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| author | Ingo Molnar <mingo@kernel.org> | 2015-05-08 13:33:33 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-05-08 13:33:33 +0200 |
| commit | 7ae383be81781c5e1347f71c3eb0d53ce5188200 (patch) | |
| tree | d2dfedb78cf4ee2bc9cc460af3be106b08e01050 /arch/x86/kernel/entry_64.S | |
| parent | 2a4e90b18c256d52a7f3f77d58114f6d4e4a7f9f (diff) | |
| parent | 3e0283a53f7d2f2dae7bc4aa7f3104cb5988018f (diff) | |
Merge branch 'linus' into x86/asm, before applying dependent patch
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/kernel/entry_64.S')
| -rw-r--r-- | arch/x86/kernel/entry_64.S | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 60705b032521..7423e3e2f5c5 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -295,6 +295,15 @@ system_call_fastpath: * rflags from r11 (but RF and VM bits are forced to 0), * cs and ss are loaded from MSRs. * Restoration of rflags re-enables interrupts. + * + * NB: On AMD CPUs with the X86_BUG_SYSRET_SS_ATTRS bug, the ss + * descriptor is not reinitialized. This means that we should + * 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. (Actually + * detecting the failure in 64-bit userspace is tricky but can be + * done.) */ USERGS_SYSRET64 |