33#include <asm/prctl.h>
44#include <sys/prctl.h>
55#include <sys/mman.h>
6+ #include <sys/auxv.h>
7+ #include <elf.h>
8+ #include <immintrin.h>
69
710int arch_prctl (int code , unsigned long * addr );
811
12+ #ifndef HWCAP2_FSGSBASE
13+ #define HWCAP2_FSGSBASE (1 << 1)
14+ #endif
15+
916#define EOSVMOC_MEMORY_PTR_cb_ptr GS_PTR struct eos_vm_oc_control_block* const cb_ptr = ((GS_PTR struct eos_vm_oc_control_block* const)(EOS_VM_OC_CONTROL_BLOCK_OFFSET));
1017
1118int32_t eos_vm_oc_grow_memory (int32_t grow , int32_t max ) {
@@ -37,10 +44,9 @@ int32_t eos_vm_oc_grow_memory(int32_t grow, int32_t max) {
3744 gs_diff = grow_amount ;
3845 }
3946
40- uint64_t current_gs ;
41- arch_prctl (ARCH_GET_GS , & current_gs );
47+ uint64_t current_gs = eos_vm_oc_getgs ();
4248 current_gs += gs_diff * EOS_VM_OC_MEMORY_STRIDE ;
43- arch_prctl ( ARCH_SET_GS , ( unsigned long * ) current_gs );
49+ eos_vm_oc_setgs ( current_gs );
4450 cb_ptr -> current_linear_memory_pages += grow_amount ;
4551 cb_ptr -> first_invalid_memory_address += grow_amount * 64 * 1024 ;
4652
@@ -64,3 +70,56 @@ void* eos_vm_oc_get_bounce_buffer_list() {
6470 EOSVMOC_MEMORY_PTR_cb_ptr ;
6571 return cb_ptr -> bounce_buffers ;
6672}
73+
74+ uint64_t eos_vm_oc_getgs_syscall () {
75+ uint64_t gs ;
76+ arch_prctl (ARCH_GET_GS , & gs );
77+ return gs ;
78+ }
79+
80+ uint64_t __attribute__ ((__target__ ("fsgsbase" ))) eos_vm_oc_getgs_fsgsbase () {
81+ return _readgsbase_u64 ();
82+ }
83+
84+ void eos_vm_oc_setgs_syscall (uint64_t gs ) {
85+ arch_prctl (ARCH_SET_GS , (unsigned long * )gs ); //cast to a (unsigned long*) to match local declaration above
86+ }
87+
88+ void __attribute__ ((__target__ ("fsgsbase" ))) eos_vm_oc_setgs_fsgsbase (uint64_t gs ) {
89+ return _writegsbase_u64 (gs );
90+ }
91+
92+ extern char * * _dl_argv ;
93+ static int eos_vm_oc_use_fsgsbase () {
94+ /* ifunc resolvers run _super_ early -- before getenv() is set up even! This is relying on the layout of _dl_argv to be
95+ _dl_argv
96+ ↓
97+ argc, argv[0], ..., argv[argc - 1], NULL, evniron0, environ1, ..., NULL
98+ */
99+ const int argc = * (int * )(_dl_argv - 1 );
100+ char * * my_environ = _dl_argv + argc + 1 ;
101+ while (* my_environ != NULL ) {
102+ const char disable_str [] = "SPRING_DISABLE_FSGSBASE" ;
103+ if (strncmp (* my_environ ++ , disable_str , strlen (disable_str )) == 0 )
104+ return 0 ;
105+ }
106+
107+ //see linux Documentation/arch/x86/x86_64/fsgs.rst; check that kernel has enabled userspace fsgsbase
108+ return getauxval (AT_HWCAP2 ) & HWCAP2_FSGSBASE ;
109+ }
110+
111+ uint64_t (* resolve_eos_vm_oc_getgs ())() {
112+ if (eos_vm_oc_use_fsgsbase ())
113+ return eos_vm_oc_getgs_fsgsbase ;
114+ return eos_vm_oc_getgs_syscall ;
115+ }
116+
117+ uint64_t eos_vm_oc_getgs () __attribute__ ((ifunc ("resolve_eos_vm_oc_getgs" )));
118+
119+ void (* resolve_eos_vm_oc_setgs ())(uint64_t ) {
120+ if (eos_vm_oc_use_fsgsbase ())
121+ return eos_vm_oc_setgs_fsgsbase ;
122+ return eos_vm_oc_setgs_syscall ;
123+ }
124+
125+ void eos_vm_oc_setgs (uint64_t ) __attribute__ ((ifunc ("resolve_eos_vm_oc_setgs" )));
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