From 21ecc179a94445bac3eb717b839bf88003b6f872 Mon Sep 17 00:00:00 2001
From: Stas Sergeev <stsp2@yandex.ru>
Date: Tue, 17 Oct 2023 09:59:08 +0500
Subject: [PATCH] elf: allow non-zero load offset [#172]

Incompatible API change again. :(
---
 fdpp/elf.c            | 6 ++++++
 fdpp/elf_priv.h       | 1 +
 fdpp/thunks.cc        | 7 ++++++-
 include/fdpp/thunks.h | 4 ++--
 4 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/fdpp/elf.c b/fdpp/elf.c
index f2e2adf6..f2884528 100644
--- a/fdpp/elf.c
+++ b/fdpp/elf.c
@@ -181,3 +181,9 @@ void *elf_getloadaddr(void *arg)
     struct elfstate *state = (struct elfstate *)arg;
     return state->addr + state->load_offs;
 }
+
+int elf_getloadoff(void *arg)
+{
+    struct elfstate *state = (struct elfstate *)arg;
+    return state->load_offs;
+}
diff --git a/fdpp/elf_priv.h b/fdpp/elf_priv.h
index 03d519e2..e26a53e1 100644
--- a/fdpp/elf_priv.h
+++ b/fdpp/elf_priv.h
@@ -4,3 +4,4 @@ void elf_close(void *arg);
 void *elf_getsym(void *arg, const char *name);
 int elf_getsymoff(void *arg, const char *name);
 void *elf_getloadaddr(void *arg);
+int elf_getloadoff(void *arg);
diff --git a/fdpp/thunks.cc b/fdpp/thunks.cc
index 8908a470..6a6f391f 100644
--- a/fdpp/thunks.cc
+++ b/fdpp/thunks.cc
@@ -711,11 +711,15 @@ void *FdppKernelLoad(const char *dname, int *len, struct fdpp_bss_list **bss,
     return NULL;
 }
 
-const void *FdppKernelReloc(void *handle, uint16_t seg)
+const void *FdppKernelReloc(void *handle, uint16_t seg, uint16_t *r_seg)
 {
     int i;
     far_s f;
     struct krnl_hndl *h = (struct krnl_hndl *)handle;
+    unsigned load_off = elf_getloadoff(h->elf);
+
+    assert(!(load_off & 0xf));
+    seg -= load_off >> 4;
     elf_reloc(h->elf, seg);
 
     farhlp_init(&sym_tab);
@@ -743,6 +747,7 @@ const void *FdppKernelReloc(void *handle, uint16_t seg)
     f.off = elf_getsymoff(h->elf, "init_near_wrp");
     near_wrp[1] = f;
 
+    *r_seg = seg;
     return h->start;
 }
 
diff --git a/include/fdpp/thunks.h b/include/fdpp/thunks.h
index c50f8bde..bf6805f4 100644
--- a/include/fdpp/thunks.h
+++ b/include/fdpp/thunks.h
@@ -23,7 +23,7 @@
 #include <stdarg.h>
 #include <stddef.h>
 
-#define FDPP_API_VER 33
+#define FDPP_API_VER 34
 
 #ifndef FDPP
 struct fdpp_far_s {
@@ -87,7 +87,7 @@ struct fdpp_bss_list {
 
 void *FdppKernelLoad(const char *dname, int *len, struct fdpp_bss_list **bss,
                      uint32_t *_start);
-const void *FdppKernelReloc(void *handle, uint16_t seg);
+const void *FdppKernelReloc(void *handle, uint16_t seg, uint16_t *r_seg);
 void FdppKernelFree(void *handle);
 
 #ifdef __cplusplus