From d8b49cf0c891d09dd58de05ad5cfe396b612cf3b Mon Sep 17 00:00:00 2001 From: Yao Qi Date: Thu, 26 Jan 2017 14:29:20 +0000 Subject: [PATCH] Don't throw exception in dis_asm_memory_error Hi, GDB calls some APIs from opcodes to do disassembly and provide some call backs. This model makes troubles on C++ exception unwinding, because GDB is a C++ program, and opcodes is still compiled as C. As we can see, frame #10 and #12 are C++, while #frame 11 is C, #10 0x0000000000544228 in memory_error (err=TARGET_XFER_E_IO, memaddr=) at ../../binutils-gdb/gdb/corefile.c:237 #11 0x00000000006b0a54 in print_insn_aarch64 (pc=0, info=0xffffffffeeb0) at ../../binutils-gdb/opcodes/aarch64-dis.c:3185 #12 0x0000000000553590 in gdb_pretty_print_insn (gdbarch=gdbarch@entry=0xbbceb0, uiout=uiout@entry=0xbc73d0, di=di@entry=0xffffffffeeb0, insn=0xffffffffed40, insn@entry=0xffffffffed90, flags=flags@entry=0, C++ exception unwinder can't go across frame #11 unless it has unwind table. However, C program on many architectures doesn't have it in default. As a result, GDB aborts, which is described in PR 20939. This is not the first time we see this kind of problem. We've had a commit 89525768cd086a0798a504c81fdf7ebcd4c904e1 "Propagate GDB/C++ exceptions across readline using sj/lj-based TRY/CATCH". We can fix the disassembly bug in a similar way, this is the option one. Since opcodes is built with gdb, we fix this problem in a different way as we did for the same issue with readline. Instead of throwing exception in dis_asm_memory_error, we record the failed memory address, and throw exception when GDB returns from opcodes disassemblers. gdb: 2017-01-26 Yao Qi Pedro Alves PR gdb/20939 * disasm.c (gdb_disassembler::dis_asm_memory_error): Don't call memory_error, save memaddr instead. (gdb_disassembler::print_insn): If gdbarch_print_insn returns negative, cal memory_error. * disasm.h (gdb_disassembler) : New field. gdb/testsuite: 2017-01-26 Yao Qi * gdb.base/all-architectures.exp.in (do_arch_tests): Test disassemble on address 0. --- gdb/ChangeLog | 10 ++++++++++ gdb/disasm.c | 13 +++++++++++-- gdb/disasm.h | 1 + gdb/testsuite/ChangeLog | 5 +++++ gdb/testsuite/gdb.base/all-architectures.exp.in | 5 +++++ 5 files changed, 32 insertions(+), 2 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 2e8a96fb20..4e85fcdc5c 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,13 @@ +2017-01-26 Yao Qi + Pedro Alves + + PR gdb/20939 + * disasm.c (gdb_disassembler::dis_asm_memory_error): Don't + call memory_error, save memaddr instead. + (gdb_disassembler::print_insn): If gdbarch_print_insn returns + negative, cal memory_error. + * disasm.h (gdb_disassembler) : New field. + 2017-01-26 Yao Qi * disasm-selftests.c (memory_error_test): New function. diff --git a/gdb/disasm.c b/gdb/disasm.c index b58da0f86f..897f2f1412 100644 --- a/gdb/disasm.c +++ b/gdb/disasm.c @@ -135,7 +135,10 @@ void gdb_disassembler::dis_asm_memory_error (int err, bfd_vma memaddr, struct disassemble_info *info) { - memory_error (TARGET_XFER_E_IO, memaddr); + gdb_disassembler *self + = static_cast(info->application_data); + + self->m_err_memaddr = memaddr; } /* Wrapper of print_address. */ @@ -765,7 +768,8 @@ fprintf_disasm (void *stream, const char *format, ...) gdb_disassembler::gdb_disassembler (struct gdbarch *gdbarch, struct ui_file *file, di_read_memory_ftype read_memory_func) - : m_gdbarch (gdbarch) + : m_gdbarch (gdbarch), + m_err_memaddr (0) { init_disassemble_info (&m_di, file, fprintf_disasm); m_di.flavour = bfd_target_unknown_flavour; @@ -792,8 +796,13 @@ int gdb_disassembler::print_insn (CORE_ADDR memaddr, int *branch_delay_insns) { + m_err_memaddr = 0; + int length = gdbarch_print_insn (arch (), memaddr, &m_di); + if (length < 0) + memory_error (TARGET_XFER_E_IO, m_err_memaddr); + if (branch_delay_insns != NULL) { if (m_di.insn_info_valid) diff --git a/gdb/disasm.h b/gdb/disasm.h index c6cb13ba6a..7bbfa31da4 100644 --- a/gdb/disasm.h +++ b/gdb/disasm.h @@ -66,6 +66,7 @@ private: /* Stores data required for disassembling instructions in opcodes. */ struct disassemble_info m_di; + CORE_ADDR m_err_memaddr; static int dis_asm_read_memory (bfd_vma memaddr, gdb_byte *myaddr, unsigned int len, diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog index 28e337a955..404b408e82 100644 --- a/gdb/testsuite/ChangeLog +++ b/gdb/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2017-01-26 Yao Qi + + * gdb.base/all-architectures.exp.in (do_arch_tests): Test + disassemble on address 0. + 2017-01-25 Andreas Arnez Yao Qi diff --git a/gdb/testsuite/gdb.base/all-architectures.exp.in b/gdb/testsuite/gdb.base/all-architectures.exp.in index c7615acfdb..b07caf5db6 100644 --- a/gdb/testsuite/gdb.base/all-architectures.exp.in +++ b/gdb/testsuite/gdb.base/all-architectures.exp.in @@ -152,6 +152,11 @@ proc print_floats {} { proc do_arch_tests {} { print_floats + + # GDB can't access memory because there is no loaded executable + # nor live inferior. + gdb_test_internal "disassemble 0x0,+4" \ + "Cannot access memory at address 0x0" } # Given we can't change arch, osabi, endianness, etc. atomically, we -- 2.34.1