brcm63xx/lzma-loader: fix O32 ABI conformance

According to the calling convention of the o32 ABI the caller
function must reserve stack space for $a0-$a3 registers in case
the callee needs to save its arguments.

The assembly code of the loader does not reserve stack space for
these registers thus when the 'loader_main' function needs to save
its arguments, those will be stored in the 'workspace' area instead
of the stack.

Because the workspace area is also used by other part of the code, the
saved register values gets overwritten and this often leads to failed
kernel boots.

Fix the code to reserve stack space for the registers to avoid this
error.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
[noltari: apply the fix for brcm63xx too]
Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
SVN-Revision: 48979

diff --git a/target/linux/brcm63xx/image/lzma-loader/src/head.S b/target/linux/brcm63xx/image/lzma-loader/src/head.S
index 543996a0da4701cca80481aa181cd7bddc6df5c6..47a7c9bd6300ad92e6a0d426c5f44bc0f3e7e85f 100644 (file)
--- a/target/linux/brcm63xx/image/lzma-loader/src/head.S
+++ b/target/linux/brcm63xx/image/lzma-loader/src/head.S
@@ -109,6 +109,9 @@ __bss_check:
        /* Setup new "C" stack */
        la      sp, _stack
 
+       /* reserve stack space for a0-a3 registers */
+       subu    sp, 16
+
        /* jump to the decompressor routine */
        la      t0, loader_main
        jr      t0