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Re: [PATCH v3 1/4] xen: introduce CONFIG_GENERIC_BUG_FRAME
Hi Oleksii,
On 24/02/2023 11:31, Oleksii Kurochko wrote:
A large part of the content of the bug.h is repeated among all
architectures, so it was decided to create a new config
CONFIG_GENERIC_BUG_FRAME.
The version of <bug.h> from x86 was taken as the base version.
The patch introduces the following stuff:
* common bug.h header
* generic implementation of do_bug_frame
* new config CONFIG_GENERIC_BUG_FRAME
Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
Changes in V3:
* Add debugger_trap_fatal() to do_bug_frame(). It simplifies usage of
do_bug_frame() for x86 so making handle_bug_frame() and find_bug_frame()
not needed anymore.
* Update do_bug_frame() to return -EINVAL if something goes wrong; otherwise
id of bug_frame
* Update _ASM_BUGFRAME_TEXT to make it more portable.
* Drop unnecessary comments.
* define stub value for TRAP_invalid_op in case if wasn't defined in
arch-specific folders.
---
Changes in V2:
- Switch to x86 implementation as generic as it is more compact
( at least from the point of view of bug frame structure ).
- Rename CONFIG_GENERIC_DO_BUG_FRAME to CONFIG_GENERIC_BUG_FRAME.
- Change the macro bug_loc(b) to avoid the need for a cast:
#define bug_loc(b) ((unsigned long)(b) + (b)->loc_disp)
- Rename BUG_FRAME_STUFF to BUG_FRAME_STRUCT
- Make macros related to bug frame structure more generic.
- Introduce BUG_INSTR and MODIFIER to make _ASM_BUGFRAME_TEXT reusable
between x86 and RISC-V.
- Rework do_bug_frame() and introduce find_bug_frame() and handle_bug_frame()
functions to make it reusable by x86.
- code style fixes
---
xen/common/Kconfig | 3 +
xen/common/Makefile | 1 +
xen/common/bug.c | 109 ++++++++++++++++++++++++++++++
xen/include/xen/bug.h | 150 ++++++++++++++++++++++++++++++++++++++++++
4 files changed, 263 insertions(+)
create mode 100644 xen/common/bug.c
create mode 100644 xen/include/xen/bug.h
diff --git a/xen/common/Kconfig b/xen/common/Kconfig
index f1ea3199c8..b226323537 100644
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -28,6 +28,9 @@ config ALTERNATIVE_CALL
config ARCH_MAP_DOMAIN_PAGE
bool
+config GENERIC_BUG_FRAME
+ bool
+
config HAS_ALTERNATIVE
bool
diff --git a/xen/common/Makefile b/xen/common/Makefile
index bbd75b4be6..46049eac35 100644
--- a/xen/common/Makefile
+++ b/xen/common/Makefile
@@ -1,5 +1,6 @@
obj-$(CONFIG_ARGO) += argo.o
obj-y += bitmap.o
+obj-$(CONFIG_GENERIC_BUG_FRAME) += bug.o
obj-$(CONFIG_HYPFS_CONFIG) += config_data.o
obj-$(CONFIG_CORE_PARKING) += core_parking.o
obj-y += cpu.o
diff --git a/xen/common/bug.c b/xen/common/bug.c
new file mode 100644
index 0000000000..f81724fc9b
--- /dev/null
+++ b/xen/common/bug.c
@@ -0,0 +1,109 @@
+#include <xen/bug.h>
+#include <xen/debugger.h>
+#include <xen/errno.h>
+#include <xen/kernel.h>
+#include <xen/livepatch.h> > +#include <xen/string.h>
+#include <xen/types.h>
+#include <xen/virtual_region.h>
+
+#include <asm/processor.h>
+
+/* Set default value for TRAP_invalid_op as it is defined only for X86 now */
+#ifndef TRAP_invalid_op
+#define TRAP_invalid_op 0
+#endif
It feels to me that this value should be defined in the else part in
xen/debugger.h.
+
+int do_bug_frame(const struct cpu_user_regs *regs, unsigned long pc)
I would suggest to document what this function is meant to return.
AFAUI, it would return a negative value in case of an error otherwise
the bug type.
+{
+ const struct bug_frame *bug = NULL;
+ const struct virtual_region *region;
+ const char *prefix = "", *filename, *predicate;
+ unsigned long fixup;
+ unsigned int id = BUGFRAME_NR, lineno;
+
+ region = find_text_region(pc);
+ if ( region )
NIT: If you invert the condition here, then you can reduce the indention
by one below.
+ {
+ for ( id = 0; id < BUGFRAME_NR; id++ )
+ {
+ const struct bug_frame *b;
+ unsigned int i;
You compare this against n_bugs which is a size_t. So, this wants to be
a size_t.
