diff options
Diffstat (limited to 'arch/x86/ia32/ia32entry.S')
| -rw-r--r-- | arch/x86/ia32/ia32entry.S | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S index 56fd6dd2e342..2ab0f7182df3 100644 --- a/arch/x86/ia32/ia32entry.S +++ b/arch/x86/ia32/ia32entry.S @@ -418,6 +418,13 @@ sysretl_from_sys_call: * cs and ss are loaded from MSRs. * (Note: 32bit->32bit SYSRET is different: since r11 * does not exist, it merely sets eflags.IF=1). + * + * NB: On AMD CPUs with the X86_BUG_SYSRET_SS_ATTRS bug, the ss + * descriptor is not reinitialized. This means that we must + * avoid SYSRET with SS == NULL, which could happen if we schedule, + * exit the kernel, and re-enter using an interrupt vector. (All + * interrupt entries on x86_64 set SS to NULL.) We prevent that + * from happening by reloading SS in __switch_to. */ USERGS_SYSRET32 |