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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH] xen/arm: Correctly support WARN_ON
Currently the hypervisor will hang if it hits a WARN_ON.
The implemention uses an undefined instruction, made ourself because ARM
doesn't provide one, to implement BUG/ASSERT/WARN_ON, and sets up the
different tables (one for each type) which contain useful information.
This is based on the x86 implementation (include/asm-x86/bug.h). Unfortunately
the structure can't be shared because many ARM{32,64} gcc versions doesn't
correctly support %c. The support of executing a function in an exception
handler
is also keep unimplemented on ARM.
TODO:
I haven't yet hook the code on ARM64 as I'm not sure how undefined instruction
are handled. It looks like there is multiple way to get it via HSR.
Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
---
xen/arch/arm/arm32/traps.c | 2 +-
xen/arch/arm/traps.c | 96 +++++++++++++++++++++++++++++++++++++++
xen/arch/arm/xen.lds.S | 8 ++++
xen/include/asm-arm/bug.h | 72 +++++++++++++++++++++++++++--
xen/include/asm-arm/debugger.h | 2 +-
xen/include/asm-arm/processor.h | 2 +
6 files changed, 177 insertions(+), 5 deletions(-)
diff --git a/xen/arch/arm/arm32/traps.c b/xen/arch/arm/arm32/traps.c
index ff0b945..f79edcb 100644
--- a/xen/arch/arm/arm32/traps.c
+++ b/xen/arch/arm/arm32/traps.c
@@ -25,7 +25,7 @@
asmlinkage void do_trap_undefined_instruction(struct cpu_user_regs *regs)
{
- do_unexpected_trap("Undefined Instruction", regs);
+ do_undefined_instruction(regs);
}
asmlinkage void do_trap_supervisor_call(struct cpu_user_regs *regs)
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 686d8b7..921ae54 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -32,6 +32,7 @@
#include <xen/domain_page.h>
#include <public/sched.h>
#include <public/xen.h>
+#include <asm/debugger.h>
#include <asm/event.h>
#include <asm/regs.h>
#include <asm/cpregs.h>
@@ -1002,6 +1003,101 @@ void do_unexpected_trap(const char *msg, struct
cpu_user_regs *regs)
panic("CPU%d: Unexpected Trap: %s\n", smp_processor_id(), msg);
}
+int do_bug_frame(struct cpu_user_regs *regs, vaddr_t pc)
+{
+ const struct bug_frame *bug;
+ const char *prefix = "", *filename, *predicate;
+ unsigned long fixup;
+ int id, lineno;
+ static const struct bug_frame *const stop_frames[] = {
+ __stop_bug_frames_0,
+ __stop_bug_frames_1,
+ __stop_bug_frames_2,
+ NULL
+ };
+
+ for ( bug = __start_bug_frames, id = 0; stop_frames[id]; ++bug )
+ {
+ while ( unlikely(bug == stop_frames[id]) )
+ ++id;
+
+ if ( ((vaddr_t)bug_loc(bug)) == pc )
+ break;
+ }
+
+ if ( !stop_frames[id] )
+ return -ENOENT;
+
+ /* 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);
+
+ if ( debugger_trap_fatal(TRAP_invalid_op, regs) )
+ return 0;
+
+ show_execution_state(regs);
+ panic("Xen BUG at %s%s:%d", 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);
+ if ( debugger_trap_fatal(TRAP_invalid_op, regs) )
+ return 0;
+ show_execution_state(regs);
+ panic("Assertion '%s' failed at %s%s:%d",
+ predicate, prefix, filename, lineno);
+ }
+
+ return -EINVAL;
+}
+
+void do_undefined_instruction(struct cpu_user_regs *regs)
+{
+ uint64_t pc = regs->pc;
+ uint32_t instr;
+
+ if ( !is_kernel_text(pc) &&
+ (system_state >= SYS_STATE_active || !is_kernel_inittext(pc)) )
+ goto die;
+
+ /* PC is always 4-byte align, as Xen is using ARM instruction set */
