The format string for %s has two format characters. This causes it to
emit strings like "466f5bd8/6x" instead of "466f5bd8/6". GDB detects
this and returns EIO, causing all open File I/O calls to fail.

Fixes: 0820a075af ("gdbstub: Adjust gdb_do_syscall to only use uint32_t and uint64_t")
Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
---

 gdbstub/syscalls.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gdbstub/syscalls.c b/gdbstub/syscalls.c
index e855df21ab..d8bb90cc1c 100644
--- a/gdbstub/syscalls.c
+++ b/gdbstub/syscalls.c
@@ -127,7 +127,7 @@ void gdb_do_syscall(gdb_syscall_complete_cb cb, const char *fmt, ...)
             case 's':
                 i64 = va_arg(va, uint64_t);
                 i32 = va_arg(va, uint32_t);
-                p += snprintf(p, p_end - p, "%" PRIx64 "/%x" PRIx32, i64, i32);
+                p += snprintf(p, p_end - p, "%" PRIx64 "/%" PRIx32, i64, i32);
                 break;
             default:
             bad_format:
-- 
2.35.1.1320.gc452695387.dirty

Sean Anderson <sean.anderson@linux.dev> writes:

> The format string for %s has two format characters. This causes it to
> emit strings like "466f5bd8/6x" instead of "466f5bd8/6". GDB detects
> this and returns EIO, causing all open File I/O calls to fail.
>
> Fixes: 0820a075af ("gdbstub: Adjust gdb_do_syscall to only use uint32_t and uint64_t")
> Signed-off-by: Sean Anderson <sean.anderson@linux.dev>

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro

On 10/17/25 14:35, Sean Anderson wrote:
> The format string for %s has two format characters. This causes it to
> emit strings like "466f5bd8/6x" instead of "466f5bd8/6". GDB detects
> this and returns EIO, causing all open File I/O calls to fail.
> 
> Fixes: 0820a075af ("gdbstub: Adjust gdb_do_syscall to only use uint32_t and uint64_t")
> Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
> ---
> 
>   gdbstub/syscalls.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/gdbstub/syscalls.c b/gdbstub/syscalls.c
> index e855df21ab..d8bb90cc1c 100644
> --- a/gdbstub/syscalls.c
> +++ b/gdbstub/syscalls.c
> @@ -127,7 +127,7 @@ void gdb_do_syscall(gdb_syscall_complete_cb cb, const char *fmt, ...)
>               case 's':
>                   i64 = va_arg(va, uint64_t);
>                   i32 = va_arg(va, uint32_t);
> -                p += snprintf(p, p_end - p, "%" PRIx64 "/%x" PRIx32, i64, i32);
> +                p += snprintf(p, p_end - p, "%" PRIx64 "/%" PRIx32, i64, i32);
>                   break;
>               default:
>               bad_format:

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~