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[arch][riscv] fix bug with gcc 10.2 & binutils 2.35 with section padding

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In a two segment binary was previously trying to use MAXPAGESIZE set to 4
to cram the sections in very tight for embedded. This seemed to with this
toolchain cause the linker to get confused and sometimes appear to stuff in
an extra 4 bytes in the output file, thus misaligning the data segment.

It's possible it's still a bug on my side in the linker, but setting
max_page_size to 8 seems to work around it for now. Possible there's some
implicit 64bit aligning slipped in a stage somewhere in binutils thats
causing it to get confused. Either way, 8 byte alignment is no large loss
here.
This commit is contained in:
Travis Geiselbrecht
2020-12-09 01:59:16 -08:00
parent 11ca56717e
commit 8869020ae2
3 changed files with 10 additions and 2 deletions
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2
arch/riscv/linker-onesegment.ld
View File

@@ -32,7 +32,9 @@ SECTIONS
*(.rodata .rodata.* .gnu.linkonce.r.*)
} :rodata
/* trick to force any extra sections to be emitted here */
. = .;
__rodata_end = .;
__rom_end = . ;
. = ALIGN(CONSTANT(MAXPAGESIZE));

4
arch/riscv/linker-twosegment.ld
View File

@@ -36,7 +36,9 @@ SECTIONS
*(.rodata .rodata.* .gnu.linkonce.r.*)
} :rodata
/* trick to force any extra sections to be emitted here */
. = .;
__rodata_end = .;
__rom_end = . ;
. = ALIGN(CONSTANT(MAXPAGESIZE));
@@ -50,7 +52,7 @@ SECTIONS
*/
. = %MEMBASE%;
.data : AT ( ADDR (.dummy_post_rodata) + SIZEOF (.dummy_post_rodata) ) {
.data : AT ( ADDR (.dummy_post_rodata) ) {
__data_start = .;
*(.data .data.* .gnu.linkonce.d.*)
__ctor_list = .;

6
arch/riscv/rules.mk
View File

@@ -175,7 +175,11 @@ linkerscript.phony:
ifeq (true,$(call TOBOOL,$(ARCH_RISCV_TWOSEGMENT)))
GLOBAL_DEFINES += ARCH_RISCV_TWOSEGMENT=1
LINKER_SCRIPT += $(BUILDDIR)/linker-twosegment.ld
ARCH_LDFLAGS += -z max-page-size=4
# set MAXPAGESIZE to 8 to cause the linker script to pack things in much tighter than
# a paged sytem would.
# NOTE: 8 seems to be about as far as you can go. experienced some extra stuffed words
# when using 4.
ARCH_LDFLAGS += -z max-page-size=8
else
GLOBAL_DEFINES += ARCH_RISCV_TWOSEGMENT=0
LINKER_SCRIPT += $(BUILDDIR)/linker-onesegment.ld