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Subject[PATCH 09/13] riscv: compat: init: Add hw-cap detect in setup_arch
Date
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>
---
arch/riscv/include/asm/elf.h | 5 ++++-
arch/riscv/include/asm/processor.h | 1 +
arch/riscv/kernel/process.c | 22 ++++++++++++++++++++++
arch/riscv/kernel/setup.c | 5 +++++
4 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/include/asm/elf.h b/arch/riscv/include/asm/elf.h
index 37f1cbdaa242..6baa49c4fba1 100644
--- a/arch/riscv/include/asm/elf.h
+++ b/arch/riscv/include/asm/elf.h
@@ -35,7 +35,10 @@
*/
#define elf_check_arch(x) ((x)->e_machine == EM_RISCV)

-#define compat_elf_check_arch(x) ((x)->e_machine == EM_RISCV)
+#ifdef CONFIG_COMPAT
+extern bool compat_elf_check_arch(Elf32_Ehdr *hdr);
+#define compat_elf_check_arch compat_elf_check_arch
+#endif

#define CORE_DUMP_USE_REGSET
#define ELF_EXEC_PAGESIZE (PAGE_SIZE)
diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
index 9544c138d9ce..8b288ac0d704 100644
--- a/arch/riscv/include/asm/processor.h
+++ b/arch/riscv/include/asm/processor.h
@@ -64,6 +64,7 @@ extern void start_thread(struct pt_regs *regs,
#ifdef CONFIG_COMPAT
extern void compat_start_thread(struct pt_regs *regs,
unsigned long pc, unsigned long sp);
+extern void compat_mode_detect(void);

#define DEFAULT_MAP_WINDOW_64 TASK_SIZE_64
#else
diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index 9ebf9a95e5ea..496d09c5d384 100644
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -101,6 +101,28 @@ void start_thread(struct pt_regs *regs, unsigned long pc,
}

#ifdef CONFIG_COMPAT
+static bool compat_mode_support __read_mostly = false;
+
+bool compat_elf_check_arch(Elf32_Ehdr *hdr)
+{
+ if (compat_mode_support && (hdr->e_machine == EM_RISCV))
+ return true;
+
+ return false;
+}
+
+void compat_mode_detect(void)
+{
+ csr_write(CSR_STATUS, (csr_read(CSR_STATUS) & ~SR_UXL) | SR_UXL_32);
+
+ if ((csr_read(CSR_STATUS) & SR_UXL) != SR_UXL_32)
+ return;
+
+ compat_mode_support = true;
+
+ pr_info("riscv: compat: 32bit U-mode applications support\n");
+}
+
void compat_start_thread(struct pt_regs *regs, unsigned long pc,
unsigned long sp)
{
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index b42bfdc67482..be131219d549 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -12,6 +12,7 @@
#include <linux/mm.h>
#include <linux/memblock.h>
#include <linux/sched.h>
+#include <linux/compat.h>
#include <linux/console.h>
#include <linux/screen_info.h>
#include <linux/of_fdt.h>
@@ -294,6 +295,10 @@ void __init setup_arch(char **cmdline_p)
setup_smp();
#endif

+#ifdef CONFIG_COMPAT
+ compat_mode_detect();
+#endif
+
riscv_fill_hwcap();
}

--
2.25.1
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