+
+ for ( i = 0, b = region->frame[id].bugs;
+ i < region->frame[id].n_bugs; b++, i++ )
+ {
+ if ( bug_loc(b) == pc )
+ {
+ bug = b;
+ goto found;
+ }
+ }
+ }
+ }
+
+ found:
+ if ( !bug )
+ return -EINVAL;
+
+ if ( id == BUGFRAME_run_fn )
+ {
+#ifdef BUG_FN_REG
+ void (*fn)(const struct cpu_user_regs *) = (void *)regs->BUG_FN_REG;
AFAIU, this is necessary so Arm can use the generic do_bug_frame().
I was under the impression that RISC-V and Arm had the similar issue
with %c. It seems like you managed to resolve it on RISC-V, so can we
fully switch Arm to the generic implementation of bug?
+#else
+ void (*fn)(const struct cpu_user_regs *) = bug_ptr(bug);
+#endif
+
+ fn(regs);
+
+ return id;
+ }
+
+ /* WARN, BUG or ASSERT: decode the filename pointer and line number. */
+ filename = bug_ptr(bug);
+ if ( !is_kernel(filename) && !is_patch(filename) )
+ return -EINVAL;
+ fixup = strlen(filename);
+ if ( fixup > 50 )
+ {
+ filename += fixup - 47;
+ prefix = "...";
+ }
+ lineno = bug_line(bug);
+
+ switch ( id )
+ {
+ case BUGFRAME_warn:
+ printk("Xen WARN at %s%s:%d\n", prefix, filename, lineno);
+ show_execution_state(regs);
+
+ return id;
+
+ case BUGFRAME_bug:
+ printk("Xen BUG at %s%s:%d\n", prefix, filename, lineno);
+
+ if ( debugger_trap_fatal(TRAP_invalid_op, regs) )
+ return id;
+
+ show_execution_state(regs);
+ panic("Xen BUG at %s%s:%d\n", prefix, filename, lineno);
+
+ case BUGFRAME_assert:
+ /* ASSERT: decode the predicate string pointer. */
+ predicate = bug_msg(bug);
+ if ( !is_kernel(predicate) && !is_patch(predicate) )
+ predicate = "<unknown>";
+
+ printk("Assertion '%s' failed at %s%s:%d\n",
+ predicate, prefix, filename, lineno);
+
+ if ( debugger_trap_fatal(TRAP_invalid_op, regs) )
+ return id;
+
+ show_execution_state(regs);
+ panic("Assertion '%s' failed at %s%s:%d\n",
+ predicate, prefix, filename, lineno);
+ }
+
+ return id;
+}
diff --git a/xen/include/xen/bug.h b/xen/include/xen/bug.h
new file mode 100644
index 0000000000..4b18cfa69c
--- /dev/null
+++ b/xen/include/xen/bug.h
@@ -0,0 +1,150 @@
+#ifndef __XEN_BUG_H__
+#define __XEN_BUG_H__
+
+#define BUG_DISP_WIDTH 24
+#define BUG_LINE_LO_WIDTH (31 - BUG_DISP_WIDTH)
+#define BUG_LINE_HI_WIDTH (31 - BUG_DISP_WIDTH)
+
+#define BUGFRAME_run_fn 0
+#define BUGFRAME_warn 1
+#define BUGFRAME_bug 2
+#define BUGFRAME_assert 3
+
+#define BUGFRAME_NR 4
+
+#include <asm/bug.h>
+
+#ifndef __ASSEMBLY__
+
+#include <xen/errno.h>
errno.h doesn't look to be used within this here. So is it necessary to
import it?
+#include <xen/lib.h>
Why is this necessary to include in the header?
+#include <xen/stringify.h>
You don't seem to use __stringify in this header. So is this necessary?
+
+#ifndef BUG_FRAME_STRUCT
+
+struct bug_frame {
+ signed int loc_disp:BUG_DISP_WIDTH;
+ unsigned int line_hi:BUG_LINE_HI_WIDTH;
+ signed int ptr_disp:BUG_DISP_WIDTH;
+ unsigned int line_lo:BUG_LINE_LO_WIDTH;
+ signed int msg_disp[];
+};
+
+#endif /* BUG_FRAME_STRUCT */
+
+#ifndef bug_loc
+#define bug_loc(b) ((unsigned long)(b) + (b)->loc_disp)
+#endif
+
+#ifndef bug_ptr
+#define bug_ptr(b) ((const void *)(b) + (b)->ptr_disp)
+#endif
+
+#ifndef bug_line
+#define bug_line(b) (((((b)->line_hi + ((b)->loc_disp < 0)) & \
+ ((1 << BUG_LINE_HI_WIDTH) - 1)) << \
+ BUG_LINE_LO_WIDTH) + \
+ (((b)->line_lo + ((b)->ptr_disp < 0)) & \
+ ((1 << BUG_LINE_LO_WIDTH) - 1)))
+#endif
+
+#ifndef bug_msg
+#define bug_msg(b) ((const char *)(b) + (b)->msg_disp[1])
+#endif
For all the macro above, it feels wrong to me to allow an architecture
to override them if the default BUG_FRAME_STRUCT.
