[COMMIT osv master] auxv: expose AT_MINSIGSTKSZ and AT_RANDOM

[Commit Bot]

From: Waldemar Kozaczuk <jwkoz...@gmail.com>
Committer: WALDEMAR KOZACZUK <jwkoz...@gmail.com>
Branch: master

auxv: expose AT_MINSIGSTKSZ and AT_RANDOM

This patch adds AT_MINSIGSTKSZ and AT_RANDOM to auxiliary vector.
These two values are needed to support static executables.

Signed-off-by: Waldemar Kozaczuk <jwkoz...@gmail.com>

---
diff --git a/core/app.cc b/core/app.cc
--- a/core/app.cc
+++ b/core/app.cc
@@ -20,6 +20,7 @@
#include <boost/range/algorithm/transform.hpp>
#include <osv/wait_record.hh>
#include "libc/pthread.hh"
+#include <sys/random.h>

using namespace boost::range;

@@ -333,6 +334,8 @@ void application::main()
// _entry_point() doesn't return
}

+static u64 random_bytes[2];
+
void application::prepare_argv(elf::program *program)
{
// Prepare program_* variable used by the libc
@@ -360,13 +363,23 @@ void application::prepare_argv(elf::program *program)
}

// Load vdso library if available
- int auxv_parameters_count = 2;
+ int auxv_parameters_count = 4;
_libvdso = program->get_library("libvdso.so");
if (!_libvdso) {
auxv_parameters_count--;
WARN_ONCE("application::prepare_argv(): missing libvdso.so -> may prevent shared libraries specifically Golang ones from functioning\n");
}

+ // Initialize random bytes array so it can be passed as AT_RANDOM auxv vector
+ if (getrandom(random_bytes, sizeof(random_bytes), 0) != sizeof(random_bytes)) {
+ // Fall back to rand_r()
+ auto d = osv::clock::wall::now().time_since_epoch();
+ unsigned seed = std::chrono::duration_cast<std::chrono::nanoseconds>(d).count() % 1000000000;
+ for (unsigned idx = 0; idx < sizeof(random_bytes)/(sizeof(int)); idx++) {
+ reinterpret_cast<int*>(random_bytes)[idx] = rand_r(&seed);
+ }
+ }
+
// Allocate the continuous buffer for argv[] and envp[]
_argv.reset(new char*[_args.size() + 1 + envcount + 1 + sizeof(Elf64_auxv_t) * (auxv_parameters_count + 1)]);

@@ -388,7 +401,6 @@ void application::prepare_argv(elf::program *program)
}
contig_argv[_args.size() + 1 + envcount] = nullptr;

-
// Pass the VDSO library to the application.
Elf64_auxv_t* _auxv =
reinterpret_cast<Elf64_auxv_t *>(&contig_argv[_args.size() + 1 + envcount + 1]);
@@ -401,6 +413,12 @@ void application::prepare_argv(elf::program *program)
_auxv[auxv_idx].a_type = AT_PAGESZ;
_auxv[auxv_idx++].a_un.a_val = sysconf(_SC_PAGESIZE);

+ _auxv[auxv_idx].a_type = AT_MINSIGSTKSZ;
+ _auxv[auxv_idx++].a_un.a_val = sysconf(_SC_MINSIGSTKSZ);
+
+ _auxv[auxv_idx].a_type = AT_RANDOM;
+ _auxv[auxv_idx++].a_un.a_val = reinterpret_cast<uint64_t>(random_bytes);
+
_auxv[auxv_idx].a_type = AT_NULL;
_auxv[auxv_idx].a_un.a_val = 0;
}