linux.git/kernel/debug/kdb/kdb_io.c, branch v6.18.21

kdb: Replace deprecated strcpy() with memmove() in vkdb_printf()

2025-09-20T18:56:28+00:00

strcpy() is deprecated and its behavior is undefined when the source and
destination buffers overlap. Use memmove() instead to avoid any
undefined behavior.

Adjust comments for clarity.

Link: https://github.com/KSPP/linux/issues/88
Fixes: 5d5314d6795f ("kdb: core for kgdb back end (1 of 2)")
Reviewed-by: Douglas Anderson 
Signed-off-by: Thorsten Blum 
Signed-off-by: Daniel Thompson (RISCstar)

kdb: Remove optional size arguments from strscpy() calls

2025-03-28T21:28:28+00:00

If the destination buffer has a fixed length, strscpy() automatically
determines the size of the destination buffer using sizeof() if the
argument is omitted. This makes the explicit sizeof() unnecessary.

Furthermore, CMD_BUFLEN is equal to sizeof(kdb_prompt_str) and can also
be removed. Remove them to shorten and simplify the code.

No functional changes intended.

Signed-off-by: Thorsten Blum 
Reviewed-by: Douglas Anderson 
Reviewed-by: Justin Stitt 
Link: https://lore.kernel.org/r/20250319163341.2123-2-thorsten.blum@linux.dev
Signed-off-by: Daniel Thompson

kdb: Use the passed prompt in kdb_position_cursor()

2024-06-21T13:44:26+00:00

The function kdb_position_cursor() takes in a "prompt" parameter but
never uses it. This doesn't _really_ matter since all current callers
of the function pass the same value and it's a global variable, but
it's a bit ugly. Let's clean it up.

Found by code inspection. This patch is expected to functionally be a
no-op.

Fixes: 09b35989421d ("kdb: Use format-strings rather than '\0' injection in kdb_read()")
Signed-off-by: Douglas Anderson 
Link: https://lore.kernel.org/r/20240528071144.1.I0feb49839c6b6f4f2c4bf34764f5e95de3f55a66@changeid
Signed-off-by: Daniel Thompson

kdb: address -Wformat-security warnings

2024-06-21T13:33:17+00:00

When -Wformat-security is not disabled, using a string pointer
as a format causes a warning:

kernel/debug/kdb/kdb_io.c: In function 'kdb_read':
kernel/debug/kdb/kdb_io.c:365:36: error: format not a string literal and no format arguments [-Werror=format-security]
  365 |                         kdb_printf(kdb_prompt_str);
      |                                    ^~~~~~~~~~~~~~
kernel/debug/kdb/kdb_io.c: In function 'kdb_getstr':
kernel/debug/kdb/kdb_io.c:456:20: error: format not a string literal and no format arguments [-Werror=format-security]
  456 |         kdb_printf(kdb_prompt_str);
      |                    ^~~~~~~~~~~~~~

Use an explcit "%s" format instead.

Signed-off-by: Arnd Bergmann 
Fixes: 5d5314d6795f ("kdb: core for kgdb back end (1 of 2)")
Reviewed-by: Douglas Anderson 
Link: https://lore.kernel.org/r/20240528121154.3662553-1-arnd@kernel.org
Signed-off-by: Daniel Thompson

kdb: Simplify management of tmpbuffer in kdb_read()

2024-04-26T16:13:31+00:00

The current approach to filling tmpbuffer with completion candidates is
confusing, with the buffer management being especially hard to reason
about. That's because it doesn't copy the completion canidate into
tmpbuffer, instead of copies a whole bunch of other nonsense and then
runs the completion search from the middle of tmpbuffer!

Change this to copy nothing but the completion candidate into tmpbuffer.

