riscv: allow resume after exception
If CSRs like seed are readable by S-mode, may not be determinable by
S-mode. For safe driver probing allow to resume via a longjmp after an
exception.
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
diff --git a/arch/riscv/lib/interrupts.c b/arch/riscv/lib/interrupts.c
index 02dbcfd..a26ccc7 100644
--- a/arch/riscv/lib/interrupts.c
+++ b/arch/riscv/lib/interrupts.c
@@ -12,6 +12,7 @@
#include <linux/compat.h>
#include <efi_loader.h>
#include <hang.h>
+#include <interrupt.h>
#include <irq_func.h>
#include <asm/global_data.h>
#include <asm/ptrace.h>
@@ -21,6 +22,13 @@
DECLARE_GLOBAL_DATA_PTR;
+static struct resume_data *resume;
+
+void set_resume(struct resume_data *data)
+{
+ resume = data;
+}
+
static void show_efi_loaded_images(uintptr_t epc)
{
efi_print_image_infos((void *)epc);
@@ -105,6 +113,11 @@
"Store/AMO page fault",
};
+ if (resume) {
+ resume->code = code;
+ longjmp(resume->jump, 1);
+ }
+
if (code < ARRAY_SIZE(exception_code))
printf("Unhandled exception: %s\n", exception_code[code]);
else
diff --git a/doc/api/index.rst b/doc/api/index.rst
index 2f0218c..51b2013 100644
--- a/doc/api/index.rst
+++ b/doc/api/index.rst
@@ -12,6 +12,7 @@
efi
event
getopt
+ interrupt
linker_lists
lmb
logging
diff --git a/doc/api/interrupt.rst b/doc/api/interrupt.rst
new file mode 100644
index 0000000..5721231
--- /dev/null
+++ b/doc/api/interrupt.rst
@@ -0,0 +1,6 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+Interrupt API
+=============
+
+.. kernel-doc:: include/interrupt.h
diff --git a/include/interrupt.h b/include/interrupt.h
new file mode 100644
index 0000000..46ef2e1
--- /dev/null
+++ b/include/interrupt.h
@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include <asm/setjmp.h>
+
+/**
+ * struct resume_data - data for resume after interrupt
+ */
+struct resume_data {
+ /** @jump: longjmp buffer */
+ jmp_buf jump;
+ /** @code: exception code */
+ ulong code;
+};
+
+/**
+ * set_resume() - set longjmp buffer for resuming after exception
+ *
+ * By calling this function it is possible to use a long jump to catch an
+ * exception. The caller sets the long jump buffer with set_resume() and then
+ * executes setjmp(). If an exception occurs, the code will return to the
+ * setjmp caller(). The exception code will be returned in @data->code.
+ *
+ * After the critical operation call set_resume(NULL) so that an exception in
+ * another part of the code will not accidently invoke the long jump.
+ *
+ * .. code-block:: c
+ *
+ * // This example shows how to use set_resume().
+ *
+ * struct resume_data resume;
+ * int ret;
+ *
+ * set_resume(&resume);
+ * ret = setjmp(resume.jump);
+ * if (ret) {
+ * printf("An exception %ld occurred\n", resume.code);
+ * } else {
+ * // Do what might raise an exception here.
+ * }
+ * set_resume(NULL);
+ *
+ * @data: pointer to structure with longjmp address
+ * Return: 0 before an exception, 1 after an exception occurred
+ */
+void set_resume(struct resume_data *data);