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Subject[RFC PATCH -tip 15/16] x86/kdb: Add x86 disassembe command
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Add a simple 'dis' command for x86 on KDB.
This command takes 2 arguments, the first one is the address
and the second one is the length of disassembling bytes.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu@gmail.com>
---
arch/x86/kernel/dumpstack.c | 6 ++--
arch/x86/kernel/kgdb.c | 72 +++++++++++++++++++++++++++++++++++++++++++
include/linux/kdb.h | 3 ++
kernel/debug/kdb/kdb_main.c | 35 +++++++++++++++++++++
4 files changed, 113 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 098e61a..1441efc 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -297,9 +297,9 @@ int __kprobes __die(const char *str, struct pt_regs *regs, long err)
#ifdef CONFIG_X86_DISASSEMBLER

/* Find the instruction boundary address */
-static unsigned long find_instruction_boundary(unsigned long saddr,
- unsigned long *poffs,
- char **modname, char *namebuf)
+unsigned long find_instruction_boundary(unsigned long saddr,
+ unsigned long *poffs,
+ char **modname, char *namebuf)
{
kprobe_opcode_t buf[MAX_INSN_SIZE];
unsigned long offs, addr, fixed;
diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c
index db6720e..0215a67 100644
--- a/arch/x86/kernel/kgdb.c
+++ b/arch/x86/kernel/kgdb.c
@@ -39,13 +39,17 @@
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/kgdb.h>
+#include <linux/kdb.h>
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/nmi.h>
#include <linux/hw_breakpoint.h>
+#include <linux/kallsyms.h>
+#include <linux/kprobes.h>

#include <asm/debugreg.h>
#include <asm/apicdef.h>
+#include <asm/disasm.h>
#include <asm/apic.h>
#include <asm/nmi.h>

@@ -751,3 +755,71 @@ struct kgdb_arch arch_kgdb_ops = {
.remove_all_hw_break = kgdb_remove_all_hw_break,
.correct_hw_break = kgdb_correct_hw_break,
};
+
+#if defined(CONFIG_X86_DISASSEMBLER)
+extern unsigned long find_instruction_boundary(unsigned long addr,
+ unsigned long *poffs,
+ char **modname, char *namebuf);
+
+static int kdb_disasm_printk(unsigned long addr, unsigned long *next)
+{
+ char buf[DISASM_STR_LEN];
+ u8 kbuf[MAX_INSN_SIZE];
+ struct insn insn;
+ unsigned long fixed;
+ int i, ret;
+ u8 *v = (u8 *)addr;
+
+ /* recover if the instruction is probed */
+ fixed = recover_probed_instruction(kbuf, addr);
+ kernel_insn_init(&insn, (void *)fixed);
+ insn_get_length(&insn);
+ insn.kaddr = (void *)addr;
+
+ kdb_printf("%p: ", v);
+ for (i = 0; i < MAX_INSN_SIZE / 2 && i < insn.length; i++)
+ kdb_printf("%02x ", ((u8 *)v)[i]);
+ if (i != MAX_INSN_SIZE / 2)
+ kdb_printf("%*s", 3 * (MAX_INSN_SIZE / 2 - i), " ");
+
+ /* print assembly code */
+ ret = disassemble(buf, DISASM_STR_LEN, &insn);
+ if (ret < 0)
+ return ret;
+ kdb_printf("%s%s\n", (fixed != addr) ? "(probed)" : "", buf);
+
+ if (i < insn.length) {
+ kdb_printf("%p: ", v + i);
+ for (; i < insn.length - 1; i++)
+ kdb_printf("%02x ", ((u8 *)v)[i]);
+ kdb_printf("%02x\n", ((u8 *)v)[i]);
+ }
+
+ if (next)
+ *next = addr + insn.length;
+
+ return 0;
+}
+
+int kdb_show_disasm(unsigned long addr, size_t len)
+{
+ unsigned long offs, eaddr = addr + len;
+ char buf[KSYM_NAME_LEN] = {0};
+ char *modname;
+
+ addr = find_instruction_boundary(addr, &offs, &modname, buf);
+ if (!addr)
+ return KDB_BADADDR;
+
+ if (modname)
+ kdb_printf("<%s+0x%lx [%s]>:\n", buf, offs, modname);
+ else
+ kdb_printf("<%s+0x%lx>:\n", buf, offs);
+
+ do {
+ kdb_disasm_printk(addr, &addr);
+ } while (addr < eaddr);
+
+ return 0;
+}
+#endif
diff --git a/include/linux/kdb.h b/include/linux/kdb.h
index 0647258..ff4b765 100644
--- a/include/linux/kdb.h
+++ b/include/linux/kdb.h
@@ -166,4 +166,7 @@ enum {
extern int kdbgetintenv(const char *, int *);
extern int kdb_set(int, const char **);

+/* Some architectures support disassembling in kernel */
+extern int kdb_show_disasm(unsigned long addr, size_t len);
+
#endif /* !_KDB_H */
diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index 67b847d..f09aca4 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -2672,6 +2672,39 @@ static int kdb_per_cpu(int argc, const char **argv)
return 0;
}

+int __weak kdb_show_disasm(unsigned long addr, size_t len)
+{
+ return KDB_NOTIMP;
+}
+
+/*
+ * kdb_dis - This function implements the 'dis' command.
+ */
+static int kdb_dis(int argc, const char **argv)
+{
+ int diag;
+ unsigned long addr;
+ long offset;
+ int nextarg;
+ unsigned long len;
+
+ if (argc > 3)
+ return KDB_ARGCOUNT;
+
+ nextarg = 1;
+ diag = kdbgetaddrarg(argc, argv, &nextarg, &addr, &offset, NULL);
+ if (diag)
+ return diag;
+
+ if (argc == 2) {
+ if (kstrtoul(argv[2], 0, &len) < 0)
+ return KDB_BADINT;
+ } else
+ len = 0;
+
+ return kdb_show_disasm(addr + offset, (size_t)len);
+}
+
/*
* display help for the use of cmd | grep pattern
*/
@@ -2899,6 +2932,8 @@ static void __init kdb_inittab(void)
"Display per_cpu variables", 3, KDB_REPEAT_NONE);
kdb_register_repeat("grephelp", kdb_grep_help, "",
"Display help on | grep", 0, KDB_REPEAT_NONE);
+ kdb_register_repeat("dis", kdb_dis, "<addr> [<len>]",
+ "Display disassmbled code", 2, KDB_REPEAT_NONE);
}

/* Execute any commands defined in kdb_cmds. */


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