diff options
| author |   Heiko Carstens <heiko.carstens@de.ibm.com> | 2019-11-18 09:38:37 +0100 |
|---|---|---|
| committer |   Vasily Gorbik <gor@linux.ibm.com> | 2019-11-30 10:52:44 +0100 |
| commit | 5a5525b0488ce31e19065f8527dbf50266b5b712 (patch) | |
| tree | 962f0b570a299c36ea29f9dd2cb14943b488ca68 | |
| parent | s390/smp,vdso: fix ASCE handling (diff) | |
| download | linux-dev-5a5525b0488ce31e19065f8527dbf50266b5b712.tar.xz linux-dev-5a5525b0488ce31e19065f8527dbf50266b5b712.zip | |
s390/vdso: fix getcpu
getcpu reads the required values for cpu and node with two
instructions. This might lead to an inconsistent result if user space
gets preempted and migrated to a different CPU between the two
instructions.
Fix this by using just a single instruction to read both values at
once.
This is currently rather a theoretical bug, since there is no real
NUMA support available (except for NUMA emulation).
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
| -rw-r--r-- | arch/s390/include/asm/vdso.h | 13 | ||||
| -rw-r--r-- | arch/s390/kernel/asm-offsets.c | 3 | ||||
| -rw-r--r-- | arch/s390/kernel/vdso32/getcpu.S | 4 | ||||
| -rw-r--r-- | arch/s390/kernel/vdso64/getcpu.S | 4 |
4 files changed, 14 insertions, 10 deletions
diff --git a/arch/s390/include/asm/vdso.h b/arch/s390/include/asm/vdso.h index 169d7604eb80..3bcfdeb01395 100644 --- a/arch/s390/include/asm/vdso.h +++ b/arch/s390/include/asm/vdso.h @@ -41,8 +41,17 @@ struct vdso_data { struct vdso_per_cpu_data { __u64 ectg_timer_base; __u64 ectg_user_time; - __u32 cpu_nr; - __u32 node_id; + /* + * Note: node_id and cpu_nr must be at adjacent memory locations. + * VDSO userspace must read both values with a single instruction. + */ + union { + __u64 getcpu_val; + struct { + __u32 node_id; + __u32 cpu_nr; + }; + }; }; extern struct vdso_data *vdso_data; diff --git a/arch/s390/kernel/asm-offsets.c b/arch/s390/kernel/asm-offsets.c index 41ac4ad21311..ce33406cfe83 100644 --- a/arch/s390/kernel/asm-offsets.c +++ b/arch/s390/kernel/asm-offsets.c @@ -78,8 +78,7 @@ int main(void) OFFSET(__VDSO_TS_END, vdso_data, ts_end); OFFSET(__VDSO_ECTG_BASE, vdso_per_cpu_data, ectg_timer_base); OFFSET(__VDSO_ECTG_USER, vdso_per_cpu_data, ectg_user_time); - OFFSET(__VDSO_CPU_NR, vdso_per_cpu_data, cpu_nr); - OFFSET(__VDSO_NODE_ID, vdso_per_cpu_data, node_id); + OFFSET(__VDSO_GETCPU_VAL, vdso_per_cpu_data, getcpu_val); BLANK(); /* constants used by the vdso */ DEFINE(__CLOCK_REALTIME, CLOCK_REALTIME); diff --git a/arch/s390/kernel/vdso32/getcpu.S b/arch/s390/kernel/vdso32/getcpu.S index 25515f3fbcea..dc79e169f0ad 100644 --- a/arch/s390/kernel/vdso32/getcpu.S +++ b/arch/s390/kernel/vdso32/getcpu.S @@ -16,10 +16,8 @@ .type __kernel_getcpu,@function __kernel_getcpu: CFI_STARTPROC - la %r4,0 sacf 256 - l %r5,__VDSO_CPU_NR(%r4) - l %r4,__VDSO_NODE_ID(%r4) + lm %r4,%r5,__VDSO_GETCPU_VAL(%r0) sacf 0 ltr %r2,%r2 jz 2f diff --git a/arch/s390/kernel/vdso64/getcpu.S b/arch/s390/kernel/vdso64/getcpu.S index 2446e9dac8ab..3c04f7328500 100644 --- a/arch/s390/kernel/vdso64/getcpu.S +++ b/arch/s390/kernel/vdso64/getcpu.S @@ -16,10 +16,8 @@ .type __kernel_getcpu,@function __kernel_getcpu: CFI_STARTPROC - la %r4,0 sacf 256 - l %r5,__VDSO_CPU_NR(%r4) - l %r4,__VDSO_NODE_ID(%r4) + lm %r4,%r5,__VDSO_GETCPU_VAL(%r0) sacf 0 ltgr %r2,%r2 jz 2f |