[PATCH v2 6/8] [gdb/testsuite] use -Ttext-segment for jit-elf tests

[Mihails Strasuns <mihails.strasuns@intel.com>]

Removes the need to manually relocate loaded ELF binary by using a fixed
constant as both mmap base address and as a requested first segment
address supplied to the linker.

In future will enable JIT tests with a valid DWARF debug info.  Current
tests still need to compile without a debug info though, because they do
a function name modification.

gdb/testsuite/ChangeLog:

2020-02-18  Mihails Strasuns  <mihails.strasuns@intel.com>

	* lib/jit-elf-helpers.exp: supply -Ttext-segment linker flag and
	  define LOAD_ADDRESS/LOAD_INCREMENT macros for the compiled binaries
	* gdb.base/jit-elf-main.c: use LOAD_ADDRESS/LOAD_INCREMENT to
	  calculate the mmap address

Change-Id: Ifdd70d2838d9235e5d4fb49b7cafd03cb4865751
Signed-off-by: Mihails Strasuns <mihails.strasuns@intel.com>
---
 gdb/testsuite/gdb.base/jit-elf-main.c | 27 +++++++++++++++------------
 gdb/testsuite/lib/jit-elf-helpers.exp | 21 ++++++++++++++++++++-
 2 files changed, 35 insertions(+), 13 deletions(-)

diff --git a/gdb/testsuite/gdb.base/jit-elf-main.c b/gdb/testsuite/gdb.base/jit-elf-main.c
index 0e4b2e9a40..5bd8a05926 100644
--- a/gdb/testsuite/gdb.base/jit-elf-main.c
+++ b/gdb/testsuite/gdb.base/jit-elf-main.c
@@ -51,20 +51,16 @@ usage ()
   exit (1);
 }
 
-/* Update .p_vaddr and .sh_addr as if the code was JITted to ADDR.  */
+/* Rename jit_function_XXXX to match idx  */
 
 static void
-update_locations (const void *const addr, int idx)
+update_name (const void *const addr, int idx)
 {
   const ElfW (Ehdr) *const ehdr = (ElfW (Ehdr) *)addr;
   ElfW (Shdr) *const shdr = (ElfW (Shdr) *)((char *)addr + ehdr->e_shoff);
   ElfW (Phdr) *const phdr = (ElfW (Phdr) *)((char *)addr + ehdr->e_phoff);
   int i;
 
-  for (i = 0; i < ehdr->e_phnum; ++i)
-    if (phdr[i].p_type == PT_LOAD)
-      phdr[i].p_vaddr += (ElfW (Addr))addr;
-
   for (i = 0; i < ehdr->e_shnum; ++i)
     {
       if (shdr[i].sh_type == SHT_STRTAB)
@@ -81,9 +77,6 @@ update_locations (const void *const addr, int idx)
             if (strcmp (p, "jit_function_XXXX") == 0)
               sprintf (p, "jit_function_%04d", idx);
         }
-
-      if (shdr[i].sh_flags & SHF_ALLOC)
-        shdr[i].sh_addr += (ElfW (Addr))addr;
     }
 }
 
@@ -96,6 +89,15 @@ update_locations (const void *const addr, int idx)
 #define MAIN main
 #endif
 
+/* Must be defined by .exp file when compiling to know
+   what address to map the ELF binary to.  */
+#ifndef LOAD_ADDRESS
+#error "Must define LOAD_ADDRESS"
+#endif
+#ifndef LOAD_INCREMENT
+#error "Must define LOAD_INCREMENT"
+#endif
+
 /* Used to spin waiting for GDB.  */
 volatile int wait_for_gdb = ATTACH;
 #define WAIT_FOR_GDB while (wait_for_gdb)
@@ -137,8 +139,9 @@ MAIN (int argc, char *argv[])
 	  exit (1);
 	}
 
-      const void *const addr = mmap (0, st.st_size, PROT_READ|PROT_WRITE,
-				     MAP_PRIVATE, fd, 0);
+      void* load_addr = (void*) (size_t) (LOAD_ADDRESS + (i - 1) * LOAD_INCREMENT);
+      const void *const addr = mmap (load_addr, st.st_size, PROT_READ|PROT_WRITE,
+				     MAP_PRIVATE | MAP_FIXED, fd, 0);
       struct jit_code_entry *const entry = calloc (1, sizeof (*entry));
 
       if (addr == MAP_FAILED)
@@ -147,7 +150,7 @@ MAIN (int argc, char *argv[])
 	  exit (1);
 	}
 
-      update_locations (addr, i);
+      update_name (addr, i);
 
       /* Link entry at the end of the list.  */
       entry->symfile_addr = (const char *)addr;
diff --git a/gdb/testsuite/lib/jit-elf-helpers.exp b/gdb/testsuite/lib/jit-elf-helpers.exp
index 7e3dfd2c7a..8f17c2f972 100644
--- a/gdb/testsuite/lib/jit-elf-helpers.exp
+++ b/gdb/testsuite/lib/jit-elf-helpers.exp
@@ -13,15 +13,25 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+# Magic constants used to calculate a starting address when linking
+# "jit" shared libraries.  When loaded, will be mapped by jit-elf-main
+# to the same address.
+
+set load_address   0x7000000
+set load_increment 0x1000000
+
 # Compiles jit-elf-main.c as a regular executable
 
 proc compile_jit_main {binsuffix options} {
     global srcdir subdir
+    global load_address load_increment
     set testfile jit-elf-main
     set srcfile ${testfile}.c
     set binfile [standard_output_file $testfile$binsuffix]
     set options [concat \
 	$options \
+	additional_flags=-DLOAD_ADDRESS=$load_address \
+	additional_flags=-DLOAD_INCREMENT=$load_increment \
 	debug]
     if { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" \
 	executable $options] != "" } {
@@ -34,12 +44,15 @@ proc compile_jit_main {binsuffix options} {
 
 proc compile_jit_main_as_so {binsuffix options} {
     global srcdir subdir
+    global load_address load_increment
     set testfile jit-elf-main
     set srcfile ${testfile}.c
     set binfile [standard_output_file $testfile$binsuffix]
     set options [concat \
 	$options \
 	additional_flags="-DMAIN=jit_dl_main" \
+	additional_flags=-DLOAD_ADDRESS=$load_address \
+	additional_flags=-DLOAD_INCREMENT=$load_increment \
 	debug]
     if { [gdb_compile_shlib "${srcdir}/${subdir}/${srcfile}" "${binfile}" \
 	 $options] != "" } {
@@ -53,6 +66,7 @@ proc compile_jit_main_as_so {binsuffix options} {
 
 proc compile_n_jit_so {count binsuffix options} {
     global srcdir subdir
+    global load_address load_increment
     set solib_binfile_targets {}
     set solib_testfile jit-elf-solib
 
@@ -65,7 +79,12 @@ proc compile_n_jit_so {count binsuffix options} {
 	# do symbol renaming by munging on ELF symbol table, and that
 	# wouldn't work for .debug sections.  Also, output for "info
 	# function" changes when debug info is present.
-	if { [gdb_compile_shlib $solib_srcfile $solib_binfile $options] != "" } {
+	set addr [format 0x%x [expr $load_address + $load_increment * [expr $i-1]]]
+	set comp_options [concat \
+	    $options \
+	    additional_flags=-Xlinker \
+	    additional_flags=-Ttext-segment=$addr]
+	if { [gdb_compile_shlib $solib_srcfile $solib_binfile $comp_options] != "" } {
 	    untested "Failure to compile $solib_binfile_test_msg"
 	}
 
-- 
2.25.2

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