[PATCH v1 1/4] xen: introduce CONFIG_GENERIC_BUG_FRAME

[Oleksii Kurochko <oleksii.kurochko@gmail.com>]

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 ARM was taken as the base version,
as it looks the most portable.

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>
---
 xen/common/Kconfig    |   6 ++
 xen/common/Makefile   |   1 +
 xen/common/bug.c      |  88 +++++++++++++++++++++++++++++
 xen/include/xen/bug.h | 127 ++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 222 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..811b4eaf3b 100644
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -92,6 +92,12 @@ config STATIC_MEMORY
 
 	  If unsure, say N.
 
+config GENERIC_DO_BUG_FRAME
+	bool
+	help
+	  Generic do_bug_frame() function is needed to handle the type of bug
+	  frame and print an information about it.
+
 menu "Speculative hardening"
 
 config INDIRECT_THUNK
diff --git a/xen/common/Makefile b/xen/common/Makefile
index bbd75b4be6..7d04c8d3b2 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_DO_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..393e58d571
--- /dev/null
+++ b/xen/common/bug.c
@@ -0,0 +1,88 @@
+#include <xen/bug.h>
+#include <xen/errno.h>
+#include <xen/types.h>
+#include <xen/kernel.h>
+#include <xen/string.h>
+#include <xen/virtual_region.h>
+
+#include <asm/processor.h>
+
+int do_bug_frame(const struct cpu_user_regs *regs, vaddr_t pc)
+{
+    const struct bug_frame *bug = NULL;
+    const char *prefix = "", *filename, *predicate;
+    unsigned long fixup;
+    int id = -1, lineno;
+    const struct virtual_region *region;
+
+    region = find_text_region(pc);
+    if ( region )
+    {
+        for ( id = 0; id < BUGFRAME_NR; id++ )
+        {
+            const struct bug_frame *b;
+            unsigned int i;
+
+            for ( i = 0, b = region->frame[id].bugs;
+                  i < region->frame[id].n_bugs; b++, i++ )
+            {
+                if ( ((vaddr_t)bug_loc(b)) == pc )
+                {
+                    bug = b;
+                    goto found;
+                }
+            }
+        }
+    }
+ found:
+    if ( !bug )
+        return -ENOENT;
+
+    if ( id == BUGFRAME_run_fn )
+    {
+        void (*fn)(const struct cpu_user_regs *) = (void *)regs->BUG_FN_REG;
+
+        fn(regs);
+        return 0;
+    }
+
+    /* WARN, BUG or ASSERT: decode the filename pointer and line number. */
+    filename = bug_file(bug);
+    if ( !is_kernel(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 0;
+
+    case BUGFRAME_bug:
+        printk("Xen BUG at %s%s:%d\n", prefix, filename, lineno);
+        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) )
+            predicate = "<unknown>";
+
+        printk("Assertion '%s' failed at %s%s:%d\n",
+               predicate, prefix, filename, lineno);
+        show_execution_state(regs);
+        panic("Assertion '%s' failed at %s%s:%d\n",
+              predicate, prefix, filename, lineno);
+    }
+
+    return -EINVAL;
+}
+
diff --git a/xen/include/xen/bug.h b/xen/include/xen/bug.h
new file mode 100644
index 0000000000..b46dae035e
--- /dev/null
+++ b/xen/include/xen/bug.h
@@ -0,0 +1,127 @@
+#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
+
+#ifndef __ASSEMBLY__
+
+#include <xen/errno.h>
+#include <xen/stringify.h>
+#include <xen/types.h>
+#include <xen/lib.h>
+
+#include <asm/bug.h>
+
+#ifndef BUG_FRAME_STUFF
+struct bug_frame {
+    signed int loc_disp;    /* Relative address to the bug address */
+    signed int file_disp;   /* Relative address to the filename */
+    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_line(b) ((b)->line)
+#define bug_msg(b) ((const char *)(b) + (b)->msg_disp)
+#endif /* BUG_FRAME_STUFF */
+
+#ifndef BUG_FRAME
+/* 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. BUGFRAME_run_fn needs to be handled separately.
+ */
+#define BUG_FRAME(type, line, 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"                               \
+         "3:\n"                                                             \
+         ".if " #has_msg "\n"                                               \
+         "\t.asciz " #msg "\n"                                              \
+         ".endif\n"                                                         \
+         ".popsection\n"                                                    \
+         ".pushsection .bug_frames." __stringify(type) ", \"a\", %progbits\n"\
+         "4:\n"                                                             \
+         ".p2align 2\n"                                                     \
+         ".long (1b - 4b)\n"                                                \
+         ".long (2b - 4b)\n"                                                \
+         ".long (3b - 4b)\n"                                                \
+         ".hword " __stringify(line) ", 0\n"                                \
+         ".popsection");                                                    \
+} while (0)
+#endif /* BUG_FRAME */
+
+#ifndef run_in_exception_handler
+/*
+ * GCC will not allow to use "i"  when PIE is enabled (Xen doesn't set the
+ * flag but instead rely on the default value from the compiler). So the
+ * easiest way to implement run_in_exception_handler() is to pass the to
+ * be called function in a fixed register.
+ */
+#define  run_in_exception_handler(fn) do {                                  \
+    register void *fn_ asm(__stringify(BUG_FN_REG)) = (fn);                 \
+    asm ("1:"BUG_INSTR"\n"                                                  \
+         ".pushsection .bug_frames." __stringify(BUGFRAME_run_fn) ","       \
+         "             \"a\", %%progbits\n"                                 \
+         "2:\n"                                                             \
+         ".p2align 2\n"                                                     \
+         ".long (1b - 2b)\n"                                                \
+         ".long 0, 0, 0\n"                                                  \
+         ".popsection" :: "r" (fn_));                                       \
+} while (0)
+#endif /* run_in_exception_handler */
+
+#ifndef WARN
+#define WARN() BUG_FRAME(BUGFRAME_warn, __LINE__, __FILE__, 0, "")
+#endif /* WARN */
+
+#ifndef BUG
+#define BUG() do {                                              \
+    BUG_FRAME(BUGFRAME_bug,  __LINE__, __FILE__, 0, "");        \
+    unreachable();                                              \
+} while (0)
+#endif
+
+#ifndef assert_failed
+#define assert_failed(msg) do {                                 \
+    BUG_FRAME(BUGFRAME_assert, __LINE__, __FILE__, 1, msg);     \
+    unreachable();                                              \
+} while (0)
+#endif
+
+extern const struct bug_frame __start_bug_frames[],
+                              __stop_bug_frames_0[],
+                              __stop_bug_frames_1[],
+                              __stop_bug_frames_2[],
+                              __stop_bug_frames_3[];
+
+#else /* !__ASSEMBLY__ */
+
+#ifdef CONFIG_X86
+#include <asm/bug.h>
+#endif
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* __XEN_BUG_H__ */
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
-- 
2.39.0