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start: Add a comment explaining our paranoid stance on ABI guarantees.

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Alex Rønne Petersen 2024-07-24 17:38:54 +02:00
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lib/std/start.zig
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@ -272,6 +272,12 @@ fn _start() callconv(.Naked) noreturn {
: [tos] "={rax}" (-> *std.os.plan9.Tos), : [tos] "={rax}" (-> *std.os.plan9.Tos),
); );
} }
// Note that we maintain a very low level of trust with regards to ABI guarantees at this point.
// We will redundantly align the stack, clear the link register, etc. While e.g. the Linux
// kernel is usually good about upholding the ABI guarantees, the same cannot be said of dynamic
// linkers; musl's ldso, for example, opts to not align the stack when invoking the dynamic
// linker explicitly.
asm volatile (switch (native_arch) { asm volatile (switch (native_arch) {
.x86_64 => .x86_64 =>
\\ xorl %%ebp, %%ebp \\ xorl %%ebp, %%ebp