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Re: [PATCH v4 1/3] xen/arm: add support for run_in_exception_handler()
Hi Juergen,
On 14/12/2020 07:56, Juergen Gross wrote:
Add support to run a function in an exception handler for Arm. Do it
the same way as on x86 via a bug_frame.
Unfortunately inline assembly on Arm seems to be less capable than on
x86, leading to functions called via run_in_exception_handler() having
to be globally visible.
Jan already commented on this, so I am not going to comment again.
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V4:
- new patch
I have verified the created bugframe is correct by inspecting the
created binary.
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
xen/arch/arm/traps.c | 10 +++++++++-
xen/drivers/char/ns16550.c | 3 ++-
xen/include/asm-arm/bug.h | 32 +++++++++++++++++++++-----------
3 files changed, 32 insertions(+), 13 deletions(-)
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 22bd1bd4c6..6e677affe2 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -1236,8 +1236,16 @@ int do_bug_frame(const struct cpu_user_regs *regs,
vaddr_t pc)
if ( !bug )
return -ENOENT;
+ if ( id == BUGFRAME_run_fn )
+ {
+ void (*fn)(const struct cpu_user_regs *) = bug_ptr(bug);
+
+ fn(regs);
+ return 0;
+ }
+
/* WARN, BUG or ASSERT: decode the filename pointer and line number. */
- filename = bug_file(bug);
+ filename = bug_ptr(bug);
if ( !is_kernel(filename) )
return -EINVAL;
fixup = strlen(filename);
diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c
index 9235d854fe..dd6500acc8 100644
--- a/xen/drivers/char/ns16550.c
+++ b/xen/drivers/char/ns16550.c
@@ -192,7 +192,8 @@ static void ns16550_interrupt(
/* Safe: ns16550_poll() runs as softirq so not reentrant on a given CPU. */
static DEFINE_PER_CPU(struct serial_port *, poll_port);
-static void __ns16550_poll(struct cpu_user_regs *regs)
+/* run_in_exception_handler() on Arm requires globally visible symbol. */
+void __ns16550_poll(struct cpu_user_regs *regs)
{
struct serial_port *port = this_cpu(poll_port);
struct ns16550 *uart = port->uart;
diff --git a/xen/include/asm-arm/bug.h b/xen/include/asm-arm/bug.h
index 36c803357c..a7da2c306f 100644
--- a/xen/include/asm-arm/bug.h
+++ b/xen/include/asm-arm/bug.h
@@ -15,34 +15,38 @@
struct bug_frame {
signed int loc_disp; /* Relative address to the bug address */
- signed int file_disp; /* Relative address to the filename */
+ signed int ptr_disp; /* Relative address to the filename or function */
signed int msg_disp; /* Relative address to the predicate (for ASSERT)
*/
uint16_t line; /* Line number */
uint32_t pad0:16; /* Padding for 8-bytes align */
};
#define bug_loc(b) ((const void *)(b) + (b)->loc_disp)
-#define bug_file(b) ((const void *)(b) + (b)->file_disp);
+#define bug_ptr(b) ((const void *)(b) + (b)->ptr_disp);
#define bug_line(b) ((b)->line)
#define bug_msg(b) ((const char *)(b) + (b)->msg_disp)
-#define BUGFRAME_warn 0
-#define BUGFRAME_bug 1
-#define BUGFRAME_assert 2
+#define BUGFRAME_run_fn 0
+#define BUGFRAME_warn 1
+#define BUGFRAME_bug 2
+#define BUGFRAME_assert 3
Why did you renumber it? IOW, why can't BUGFRAME_run_fn be defined as 3?
-#define BUGFRAME_NR 3
+#define BUGFRAME_NR 4
/* Many versions of GCC doesn't support the asm %c parameter which would
* be preferable to this unpleasantness. We use mergeable string
* sections to avoid multiple copies of the string appearing in the
* Xen image.
*/
-#define BUG_FRAME(type, line, file, has_msg, msg) do { \
+#define BUG_FRAME(type, line, ptr, ptr_is_file, has_msg, msg) do { \
BUILD_BUG_ON((line) >> 16); \
BUILD_BUG_ON((type) >= BUGFRAME_NR); \
asm ("1:"BUG_INSTR"\n" \
".pushsection .rodata.str, \"aMS\", %progbits, 1\n" \
- "2:\t.asciz " __stringify(file) "\n" \
+ "2:\n" \
+ ".if " #ptr_is_file "\n" \
+ "\t.asciz " __stringify(ptr) "\n" \
+ ".endif\n" \
"3:\n" \
".if " #has_msg "\n" \
"\t.asciz " #msg "\n" \
@@ -52,21 +56,27 @@ struct bug_frame {
"4:\n" \
".p2align 2\n" \
".long (1b - 4b)\n" \
+ ".if " #ptr_is_file "\n" \
".long (2b - 4b)\n" \
+ ".else\n" \
+ ".long (" #ptr " - 4b)\n" \
+ ".endif\n" \
".long (3b - 4b)\n" \
".hword " __stringify(line) ", 0\n" \
".popsection"); \
} while (0)
-#define WARN() BUG_FRAME(BUGFRAME_warn, __LINE__, __FILE__, 0, "")
+#define run_in_exception_handler(fn) BUG_FRAME(BUGFRAME_run_fn, 0, fn, 0, 0,
"")
+
+#define WARN() BUG_FRAME(BUGFRAME_warn, __LINE__, __FILE__, 1, 0, "")
#define BUG() do { \
- BUG_FRAME(BUGFRAME_bug, __LINE__, __FILE__, 0, ""); \
+ BUG_FRAME(BUGFRAME_bug, __LINE__, __FILE__, 1, 0, ""); \
unreachable(); \
} while (0)
#define assert_failed(msg) do { \
- BUG_FRAME(BUGFRAME_assert, __LINE__, __FILE__, 1, msg); \
+ BUG_FRAME(BUGFRAME_assert, __LINE__, __FILE__, 1, 1, msg); \
unreachable(); \
} while (0)
Cheers,
--
Julien Grall
|
