r11 is a volatile register on PPC as per calling conventions. The safe_syscall code uses it to check if the signal_pending is set during the safe_syscall. When a syscall is interrupted on return from signal handling, the r11 might be corrupted before we retry the syscall leading to a crash. The registers r0-r13 are not to be used here as they have volatile/designated/reserved usages. Change the code to use r14 which is non-volatile and is appropriate for local use in safe_syscall.
Signed-off-by: Shivaprasad G Bhat <sb...@linux.vnet.ibm.com> --- Steps to reproduce: On PPC host, issue `qemu-ppc64le /usr/bin/cc -E -` Attempt Ctrl-C, the issue is reproduced. Reference: https://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi-1.9.html#REG linux-user/host/ppc64/safe-syscall.inc.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/linux-user/host/ppc64/safe-syscall.inc.S b/linux-user/host/ppc64/safe-syscall.inc.S index d30050a67c..b0cbbe6a69 100644 --- a/linux-user/host/ppc64/safe-syscall.inc.S +++ b/linux-user/host/ppc64/safe-syscall.inc.S @@ -49,7 +49,7 @@ safe_syscall_base: * and returns the result in r3 * Shuffle everything around appropriately. */ - mr 11, 3 /* signal_pending */ + mr 14, 3 /* signal_pending */ mr 0, 4 /* syscall number */ mr 3, 5 /* syscall arguments */ mr 4, 6 @@ -67,7 +67,7 @@ safe_syscall_base: */ safe_syscall_start: /* if signal_pending is non-zero, don't do the call */ - lwz 12, 0(11) + lwz 12, 0(14) cmpwi 0, 12, 0 bne- 0f sc
