From patchwork Wed Aug 6 03:18:10 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yao Qi X-Patchwork-Id: 2308 Received: (qmail 29489 invoked by alias); 6 Aug 2014 03:22:40 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Delivered-To: mailing list gdb-patches@sourceware.org Received: (qmail 29467 invoked by uid 89); 6 Aug 2014 03:22:35 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.7 required=5.0 tests=AWL, BAYES_00 autolearn=ham version=3.3.2 X-HELO: relay1.mentorg.com Received: from relay1.mentorg.com (HELO relay1.mentorg.com) (192.94.38.131) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Wed, 06 Aug 2014 03:22:27 +0000 Received: from svr-orw-exc-10.mgc.mentorg.com ([147.34.98.58]) by relay1.mentorg.com with esmtp id 1XErnw-0006Ds-Sa from Yao_Qi@mentor.com for gdb-patches@sourceware.org; Tue, 05 Aug 2014 20:22:20 -0700 Received: from SVR-ORW-FEM-04.mgc.mentorg.com ([147.34.97.41]) by SVR-ORW-EXC-10.mgc.mentorg.com with Microsoft SMTPSVC(6.0.3790.4675); Tue, 5 Aug 2014 20:22:20 -0700 Received: from qiyao.dyndns.org.com (147.34.91.1) by svr-orw-fem-04.mgc.mentorg.com (147.34.97.41) with Microsoft SMTP Server id 14.2.247.3; Tue, 5 Aug 2014 20:22:28 -0700 From: Yao Qi To: Subject: [PATCH] arm software watchpoint: return to epilogue Date: Wed, 6 Aug 2014 11:18:10 +0800 Message-ID: <1407295090-17296-1-git-send-email-yao@codesourcery.com> MIME-Version: 1.0 X-IsSubscribed: yes Hi, This patch is to handle a software watchpoint case that program returns to caller's epilogue, and it causes the fail in thumb mode, finish^M Run till exit from #0 func () at gdb/testsuite/gdb.base/watchpoint-cond-gone.c:26^M 0x000001f6 in jumper ()^M (gdb) FAIL: gdb.base/watchpoint-cond-gone.exp: Catch the no longer valid watchpoint In the test, jumper calls func, and programs returns from func to jumper's epilogue, IOW, the branch instruction is the last instruction of jumper's function body. jumper: ..... 0x000001f2 <+10>: bl 0x200 [1] <---- indirect call to func 0x000001f6 <+14>: mov sp, r7 [2] <---- start of the epilogue 0x000001f8 <+16>: add sp, #8 0x000001fa <+18>: pop {r7} 0x000001fc <+20>: pop {r0} 0x000001fe <+22>: bx r0 When the inferior returns from func back to jumper, it is expected that an expression of a software watchpoint becomes out-of-scope. GDB validates the expression by checking the corresponding frame, but this check is guarded by gdbarch_in_function_epilogue_p. See breakpoint.c:watchpoint_check. It doesn't work in this case, because program returns from func's epilogue back to jumper's epilogue [2], GDB thinks the program is still within the epilogue, but in fact it goes to a different one. When PC points at [2], the sp-restore instruction is to be executed, so the stack frame isn't destroyed yet and we can still use the frame mechanism reliably. Note that when PC points to the first instruction of restoring SP, it is part of epilogue, but we still return zero. When goes to the next instruction, the backward scan will still match the epilogue sequence correctly. The reason for doing this is to handle the "return-to-epilogue" case. What this patch does is to restrict the epilogue matching that let GDB think the first SP restore instruction isn't part of the epilogue, and fall back to use frame mechanism. We set 'found_stack_adjust' zero before backward scan (although found_stack_adjust is initialized to zero, it is safe to set it again before using it), and we've done this for arm mode counterpart (arm_in_function_epilogue_p) too. The patch is tested in arm-none-eabi and arm-none-linux-gnueabi with various multilibs. OK to apply? gdb: 2014-08-06 Yao Qi * arm-tdep.c (thumb_in_function_epilogue_p): Don't set found_stack_adjust in forward scan. Set it zero before backward scan. Remove condition check on found_stack_adjust which is always true. Indent the code. --- gdb/arm-tdep.c | 43 +++++++++++++++++++------------------------ 1 file changed, 19 insertions(+), 24 deletions(-) diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c index cb0030c..4e223cb 100644 --- a/gdb/arm-tdep.c +++ b/gdb/arm-tdep.c @@ -3275,7 +3275,6 @@ thumb_in_function_epilogue_p (struct gdbarch *gdbarch, CORE_ADDR pc) found_return = 1; else if (thumb_instruction_restores_sp (insn)) { - found_stack_adjust = 1; if ((insn & 0xfe00) == 0xbd00) /* pop */ found_return = 1; } @@ -3289,20 +3288,18 @@ thumb_in_function_epilogue_p (struct gdbarch *gdbarch, CORE_ADDR pc) if (insn == 0xe8bd) /* ldm.w sp!, */ { - found_stack_adjust = 1; if (insn2 & 0x8000) /* include PC. */ found_return = 1; } else if (insn == 0xf85d /* ldr.w , [sp], #4 */ && (insn2 & 0x0fff) == 0x0b04) { - found_stack_adjust = 1; if ((insn2 & 0xf000) == 0xf000) /* is PC. */ found_return = 1; } else if ((insn & 0xffbf) == 0xecbd /* vldm sp!, */ && (insn2 & 0x0e00) == 0x0a00) - found_stack_adjust = 1; + ; else break; } @@ -3318,28 +3315,26 @@ thumb_in_function_epilogue_p (struct gdbarch *gdbarch, CORE_ADDR pc) scan backwards for at most one instruction. Try either a 16-bit or a 32-bit instruction. This is just a heuristic, so we do not worry too much about false positives. */ + found_stack_adjust = 0; - if (!found_stack_adjust) - { - if (pc - 4 < func_start) - return 0; - if (target_read_memory (pc - 4, buf, 4)) - return 0; - - insn = extract_unsigned_integer (buf, 2, byte_order_for_code); - insn2 = extract_unsigned_integer (buf + 2, 2, byte_order_for_code); + if (pc - 4 < func_start) + return 0; + if (target_read_memory (pc - 4, buf, 4)) + return 0; - if (thumb_instruction_restores_sp (insn2)) - found_stack_adjust = 1; - else if (insn == 0xe8bd) /* ldm.w sp!, */ - found_stack_adjust = 1; - else if (insn == 0xf85d /* ldr.w , [sp], #4 */ - && (insn2 & 0x0fff) == 0x0b04) - found_stack_adjust = 1; - else if ((insn & 0xffbf) == 0xecbd /* vldm sp!, */ - && (insn2 & 0x0e00) == 0x0a00) - found_stack_adjust = 1; - } + insn = extract_unsigned_integer (buf, 2, byte_order_for_code); + insn2 = extract_unsigned_integer (buf + 2, 2, byte_order_for_code); + + if (thumb_instruction_restores_sp (insn2)) + found_stack_adjust = 1; + else if (insn == 0xe8bd) /* ldm.w sp!, */ + found_stack_adjust = 1; + else if (insn == 0xf85d /* ldr.w , [sp], #4 */ + && (insn2 & 0x0fff) == 0x0b04) + found_stack_adjust = 1; + else if ((insn & 0xffbf) == 0xecbd /* vldm sp!, */ + && (insn2 & 0x0e00) == 0x0a00) + found_stack_adjust = 1; return found_stack_adjust; }