diff options
Diffstat (limited to 'Documentation/x86')
| -rw-r--r-- | Documentation/x86/entry_64.rst (renamed from Documentation/x86/entry_64.txt) | 12 | ||||
| -rw-r--r-- | Documentation/x86/index.rst | 1 |
2 files changed, 10 insertions, 3 deletions
diff --git a/Documentation/x86/entry_64.txt b/Documentation/x86/entry_64.rst index c1df8eba9dfd..a48b3f6ebbe8 100644 --- a/Documentation/x86/entry_64.txt +++ b/Documentation/x86/entry_64.rst @@ -1,3 +1,9 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============== +Kernel Entries +============== + This file documents some of the kernel entries in arch/x86/entry/entry_64.S. A lot of this explanation is adapted from an email from Ingo Molnar: @@ -59,7 +65,7 @@ Now, there's a secondary complication: there's a cheap way to test which mode the CPU is in and an expensive way. The cheap way is to pick this info off the entry frame on the kernel -stack, from the CS of the ptregs area of the kernel stack: +stack, from the CS of the ptregs area of the kernel stack:: xorl %ebx,%ebx testl $3,CS+8(%rsp) @@ -67,7 +73,7 @@ stack, from the CS of the ptregs area of the kernel stack: SWAPGS The expensive (paranoid) way is to read back the MSR_GS_BASE value -(which is what SWAPGS modifies): +(which is what SWAPGS modifies):: movl $1,%ebx movl $MSR_GS_BASE,%ecx @@ -76,7 +82,7 @@ The expensive (paranoid) way is to read back the MSR_GS_BASE value js 1f /* negative -> in kernel */ SWAPGS xorl %ebx,%ebx -1: ret + 1: ret If we are at an interrupt or user-trap/gate-alike boundary then we can use the faster check: the stack will be a reliable indicator of diff --git a/Documentation/x86/index.rst b/Documentation/x86/index.rst index f6f4e0fc79f2..0e3e73458738 100644 --- a/Documentation/x86/index.rst +++ b/Documentation/x86/index.rst @@ -12,3 +12,4 @@ x86-specific Documentation topology exception-tables kernel-stacks + entry_64 |