Re: [Qemu-devel] Mips target '-kernel' option bug

[Thiemo Seufer]

J. Mayer wrote:
> I failed to run Mips target test image on my amd64 machine and I now
> found the reason of the bug:
> the kernel loader code used in hw/mips_r4k.c and hw/mips_malta.c
> implicitelly assumes that the ram_addr_t is 32 bits long.
> Unfortunatelly, on 64 bits hosts, this won't be the case and the kernel
> load address then is over 4 GB. Then, when computing the initrd_offset,
> the code always concludes that there's not enough RAM available to load
> it at the top of the kernel.
> I found 2 ways of fixing the bug, but I don't know which one is correct
> in Mips execution environment.
> The first patch is to make the VIRT_TO_PHYS_ADDEND negative, thus
> translating the kernel virtual address from 0x8000nnnn to the physical
> one 0x0000nnnn (instead of 0x10000nnnn, when running on 64 bits hosts).
> The second solution would be to explicitelly always cast the kernel_high
> value to 32 bits.
> As I do not really know if some Mips target specific constraints would
> make one of the other solution prefered, I'd better let the specialist
> choose !
> 
> The good news is that, once this issue is fixed, the Mips test images
> run with the reverse-endian softmmu patch applied.

I think this patch is the correct fix. Please test and comment.


Thiemo


Index: qemu-work/elf_ops.h
===================================================================
--- qemu-work.orig/elf_ops.h    2007-10-17 14:18:09.000000000 +0100
+++ qemu-work/elf_ops.h 2007-10-17 14:20:20.000000000 +0100
@@ -159,7 +159,7 @@
         goto fail;
 
     if (pentry)
-       *pentry = (uint64_t)ehdr.e_entry;
+       *pentry = (uint64_t)(elf_sword)ehdr.e_entry;
 
     glue(load_symbols, SZ)(&ehdr, fd, must_swab);
 
@@ -206,9 +206,9 @@
     }
     qemu_free(phdr);
     if (lowaddr)
-        *lowaddr = (uint64_t)low;
+        *lowaddr = (uint64_t)(elf_sword)low;
     if (highaddr)
-        *highaddr = (uint64_t)high;
+        *highaddr = (uint64_t)(elf_sword)high;
     return total_size;
  fail:
     qemu_free(data);
Index: qemu-work/loader.c
===================================================================
--- qemu-work.orig/loader.c     2007-10-17 14:18:09.000000000 +0100
+++ qemu-work/loader.c  2007-10-17 14:20:19.000000000 +0100
@@ -173,6 +173,7 @@
 
 #define SZ             32
 #define elf_word        uint32_t
+#define elf_sword        int32_t
 #define bswapSZs       bswap32s
 #include "elf_ops.h"
 
@@ -182,6 +183,7 @@
 #undef elf_sym
 #undef elf_note
 #undef elf_word
+#undef elf_sword
 #undef bswapSZs
 #undef SZ
 #define elfhdr         elf64_hdr
@@ -190,6 +192,7 @@
 #define elf_shdr       elf64_shdr
 #define elf_sym                elf64_sym
 #define elf_word        uint64_t
+#define elf_sword        int64_t
 #define bswapSZs       bswap64s
 #define SZ             64
 #include "elf_ops.h"