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core/crypto/_fiat: Hedge against LLVM cleverness

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Recent LLVM is getting smart to the point where the optimizer can change
a traditional constant-time conditional swap into a pointer swap.

Ensure that this does not happen by force-disabling optimization.
Additionally, disable inlining the relevant routines such that manual
inspection in optimized builds is still reasonably easy to do.
This commit is contained in:
Yawning Angel
2023-04-08 09:57:47 +09:00
parent f863264af6
commit d72db2698b
3 changed files with 12 additions and 6 deletions
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core/crypto/_fiat/field_poly1305/field4344.odin
+4 -2
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@@ -201,7 +201,8 @@ fe_opp :: proc "contextless" (out1: ^Loose_Field_Element, arg1: ^Tight_Field_Ele
out1[2] = x3
}
fe_cond_assign :: proc "contextless" (out1, arg1: ^Tight_Field_Element, arg2: bool) {
@(optimization_mode="none")
fe_cond_assign :: #force_no_inline proc "contextless" (out1, arg1: ^Tight_Field_Element, arg2: bool) {
x1 := fiat.cmovznz_u64(fiat.u1(arg2), out1[0], arg1[0])
x2 := fiat.cmovznz_u64(fiat.u1(arg2), out1[1], arg1[1])
x3 := fiat.cmovznz_u64(fiat.u1(arg2), out1[2], arg1[2])
@@ -342,7 +343,8 @@ fe_set :: #force_inline proc "contextless" (out1, arg1: ^Tight_Field_Element) {
out1[2] = x3
}
fe_cond_swap :: proc "contextless" (out1, out2: ^Tight_Field_Element, arg1: bool) {
@(optimization_mode="none")
fe_cond_swap :: #force_no_inline proc "contextless" (out1, out2: ^Tight_Field_Element, arg1: bool) {
mask := -u64(arg1)
x := (out1[0] ~ out2[0]) & mask
x1, y1 := out1[0] ~ x, out2[0] ~ x