[U-Boot] [PATCH v2] ARM64: zynqmp: Add support for standard distro boot commands

Alexander Graf
2016-06-02T08:30:47Z

On 02.06.16 10:22, Michal Simek wrote:
> Nand and QSPI are not defined now but this will be extended.
> Based on selected bootmode boot_targets are rewritten.
> Patch also contains detection if variables are saved. If yes don't
> rewrite boot_targets variable.
>
> Also move variable setup to the end of file because SCSI needs to be
> defined before others macros are using it.
>
> Signed-off-by: Michal Simek <michal.simek@xilinx.com>
> ---
>
> Changes in v2:
> - Append default boot_targets to the list
>
> Patch depends on
> "env: Setup GD_FLG_ENV_DEFAULT flag when default environment are used"
>
> ---
> board/xilinx/zynqmp/zynqmp.c | 27 ++++++++++++++-----
> include/configs/xilinx_zynqmp.h | 59 ++++++++++++++++++++++++++++++-----------
> 2 files changed, 64 insertions(+), 22 deletions(-)
>
> diff --git a/board/xilinx/zynqmp/zynqmp.c b/board/xilinx/zynqmp/zynqmp.c
> index 4623cd49e9c7..204f8c526ab4 100644
> --- a/board/xilinx/zynqmp/zynqmp.c
> +++ b/board/xilinx/zynqmp/zynqmp.c
> @@ -215,6 +215,11 @@ int board_late_init(void)
> u32 reg = 0;
> u8 bootmode;
>
> + if (!(gd->flags & GD_FLG_ENV_DEFAULT)) {
> + debug("Saved variables - Skipping\n");
> + return 0;
> + }
> +
> reg = readl(&crlapb_base->boot_mode);
> bootmode = reg & BOOT_MODES_MASK;
>
> @@ -222,31 +227,39 @@ int board_late_init(void)
> switch (bootmode) {
> case JTAG_MODE:
> puts("JTAG_MODE\n");
> - setenv("modeboot", "jtagboot");
> + setenv("boot_targets", strcat("pxe dhcp ",
> + getenv("boot_targets")));

The strcat() function appends the src string to the dest
string, overwriting the terminating null byte ('\0') at the end of dest,
and then adds a terminating null byte. The strings may
not overlap, and the dest string must have enough space for the
result. If dest is not large enough, program behavior is unpredictable;
buffer overruns are a favorite avenue for attacking
secure programs.

---

In other words, the code above creates a buffer overflow :). You need
something like

const char *new_targets = "pxe dhcp"; // <- make this a parameter to a
function

new_targets = malloc(strlen(new_targets) +
strlen(getenv("boot_targets") + 2); // one byte for the space, one for
the null-terminator
sprintf(new_targets, "%s %s", new_targets, boot_targets);
setenv("boot_targets", new_targets);

Isn't string handling in C awesome? It's almost as readable and easy as
doing it in assembly.

Alex