+ instr = *((uint32_t *)regs->pc);
+ if ( instr != BUG_INSTR )
+ goto die;
+
+ if ( do_bug_frame(regs, regs->pc) )
+ goto die;
+
+ regs->pc += 4;
+ return;
+
+die:
+ do_unexpected_trap("undefined instruction", regs);
+}
+
typedef register_t (*arm_hypercall_fn_t)(
register_t, register_t, register_t, register_t, register_t);
diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S
index be55dad..c7a47c2 100644
--- a/xen/arch/arm/xen.lds.S
+++ b/xen/arch/arm/xen.lds.S
@@ -40,6 +40,14 @@ SECTIONS
. = ALIGN(PAGE_SIZE);
.rodata : {
_srodata = .; /* Read-only data */
+ /* Bug frames table */
+ __start_bug_frames = .;
+ *(.bug_frames.0)
+ __stop_bug_frames_0 = .;
+ *(.bug_frames.1)
+ __stop_bug_frames_1 = .;
+ *(.bug_frames.2)
+ __stop_bug_frames_2 = .;
*(.rodata)
*(.rodata.*)
_erodata = .; /* End of read-only data */
diff --git a/xen/include/asm-arm/bug.h b/xen/include/asm-arm/bug.h
index 458c818..0038df4 100644
--- a/xen/include/asm-arm/bug.h
+++ b/xen/include/asm-arm/bug.h
@@ -1,10 +1,76 @@
#ifndef __ARM_BUG_H__
#define __ARM_BUG_H__
-#define BUG() __bug(__FILE__, __LINE__)
-#define WARN() __warn(__FILE__, __LINE__)
+#include <xen/stringify.h>
-#endif /* __X86_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)
+
+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)
+
+#define BUGFRAME_warn 0
+#define BUGFRAME_bug 1
+#define BUGFRAME_assert 2
+
+/* ARM doesn't provide any undefined instruction, make our own based on
+ * a combination of bits which is not used by the instruction set
+ */
+#define BUG_INSTR 0xe7f000f0
+
+/* Many version 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 { \
+ BUILD_BUG_ON((line) >> 16); \
+ asm ("1:.word "__stringify(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" \
+ ".long (1b - 4b)\n" \
+ ".long (2b - 4b)\n" \
+ ".long (3b - 4b)\n" \
+ ".hword " __stringify(line) ", 0\n" \
+ ".popsection"); \
+} while (0)
+
+#define WARN() BUG_FRAME(BUGFRAME_warn, __LINE__, __FILE__, 0, "")
+
+#define BUG() do { \
+ BUG_FRAME(BUGFRAME_bug, __LINE__, __FILE__, 0, ""); \
+ unreachable(); \
+} while (0)
+
+#define assert_failed(msg) do { \
+ BUG_FRAME(BUGFRAME_assert, __LINE__, __FILE__, 1, msg); \
+ unreachable(); \
+} while (0)
+
+extern const struct bug_frame __start_bug_frames[],
+ __stop_bug_frames_0[],
+ __stop_bug_frames_1[],
+ __stop_bug_frames_2[];
+
+#endif /* __ARM_BUG_H__ */
/*
* Local variables:
* mode: C
diff --git a/xen/include/asm-arm/debugger.h b/xen/include/asm-arm/debugger.h
index 916860b..ac776ef 100644
--- a/xen/include/asm-arm/debugger.h
+++ b/xen/include/asm-arm/debugger.h
@@ -1,7 +1,7 @@
#ifndef __ARM_DEBUGGER_H__
#define __ARM_DEBUGGER_H__
-#define debugger_trap_fatal(v, r) ((void) 0)
+#define debugger_trap_fatal(v, r) (0)
#define debugger_trap_immediate() ((void) 0)
#endif /* __ARM_DEBUGGER_H__ */
diff --git a/xen/include/asm-arm/processor.h b/xen/include/asm-arm/processor.h
index 3be86f1..ff24ef0 100644
--- a/xen/include/asm-arm/processor.h
+++ b/xen/include/asm-arm/processor.h
@@ -480,6 +480,8 @@ void show_registers(struct cpu_user_regs *regs);
void do_unexpected_trap(const char *msg, struct cpu_user_regs *regs);
+void do_undefined_instruction(struct cpu_user_regs *regs);
+
void vcpu_regs_hyp_to_user(const struct vcpu *vcpu,
struct vcpu_guest_core_regs *regs);
void vcpu_regs_user_to_hyp(struct vcpu *vcpu,
--
1.7.10.4
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