Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   guoren@kernel.org
To:     guoren@kernel.org, palmer@dabbelt.com, arnd@arndb.de,
        anup@brainfault.org, gregkh@linuxfoundation.org,
        liush@allwinnertech.com, wefu@redhat.com, drew@beagleboard.org,
        wangjunqiang@iscas.ac.cn, hch@lst.de
Cc:     linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-riscv@lists.infradead.org, linux-csky@vger.kernel.org,
        linux-s390@vger.kernel.org, sparclinux@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, linux-parisc@vger.kernel.org,
        linux-mips@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        x86@kernel.org, Guo Ren <guoren@linux.alibaba.com>
Subject: [PATCH V6 15/20] riscv: compat: Add hw capability check for elf
Date:   Thu, 24 Feb 2022 16:54:05 +0800
Message-Id: <20220224085410.399351-16-guoren@kernel.org>
In-Reply-To: <20220224085410.399351-1-guoren@kernel.org>
References: <20220224085410.399351-1-guoren@kernel.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

From: Guo Ren <guoren@linux.alibaba.com>

Detect hardware COMPAT (32bit U-mode) capability in rv64. If not
support COMPAT mode in hw, compat_elf_check_arch would return
false by compat_binfmt_elf.c

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christoph Hellwig <hch@lst.de>
---
 arch/riscv/include/asm/elf.h |  3 ++-
 arch/riscv/kernel/process.c  | 26 ++++++++++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/include/asm/elf.h b/arch/riscv/include/asm/elf.h
index aee40040917b..3a4293dc7229 100644
--- a/arch/riscv/include/asm/elf.h
+++ b/arch/riscv/include/asm/elf.h
@@ -40,7 +40,8 @@
  * elf64_hdr e_machine's offset are different. The checker is
  * a little bit simple compare to other architectures.
  */
-#define compat_elf_check_arch(x) ((x)->e_machine == EM_RISCV)
+extern bool compat_elf_check_arch(Elf32_Ehdr *hdr);
+#define compat_elf_check_arch	compat_elf_check_arch
 
 #define CORE_DUMP_USE_REGSET
 #define ELF_EXEC_PAGESIZE	(PAGE_SIZE)
diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index 54787ca9806a..7bbe4dd95e85 100644
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -83,6 +83,32 @@ void show_regs(struct pt_regs *regs)
 		dump_backtrace(regs, NULL, KERN_DEFAULT);
 }
 
+#ifdef CONFIG_COMPAT
+static bool compat_mode_supported __read_mostly;
+
+bool compat_elf_check_arch(Elf32_Ehdr *hdr)
+{
+	return compat_mode_supported && hdr->e_machine == EM_RISCV;
+}
+
+static int __init compat_mode_detect(void)
+{
+	unsigned long tmp = csr_read(CSR_STATUS);
+
+	csr_write(CSR_STATUS, (tmp & ~SR_UXL) | SR_UXL_32);
+	compat_mode_supported =
+			(csr_read(CSR_STATUS) & SR_UXL) == SR_UXL_32;
+
+	csr_write(CSR_STATUS, tmp);
+
+	pr_info("riscv: ELF compat mode %s",
+			compat_mode_supported ? "supported" : "failed");
+
+	return 0;
+}
+early_initcall(compat_mode_detect);
+#endif
+
 void start_thread(struct pt_regs *regs, unsigned long pc,
 	unsigned long sp)
 {
-- 
2.25.1