[PATCH 1/3] kgdb: Add kgdb_mem2ebin function for converting memory to binary format

[Amal Raj T <tjarlama@gmail.com>]

From: Amal Raj T <amalrajt@meta.com>

Add a new function kgdb_mem2ebin that converts memory
to binary format, escaping special characters
('$', '#', and '}'). kgdb_mem2ebin function ensures
that memory data is properly formatted and escaped
before being sent over the wire. Additionally, this
function reduces the amount of data exchanged between
debugger compared to hex.

Signed-off-by: Amal Raj T <amalrajt@meta.com>
---
 include/linux/kgdb.h   |  1 +
 kernel/debug/gdbstub.c | 31 +++++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h
index 76e891ee9e37..fa3cf38a14de 100644
--- a/include/linux/kgdb.h
+++ b/include/linux/kgdb.h
@@ -322,6 +322,7 @@ extern struct kgdb_io *dbg_io_ops;
 
 extern int kgdb_hex2long(char **ptr, unsigned long *long_val);
 extern char *kgdb_mem2hex(char *mem, char *buf, int count);
+extern char *kgdb_mem2ebin(char *mem, char *buf, int count);
 extern int kgdb_hex2mem(char *buf, char *mem, int count);
 
 extern int kgdb_isremovedbreak(unsigned long addr);
diff --git a/kernel/debug/gdbstub.c b/kernel/debug/gdbstub.c
index f625172d4b67..6198d2eb49c4 100644
--- a/kernel/debug/gdbstub.c
+++ b/kernel/debug/gdbstub.c
@@ -257,6 +257,37 @@ char *kgdb_mem2hex(char *mem, char *buf, int count)
 	return buf;
 }
 
+/*
+ * Convert memory to binary format for GDB remote protocol
+ * transmission, escaping special characters ($, #, and }).
+ */
+char *kgdb_mem2ebin(char *mem, char *buf, int count)
+{
+	char *tmp;
+	int err;
+
+	tmp = buf + count;
+
+	err = copy_from_kernel_nofault(tmp, mem, count);
+	if (err)
+		return NULL;
+	while (count > 0) {
+		unsigned char c = *tmp;
+
+		if (c == 0x7d || c == 0x23 || c == 0x24) {
+			*buf++ = 0x7d;
+			*buf++ = c ^ 0x20;
+		} else {
+			*buf++ = c;
+		}
+		count -= 1;
+		tmp += 1;
+	}
+	*buf = 0;
+
+	return buf;
+}
+
 /*
  * Convert the hex array pointed to by buf into binary to be placed in
  * mem.  Return a pointer to the character AFTER the last byte
-- 
2.43.5