kumquat-buildroot/package/elf2flt/0004-elf2flt-add-riscv-64-bits-support.patch

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