aca8d 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/ChangeLog b/gdb/gdbserver/ChangeLog index ca82f9153e1..8d026475e57 100644 --- a/gdb/gdbserver/ChangeLog +++ b/gdb/gdbserver/ChangeLog @@ -1,3 +1,8 @@ +2016-02-12 Yao Qi + + * linux-arm-low.c (get_next_pcs_ops): Initialize it with + arm_linux_get_next_pcs_fixup. + 2016-02-12 Marcin Kościelnicki * tracepoint.c (x_tracepoint_action_download): Change diff --git a/gdb/gdbserver/linux-arm-low.c b/gdb/gdbserver/linux-arm-low.c index 0f627069e0e..365f1c93222 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 -- 2.30.2