xen: introduce CONFIG_GENERIC_BUG_FRAME

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@gmail.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Tested-by: Julien Grall <jgrall@amazon.com>
Acked-by: Julien Grall <jgrall@amazon.com>

xen/common/Kconfig

@@ -29,6 +29,9 @@ config ALTERNATIVE_CALL
 config ARCH_MAP_DOMAIN_PAGE
 	bool
 
+config GENERIC_BUG_FRAME
+	bool
+
 config HAS_ALTERNATIVE
 	bool
 

xen/common/Makefile

 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

xen/common/bug.c

+#include <xen/bug.h>
+/*
+ * Ideally <xen/debugger.h> should be included in <asm/bug.h>
+ * but an issue with compilation can occur as <xen/debugger.h> uses
+ * BUG/ASSERT/etc macros inside but they will be defined later in
+ * <xen/bug.h> after return from inclusion of <asm/bug.h>:
+ * 
+ * <xen/bug.h>:
+ *  ...
+ *   <asm/bug.h>:
+ *     ...
+ *     <xen/debugger.h> -> some of included header in it uses BUG/ASSERT/etc
+ *     ...
+ *  ...
+ *  #define BUG() ...
+ *  ...
+ *  #define ASSERT() ...
+ *  ...
+ */
+#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>
+
+/*
+ * Returns a negative value in case of an error otherwise
+ * BUGFRAME_{run_fn, warn, bug, assert}
+ */
+int do_bug_frame(struct cpu_user_regs *regs, unsigned long pc)
+{
+    const struct bug_frame *bug = NULL;
+    const struct virtual_region *region;
+    const char *prefix = "", *filename, *predicate;
+    unsigned long fixup;
+    unsigned int id, lineno;
+
+    region = find_text_region(pc);
+    if ( !region )
+        return -EINVAL;
+
+    for ( id = 0; id < BUGFRAME_NR; id++ )
+    {
+        const struct bug_frame *b;
+        size_t i;
+
+        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 -ENOENT;
+
+    if ( id == BUGFRAME_run_fn )
+    {
+        void (*fn)(struct cpu_user_regs *) = bug_ptr(bug);
+
+        fn(regs);
+
+        /* Re-enforce consistent types, because of the casts involved. */
+        if ( false )
+            run_in_exception_handler(fn);
+
+        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);
+
+        break;
+
+    case BUGFRAME_bug:
+        printk("Xen BUG at %s%s:%d\n", prefix, filename, lineno);
+
+        if ( BUG_DEBUGGER_TRAP_FATAL(regs) )
+            break;
+
+        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 ( BUG_DEBUGGER_TRAP_FATAL(regs) )
+            break;
+
+        show_execution_state(regs);
+        panic("Assertion '%s' failed at %s%s:%d\n",
+              predicate, prefix, filename, lineno);
+    }
+
+    return id;
+}

xen/include/xen/bug.h

+#ifndef __XEN_BUG_H__
+#define __XEN_BUG_H__
+
+#define BUGFRAME_run_fn 0
+#define BUGFRAME_warn   1
+#define BUGFRAME_bug    2
+#define BUGFRAME_assert 3
+
+#define BUGFRAME_NR     4
+
+#define BUG_DISP_WIDTH    24
+#define BUG_LINE_LO_WIDTH (31 - BUG_DISP_WIDTH)
+#define BUG_LINE_HI_WIDTH (31 - BUG_DISP_WIDTH)
+
+#include <asm/bug.h>
+
+#ifndef __ASSEMBLY__
+
+#ifndef BUG_DEBUGGER_TRAP_FATAL
+#define BUG_DEBUGGER_TRAP_FATAL(regs) 0
+#endif
+
+#include <xen/lib.h>
+
+#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[];
+};
+
+#define bug_loc(b) ((unsigned long)(b) + (b)->loc_disp)
+
+#define bug_ptr(b) ((const void *)(b) + (b)->ptr_disp)
+
+#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)))
+
+#define bug_msg(b) ((const char *)(b) + (b)->msg_disp[1])
+
+#define BUG_CHECK_LINE_WIDTH(line) \
+    BUILD_BUG_ON((line) >> (BUG_LINE_LO_WIDTH + BUG_LINE_HI_WIDTH))
+
+#elif !defined(BUG_CHECK_LINE_WIDTH)
+
+#define BUG_CHECK_LINE_WIDTH(line) ((void)(line))
+
+#endif /* BUG_FRAME_STRUCT */
+
+
+/*
+ * Some architectures mark immediate instruction operands in a special way.
+ * In such cases the special marking may need omitting when specifying
+ * directive operands. Allow architectures to specify a suitable
+ * modifier.
+ */
+#ifndef BUG_ASM_CONST
+#define BUG_ASM_CONST ""
+#endif
+
+#ifndef _ASM_BUGFRAME_TEXT
+
+#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 */
+
+#ifndef BUG_FRAME
+
+#define BUG_FRAME(type, line, ptr, second_frame, msg) do {                   \
+    BUG_CHECK_LINE_WIDTH(line);                                           \
+    BUILD_BUG_ON((type) >= BUGFRAME_NR);                                     \
+    asm volatile ( _ASM_BUGFRAME_TEXT(second_frame)                          \
+                   :: _ASM_BUGFRAME_INFO(type, line, ptr, msg) );            \
+} while ( false )
+
+#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 ( false )
+
+#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 ( false )
+#endif
+
+#ifndef assert_failed
+#define assert_failed(msg) do {                                 \
+    BUG_FRAME(BUGFRAME_assert, __LINE__, __FILE__, 1, msg);     \
+    unreachable();                                              \
+} while ( false )
+#endif
+
+#ifdef CONFIG_GENERIC_BUG_FRAME
+
+struct cpu_user_regs;
+
+/*
+ * Returns a negative value in case of an error otherwise
+ * BUGFRAME_{run_fn, warn, bug, assert}
+ */
+int do_bug_frame(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:
+ */