This is a net addition in code, and send to only make it harder to understand
what is happening. As such I don't think this is a good idea.
Joe Damato <ice...@gmail.com> wrote:
>Signed-off-by: Joe Damato <ice...@gmail.com>
>---
> arch/x86/include/asm/switch_to.h | 30 ++++++++++++++++++++++++++++++
> arch/x86/kernel/process_64.c | 29 ++---------------------------
> 2 files changed, 32 insertions(+), 27 deletions(-)
>
>diff --git a/arch/x86/include/asm/switch_to.h
>b/arch/x86/include/asm/switch_to.h
>index 4ec45b3..a322cc6 100644
>--- a/arch/x86/include/asm/switch_to.h
>+++ b/arch/x86/include/asm/switch_to.h
>@@ -124,6 +124,36 @@ do {
> \
> __switch_canary_iparam \
> : "memory", "cc" __EXTRA_CLOBBER)
>
>+#define loadsegment_fs(fs, index) \
>+ loadsegment(fs, index)
>+
>+#define loadsegment_gs(gs, index) \
>+ load_gs_index(index)
>+
>+#define switch_segment(prev, next, index, seg, msr) \
>+ do { \
>+ /* \
>+ * Segment register != 0 always requires a reload. Also \
>+ * reload when it has changed. When prev process used 64bit \
>+ * base always reload to avoid an information leak. \
>+ */ \
>+ if (unlikely(index | next->index | prev->seg)) { \
>+ loadsegment_##seg(seg, next->index); \
>+ /* \
>+ * Check if the user used a selector != 0; if yes \
>+ * clear 64bit base, since overloaded base is always \
>+ * mapped to the Null selector \
>+ */ \
>+ if (index) \
>+ prev->seg = 0; \
>+ } \
>+ \
>+ /* when next process has a 64bit base use it */ \
>+ if (next->seg) \
>+ wrmsrl(msr, next->seg); \
>+ prev->index = index; \
>+ } while (0)
>+
> #endif /* CONFIG_X86_32 */
>
> #endif /* _ASM_X86_SWITCH_TO_H */
>diff --git a/arch/x86/kernel/process_64.c
>b/arch/x86/kernel/process_64.c
>index 355ae06..f41d026 100644
>--- a/arch/x86/kernel/process_64.c
>+++ b/arch/x86/kernel/process_64.c
>@@ -318,34 +318,9 @@ __switch_to(struct task_struct *prev_p, struct
>task_struct *next_p)
>
> /*
> * Switch FS and GS.
>- *
>- * Segment register != 0 always requires a reload. Also
>- * reload when it has changed. When prev process used 64bit
>- * base always reload to avoid an information leak.
> */
>- if (unlikely(fsindex | next->fsindex | prev->fs)) {
>- loadsegment(fs, next->fsindex);
>- /*
>- * Check if the user used a selector != 0; if yes
>- * clear 64bit base, since overloaded base is always
>- * mapped to the Null selector
>- */
>- if (fsindex)
>- prev->fs = 0;
>- }
>- /* when next process has a 64bit base use it */
>- if (next->fs)
>- wrmsrl(MSR_FS_BASE, next->fs);
>- prev->fsindex = fsindex;
>-
>- if (unlikely(gsindex | next->gsindex | prev->gs)) {
>- load_gs_index(next->gsindex);
>- if (gsindex)
>- prev->gs = 0;
>- }
>- if (next->gs)
>- wrmsrl(MSR_KERNEL_GS_BASE, next->gs);
>- prev->gsindex = gsindex;
>+ switch_segment(prev, next, fsindex, fs, MSR_FS_BASE);
>+ switch_segment(prev, next, gsindex, gs, MSR_KERNEL_GS_BASE);
>
> switch_fpu_finish(next_p, fpu);
>
--
Sent from my mobile phone. Please excuse brevity and lack of formatting.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
