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Kernel+Userland: Make the stack alignment comply with the System V ABI
The System V ABI for both x86 and x86_64 requires that the stack pointer is 16-byte aligned on entry. Previously we did not align the stack pointer properly. As far as "main" was concerned the stack alignment was correct even without this patch due to how the C++ _start function and the kernel interacted, i.e. the kernel misaligned the stack as far as the ABI was concerned but that misalignment (read: it was properly aligned for a regular function call - but misaligned in terms of what the ABI dictates) was actually expected by our _start function.
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8 changed files with 69 additions and 17 deletions
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@ -19,9 +19,15 @@ extern u32 __stack_chk_guard;
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int main(int, char**, char**);
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// Tell the compiler that this may be called from somewhere else.
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int _start(int argc, char** argv, char** env);
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int _entry(int argc, char** argv, char** env);
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int _start(int argc, char** argv, char** env)
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asm(
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".globl _start\n"
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"_start:\n"
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"push $0\n"
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"jmp _entry@plt\n");
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int _entry(int argc, char** argv, char** env)
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{
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u32 original_stack_chk = __stack_chk_guard;
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arc4random_buf(&__stack_chk_guard, sizeof(__stack_chk_guard));
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