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target/arm: Increase MAX_PACKET_LENGTH for SME ZA remote gdb debugging

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This patch increases the value of the MAX_PACKET_LEGNTH to
131104 from 4096 to allow the GDBState.line_buf to be large enough
to accommodate the full contents of the SME ZA storage when the
vector length is maximal. This is in preparation for a related
patch that allows SME register visibility through remote GDB
debugging.

Signed-off-by: Vacha Bhavsar <vacha.bhavsar@oss.qualcomm.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 20250909161012.2561593-2-vacha.bhavsar@oss.qualcomm.com
[PMM: fixed up comment formatting]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Vacha Bhavsar 2025-09-09 16:10:10 +00:00 • committed by Peter Maydell
parent 19f6dcfe6b
commit 71cda98120
1 changed files with 21 additions and 1 deletions
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22
gdbstub/internals.h
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@ -11,7 +11,27 @@
#include "exec/cpu-common.h"
#define MAX_PACKET_LENGTH 4096
/*
* Most "large" transfers (e.g. memory reads, feature XML
* transfer) have mechanisms in the gdb protocol for splitting
* them. However, register values in particular cannot currently
* be split. This packet size must therefore be at least big enough
* for the worst-case register size. Currently that is Arm SME
* ZA storage with a 256x256 byte value. We also must account
* for the conversion from raw data to hex in gdb_memtohex(),
* which writes 2 * size bytes, and for other protocol overhead
* including command, register number and checksum which add
* another 4 bytes of overhead. However, to be consistent with
* the changes made in gdbserver to address this same requirement,
* we add a total of 32 bytes to account for protocol overhead
* (unclear why specifically 32 bytes), bringing the value of
* MAX_PACKET_LENGTH to 2 * 256 * 256 + 32 = 131104.
*
* The commit making this change for gdbserver can be found here:
* https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=
* b816042e88583f280ad186ff124ab84d31fb592b
*/
#define MAX_PACKET_LENGTH 131104
/*
* Shared structures and definitions