gcc-8.1 for xtensa miscompiles uClibc dynamic linker due to gcc PR
target/65416. The build completes successfully, but the binary is
non-functional because the following fragment in the _dl_get_ready_to_run
in ld-uClibc.so overwrites register spill area on stack causing register
corruption in the previous call frame and a subsequent crash:
419f: f0c1b2 addi a11, a1, -16
41a2: 1ba9 s32i.n a10, a11, 4
41a4: 0bc9 s32i.n a12, a11, 0
41a6: 5127f2 l32i a15, a7, 0x144
41a9: 1765b2 s32i a11, a5, 92
41ac: 4e2782 l32i a8, a7, 0x138
41af: 146af2 s32i a15, a10, 80
41b2: 001b10 movsp a1, a11
The crash terminates the init process and causes kernel panic.
The fix prevents reordering of movsp opcode and any access to the stack
frame memory and is applicable to all existing gcc versions.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
