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

From 3f1f323feb5cf25d8c80861991d0360784f4d2e6 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. To
define this symbol, the "RISCV_GP" line prefix is added. The "RISCV_GP"
string is removed if the target CPU type is riscv64 and the definition
line is dropped for other CPU types.

With these changes, buildroot and busybox build and run on riscv NOMMU
systems with Linux kernel including patch 6045ab5fea4c
("binfmt_flat: do not stop relocating GOT entries prematurely on riscv")
fixing the binfmt_flat loader. Tested on QEMU and 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     | 16 ++++++++++++++++
 elf2flt.ld.in |  1 +
 ld-elf2flt.c  |  8 ++++++++
 3 files changed, 25 insertions(+)

diff --git a/elf2flt.c b/elf2flt.c
index da25e93..a03ea3a 100644
--- a/elf2flt.c
+++ b/elf2flt.c
@@ -81,6 +81,8 @@ 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__)
@@ -123,6 +125,8 @@ 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
@@ -812,6 +816,18 @@ 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_ADD64:
+				case R_RISCV_SUB32:
+				case R_RISCV_SUB64:
+					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
diff --git a/elf2flt.ld.in b/elf2flt.ld.in
index e5aea14..950849e 100644
--- a/elf2flt.ld.in
+++ b/elf2flt.ld.in
@@ -106,6 +106,7 @@ W_RODAT:	*(.gnu.linkonce.r*)
 		. = ALIGN(0x20) ;
 		LONG(-1)
 		. = ALIGN(0x20) ;
+RISCV_GP:	__global_pointer$ = . + 0x800 ;
 R_RODAT:	*(.rodata)
 R_RODAT:	*(.rodata1)
 R_RODAT:	*(.rodata.*)
diff --git a/ld-elf2flt.c b/ld-elf2flt.c
index 7cb02d5..75ee1bb 100644
--- a/ld-elf2flt.c
+++ b/ld-elf2flt.c
@@ -324,6 +324,14 @@ static int do_final_link(void)
 		append_option(&other_options, concat(got_offset, "=", buf, NULL));
 	}
 
+	/* riscv adds a global pointer symbol to the linker file with the
+	   "RISCV_GP:" prefix. Remove the prefix for riscv64 architecture and
+	   the entire line for other architectures. */
+	if (streq(TARGET_CPU, "riscv64"))
+		append_sed(&sed, "^RISCV_GP:", "");
+	else
+		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);
-- 
2.36.1