From 5d9f3ea0817215ad4baac5aa30414e9ebbaaf0d6 Mon Sep 17 00:00:00 2001 From: Shivaprasad G Bhat Date: Tue, 31 Jul 2018 11:12:24 +0530 Subject: linux-user: ppc64: don't use volatile register during safe_syscall 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. Use SP+16 which is a slot for LR, for save/restore of previous value of r14. SP+16 can be used, as LR is preserved across the syscall. Steps to reproduce: On PPC host, issue `qemu-x86_64 /usr/bin/cc -E -` Attempt Ctrl-C, the issue is reproduced. Reference: https://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi-1.9.html#REG https://openpowerfoundation.org/wp-content/uploads/2016/03/ABI64BitOpenPOWERv1.1_16July2015_pub4.pdf Signed-off-by: Shivaprasad G Bhat Tested-by: Richard Henderson Tested-by: Laurent Vivier Reviewed-by: Richard Henderson Reviewed-by: Laurent Vivier Message-Id: <153301568965.30312.10498134581068746871.stgit@dhcp-9-109-246-16> Signed-off-by: Laurent Vivier --- linux-user/host/ppc64/safe-syscall.inc.S | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'linux-user') diff --git a/linux-user/host/ppc64/safe-syscall.inc.S b/linux-user/host/ppc64/safe-syscall.inc.S index d30050a67c..8ed73a5b86 100644 --- a/linux-user/host/ppc64/safe-syscall.inc.S +++ b/linux-user/host/ppc64/safe-syscall.inc.S @@ -49,7 +49,9 @@ safe_syscall_base: * and returns the result in r3 * Shuffle everything around appropriately. */ - mr 11, 3 /* signal_pending */ + std 14, 16(1) /* Preserve r14 in SP+16 */ + .cfi_offset 14, 16 + mr 14, 3 /* signal_pending */ mr 0, 4 /* syscall number */ mr 3, 5 /* syscall arguments */ mr 4, 6 @@ -67,12 +69,13 @@ 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 safe_syscall_end: /* code path when we did execute the syscall */ + ld 14, 16(1) /* restore r14 to its original value */ bnslr+ /* syscall failed; return negative errno */ @@ -81,6 +84,7 @@ safe_syscall_end: /* code path when we didn't execute the syscall */ 0: addi 3, 0, -TARGET_ERESTARTSYS + ld 14, 16(1) /* restore r14 to its orginal value */ blr .cfi_endproc -- cgit v1.2.3-70-g09d2