2017-08-25 21:58:04

by Thomas Gleixner

Subject: [patch V2 25/44] x86: Replace access to desc_struct:a/b fields

The union inside of desc_struct which allows access to the raw u32 parts of
the descriptors. This raw access part is about to go away.

Replace the few code parts which access those fields.

Signed-off-by: Thomas Gleixner <[email protected]>
Cc: Boris Ostrovsky <[email protected]>
Cc: Juergen Gross <[email protected]>
---
arch/x86/include/asm/xen/hypercall.h | 6 ++++--
arch/x86/kernel/tls.c | 2 +-
arch/x86/xen/enlighten_pv.c | 2 +-
3 files changed, 6 insertions(+), 4 deletions(-)

--- a/arch/x86/include/asm/xen/hypercall.h
+++ b/arch/x86/include/asm/xen/hypercall.h
@@ -552,6 +552,8 @@ static inline void
MULTI_update_descriptor(struct multicall_entry *mcl, u64 maddr,
struct desc_struct desc)
{
+ u32 *p = (u32 *) &desc;
+
mcl->op = __HYPERVISOR_update_descriptor;
if (sizeof(maddr) == sizeof(long)) {
mcl->args[0] = maddr;
@@ -559,8 +561,8 @@ MULTI_update_descriptor(struct multicall
} else {
mcl->args[0] = maddr;
mcl->args[1] = maddr >> 32;
- mcl->args[2] = desc.a;
- mcl->args[3] = desc.b;
+ mcl->args[2] = *p++;
+ mcl->args[3] = *p;
}

trace_xen_mc_entry(mcl, sizeof(maddr) == sizeof(long) ? 2 : 4);
--- a/arch/x86/kernel/tls.c
+++ b/arch/x86/kernel/tls.c
@@ -93,7 +93,7 @@ static void set_tls_desc(struct task_str

while (n-- > 0) {
if (LDT_empty(info) || LDT_zero(info)) {
- desc->a = desc->b = 0;
+ memset(desc, 0, sizeof(*desc));
} else {
fill_ldt(desc, info);

--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -494,7 +494,7 @@ static void __init xen_load_gdt_boot(con
static inline bool desc_equal(const struct desc_struct *d1,
const struct desc_struct *d2)
{
- return d1->a == d2->a && d1->b == d2->b;
+ return !memcmp(d1, d2, sizeof(*d1));
}

static void load_TLS_descriptor(struct thread_struct *t,

2017-08-26 02:18:01

by Boris Ostrovsky

Subject: Re: [patch V2 25/44] x86: Replace access to desc_struct:a/b fields

On 08/25/2017 05:47 PM, Thomas Gleixner wrote:
> The union inside of desc_struct which allows access to the raw u32 parts of
> the descriptors. This raw access part is about to go away.
>
> Replace the few code parts which access those fields.
>
> Signed-off-by: Thomas Gleixner <[email protected]>
> Cc: Boris Ostrovsky <[email protected]>
> Cc: Juergen Gross <[email protected]>

Reviewed-by: Boris Ostrovsky <[email protected]>