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Re: [RFA] gdbserver support for qCRC: (compare-sections)
- From: Pedro Alves <pedro at codesourcery dot com>
- To: gdb-patches at sourceware dot org
- Cc: Michael Snyder <msnyder at vmware dot com>
- Date: Tue, 23 Mar 2010 16:26:13 +0000
- Subject: Re: [RFA] gdbserver support for qCRC: (compare-sections)
- References: <4BA40867.4090703@vmware.com> <4BA7AFFD.6050308@vmware.com>
On Monday 22 March 2010 17:59:25, Michael Snyder wrote:
> 2010-03-19 Michael Snyder <msnyder@vmware.com>
>
> * server.c (crc32): New function.
> (handle_query): Add handling for 'qCRC:' request.
>
> Index: server.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/gdbserver/server.c,v
> retrieving revision 1.108
> diff -u -p -r1.108 server.c
> --- server.c 20 Jan 2010 22:55:38 -0000 1.108
> +++ server.c 22 Mar 2010 17:57:32 -0000
> @@ -788,6 +788,47 @@ handle_threads_qxfer (const char *annex,
>
> }
>
> +/* Table used by the crc32 function to calcuate the checksum. */
> +
> +static unsigned long crc32_table[256] =
> +{0, 0};
> +
I know you've copied this from remote.c, but, can't
we make this an `unsigned int' table? longs are 64-bit
on most 64-bit archs, so this uses up double more memory
than needed.
> +/* Compute 32 bit CRC from inferior memory.
> +
> + On success, return 32 bit CRC.
> + On failure, return (unsigned long long) -1. */
> +
> +static unsigned long long
> +crc32 (CORE_ADDR base, int len, unsigned int crc)
Can't say I'm thrilled by assuming
sizeof (long long) > sizeof (long), but I guess
it works on all targets gdbserver cares for presently.
> +{
> + if (!crc32_table[1])
> + {
> + /* Initialize the CRC table and the decoding table. */
> + int i, j;
> + unsigned int c;
> +
> + for (i = 0; i < 256; i++)
> + {
> + for (c = i << 24, j = 8; j > 0; --j)
> + c = c & 0x80000000 ? (c << 1) ^ 0x04c11db7 : (c << 1);
> + crc32_table[i] = c;
> + }
> + }
> +
> + while (len--)
> + {
> + unsigned char byte = 0;
> +
> + /* Return failure if memory read fails. */
> + if (read_inferior_memory (base, &byte, 1) != 0)
> + return (unsigned long long) -1;
> +
> + crc = (crc << 8) ^ crc32_table[((crc >> 24) ^ byte) & 255];
> + base++;
> + }
> + return (unsigned long long) crc;
> +}
> +
> /* Handle all of the extended 'q' packets. */
> void
> handle_query (char *own_buf, int packet_len, int *new_packet_len_p)
> @@ -1421,6 +1462,31 @@ handle_query (char *own_buf, int packet_
> return;
> }
>
> + if (strncmp ("qCRC:", own_buf, 5) == 0)
> + {
> + /* CRC check (compare-segment). */
> + char *comma;
> + CORE_ADDR base = strtoul (own_buf + 5, &comma, 16);
> + int len;
> + unsigned long long crc;
> +
A `require_running' call is missing here.
> + if (*comma++ != ',')
> + {
> + write_enn (own_buf);
> + return;
> + }
> + len = strtoul (comma, NULL, 16);
> + crc = crc32 (base, len, 0xffffffff);
> + /* Check for memory failure. */
> + if (crc == (unsigned long long) -1)
> + {
> + write_enn (own_buf);
> + return;
> + }
> + sprintf (own_buf, "C%lx", (unsigned long) crc);
> + return;
> + }
> +
> /* Otherwise we didn't know what packet it was. Say we didn't
> understand it. */
> own_buf[0] = 0;
Otherwise, looks fine to me.
--
Pedro Alves