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Don't throw exception in dis_asm_memory_error

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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=<optimized out>) 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  <yao.qi@linaro.org>
	    Pedro Alves  <palves@redhat.com>

	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) <m_err_memaddr>: New field.

gdb/testsuite:

2017-01-26  Yao Qi  <yao.qi@linaro.org>

	* gdb.base/all-architectures.exp.in (do_arch_tests): Test
	disassemble on address 0.
This commit is contained in:
Yao Qi 2017-01-26 14:29:20 +00:00
parent 658ca58c4d
commit d8b49cf0c8
5 changed files with 32 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
gdb/ChangeLog
View File

@ -1,3 +1,13 @@
2017-01-26 Yao Qi <yao.qi@linaro.org>
Pedro Alves <palves@redhat.com>
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) <m_err_memaddr>: New field.
2017-01-26 Yao Qi <yao.qi@linaro.org>
* disasm-selftests.c (memory_error_test): New function.

13
gdb/disasm.c
View File

@ -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<gdb_disassembler *>(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)

1
gdb/disasm.h
View File

@ -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,

5
gdb/testsuite/ChangeLog
View File

@ -1,3 +1,8 @@
2017-01-26 Yao Qi <yao.qi@linaro.org>
* gdb.base/all-architectures.exp.in (do_arch_tests): Test
disassemble on address 0.
2017-01-25 Andreas Arnez <arnez@linux.vnet.ibm.com>
Yao Qi <yao.qi@linaro.org>

5
gdb/testsuite/gdb.base/all-architectures.exp.in
View File

@ -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