[PATCH v4 3/5] [gdb/testsuite] use -Ttext-segment for jit-elf tests

[Simon Marchi]

On 2020-04-21 9:31 a.m., Mihails Strasuns via Gdb-patches wrote:
> 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.
> ---
>  gdb/testsuite/gdb.base/jit-elf-main.c | 27 ++++++++++++++------------
>  gdb/testsuite/lib/jit-elf-helpers.exp | 28 ++++++++++++++++++++++++---
>  2 files changed, 40 insertions(+), 15 deletions(-)
> 
> diff --git a/gdb/testsuite/gdb.base/jit-elf-main.c b/gdb/testsuite/gdb.base/jit-elf-main.c
> index acfd17d417..ca150f3b1b 100644
> --- a/gdb/testsuite/gdb.base/jit-elf-main.c
> +++ b/gdb/testsuite/gdb.base/jit-elf-main.c
> @@ -51,20 +51,16 @@ usage (void)
>    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 do {} while (wait_for_gdb)
> @@ -139,8 +141,9 @@ 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);

Space before asterisk.

Otherwise, this patch LGTM.

Simon