[PATCH V12 15/20] riscv: compat: Add hw capability check for elf

guoren
2022-04-05T07:15:15Z

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

Add CLASS to enhance (compat_)elf_check_arch to distinguish
32BIT/64BIT elf.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christoph Hellwig <hch@lst.de>
---
arch/riscv/include/asm/elf.h | 6 ++++--
arch/riscv/kernel/process.c | 28 ++++++++++++++++++++++++++++
2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/include/asm/elf.h b/arch/riscv/include/asm/elf.h
index a234656cfb5d..754fdb8cee96 100644
--- a/arch/riscv/include/asm/elf.h
+++ b/arch/riscv/include/asm/elf.h
@@ -33,9 +33,11 @@
/*
* This is used to ensure we don't load something for the wrong architecture.
*/
-#define elf_check_arch(x) ((x)->e_machine == EM_RISCV)
+#define elf_check_arch(x) (((x)->e_machine == EM_RISCV) && \
+ ((x)->e_ident[EI_CLASS] == ELF_CLASS))

-#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 b4421c16198c..1c7be865ab31 100644
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -84,6 +84,34 @@ 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 &&
+ hdr->e_ident[EI_CLASS] == ELFCLASS32;
+}
+
+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