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From 1dea576eac4289602adc4a37f48c80330bf82e63 Mon Sep 17 00:00:00 2001
From: Damien Le Moal <damien.lemoal@wdc.com>
Date: Wed, 9 Sep 2020 17:31:33 +0900
Subject: [PATCH] elf2flt: add riscv 64-bits support
Add support for riscv 64bits ISA by defining the relocation types
R_RISCV_32_PCREL, R_RISCV_ADD32, R_RISCV_SUB32, R_RISCV_32 and
R_RISCV_64. riscv64 support also needs the __global_pointer$ symbol to
be defined right after the relocation tables in the data section.
Furthermore, the .got and .got.plt sections must be reversed. These 2
requirements are handled with runtime modifications of the default
linker script using the append_sed() function.
(1) For the .got.plt and .got sections order swap, append_sed() is used
to rename "(.got.plt)" to "(.got.tmp)" and to rename "(.got)" to
"(.got.plt)". A last call finalize the name swap by replacing
"(.got.tmp)" with "(.got)"
(2) For the global pointer synbol, a definition line starting with
"RISCV_GP" is added. The "RISCV_GP" string is removed if the target CPU
type is riscv64. The definition line is dropped for other CPU types.
With these changes, buildroot/busybox builds and run on NOMMU
systems with kernel 5.13. Tested on Canaan Kendryte K210 boards.
This patch is based on earlier work by Christoph Hellwig <hch@lst.de>.
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
---
elf2flt.c | 23 +++++++++++++++++++++++
elf2flt.ld.in | 9 +++++----
ld-elf2flt.c | 16 ++++++++++++++++
3 files changed, 44 insertions(+), 4 deletions(-)
diff --git a/elf2flt.c b/elf2flt.c
index f87f1fc..dbce467 100644
--- a/elf2flt.c
+++ b/elf2flt.c
@@ -80,6 +80,8 @@ const char *elf2flt_progname;
#include <elf/v850.h>
#elif defined(TARGET_xtensa)
#include <elf/xtensa.h>
+#elif defined(TARGET_riscv64)
+#include <elf/riscv.h>
#endif
#if defined(__MINGW32__)
@@ -122,6 +124,8 @@ const char *elf2flt_progname;
#define ARCH "nios2"
#elif defined(TARGET_xtensa)
#define ARCH "xtensa"
+#elif defined(TARGET_riscv64)
+#define ARCH "riscv64"
#else
#error "Don't know how to support your CPU architecture??"
#endif
@@ -797,6 +801,16 @@ output_relocs (
goto good_32bit_resolved_reloc;
default:
goto bad_resolved_reloc;
+#elif defined(TARGET_riscv64)
+ case R_RISCV_32_PCREL:
+ case R_RISCV_ADD32:
+ case R_RISCV_SUB32:
+ continue;
+ case R_RISCV_32:
+ case R_RISCV_64:
+ goto good_32bit_resolved_reloc;
+ default:
+ goto bad_resolved_reloc;
#else
default:
/* The default is to assume that the
@@ -1806,6 +1820,15 @@ int main(int argc, char *argv[])
if (!load_to_ram && !pfile)
load_to_ram = 1;
+#if defined(TARGET_riscv64)
+ /*
+ * riscv only supports loading text and data contiguously.
+ * So fail if load_to_ram is false.
+ */
+ if (!load_to_ram)
+ fatal("Loading to RAM ('-r' option) is required");
+#endif
+
fname = argv[argc-1];
if (pfile) {
diff --git a/elf2flt.ld.in b/elf2flt.ld.in
index ec1fe6f..c0c44b8 100644
--- a/elf2flt.ld.in
+++ b/elf2flt.ld.in
@@ -70,10 +70,11 @@ W_RODAT *(.gnu.linkonce.r*)
. = ALIGN(0x20) ;
LONG(-1)
. = ALIGN(0x20) ;
-R_RODAT *(.rodata)
-R_RODAT *(.rodata1)
-R_RODAT *(.rodata.*)
-R_RODAT *(.gnu.linkonce.r*)
+RISCV_GP: __global_pointer$ = . + 0x800 ;
+R_RODAT *(.rodata)
+R_RODAT *(.rodata1)
+R_RODAT *(.rodata.*)
+R_RODAT *(.gnu.linkonce.r*)
*(.data)
*(.data1)
*(.data.*)
diff --git a/ld-elf2flt.c b/ld-elf2flt.c
index e5de506..31b565f 100644
--- a/ld-elf2flt.c
+++ b/ld-elf2flt.c
@@ -324,6 +324,22 @@ static int do_final_link(void)
append_option(&other_options, concat(got_offset, "=", buf, NULL));
}
+ if (streq(TARGET_CPU, "riscv64")) {
+ /*
+ * The .got section must come before the .got.plt section
+ * (gcc/ld bug ?).
+ */
+ append_sed(&sed, "(.got.plt)", "(.got.tmp)");
+ append_sed(&sed, "(.got.plt)", "(.got)");
+ append_sed(&sed, "(.got.tmp)", "(.got.plt)");
+
+ /* The global pointer symbol is defined after the GOT. */
+ append_sed(&sed, "^RISCV_GP:", "");
+ } else {
+ /* Get rid of the global pointer definition. */
+ append_sed(&sed, "^RISCV_GP:", NULL);
+ }
+
/* Locate the default linker script, if we don't have one provided. */
if (!linker_script)
linker_script = concat(ldscriptpath, "/elf2flt.ld", NULL);
--
2.31.1
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