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libc/gdbstub: avoid RLE decoding special characters

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Read/write special data like 0x2a2a2a2a will trigger this issue.
The current GDB implementation has this flaw. GDB processes the RLE
decoding before espaping the data, make it impossible to repeate special
characters.

The details can be seen in GDB source code remote.c
remote_target::read_frame function.

Signed-off-by: xuxingliang <xuxingliang@xiaomi.com>
This commit is contained in:
xuxingliang
2024-12-26 11:56:29 +08:00
committed by Xiang Xiao
parent 03765a6a1e
commit dc3ab55e6d
1 changed files with 17 additions and 1 deletions
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libs/libc/gdbstub/lib_gdbstub.c
+17 -1
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@@ -58,6 +58,9 @@
#define REPBIAS 29
#define REPSIZE (255 - REPBIAS)
#define IS_SPECIAL_CHARACTERS(c) \
((c) == '#' || (c) == '$' || (c) == '}' || (c) == '*')
/****************************************************************************
* Private Types
****************************************************************************/
@@ -313,7 +316,7 @@ static int gdb_putchar(FAR struct gdb_state_s *state, int ch,
static void gdb_escapechar(FAR struct gdb_state_s *state, char c,
FAR char *csum)
{
if (c == '#' || c == '$' || c == '}' || c == '*')
if (IS_SPECIAL_CHARACTERS(c))
{
gdb_putchar(state, '}', csum);
gdb_putchar(state, c ^ 0x20, csum); /* See https://sourceware.org/gdb/current/onlinedocs/gdb.html/Overview.html#Binary-Data */
@@ -409,6 +412,19 @@ static int gdb_send_packet(FAR struct gdb_state_s *state)
size_t count = gdb_count_repeat(&buf[i], len - i);
i += count;
/* GDB cannot process repeated special characters. */
if (IS_SPECIAL_CHARACTERS(c))
{
while (count--)
{
gdb_escapechar(state, c, &csum);
}
continue;
}
if (count <= 3)
{
while (count-- > 0)