It would also feels wrong to me that if the default BUG_FRAME_STRUCT is
not used to still partially rely on the generic version of the helper.\
So I would suggest to move them in the #ifndef BUG_FRAME_STRUCT and drop
the #ifndef <helper>.
+
+#ifndef BUG_ASM_CONST
+#define BUG_ASM_CONST ""
+#endif
This line is a bit misterious to me. Would you be able to outline why an
architecture would override this?
+
+#if !defined(_ASM_BUGFRAME_TEXT) || !defined(_ASM_BUGFRAME_INFO)
+
+#define _ASM_BUGFRAME_TEXT(second_frame)
\
+ ".Lbug%=:"BUG_INSTR"\n"
\
+ " .pushsection .bug_frames.%"BUG_ASM_CONST"[bf_type], \"a\",
%%progbits\n" \
+ " .p2align 2\n"
\
+ ".Lfrm%=:\n"
\
+ " .long (.Lbug%= - .Lfrm%=) + %"BUG_ASM_CONST"[bf_line_hi]\n"
\
+ " .long (%"BUG_ASM_CONST"[bf_ptr] - .Lfrm%=) +
%"BUG_ASM_CONST"[bf_line_lo]\n"\
+ " .if " #second_frame "\n"
\
+ " .long 0, %"BUG_ASM_CONST"[bf_msg] - .Lfrm%=\n"
\
+ " .endif\n"
\
+ " .popsection\n"
+
+#define _ASM_BUGFRAME_INFO(type, line, ptr, msg) \
+ [bf_type] "i" (type), \
+ [bf_ptr] "i" (ptr), \
+ [bf_msg] "i" (msg), \
+ [bf_line_lo] "i" ((line & ((1 << BUG_LINE_LO_WIDTH) - 1)) \
+ << BUG_DISP_WIDTH), \
+ [bf_line_hi] "i" (((line) >> BUG_LINE_LO_WIDTH) << BUG_DISP_WIDTH)
+
+#endif /* _ASM_BUGFRAME_TEXT || _ASM_BUGFRAME_INFO */
+
+#ifndef BUG_FRAME
+
+#define BUG_FRAME(type, line, ptr, second_frame, msg) do { \
+ BUILD_BUG_ON((line) >> (BUG_LINE_LO_WIDTH + BUG_LINE_HI_WIDTH)); \
+ BUILD_BUG_ON((type) >= BUGFRAME_NR); \
+ asm volatile ( _ASM_BUGFRAME_TEXT(second_frame) \
+ :: _ASM_BUGFRAME_INFO(type, line, ptr, msg) ); \
+} while (0)
+
+#endif
+
+#ifndef run_in_exception_handler
+
+/*
+ * TODO: untangle header dependences, break BUILD_BUG_ON() out of xen/lib.h,
+ * and use a real static inline here to get proper type checking of fn().
+ */
+#define run_in_exception_handler(fn) \
+ do { \
+ (void)((fn) == (void (*)(struct cpu_user_regs *))NULL); \
+ BUG_FRAME(BUGFRAME_run_fn, 0, fn, 0, NULL); \
+ } while ( 0 )
+
+#endif /* run_in_exception_handler */
+
+#ifndef WARN
+#define WARN() BUG_FRAME(BUGFRAME_warn, __LINE__, __FILE__, 0, NULL)
+#endif
+
+#ifndef BUG
+#define BUG() do { \
+ BUG_FRAME(BUGFRAME_bug, __LINE__, __FILE__, 0, NULL); \
+ unreachable(); \
+} while (0)
+#endif
+
+#ifndef assert_failed
+#define assert_failed(msg) do { \
+ BUG_FRAME(BUGFRAME_assert, __LINE__, __FILE__, 1, msg); \
+ unreachable(); \
+} while (0)
+#endif
+
+#ifdef CONFIG_GENERIC_BUG_FRAME
+
+struct cpu_user_regs;
+
+int do_bug_frame(const struct cpu_user_regs *regs, unsigned long pc);
+
+#endif /* CONFIG_GENERIC_BUG_FRAME */
+
+extern const struct bug_frame __start_bug_frames[],
+ __stop_bug_frames_0[],
+ __stop_bug_frames_1[],
+ __stop_bug_frames_2[],
+ __stop_bug_frames_3[];
+
+#endif /* !__ASSEMBLY__ */
+
+#endif /* __XEN_BUG_H__ */
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
Cheers,
--
Julien Grall
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