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Define AT_HWCAP* when <sys/auxv.h> hides them #3429

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Define AT_HWCAP* when <sys/auxv.h> hides them #3429

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43 changes: 26 additions & 17 deletions crypto/fipsmodule/cpucap/cpu_getauxval_linux.h
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,8 @@
// After including this header (on Linux), OPENSSL_HAS_GETAUXVAL is defined
// and getauxval(type) is callable -- regardless of whether <sys/auxv.h> was
// available -- so call sites do not need to special-case the libc.
// AT_NULL, AT_HWCAP, AT_HWCAP2, and AT_EXECFN are also defined when the
// system header omits them (for example under `-D_XOPEN_SOURCE=700`).

#if defined(OPENSSL_LINUX)

Expand Down Expand Up @@ -41,26 +43,15 @@

#if defined(OPENSSL_HAS_GETAUXVAL)
#include <sys/auxv.h>
#else

// When <sys/auxv.h> is not available (e.g. older uclibc without getauxval),
// fall back to reading /proc/self/auxv. The file contains sequential pairs of
// unsigned long values: [type_0, value_0, type_1, value_1, ..., AT_NULL, 0].

#include <errno.h>
#include <fcntl.h>
#include <unistd.h>

// O_CLOEXEC was added in Linux 2.6.23 / glibc 2.7. Older toolchains (e.g.
// manylinux1 / CentOS 5 with glibc 2.5) do not define it. Fall back to 0;
// the fd is opened, read, and closed synchronously within this function
// (no intervening fork), so close-on-exec is not security-relevant here.
#if !defined(O_CLOEXEC)
#define O_CLOEXEC 0
#endif

// Auxiliary vector type constants from the Linux kernel ABI
// (include/uapi/linux/auxvec.h). The specific values used here are stable.
//
// <sys/auxv.h> may exist but still hide AT_HWCAP2 when building with
// `-D_XOPEN_SOURCE=700` and without `_GNU_SOURCE` (aws-lc-sys Linux
// builds on manylinux 2.17). glibc also only advertised AT_HWCAP2 starting
// in 2.18 (see #1682).
#if !defined(AT_NULL)
#define AT_NULL 0
#endif
Expand All @@ -74,6 +65,24 @@
#define AT_EXECFN 31
#endif

#if !defined(OPENSSL_HAS_GETAUXVAL)

// When <sys/auxv.h> is not available (e.g. older uclibc without getauxval),
// fall back to reading /proc/self/auxv. The file contains sequential pairs of
// unsigned long values: [type_0, value_0, type_1, value_1, ..., AT_NULL, 0].

#include <errno.h>
#include <fcntl.h>
#include <unistd.h>

// O_CLOEXEC was added in Linux 2.6.23 / glibc 2.7. Older toolchains (e.g.
// manylinux1 / CentOS 5 with glibc 2.5) do not define it. Fall back to 0;
// the fd is opened, read, and closed synchronously within this function
// (no intervening fork), so close-on-exec is not security-relevant here.
#if !defined(O_CLOEXEC)
#define O_CLOEXEC 0
#endif

// getauxval returns the value of the auxiliary-vector entry of the given
// |type|, or 0 if no such entry exists or /proc/self/auxv is unavailable.
//
Expand Down Expand Up @@ -138,7 +147,7 @@ static OPENSSL_UNUSED unsigned long getauxval(unsigned long type) {
// the fallback above.
#define OPENSSL_HAS_GETAUXVAL

#endif // OPENSSL_HAS_GETAUXVAL
#endif // !defined(OPENSSL_HAS_GETAUXVAL)

#endif // OPENSSL_LINUX

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