g2gps opened a new pull request, #9395:
URL: https://github.com/apache/nuttx/pull/9395
## Summary
The following changes make it possible for Nuttx to load binaries in ELF
format which are fully linked.
The change does not include the necessary modifications to produce such
binaries. In order to build an applicable binary:
- The userspace applications linker script (`gnu-elf.ld`) needs to modified
so the data and text section origin's match those setup by the address
environment.
- The makefile used, in `apps/import/Make.defs` needs to remove the `-r`
LDELFFLAG.
## Impact
- No measurable impact on existing application which load relocatable ELFs.
- Massive improvement in launch time when loading fully linked ELFs, as
there's no longer any need to process relocations.
## Testing
Using existing configurations and relocatable ELFs:
- sim:elf
- rv-virt:knsh32
Using fully linked ELFs requires modifications as outlined above. For
testing on rv-virt:knsh32:
Changes to Nuttx:
```diff
diff --git a/binfmt/libelf/gnu-elf.ld b/binfmt/libelf/gnu-elf.ld
index 81928663ee..9b03039e3f 100644
--- a/binfmt/libelf/gnu-elf.ld
+++ b/binfmt/libelf/gnu-elf.ld
@@ -20,7 +20,8 @@
SECTIONS
{
- .text 0x00000000 :
+ . = 0xC0000000;
+ .text :
{
_stext = . ;
*(.text)
@@ -51,6 +52,7 @@ SECTIONS
_erodata = . ;
}
+ . = 0xC0401000;
.data :
{
_sdata = . ;
diff --git a/boards/risc-v/qemu-rv/rv-virt/scripts/Make.defs
b/boards/risc-v/qemu-rv/rv-virt/scripts/Make.defs
index ab13f19b9c..4511054841 100644
--- a/boards/risc-v/qemu-rv/rv-virt/scripts/Make.defs
+++ b/boards/risc-v/qemu-rv/rv-virt/scripts/Make.defs
@@ -57,5 +57,5 @@ else
LDELFFLAGS = --oformat elf64-littleriscv
endif
-LDELFFLAGS += -r -e main
+LDELFFLAGS += -e main
LDELFFLAGS += -T $(call CONVERT_PATH,$(TOPDIR)/binfmt/libelf/gnu-elf.ld)
```
Changes to apps:
```diff
diff --git a/import/Make.defs b/import/Make.defs
index b8377f79a..b97b260a2 100644
--- a/import/Make.defs
+++ b/import/Make.defs
@@ -90,5 +90,5 @@ endif
# ELF module definitions
-LDELFFLAGS += -r -e _start -Bstatic
+LDELFFLAGS += -s -e _start -Bstatic
LDELFFLAGS += $(addprefix -T,$(call
CONVERT_PATH,$(TOPDIR)/scripts/gnu-elf.ld))
```
As can be seen, the required changes are board, and configuration specific.
It may be possible to provide the infrastructure in NuttX (and apps) to build
fully-linked applications, picking up the necessary configuration values from
the board's directory. However, this would be quite a large change, and may
need to be addressed separately.
For our current application I'm building NuttX native applications as
relocatables and our custom applications fully linked against Nuttx export
with a custom Makefile and linker script. Loading both ELF types simultaneously
works without issues.
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