FRED and IDT differ by a Supervisor Token on the base of the shstk. This
means that switch_stack_and_jump() needs to discard one extra word when FRED
is active.
Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
---
CC: Jan Beulich <jbeul...@suse.com>
CC: Roger Pau Monné <roger....@citrix.com>
RFC. I don't like this, but it does work.
This emits opt_fred logic outside of CONFIG_XEN_SHSTK. But frankly, the
construct is already too unweildly, and all options I can think of make it
moreso.
---
xen/arch/x86/include/asm/current.h | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/xen/arch/x86/include/asm/current.h
b/xen/arch/x86/include/asm/current.h
index 962eb76a82b3..24d7d906a8c6 100644
--- a/xen/arch/x86/include/asm/current.h
+++ b/xen/arch/x86/include/asm/current.h
@@ -11,6 +11,7 @@
#include <xen/page-size.h>
#include <asm/cpu-user-regs.h>
+#include <asm/traps.h>
/*
* Xen's cpu stacks are 8 pages (8-page aligned), arranged as:
@@ -154,7 +155,6 @@ unsigned long get_stack_dump_bottom (unsigned long sp);
"rdsspd %[ssp];" \
"cmp $1, %[ssp];" \
"je .L_shstk_done.%=;" /* CET not active? Skip. */ \
- "mov $%c[skstk_base], %[val];" \
"and $%c[stack_mask], %[ssp];" \
"sub %[ssp], %[val];" \
"shr $3, %[val];" \
@@ -177,6 +177,8 @@ unsigned long get_stack_dump_bottom (unsigned long sp);
#define switch_stack_and_jump(fn, instr, constr) \
({ \
+ unsigned int token_offset = \
+ (PRIMARY_SHSTK_SLOT + 1) * PAGE_SIZE - (opt_fred ? 0 : 8); \
unsigned int tmp; \
BUILD_BUG_ON(!ssaj_has_attr_noreturn(fn)); \
__asm__ __volatile__ ( \
@@ -184,12 +186,11 @@ unsigned long get_stack_dump_bottom (unsigned long sp);
"mov %[stk], %%rsp;" \
CHECK_FOR_LIVEPATCH_WORK \
instr "[fun]" \
- : [val] "=&r" (tmp), \
+ : [val] "=r" (tmp), \
[ssp] "=&r" (tmp) \
: [stk] "r" (guest_cpu_user_regs()), \
[fun] constr (fn), \
- [skstk_base] "i" \
- ((PRIMARY_SHSTK_SLOT + 1) * PAGE_SIZE - 8), \
+ "[val]" (token_offset), \
[stack_mask] "i" (STACK_SIZE - 1), \
_ASM_BUGFRAME_INFO(BUGFRAME_bug, __LINE__, \
__FILE__, NULL) \
--
2.39.5
