1 files changed, 132 insertions, 0 deletions
diff --git a/rts/linker/elf_tlsgd.c b/rts/linker/elf_tlsgd.c
new file mode 100644
index 0000000000..9e9d6a820f
--- /dev/null
+++ b/rts/linker/elf_tlsgd.c
@@ -0,0 +1,132 @@
+#include "Rts.h"
+
+#if defined(x86_64_HOST_ARCH) && defined(freebsd_HOST_OS)
+
+#include "linker/Elf.h"
+#include "linker/SymbolExtras.h"
+#include <link.h>
+#include <string.h>
+
+/*
+ * Though for now we only get here for X86_64, also handle some other CPUs.
+ */
+#if defined(__mips__) || defined(__powerpc__) || defined(__powerpc64__)
+#define OFFSUB 0x8000
+#elif defined(__riscv__)
+#define OFFSUB 0x800
+#else
+#define OFFSUB 0x0
+#endif
+
+static unsigned long
+elfhash(const unsigned char *name)
+{
+    unsigned long h = 0, g;
+
+    while (*name)
+    {
+        h = (h << 4) + *name++;
+        if ((g = h & 0xf0000000) != 0)
+            h ^= g >> 24;
+        h &= ~g;
+    }
+    return h;
+}
+
+typedef struct tls_sym {
+    ObjectCode   *tls_sym_object;
+    const char   *tls_sym_name;
+    unsigned long tls_sym_indx;
+    unsigned long tls_sym_hash;
+    StgInt64      tls_sym_reloc;
+} tls_sym;
+
+typedef struct dl_phdr_info dlpi;
+
+static int
+find_tls_sym(dlpi *info, size_t sz __attribute__((unused)), void *data)
+{
+    tls_sym *wanted = (tls_sym *)data;
+    const Elf_Addr base = info->dlpi_addr;
+    const Elf_Dyn *dyn = NULL;
+    const Elf_Sym *dynsym = NULL;
+    const Elf_Word *dynhash = 0;
+    const char *dynstr = NULL;
+
+    for (size_t i = 0; i < info->dlpi_phnum; i++) {
+        const Elf_Phdr *phdr = &info->dlpi_phdr[i];
+
+        if (phdr->p_type == PT_DYNAMIC) {
+            dyn = (const Elf_Dyn *)(base + phdr->p_vaddr);
+            break;
+        }
+    }
+    if (dyn == NULL)
+        return 0;
+
+    for (size_t i = 0; dyn[i].d_tag != DT_NULL; ++i)
+        switch (dyn[i].d_tag) {
+        case DT_SYMTAB:
+            dynsym = (const Elf_Sym *)(base + dyn[i].d_un.d_val);
+            break;
+        case DT_STRTAB:
+            dynstr = (const char *)(base + dyn[i].d_un.d_val);
+            break;
+        case DT_HASH:
+            dynhash = (const Elf_Word *)(base + dyn[i].d_un.d_val);
+            break;
+        default:
+            break;
+        }
+
+    if (dynsym == NULL || dynstr == NULL || dynhash == NULL)
+        return 0;
+
+    unsigned long nbucket = (unsigned long)dynhash[0];
+    // unsigned long nchain = (unsigned long)dynhash[1];
+    const Elf_Word *bucket = &dynhash[2];
+    const Elf_Word *chain = &dynhash[2+nbucket];
+    unsigned long h = wanted->tls_sym_hash % nbucket;
+
+    for (unsigned long i = bucket[h]; i != STN_UNDEF; i = chain[i]) {
+        const Elf_Sym *sym = dynsym+i;
+        const char *symname = dynstr + sym->st_name;
+
+        /* Ignore undefined or non-TLS symbols */
+        if (sym->st_value == 0 || ELF_ST_TYPE(sym->st_info) != STT_TLS)
+            continue;
+
+        if (strcmp(symname, wanted->tls_sym_name) == 0) {
+            unsigned long target = sym->st_value - OFFSUB;
+            /* Store the module id as GOT[0] in a new GOT entry */
+            SymbolExtra *extra =
+                makeSymbolExtra(wanted->tls_sym_object,
+                                wanted->tls_sym_indx,
+                                info->dlpi_tls_modid);
+            /* Copy the target address to GOT[1] (a.k.a. jumpIsland) */
+            memcpy(extra->jumpIsland, &target, sizeof(target));
+            wanted->tls_sym_reloc = (StgInt64) extra;
+            /* Signal success, no more modules will be tried */
+            return 1;
+        }
+    }
+    /* Try the next module if any */
+    return 0;
+}
+
+StgInt64
+lookupTlsgdSymbol(const char *symbol, unsigned long symnum, ObjectCode *oc)
+{
+    tls_sym t;
+
+    t.tls_sym_object = oc;
+    t.tls_sym_name = symbol;
+    t.tls_sym_indx = symnum;
+    t.tls_sym_hash = elfhash((unsigned char *)symbol);
+    t.tls_sym_reloc = 0;
+
+    dl_iterate_phdr(find_tls_sym, &t);
+
+    return t.tls_sym_reloc;
+}
+#endif