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Re: [PATCH v3 12/14] add linux_infcall_mmap
- From: Pedro Alves <palves at redhat dot com>
- To: Jan Kratochvil <jan dot kratochvil at redhat dot com>, gdb-patches at sourceware dot org
- Date: Tue, 11 Nov 2014 16:43:19 +0000
- Subject: Re: [PATCH v3 12/14] add linux_infcall_mmap
- Authentication-results: sourceware.org; auth=none
- References: <20141101214552 dot 13230 dot 45564 dot stgit at host1 dot jankratochvil dot net> <20141101214719 dot 13230 dot 96367 dot stgit at host1 dot jankratochvil dot net>
On 11/01/2014 09:47 PM, Jan Kratochvil wrote:
> +/* See gdbarch.sh 'infcall_mmap'. */
> +
> +static CORE_ADDR
> +linux_infcall_mmap (CORE_ADDR size, unsigned prot)
> +{
> + struct objfile *objf;
> + /* Do there still exist any Linux systems without "mmap64"?
> + "mmap" uses 64-bit off_t on x86_64 and 32-bit off_t on i386 and x32. */
> + struct value *mmap_val = find_function_in_inferior ("mmap64", &objf);
> + struct value *addr_val;
> + struct gdbarch *gdbarch = get_objfile_arch (objf);
> + CORE_ADDR retval;
> + enum
> + {
> + ARG_ADDR, ARG_LENGTH, ARG_PROT, ARG_FLAGS, ARG_FD, ARG_OFFSET, ARG_MAX
> + };
> + struct value *arg[ARG_MAX];
> +
> + arg[ARG_ADDR] = value_from_pointer (builtin_type (gdbarch)->builtin_data_ptr,
> + 0);
> + /* Assuming sizeof (unsigned long) == sizeof (size_t). */
> + arg[ARG_LENGTH] = value_from_ulongest
> + (builtin_type (gdbarch)->builtin_unsigned_long, size);
> + gdb_assert ((prot & ~7) == 0);
> + arg[ARG_PROT] = value_from_longest (builtin_type (gdbarch)->builtin_int,
> + 0
> + | ((prot & 4) != 0 ? PROT_READ : 0)
> + | ((prot & 2) != 0 ? PROT_WRITE : 0)
> + | ((prot & 1) != 0 ? PROT_EXEC : 0));
> + arg[ARG_FLAGS] = value_from_longest (builtin_type (gdbarch)->builtin_int,
> + MAP_PRIVATE | MAP_ANONYMOUS);
PROT_READ, PROT_WRITE, PROT_EXEC, MAP_PRIVATE, MAP_ANONYMOUS
are host values/macros.
This needs to be made host independent, otherwise cross debugging to
Linux passes the wrong values to mmap.
It also likely breaks --enable-targets=all builds on hosts
that don't have mmap at all. E.g., this comes out empty on F20:
$ grep -rn PROT_READ /usr/i686-w64-mingw32/sys-root/mingw/include/
OTOH, the 4, 2 and 1 bits checked against the 'prot' argument
are magical constants; they'd best be put behind macros, like e.g.,
GDB_MMAP_PROT_READ, etc., here and at the callers
of gdbarch_infcall_mmap.
Thanks,
Pedro Alves