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[pushed][PATCH] Fix '-data-read-memory-bytes' typo/assertion
- From: Don Breazeal <donb at codesourcery dot com>
- To: <gdb-patches at sourceware dot org>, Simon Marchi <simon dot marchi at ericsson dot com>, Pedro Alves <palves at redhat dot com>
- Date: Fri, 20 Nov 2015 10:02:40 -0800
- Subject: [pushed][PATCH] Fix '-data-read-memory-bytes' typo/assertion
- Authentication-results: sourceware.org; auth=none
- References: <1447894382-1469-1-git-send-email-donb at codesourcery dot com>
On 11/19/2015 3:06 PM, Pedro Alves wrote:
> On 11/19/2015 12:53 AM, Don Breazeal wrote:
>
>> gdb/
>> 2015-11-18 Don Breazeal <donb@codesourcery.com>
>>
>> * gdb/target.c (read_memory_robust): Call
>> read_whatever_is_readable with arguments in the correct order.
>>
>
> Please drop the "gdb/" in the file name.
>
> LGTM too. Obvious even. It'd be nice to have a testcase
> for this though. Seems like the simplest would be to just try
> e.g., "-data-read-memory-bytes 8 1" and make sure that fails
> with "Unable to read memory". We'd just need to skip the
> test if [is_address_zero_readable].
This is now pushed (e084c964d61e6f8582711c73738c4df132410597),
ChangeLog is fixed.
I'll put the test on my list of tests to implement. (I *will* get
to these, incl. fork/exec tests, honest! :-) )
--Don
On 11/18/2015 4:53 PM, Don Breazeal wrote:
> This patch fixes a typo in target.c:read_memory_robust, where
> it calls read_whatever_is_readable with the function arguments
> in the wrong order. Depending on the address being read, it
> can cause an xmalloc with a huge size, resulting in an assertion
> failure, or just read something other than what was requested.
>
> The problem only arises when GDB is handling an MI
> "-data-read-memory-bytes" request and the initial target_read returns
> an error status. Note that read_memory_robust is only called from
> the MI code.
>
> Function definition:
> static void
> read_whatever_is_readable (struct target_ops *ops,
> const ULONGEST begin, const ULONGEST end,
> int unit_size,
> VEC(memory_read_result_s) **result)
>
> Function call:
> read_whatever_is_readable (ops, offset + xfered_total, unit_size,
> offset + xfered_total + to_read, &result);
>
> If we debug gdb, generate the error, and break just before the call to
> read_whatever_is_readable, we see:
>
> # Generate an error by trying to read a bogus address in the GDB
> # that is under debug.
> (gdb) interpreter-exec mi "-data-read-memory-bytes 1073741752 216"
>
> # GDB-under-debug stops at the breakpoint on the call to
> # read_whatever_is_readable.
> Breakpoint 1, read_memory_robust (ops=0xe70150, offset=1073741752, len=216)
> at /scratch/dbreazea/sandbox/gdb-5611/binutils-gdb/gdb/target.c:1825
> 1825 read_whatever_is_readable (ops, offset + xfered_total, unit_size,
> (top) p unit_size
> $1 = 1
>
> # Step into the function.
> (top) step
> read_whatever_is_readable (ops=0xe70150, begin=1073741752, end=1,
> unit_size=1073741968, result=0x7fffffffdd40)
> at /scratch/dbreazea/sandbox/gdb-5611/binutils-gdb/gdb/target.c:1658
> 1658 gdb_byte *buf = (gdb_byte *) xmalloc (end - begin);
>
> # unit_size was passed as 'end', and we are going to xmalloc a large
> # number and assert.
> (top) p end-begin
> $2 = 18446744072635809865
> (top) c
> Continuing.
> "/scratch/dbreazea/sandbox/gdb-5611/binutils-gdb/gdb/utils.c:1072: internal-error: virtual memory exhausted.\nA problem internal to GDB has been detected,\nfurther debugging may prove unreliable.\nQuit this debugging session? (y or n) "
>
> # With the fixed version, (end - begin) gives the 'len' passed to
> # read_memory_robust and specified by -data-read-memory-bytes
> (top) p end-begin
> $2 = 216
>
> Tested on native x86_64 Linux with the gdb.mi tests.
>
> OK?
> thanks
> --Don
>
> gdb/
> 2015-11-18 Don Breazeal <donb@codesourcery.com>
>
> * gdb/target.c (read_memory_robust): Call
> read_whatever_is_readable with arguments in the correct order.
>
> ---
> gdb/target.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/gdb/target.c b/gdb/target.c
> index 93786c3..950a1b7 100644
> --- a/gdb/target.c
> +++ b/gdb/target.c
> @@ -1822,8 +1822,9 @@ read_memory_robust (struct target_ops *ops,
> /* Got an error reading full chunk. See if maybe we can read
> some subrange. */
> xfree (buffer);
> - read_whatever_is_readable (ops, offset + xfered_total, unit_size,
> - offset + xfered_total + to_read, &result);
> + read_whatever_is_readable (ops, offset + xfered_total,
> + offset + xfered_total + to_read,
> + unit_size, &result);
> xfered_total += to_read;
> }
> else
>