From 694b382c67a4fc656f30acbc74776c5e9cb53622 Mon Sep 17 00:00:00 2001 From: Antoine Tremblay Date: Mon, 9 Jan 2017 12:39:07 -0500 Subject: [PATCH] Fix inferior memory reading in GDBServer for arm/aarch32 Before this patch, some functions would read the inferior memory with (*the_target)->read_memory, which returns the raw memory, rather than the shadowed memory. This is wrong since these functions do not expect to read a breakpoint instruction and can lead to invalid behavior. Use of raw memory in get_next_pcs_read_memory_unsigned_integer for example could lead to get_next_pc returning an invalid pc. Here's how this would happen: In non-stop: the user issues: thread 1 step& thread 2 step& thread 3 step& In a similar way as non-stop-fair-events.exp (threads are looping). GDBServer: linux_resume is called GDBServer has pending events, threads are not resumed and single-step breakpoint for thread 1 not installed. linux_wait_1 is called with a pending event on thread 2 at pc A GDBServer handles the event and calls proceed_all_lwps This calls proceed_one_lwp and installs single-step breakpoints on all the threads that need one. Now since thread 1 needs to install a single-step breakpoint and is at pc B (different than thread 2), a step-over is not initiated and get_next_pc is called to figure out the next instruction from pc B. However it may just be that thread 3 as a single step breakpoint at pc B. And thus get_next_pc fails. This situation is tested with non-stop-fair-events.exp. In other words, single-step breakpoints are installed in proceed_one_lwp for each thread. GDBserver proceeds two threads for resume_step, as requested by GDB, and the thread proceeded later may see the single-step breakpoints installed for the thread proceeded just now. Tested on gdbserver-native/-m{thumb,arm} no regressions. gdb/gdbserver/ChangeLog: * linux-aarch32-low.c (arm_breakpoint_kind_from_pc): Use target_read_memory. * linux-arm-low.c (get_next_pcs_read_memory_unsigned_integer): Likewise. (get_next_pcs_syscall_next_pc): Likewise. --- gdb/gdbserver/ChangeLog | 7 +++++++ gdb/gdbserver/linux-aarch32-low.c | 4 ++-- gdb/gdbserver/linux-arm-low.c | 5 +++-- 3 files changed, 12 insertions(+), 4 deletions(-) diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog index d4d01e78e80..d3fba9bfec6 100644 --- a/gdb/gdbserver/ChangeLog +++ b/gdb/gdbserver/ChangeLog @@ -1,3 +1,10 @@ +2017-01-09 Antoine Tremblay + + * linux-aarch32-low.c (arm_breakpoint_kind_from_pc): Use + target_read_memory. + * linux-arm-low.c (get_next_pcs_read_memory_unsigned_integer): Likewise. + (get_next_pcs_syscall_next_pc): Likewise. + 2016-12-23 Luis Machado * win32-i386-low.c: Fix incorrect reference to a couple source files. diff --git a/gdb/gdbserver/linux-aarch32-low.c b/gdb/gdbserver/linux-aarch32-low.c index 729b7cfa2ea..2b710ba7d61 100644 --- a/gdb/gdbserver/linux-aarch32-low.c +++ b/gdb/gdbserver/linux-aarch32-low.c @@ -237,11 +237,11 @@ arm_breakpoint_kind_from_pc (CORE_ADDR *pcptr) *pcptr = UNMAKE_THUMB_ADDR (*pcptr); /* Check whether we are replacing a thumb2 32-bit instruction. */ - if ((*the_target->read_memory) (*pcptr, buf, 2) == 0) + if (target_read_memory (*pcptr, buf, 2) == 0) { unsigned short inst1 = 0; - (*the_target->read_memory) (*pcptr, (gdb_byte *) &inst1, 2); + target_read_memory (*pcptr, (gdb_byte *) &inst1, 2); if (thumb_insn_size (inst1) == 4) return ARM_BP_KIND_THUMB2; } diff --git a/gdb/gdbserver/linux-arm-low.c b/gdb/gdbserver/linux-arm-low.c index b2b22581634..fc2b34870a1 100644 --- a/gdb/gdbserver/linux-arm-low.c +++ b/gdb/gdbserver/linux-arm-low.c @@ -263,7 +263,8 @@ get_next_pcs_read_memory_unsigned_integer (CORE_ADDR memaddr, ULONGEST res; res = 0; - (*the_target->read_memory) (memaddr, (unsigned char *) &res, len); + target_read_memory (memaddr, (unsigned char *) &res, len); + return res; } @@ -804,7 +805,7 @@ get_next_pcs_syscall_next_pc (struct arm_get_next_pcs *self) unsigned long this_instr; unsigned long svc_operand; - (*the_target->read_memory) (pc, (unsigned char *) &this_instr, 4); + target_read_memory (pc, (unsigned char *) &this_instr, 4); svc_operand = (0x00ffffff & this_instr); if (svc_operand) /* OABI. */ -- 2.30.2