On Wed, 2019-07-31 at 22:19 +0200, Helge Deller wrote:
> On 31.07.19 21:56, James Bottomley wrote:
> > On Wed, 2019-07-31 at 21:46 +0200, Helge Deller wrote:
> > > On 31.07.19 21:44, Sven Schnelle wrote:
> > > > Hi James,
> > > >
> > > > On Wed, Jul 31, 2019 at 12:40:12PM -0700, James Bottomley
> > > > wrote:
> > > >
> > > > > What about causing the compressed make to build both a
> > > > > stripped and a non-stripped bzImage (say sbzImage and
> > > > > bzImage). That way you always have the stripped one
> > > > > available for small size things like boot from tape or
> > > > > DVD? but in the usual case we use the bzImage with full
> > > > > contents.
> > > >
> > > > In that case we would also need to build two lifimages - how
> > > > about adding a config option option? Something like "Strip
> > > > debug information from compressed kernel images"?
> > >
> > > I agree, two lifimages don't make sense. Only one vmlinuz gets
> > > installed. Instead of the config option, I tink my latest patch
> > > is better.
> >
> > It doesn't solve the problem that if a stripped compressed image is
> > >
> > 128kb then it overwrites the decompress area starting at 0x00100000
> > so we can't decompress the end because we've already overwritten it
> > before the decompressor gets to it.
>
> I don't get this point.
> hppa64-linux-gnu-objdump -h vmlinuz
> shows:
> Sections:
> Idx Name Size VMA LMA File
> off Algn
> 0
> .head.text 00000084 00000000000e0000 00000000000e0000 00001000
> 2**2
> CONTENTS, ALLOC, LOAD, READONLY, CODE
> 1
> .opd 00000340 00000000000e0090 00000000000e0090 00001090
> 2**3
> CONTENTS, ALLOC, LOAD, DATA
> 2
> .dlt 00000160 00000000000e03d0 00000000000e03d0 000013d0
> 2**3
> CONTENTS, ALLOC, LOAD, DATA
> 3 .rodata.compressed
> 01f3c2b0 00000000000e0530 00000000000e0530 00001530 2**0
> CONTENTS, ALLOC, LOAD, DATA
> 4
> .text 00005cc0 000000000201d000 000000000201d000 01f3e000
> 2**7
> CONTENTS, ALLOC, LOAD, READONLY, CODE
> 5
> .data 00000060 0000000002022cc0 0000000002022cc0 01f43cc0
> 2**3
> CONTENTS, ALLOC, LOAD, DATA
>
> Only .head.text gets loaded at e0000, and it is basically just a few
> bytes which sets-up registers and jump to .text segment (at 0201d000
> in this case).
Actually, you're looking at the wrong thing, you want to look at the
program header (the segments) not the section header. It's the program
header we load. If I extract this from the current debian kernel we
get
jejb@ion:~/git/linux-build/arch/parisc/boot/compressed> readelf -l /boot/vmlinuz-4.19.0-5-parisc64-smp
Elf file type is EXEC (Executable file)
Entry point 0xe0000
There are 4 program headers, starting at offset 64
Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
PHDR 0x0000000000000040 0x0000000000001040 0x0000000000000000
0x00000000000000e0 0x00000000000000e0 R E 0x8
LOAD 0x0000000000001000 0x00000000000e0000 0x00000000000e0000
0x00000000000004d8 0x00000000000004d8 RWE 0x1000
LOAD 0x0000000000002000 0x0000000001400000 0x0000000001400000
0x00000000003dd46c 0x00000000003e1000 RWE 0x1000
GNU_STACK 0x0000000000000000 0x0000000000000000 0x0000000000000000
0x0000000000000000 0x0000000000000000 RWE 0x10
Section to Segment mapping:
Segment Sections...
00
01 .head.text .opd .dlt
02 .text .data .rodata .eh_frame .bss
03
The two LOAD sections corresponding to what PALO actually loads. The
problem happens if the length of the first load section is bigger than
0x20000. Now if you look what happens after your change:
jejb@ion:~/git/linux-build/build/parisc64/arch/parisc/boot> readelf -l bzImage
Elf file type is EXEC (Executable file)
Entry point 0xe0000
There are 4 program headers, starting at offset 64
Program Headers:
Type Offset VirtAddr PhysAddr
FileSiz MemSiz Flags Align
PHDR 0x0000000000000040 0x0000000000001040 0x0000000000000000
0x00000000000000e0 0x00000000000000e0 R E 0x8
LOAD 0x0000000000001000 0x00000000000e0000 0x00000000000e0000
0x00000000004ae760 0x00000000004ae760 RWE 0x1000
LOAD 0x00000000004b0000 0x000000000118a000 0x000000000118a000
0x0000000000006044 0x000000000000a000 RWE 0x1000
GNU_STACK 0 0x0000000000000000 0x0000000000000000 0x0000000000000000
0x0000000000000000 0x0000000000000000 RWE 0x10
Section to Segment mapping:
Segment Sections...
00
01 .head.text .opd .dlt .rodata.compressed
02 .text .data .rodata .eh_frame .bss
03
So the first section tries to load between 0x000e0000-0x0058e760 and
that's overwritten at 0x00100000 when the decompression starts because
0x00100000 is our KERNEL_BINARY_TEXT_START. The result for me is that
I get the Decompressing linux ... message followed by a HPMC.
James
