From 5948cb9b3e622e3c87216c7c6479f509c8aeb7c1 Mon Sep 17 00:00:00 2001

From: Tao Liu <ltao@redhat.com>

Date: Wed, 16 Nov 2022 17:36:03 +0800

Subject: [PATCH 18/28] Let gdb get kernel module symbols info from crash

Gdb will try to resolve an address to its corresponding symbol name such as

when printing a structure. It works fine for kernel symbols, because gdb can

find them through vmlinux. However as for kernel modules symbols, crash

resolves them by dig into "struct module", which gdb don't know. As a result,

gdb fails to translate a kernel module address to its symbol name without

"mod -s|-S" options. For example we can reproduce the issue as follows.

    crash> timer

    ....

    4331308176       336  ffff94ea24240860  ffffffffc03762c0  <estimation_timer>

    ....

    crash> sym 0xffffffffc03762c0

    ffffffffc03762c0 (t) estimation_timer [ip_vs]

Before patch:

    crash> timer_list ffff94ea24240860

    struct timer_list {

      ....

      function = 0xffffffffc03762c0,

      ....

    }

After patch:

    crash> timer_list ffff94ea24240860

    struct timer_list {

      ....

      function = 0xffffffffc03762c0 <estimation_timer>,

      ....

    }

In this patch, we add an interface for gdb, when gdb trying to build kernel

module's address symbolic, the info can be get from crash.

Signed-off-by: Tao Liu <ltao@redhat.com>

Signed-off-by: Lianbo Jiang <lijiang@redhat.com>

---

 defs.h          |  2 ++

 gdb-7.6.patch   | 33 +++++++++++++++++++++++++++++++++

 gdb_interface.c | 12 ++++++++++++

 3 files changed, 47 insertions(+)

diff --git a/defs.h b/defs.h

index f8fbfdfd1152..b7d76330141a 100644

--- a/defs.h

+++ b/defs.h

@@ -4877,6 +4877,7 @@ int patch_kernel_symbol(struct gnu_request *);

 struct syment *symbol_search(char *);

 int gdb_line_number_callback(ulong, ulong, ulong);

 int gdb_print_callback(ulong);

+char *gdb_lookup_module_symbol(ulong, ulong *);

 #endif

 #ifndef GDB_COMMON

@@ -7291,6 +7292,7 @@ int gdb_pass_through(char *, FILE *, ulong);

 int gdb_readmem_callback(ulong, void *, int, int);

 int gdb_line_number_callback(ulong, ulong, ulong);

 int gdb_print_callback(ulong);

+char *gdb_lookup_module_symbol(ulong, ulong *);

 void gdb_error_hook(void);

 void restore_gdb_sanity(void);

 int is_gdb_command(int, ulong);

diff --git a/gdb-7.6.patch b/gdb-7.6.patch

index c63ad7d81cb0..f1c3aa734241 100644

--- a/gdb-7.6.patch

+++ b/gdb-7.6.patch

@@ -2568,3 +2568,36 @@ diff -up gdb-7.6/opcodes/configure.orig gdb-7.6/opcodes/configure

  	$(CC_LD) $(INTERNAL_LDFLAGS) $(WIN32LDAPP) \

  		-o $(shell /bin/cat mergeobj) $(LIBGDB_OBS) \

  		$(TDEPLIBS) $(TUI_LIBRARY) $(CLIBS) $(LOADLIBES) $(shell /bin/cat mergelibs)

+--- gdb-7.6/gdb/printcmd.c.orig

++++ gdb-7.6/gdb/printcmd.c

+@@ -622,6 +622,10 @@ print_address_symbolic (struct gdbarch *gdbarch, CORE_ADDR addr,

+   return 1;

+ }

+

++#ifdef CRASH_MERGE

++extern char *gdb_lookup_module_symbol(unsigned long, unsigned long *);

++#endif

++

+ /* Given an address ADDR return all the elements needed to print the

+    address in a symbolic form.  NAME can be mangled or not depending

+    on DO_DEMANGLE (and also on the asm_demangle global variable,

+@@ -710,7 +714,19 @@ build_address_symbolic (struct gdbarch *gdbarch,

+	}

+     }

+   if (symbol == NULL && msymbol == NULL)

++#ifdef CRASH_MERGE

++  {

++    char *name_ptr = gdb_lookup_module_symbol(addr, (unsigned long *)offset);

++    if (name_ptr) {

++      *name = xstrdup (name_ptr);

++      return 0;

++    } else {

++      return 1;

++    }

++  }

++#else

+     return 1;

++#endif

+

+   /* If the nearest symbol is too far away, don't print anything symbolic.  */

+

diff --git a/gdb_interface.c b/gdb_interface.c

index 1f10006a2d63..f9d0018998df 100644

--- a/gdb_interface.c

+++ b/gdb_interface.c

@@ -945,6 +945,18 @@ gdb_print_callback(ulong addr)

 		return IS_KVADDR(addr);

 }

+char *

+gdb_lookup_module_symbol(ulong addr, ulong *offset)

+{

+	struct syment *sp;

+

+	if ((sp = value_search(addr, offset))) {

+		return sp->name;

+	} else {

+		return NULL;

+	}

+}

+

 /*

  *  Used by gdb_interface() to catch gdb-related errors, if desired.

  */

-- 

2.37.1