x86_64, traps: Stop using IST for #SS
On a 32-bit kernel, this has no effect, since there are no IST stacks. On a 64-bit kernel, #SS can only happen in user code, on a failed iret to user space, a canonical violation on access via RSP or RBP, or a genuine stack segment violation in 32-bit kernel code. The first two cases don't need IST, and the latter two cases are unlikely fatal bugs, and promoting them to double faults would be fine. This fixes a bug in which the espfix64 code mishandles a stack segment violation. This saves 4k of memory per CPU and a tiny bit of code. Signed-off-by: NAndy Lutomirski <luto@amacapital.net> Reviewed-by: NThomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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