use hidden visibility rather than protected for syscall internals

the use of visibility at all is purely an optimization to avoid the
need for the caller to load the GOT register or similar to prepare for
a call via the PLT. there is no reason for these symbols to be
externally visible, so hidden works just as well as protected, and
using protected visibility is undesirable due to toolchain bugs and
the lack of testing it receives.

in particular, GCC's microblaze target is known to generate symbolic
relocations in the GOT for functions with protected visibility. this
in turn results in a dynamic linker which crashes under any nontrivial
usage that requires making a syscall before symbolic relocations are
processed.

(cherry picked from commit 83c98aac4c43f9571e8f92a1c795afe02c237d4b)

diff --git a/src/internal/syscall.h b/src/internal/syscall.h
index 88fc89c9a58005a99ef597308203203ee7bd4666..dcfae003b123265b565a97e7344c05f33a1d07c5 100644 (file)
--- a/src/internal/syscall.h
+++ b/src/internal/syscall.h
@@ -10,7 +10,7 @@ typedef long syscall_arg_t;
 #endif
 
 #if defined(__PIC__) && (100*__GNUC__+__GNUC_MINOR__ >= 303)
-__attribute__((visibility("protected")))
+__attribute__((visibility("hidden")))
 #endif
 long __syscall_ret(unsigned long), __syscall(syscall_arg_t, ...),
        __syscall_cp(syscall_arg_t, syscall_arg_t, syscall_arg_t, syscall_arg_t,