Commit-ID: 2e85591a6ca2ad84741d2859753be5497d74bd42
Gitweb: http://git.kernel.org/tip/2e85591a6ca2ad84741d2859753be5497d74bd42
Author: Ingo Molnar <mingo@xxxxxxxxxx>
AuthorDate: Wed, 29 Apr 2015 08:46:26 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 19 May 2015 15:48:02 +0200
x86/fpu: Better document fpu__clear() state handling
So prior to this fix:
c88d47480d30 ("x86/fpu: Always restore_xinit_state() when use_eager_cpu()")
we leaked FPU state across execve() boundaries on eagerfpu systems:
$ /host/home/mingo/dump-xmm-regs-exec
# XMM state before execve():
XMM0 : 000000000000dede
XMM1 : 000000000000dedf
XMM2 : 000000000000dee0
XMM3 : 000000000000dee1
XMM4 : 000000000000dee2
XMM5 : 000000000000dee3
XMM6 : 000000000000dee4
XMM7 : 000000000000dee5
XMM8 : 000000000000dee6
XMM9 : 000000000000dee7
XMM10: 000000000000dee8
XMM11: 000000000000dee9
XMM12: 000000000000deea
XMM13: 000000000000deeb
XMM14: 000000000000deec
XMM15: 000000000000deed
# XMM state after execve(), in the new task context:
XMM0 : 0000000000000000
XMM1 : 2f2f2f2f2f2f2f2f
XMM2 : 0000000000000000
XMM3 : 0000000000000000
XMM4 : 00000000000000ff
XMM5 : 00000000ff000000
XMM6 : 000000000000dee4
XMM7 : 000000000000dee5
XMM8 : 0000000000000000
XMM9 : 0000000000000000
XMM10: 0000000000000000
XMM11: 0000000000000000
XMM12: 0000000000000000
XMM13: 000000000000deeb
XMM14: 000000000000deec
XMM15: 000000000000deed
Better explain what this function is supposed to do and why.
Reviewed-by: Borislav Petkov <bp@xxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/kernel/fpu/core.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 91b9935..a2e2da2 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -348,6 +348,10 @@ void fpu__restore(void)
}
EXPORT_SYMBOL_GPL(fpu__restore);
+/*
+ * Called by sys_execve() to clear the FPU fpregs, so that FPU state
+ * of the previous binary does not leak over into the exec()ed binary:
+ */
void fpu__clear(struct task_struct *tsk)
{
struct fpu *fpu = &tsk->thread.fpu;
--
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