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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0x000001f6 in jumper ()^M (gdb) FAIL: gdb.base/watchpoint-cond-gone.exp: Catch the no longer valid watchpoint In the test, jumper calls func, and programs returns from func to jumper's epilogue, IOW, the branch instruction is the last instruction of jumper's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, 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: 2014-08-28 Yao Qi <yao@codesourcery.com> * arm-tdep.c (thumb_in_function_epilogue_p): Don't set found_stack_adjust in forward scan. Remove condition check on found_stack_adjust which is always true. Indent the code.
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