[PATCH 20/24] RISC-V sim: Set brk to _end if possible.

[Jim Wilson <jimw@sifive.com>]

From: Kito Cheng <kito.cheng@gmail.com>

Search the symbol table for the address of _end and use it to initialize
brk.  Otherwise, set it to the end of the section with the highest address.

	sim/riscv/
	* interp.c (riscv_get_symbol): New.
	(sim_create_inferior): Call riscv_get_symbol to get address of
	_end.  Use it to set cpu->endbrk.
---
 sim/riscv/interp.c | 46 ++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 38 insertions(+), 8 deletions(-)

diff --git a/sim/riscv/interp.c b/sim/riscv/interp.c
index c98f6ab..7af97d5 100644
--- a/sim/riscv/interp.c
+++ b/sim/riscv/interp.c
@@ -127,14 +127,35 @@ sim_open (SIM_OPEN_KIND kind, host_callback *callback,
   return sd;
 }
 \f
+/* Search the symbol table for the symbol SYM, and return its address.  */
+
+static bfd_vma
+riscv_get_symbol (SIM_DESC sd, const char *sym)
+{
+  long symcount = STATE_PROG_SYMS_COUNT (sd);
+  asymbol **symtab = STATE_PROG_SYMS (sd);
+  int i;
+
+  for (i = 0;i < symcount; ++i)
+    {
+      if (strcmp (sym, bfd_asymbol_name (symtab[i])) == 0)
+	{
+	  bfd_vma sa;
+	  sa = bfd_asymbol_value (symtab[i]);
+	  return sa;
+	}
+    }
+
+  /* Symbol not found.  */
+  return 0;
+}
+
 SIM_RC
 sim_create_inferior (SIM_DESC sd, struct bfd *abfd,
 		     char * const *argv, char * const *env)
 {
   SIM_CPU *cpu = STATE_CPU (sd, 0);
   SIM_ADDR addr;
-  Elf_Internal_Phdr *phdr;
-  int i, phnum;
 
   /* Set the PC.  */
   if (abfd != NULL)
@@ -143,13 +164,22 @@ sim_create_inferior (SIM_DESC sd, struct bfd *abfd,
     addr = 0;
   sim_pc_set (cpu, addr);
 
-  /* Set endbrk to highest section end address.  */
-  phdr = elf_tdata (abfd)->phdr;
-  phnum = elf_elfheader (abfd)->e_phnum;
-  for (i = 0; i < phnum; i++)
+  /* Try to find _end symbol, and set it to the end of brk.  */
+  trace_load_symbols (sd);
+  cpu->endbrk = riscv_get_symbol (sd, "_end");
+
+  /* If not found, set end of brk to end of all section.  */
+  if (cpu->endbrk == 0)
     {
-      if (phdr[i].p_paddr + phdr[i].p_memsz > cpu->endbrk)
-	cpu->endbrk = phdr[i].p_paddr + phdr[i].p_memsz;
+      Elf_Internal_Phdr *phdr = elf_tdata (abfd)->phdr;
+      int phnum = elf_elfheader (abfd)->e_phnum;
+      int i;
+
+      for (i = 0; i < phnum; i++)
+	{
+	  if (phdr[i].p_paddr + phdr[i].p_memsz > cpu->endbrk)
+	    cpu->endbrk = phdr[i].p_paddr + phdr[i].p_memsz;
+	}
     }
 
   /* Standalone mode (i.e. `run`) will take care of the argv for us in
-- 
2.7.4