kaguya
60 lines
1.3 KiB
C++
60 lines
1.3 KiB
C++
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#include <errno.h>
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#include <stdint.h>
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#include <sys/auxv.h>
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#include <bits/ensure.h>
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extern "C" uintptr_t *__dlapi_entrystack();
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int peekauxval(unsigned long type, unsigned long *out) {
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// Find the auxiliary vector by skipping args and environment.
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auto aux = __dlapi_entrystack();
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aux += *aux + 1; // Skip argc and all arguments
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__ensure(!*aux);
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aux++;
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while(*aux) // Now, we skip the environment.
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aux++;
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aux++;
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// Parse the auxiliary vector.
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while(true) {
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auto value = aux + 1;
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if(*aux == AT_NULL) {
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errno = ENOENT;
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return -1;
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}else if(*aux == type) {
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*out = *value;
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return 0;
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}
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aux += 2;
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}
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}
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unsigned long getauxval(unsigned long type) {
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unsigned long value = 0;
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if(peekauxval(type, &value))
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return 0;
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return value;
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}
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// XXX(qookie):
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// This is here because libgcc will call into __getauxval on glibc Linux
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// (which is what it believes we are due to the aarch64-linux-gnu toolchain)
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// in order to find AT_HWCAP to discover if LSE atomics are supported.
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//
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// This is not necessary on a custom Linux toolchain and is purely an artifact of
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// using the host toolchain.
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// __gnu_linux__ is the define checked by libgcc
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#if defined(__aarch64__) && defined(__gnu_linux__)
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extern "C" unsigned long __getauxval(unsigned long type) {
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unsigned long value = 0;
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if(peekauxval(type, &value))
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return 0;
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return value;
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}
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#endif
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