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authorYao Qi <yao.qi@linaro.org>2016-01-14 09:36:43 +0000
committerYao Qi <yao.qi@linaro.org>2016-01-14 09:36:43 +0000
commit1b451dda5f8905b26bafafe00423335d4fffe8dd (patch)
tree8cfa5c475efdfc65af696a902f24cacfb5522521 /gdb/gdbserver/linux-aarch32-low.c
parentfccbac73f9328cdde552d8dd82927481a60c388b (diff)
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[ARM] Make thumb2_breakpoint static again
This patch makes thumb2_breakpoint static. When writing this patch, I find the only reason we keep thumb2_breakpoint extern is that it is used as an argument passed to arm_gdbserver_get_next_pcs. However, field arm_thumb2_breakpoint is only used in a null check in thumb_get_next_pcs_raw, so I wonder why do need to pass thumb2_breakpoint to arm_gdbserver_get_next_pcs. thumb2_breakpoint was added by Daniel Jacobowitz in order to support single-step IT block https://sourceware.org/ml/gdb-patches/2010-01/msg00624.html the logic there was if we have 32-bit thumb-2 breakpoint defined, we can safely single-step IT block, otherwise, we can't. Daniel didn't want to use 16-bit thumb BKPT instruction, because it triggers even on instruction which should be executed. Secondly, using 16-bit thumb illegal instruction on top of 32-bit thumb instruction may break the meaning of original IT blocks, because the other 16-bit can be regarded as an instruction. See more explanations from Daniel's kernel patch http://www.spinics.net/lists/arm-kernel/msg80476.html Let us back to this patch, GDB/GDBserver can safely single step IT block if thumb2_breakpoint is defined, but the single step logic doesn't have to know the thumb-2 breakpoint instruction. Only breakpoint insertion mechanism decides to use which breakpoint instruction. In the software single step code, instead of pass thumb2_breakpoint, we can pass a boolean variable has_thumb2_breakpoint indicate whether the target has thumb-2 breakpoint defined, which is equivalent to the original code. Regression tested on arm-linux. No regression. gdb: 2016-01-14 Yao Qi <yao.qi@linaro.org> * arch/arm-get-next-pcs.c (arm_get_next_pcs_ctor): Change argument arm_thumb2_breakpoint to has_thumb2_breakpoint. (thumb_get_next_pcs_raw): Check has_thumb2_breakpoint instead. * arch/arm-get-next-pcs.h (struct arm_get_next_pcs) <arm_thumb2_breakpoint>: Remove. <has_thumb2_breakpoint>: New field. (arm_get_next_pcs_ctor): Update declaration. * arm-linux-tdep.c (arm_linux_software_single_step): Pass 1 to arm_get_next_pcs_ctor. * arm-tdep.c (arm_software_single_step): Pass 0 to arm_get_next_pcs_ctor. gdb/gdbserver: 2016-01-14 Yao Qi <yao.qi@linaro.org> * linux-aarch32-low.c (thumb2_breakpoint): Make it static. * linux-aarch32-low.h (thumb2_breakpoint): Remove declaration. * linux-arm-low.c (arm_gdbserver_get_next_pcs): Pass 1 to arm_get_next_pcs_ctor.
Diffstat (limited to 'gdb/gdbserver/linux-aarch32-low.c')
-rw-r--r--gdb/gdbserver/linux-aarch32-low.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/gdb/gdbserver/linux-aarch32-low.c b/gdb/gdbserver/linux-aarch32-low.c
index ed66e08..2bbbb24 100644
--- a/gdb/gdbserver/linux-aarch32-low.c
+++ b/gdb/gdbserver/linux-aarch32-low.c
@@ -45,7 +45,7 @@ static const unsigned long arm_breakpoint = arm_abi_breakpoint;
#define arm_breakpoint_len 4
static const unsigned short thumb_breakpoint = 0xde01;
#define thumb_breakpoint_len 2
-const unsigned short thumb2_breakpoint[] = { 0xf7f0, 0xa000 };
+static const unsigned short thumb2_breakpoint[] = { 0xf7f0, 0xa000 };
#define thumb2_breakpoint_len 4
/* Some older versions of GNU/Linux and Android do not define