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From: Alexey Dobriyan <>
Subject: [PATCH] x86_64: fixup TASK_SIZE_MAX comment
Date: Thu, 5 Mar 2020 21:17:19 +0300	[thread overview]
Message-ID: <20200305181719.GA5490@avx2> (raw)

Comment says "by preventing anything executable" which is not true.
Even PROT_NONE mapping can't be installed at (1<<47 - 4096).

	mmap(0x7ffffffff000, 4096, PROT_NONE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = -1 ENOMEM

I wonder if CPUs with wider address space carried the bugs...

Signed-off-by: Alexey Dobriyan <>

 arch/x86/include/asm/processor.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -887,7 +887,7 @@ static inline void spin_lock_prefetch(const void *x)
  * On Intel CPUs, if a SYSCALL instruction is at the highest canonical
  * address, then that syscall will enter the kernel with a
  * non-canonical return address, and SYSRET will explode dangerously.
- * We avoid this particular problem by preventing anything executable
+ * We avoid this particular problem by preventing anything
  * from being mapped at the maximum canonical address.
  * On AMD CPUs in the Ryzen family, there's a nasty bug in which the

             reply	other threads:[~2020-03-05 18:17 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-05 18:17 Alexey Dobriyan [this message]
2020-03-06 18:09 ` Andy Lutomirski
2021-02-05  9:43 ` [tip: x86/cleanups] x86/asm: Fixup " tip-bot2 for Alexey Dobriyan

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