linux-kernel - [PATCH] x86_64: fixup TASK_SIZE

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Date:   Thu, 5 Mar 2020 21:17:19 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] x86_64: fixup TASK_SIZE_MAX comment

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 <adobriyan@...il.com>
---

 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