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gdb_server: fix GDB_BUFFER_SIZE usage, fix unaligned access during bulk transfers

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Currently size of the GDB buffer is 16384 bytes but it is treated as
nul-terminated string in most of the code, so effective size of the
buffer is actually 16383 bytes. OpenOCD responds with `PacketSize=3fff`
to qSupported request. Result of GDB's `m` command is encoded in hex so
each data byte uses two bytes in the buffer. As a result GDB will split
bulk read requests into chunks 0x1fff bytes each. This causes troubles
on targets (or memory regions) which support only aligned, word-sized
access (such as MMIO buffers).

Steps to reproduce (psoc6 target):
gdb> dump binary memory dump.bin 0x040320000 (0x040320000 + 65536)

OpenOCD:
Error: Failed to read memory at 0x40321ffe
Error: Failed to read memory at 0x40321000
Error: Failed to read memory at 0x40323000
Error: Failed to read memory at 0x40325ffe
Error: Failed to read memory at 0x40329ffa
Error: Failed to read memory at 0x40329ffc
Error: Failed to read memory at 0x4032bffc
Error: Failed to read memory at 0x4032dffa

Consolidate GDB_BUFFER_SIZE usage: ensure size of each buffer is
(GDB_BUFFER_SIZE + 1), add explicit comment that additional byte is used
for nul-termination. Report correct size of the buffer to GDB (0x4000)
as recommended in GDB's docummentation: `if the stub stores packets in a
NUL-terminated format, it should allow an extra byte in its buffer for
the NUL`

Checked with clang-asan, clang-analyzer, valgrind - no new errors.

Change-Id: I909e8a2c6b010c5d4a304641808d4a807a4ec18d
Signed-off-by: Bohdan Tymkiv <bhdt@cypress.com>
Reviewed-on: http://openocd.zylin.com/5109
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>
This commit is contained in:
Bohdan Tymkiv
2019-04-16 17:28:29 +03:00
committed by Tomas Vanek
parent 85ed41d210
commit eea508d9af
3 changed files with 6 additions and 8 deletions
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2
src/rtos/rtos.c
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@@ -223,7 +223,7 @@ int rtos_qsymbol(struct connection *connection, char const *packet, int packet_s
int rtos_detected = 0;
uint64_t addr = 0;
size_t reply_len;
char reply[GDB_BUFFER_SIZE], cur_sym[GDB_BUFFER_SIZE / 2] = "";
char reply[GDB_BUFFER_SIZE + 1], cur_sym[GDB_BUFFER_SIZE / 2 + 1] = ""; /* Extra byte for nul-termination */
symbol_table_elem_t *next_sym = NULL;
struct target *target = get_target_from_connection(connection);
struct rtos *os = target->rtos;