diff options
| author | Shivaprasad G Bhat <sbhat@linux.vnet.ibm.com> | 2018-07-31 11:12:24 +0530 |
|---|---|---|
| committer | Laurent Vivier <laurent@vivier.eu> | 2018-07-31 09:57:43 +0200 |
| commit | 5d9f3ea0817215ad4baac5aa30414e9ebbaaf0d6 (patch) | |
| tree | a49e7a8bfd326c48250dfe272cf6768bd2ff5847 | |
| parent | 28cbb997d66e4d1904a231bef1ce15c2cbb6bf73 (diff) | |
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 <sbhat@linux.vnet.ibm.com>
Tested-by: Richard Henderson <richard.henderson@linaro.org>
Tested-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <153301568965.30312.10498134581068746871.stgit@dhcp-9-109-246-16>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
| -rw-r--r-- | linux-user/host/ppc64/safe-syscall.inc.S | 8 |
1 files changed, 6 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..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 |