From 1b451dda5f8905b26bafafe00423335d4fffe8dd Mon Sep 17 00:00:00 2001 From: Yao Qi Date: Thu, 14 Jan 2016 09:36:43 +0000 Subject: [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 * 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) : Remove. : 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 * 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. --- gdb/arch/arm-get-next-pcs.h | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'gdb/arch/arm-get-next-pcs.h') diff --git a/gdb/arch/arm-get-next-pcs.h b/gdb/arch/arm-get-next-pcs.h index 895e866..4a0fc16 100644 --- a/gdb/arch/arm-get-next-pcs.h +++ b/gdb/arch/arm-get-next-pcs.h @@ -41,8 +41,9 @@ struct arm_get_next_pcs int byte_order; /* Byte order for code. */ int byte_order_for_code; - /* Thumb2 breakpoint instruction. */ - const gdb_byte *arm_thumb2_breakpoint; + /* Whether the target has 32-bit thumb-2 breakpoint defined or + not. */ + int has_thumb2_breakpoint; /* Registry cache. */ struct regcache *regcache; }; @@ -52,7 +53,7 @@ void arm_get_next_pcs_ctor (struct arm_get_next_pcs *self, struct arm_get_next_pcs_ops *ops, int byte_order, int byte_order_for_code, - const gdb_byte *arm_thumb2_breakpoint, + int has_thumb2_breakpoint, struct regcache *regcache); /* Find the next possible PCs after the current instruction executes. */ -- cgit v1.1