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Fix MXCSR configuration dependent timing #111139

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merged 1 commit into from
May 6, 2023
Merged

Fix MXCSR configuration dependent timing #111139

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6 changes: 5 additions & 1 deletion library/std/src/sys/sgx/abi/entry.S
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Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,7 @@ IMAGE_BASE:
.Lxsave_clear:
.org .+24
.Lxsave_mxcsr:
.short 0x1f80
.short 0x1fbf

/* We can store a bunch of data in the gap between MXCSR and the XSAVE header */

Expand Down Expand Up @@ -178,6 +178,7 @@ sgx_entry:
mov $-1, %rax
mov $-1, %rdx
xrstor .Lxsave_clear(%rip)
lfence
mov %r10, %rdx

/* check if returning from usercall */
Expand Down Expand Up @@ -311,6 +312,9 @@ usercall:
movq $0,%gs:tcsls_last_rsp
/* restore callee-saved state, cf. "save" above */
mov %r11,%rsp
/* MCDT mitigation requires an lfence after ldmxcsr _before_ any of the affected */
/* vector instructions is used. We omit the lfence here as one is required before */
/* the jmp instruction anyway. */
ldmxcsr (%rsp)
fldcw 4(%rsp)
add $8, %rsp
Expand Down