[haiku-bugs] Re: [Haiku] #6271: support for images with a single rwx PT_LOAD program header
- From: "bonefish" <trac@xxxxxxxxxxxx>
- Date: Tue, 06 Jul 2010 16:00:18 -0000
#6271: support for images with a single rwx PT_LOAD program header
----------------------------+-----------------------------------------------
Reporter: lucian | Owner: axeld
Type: bug | Status: new
Priority: normal | Milestone: R1
Component: System/Kernel | Version: R1/Development
Resolution: | Keywords:
Blocked By: | Has a Patch: 1
Platform: All | Blocking:
----------------------------+-----------------------------------------------
Comment (by bonefish):
Replying to [comment:6 lucian]:
> Ok, on PPC the data segments may be executable, but are there two
{{{PT_LOAD}}} program headers: one that is .data (rwx) and .text?
Yes, e.g.:
{{{
bonefish@backbone:~/develop/haiku/haiku/generated-ppc> readelf --segments
objects/haiku/ppc/release/add-ons/kernel/bus_managers/pci/pci
Elf file type is DYN (Shared object file)
Entry point 0x3f270
There are 3 program headers, starting at offset 52
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
LOAD 0x000000 0x00000000 0x00000000 0xa5c50 0xa5c50 R E 0x1000
LOAD 0x0a5c50 0x000a6c50 0x000a6c50 0x464d0 0x46678 RWE 0x1000
DYNAMIC 0x0a5c6c 0x000a6c6c 0x000a6c6c 0x000c0 0x000c0 RW 0x4
Section to Segment mapping:
Segment Sections...
00 .hash .dynsym .dynstr .gnu.version .gnu.version_r .rela.dyn
.rela.plt .init .text .fini .rodata
01 .eh_frame .ctors .dtors .data.rel.ro .dynamic .data .got .sdata
.sbss .plt .bss
02 .dynamic
}}}
> Initially, for me, the single {{{PT_LOAD}}} program header was loaded in
{{{.data}}} and nothing in {{{.text}}}.
>
> The problem appeared when it tried to run
{{{elf_parse_dynamic_section}}} because of
> image->dynamic_section += image->text_region.delta
> from {{{load_kernel_add_on()}}} in {{{src/system/kernel/elf.cpp}}}.
>
> If there is only a single rwx {{{.data}}} section and no {{{.text}}}
section, {{{image->text_region.delta}}} will be {{{0}}} => the dynamic
section will not begin after the {{{.text}}} but after {{{NULL}}}. This
will most surely result in a page fault.
I understand the problem and I'm fine in principle with the patch, but it
should be adjusted so that things continue to work on PPC.
--
Ticket URL: <http://dev.haiku-os.org/ticket/6271#comment:7>
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