[PATCH V6 15/20] riscv: compat: Add hw capability check for elf

guoren
2022-02-24T08:57:44Z

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