On 05/11/2017 02:05 AM, Bjorn Andersson wrote:
On Wed 03 May 05:12 PDT 2017, Henri Roosen wrote:
Consider a system with 2 memory regions:
0x1fff8000 - 0x1fffffff: iram
So I presume there's a hole here.
0x21000000 - 0x21007fff: dram
The .elf file for this system contains the following Program Headers:
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
LOAD 0x000094 0x1fff8000 0x1fff8000 0x00240 0x00240 R 0x4
LOAD 0x0002e0 0x1fff8240 0x1fff8240 0x03d1c 0x03d1c RWE 0x10
LOAD 0x003ffc 0x21000000 0x1fffbf5c 0x001cc 0x048a0 RW 0x4
Your ELF header states that there is a segment of 0x48a0 bytes starting
at 0x1fffbf5c, but your iram ends after 0x40a3 bytes. I assume your
MemSiz comes from some linker script, which would mean that your
firmware expects to be able to use all 0x48a0 bytes, which should be
invalid.
I had a closer look at the linker script. The .data section uses the
"AT"-keyword to place the initialized .data right after the .text
section (0x1fffbf5c/PhysAddr).
Some run-time startup-code is responsible for copying the initialized
data to its runtime address (0x21000000/VirtAddr). The run-time
startup-code is also responsible for zero-ing the .bss section.
The size of the initialized data is 0x1cc (FileSiz). The size of the
whole 3rd segment at run-time is 0x048a0 (MemSiz), starting from
0x21000000 (VirtAddr), which also includes the .bss .heap and .stack
sections.
Section to Segment mapping:
Segment Sections...
00 .interrupts
01 .text .ARM .init_array .fini_array
02 .data .bss .heap .stack
The problem is with the 3rd segment: it has 0x1cc bytes of ROM .data
which need to be placed at PhysAddr 0x1fffbf5c. Using MemSiz as len
parameter for rproc_da_to_va is incorrect (goes beyond 0x1fffffff). The
correct len parameter to be used here is FileSiz.
The fact that MemSiz is larger than FileSiz makes sense because you have
.bss, .heap and .stack there - which we conveniently clear for you.
I agree the value of MemSiz being larger than FileSiz is correct; this
is the case when there are uninitialized data sections like .bss. In my
opinion this reflects the run-time size of the segment, starting from
address 0x21000000. However the remoteproc-elf-loader is clearing with
the load-time-address (0x1fffbf5c) as base.
Note that the linker-scripts which are not using the "AT"-keyword have
the VirtAddr and PhysAddr to be the same, so would not cause trouble;
the remoteproc-elf-loader seems to have a problem when VirtAddr and
PhysAddr have different values.
The actual memcpy of the segment was already correctly using the FileSiz
for length, however the unnecessary "Zero out remaining memory" would
write beyond the 0x1fffffff end of the memory region! This patch removes
the harmful code.
Perhaps I'm missing something, but I think the problem is that your
memory map is broken. We do want to clear out the remaining part of each
segment.
I'm not sure it's the memory map which is broken. The "AT"-keyword
should be valid to use I guess. However, remoteproc might decide not to
support such elf-files. A detection for equality of VirtAddr and
PhysAddr could then be used for that.
Please find below some dummy test code (which leaves out the
initialization code for copying .data and clearing .bss) and a linker
script to reproduce:
test.ld
------------
SECTIONS {
. = 0x1fff0000;
.text : { *(.text); }
__flash_sdata = .;
. = 0x21000000;
.data : AT (__flash_sdata) { *(.data); }
.bss : { *(.bss) *(COMMON); }
}
test.s
------------
.bss
uninit_data: .space 0x8000-8
.data
data1: .4byte 1
data2: .4byte 2
.text
_start: b _start
reproduce
------------
arm-none-eabi-as -o test.o test.s
arm-none-eabi-ld -T test.ld -o test.elf test.o
arm-none-eabi-objdump -x test.elf
Note though that we don't yet have means to direct your carveout
allocations to the two segments and get the firmware loaded at the
physical addresses specified.
I'm currently using the .da_to_va callback and translate with offsets
read by custom devicetree bindings.
Regards,
Henri
Regards,
Bjorn
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