On Sun, May 13, 2018 at 7:02 AM, Commit Bot <b...@cloudius-systems.com>
wrote:
> From: Waldemar Kozaczuk <jwkozac...@gmail.com>
> Committer: Waldemar Kozaczuk <jwkozac...@gmail.com>
> Branch: master
>
> Gracefully handle the case of missing libvsdo.so
>
> Current implementation of application::prepare_argv() aborts execution
> if it fails to load libvdso library. So far libvdso library is only
> used by Golang programs and other applications can function just fine
> without it. Unfortunately this prevents older OSv images (especially
> those created by Mikelangelo capstan) to boot.
>
> This patch changes prepare_argv() implementation to print warning
> if libvdso is missing and skip passing its address in auxv array.
>
> Fixes #966
>
> Signed-off-by: Waldemar Kozaczuk <jwkozac...@gmail.com>
>
> ---
> diff --git a/core/app.cc b/core/app.cc
> --- a/core/app.cc
> +++ b/core/app.cc
> @@ -6,6 +6,7 @@
> */
>
> #include <osv/app.hh>
> +#include <osv/stubbing.hh>
> #include <string>
> #include <osv/run.hh>
> #include <osv/power.hh>
> @@ -359,8 +360,16 @@ void application::prepare_argv(elf::program *program)
> envcount++;
> }
>
> + // Load vdso library if available
> + int auxv_parameters_count = 2;
> + _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");
> + }
> +
> // Allocate the continuous buffer for argv[] and envp[]
> - _argv.reset(new char*[_args.size() + 1 + envcount + 1 +
> sizeof(Elf64_auxv_t) * 3]);
> + _argv.reset(new char*[_args.size() + 1 + envcount + 1 +
> sizeof(Elf64_auxv_t) * (auxv_parameters_count + 1)]);
>
// Fill the argv part of these buffers
> char *ab = _argv_buf.get();
> @@ -380,22 +389,21 @@ void application::prepare_argv(elf::program
> *program)
> }
> contig_argv[_args.size() + 1 + envcount] = nullptr;
>
> - _libvdso = program->get_library("libvdso.so");
> - if (!_libvdso) {
> - abort("could not load libvdso.so\n");
> - }
>
> // Pass the VDSO library to the application.
> Elf64_auxv_t* _auxv =
> reinterpret_cast<Elf64_auxv_t *>(&contig_argv[_args.size() + 1 +
> envcount + 1]);
> - _auxv[0].a_type = AT_SYSINFO_EHDR;
> - _auxv[0].a_un.a_val = reinterpret_cast<uint64_t>(_libvdso->base());
> + int auxv_idx = 0;
> + if (_libvdso) {
> + _auxv[auxv_idx].a_type = AT_SYSINFO_EHDR;
> + _auxv[auxv_idx++].a_un.a_val = reinterpret_cast<uint64_t>(_li
> bvdso->base());
> + }
>
> - _auxv[1].a_type = AT_PAGESZ;
> - _auxv[1].a_un.a_val = sysconf(_SC_PAGESIZE);
> + _auxv[auxv_idx].a_type = AT_PAGESZ;
> + _auxv[auxv_idx++].a_un.a_val = sysconf(_SC_PAGESIZE);
>
> - _auxv[2].a_type = AT_NULL;
> - _auxv[2].a_un.a_val = 0;
> + _auxv[auxv_idx].a_type = AT_NULL;
> + _auxv[auxv_idx].a_un.a_val = 0;
>
Nitpick: I would add an assert that at this point auxv_idx ==
auxv_parameters_count. So if someone wants to add a new variable to this
array and forgets to update auxv_parameters_count, or botches up the
auxv_idx++ somewhere, it won't go unnoticed.
> }
>
> void application::run_main()
>
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