Pretty much everything else in this patch is renaming to reflect the
above change:

    s/p_tmp/tmpbuffer/
    s/buf_size/sizeof(tmpbuffer)/

Reviewed-by: Douglas Anderson 
Tested-by: Justin Stitt 
Link: https://lore.kernel.org/r/20240424-kgdb_read_refactor-v3-7-f236dbe9828d@linaro.org
Signed-off-by: Daniel Thompson

kdb: Replace double memcpy() with memmove() in kdb_read()

2024-04-26T16:13:31+00:00

At several points in kdb_read() there are variants of the following
code pattern (with offsets slightly altered):

    memcpy(tmpbuffer, cp, lastchar - cp);
    memcpy(cp-1, tmpbuffer, lastchar - cp);
    *(--lastchar) = '\0';

There is no need to use tmpbuffer here, since we can use memmove() instead
so refactor in the obvious way. Additionally the strings that are being
copied are already properly terminated so let's also change the code so
that the library calls also move the terminator.

Changing how the terminators are managed has no functional effect for now
but might allow us to retire lastchar at a later point. lastchar, although
stored as a pointer, is functionally equivalent to caching strlen(buffer).

Reviewed-by: Douglas Anderson 
Tested-by: Justin Stitt 
Link: https://lore.kernel.org/r/20240424-kgdb_read_refactor-v3-6-f236dbe9828d@linaro.org
Signed-off-by: Daniel Thompson

kdb: Use format-specifiers rather than memset() for padding in kdb_read()

2024-04-26T16:13:30+00:00

Currently when the current line should be removed from the display
kdb_read() uses memset() to fill a temporary buffer with spaces.
The problem is not that this could be trivially implemented using a
format string rather than open coding it. The real problem is that
it is possible, on systems with a long kdb_prompt_str, to write past
the end of the tmpbuffer.

Happily, as mentioned above, this can be trivially implemented using a
format string. Make it so!

Cc: stable@vger.kernel.org
Reviewed-by: Douglas Anderson 
Tested-by: Justin Stitt 
Link: https://lore.kernel.org/r/20240424-kgdb_read_refactor-v3-5-f236dbe9828d@linaro.org
Signed-off-by: Daniel Thompson

kdb: Merge identical case statements in kdb_read()

2024-04-26T16:13:30+00:00

The code that handles case 14 (down) and case 16 (up) has been copy and
pasted despite being byte-for-byte identical. Combine them.

Cc: stable@vger.kernel.org # Not a bug fix but it is needed for later bug fixes
Reviewed-by: Douglas Anderson 
Tested-by: Justin Stitt 
Link: https://lore.kernel.org/r/20240424-kgdb_read_refactor-v3-4-f236dbe9828d@linaro.org
Signed-off-by: Daniel Thompson

kdb: Fix console handling when editing and tab-completing commands

2024-04-26T16:13:30+00:00

Currently, if the cursor position is not at the end of the command buffer
and the user uses the Tab-complete functions, then the console does not
leave the cursor in the correct position.

For example consider the following buffer with the cursor positioned
at the ^:

md kdb_pro 10
          ^

Pressing tab should result in:

md kdb_prompt_str 10
                 ^

However this does not happen. Instead the cursor is placed at the end
(after then 10) and further cursor movement redraws incorrectly. The
same problem exists when we double-Tab but in a different part of the
code.

Fix this by sending a carriage return and then redisplaying the text to
the left of the cursor.

Cc: stable@vger.kernel.org
Reviewed-by: Douglas Anderson 
Tested-by: Justin Stitt 
Link: https://lore.kernel.org/r/20240424-kgdb_read_refactor-v3-3-f236dbe9828d@linaro.org
Signed-off-by: Daniel Thompson

kdb: Use format-strings rather than '\0' injection in kdb_read()

2024-04-26T16:13:30+00:00

Currently when kdb_read() needs to reposition the cursor it uses copy and
paste code that works by injecting an '\0' at the cursor position before
delivering a carriage-return and reprinting the line (which stops at the
'\0').

Tidy up the code by hoisting the copy and paste code into an appropriately
named function. Additionally let's replace the '\0' injection with a
proper field width parameter so that the string will be abridged during
formatting instead.

Cc: stable@vger.kernel.org # Not a bug fix but it is needed for later bug fixes
Tested-by: Justin Stitt 
Reviewed-by: Douglas Anderson 
Link: https://lore.kernel.org/r/20240424-kgdb_read_refactor-v3-2-f236dbe9828d@linaro.org
Signed-off-by: Daniel Thompson