Hi, Tao
Thanks for the comments.
On Wed, Apr 3, 2024 at 11:45 AM Tao Liu <ltao@xxxxxxxxxx> wrote:
Hi Lianbo,
On Wed, Mar 6, 2024 at 2:32 PM Lianbo Jiang <lijiang@xxxxxxxxxx> wrote:
>
> Some objects format may potentially support copy relocations, but
> currently the maybe_copied is always initialized to 0 in the symbol().
> And the type is 'mst_file_bss', not always the 'mst_bss' or 'mst_data'
> in the lookup_minimal_symbol_linkage(). For example:
>
> (gdb) p *msymbol
> $42 = {<general_symbol_info> = {m_name = 0x349812f "test_no_static", value = {ivalue = 8, block = 0x8,
> bytes = 0x8 <error: Cannot access memory at address 0x8>, address = 8, common_block = 0x8, chain = 0x8}, language_specific = {
> obstack = 0x0, demangled_name = 0x0}, m_language = language_auto, ada_mangled = 0, section = 20}, size = 4,
> filename = 0x6db3440 "test_sanity.c", type = mst_file_bss, created_by_gdb = 0, target_flag_1 = 0, target_flag_2 = 0, has_size = 1,
> maybe_copied = 0, name_set = 1, hash_next = 0x0, demangled_hash_next = 0x0}
>
The whole bug is around test_no_static, which is a static variable in
the ko. However the added code to lookup_minimal_symbol_linkage() is
mst_file_bss/mst_file_data. So I guess test_no_static's symbol type
Just to be safe I added the type 'mst_file_data' check, because there might be a similar situation, but I can not prove it for the time being. Do you have any specific concerns about it?
should be one of the 2 right? If that is the case, I suggest printing
"test_no_static" instead of "test_sanity.c" for "p *msymbol", so it
can be clearer for the adding of mst_file_bss/mst_file_data.
Personally I think the symbol "test_sanity.c" doesn't make sense here.
The "test_sanity.c" is a module name, and the "test_no_static" is a static variable in this module.
I just printed the debug info to help understand the current issue. In fact, the current issue happened in the productive environment, and the test module "test_sanity.c" is only used to help reproduce this issue.
Hope this helps.
Thanks
Lianbo
Thanks,
Tao Liu
> This causes a problem that the 'p' command can not work well as
> expected, and always gets an error:
>
> crash> mod -s test_sanity /home/test_sanity.ko
> MODULE NAME BASE SIZE OBJECT FILE
> ffffffffc1084040 test_sanity ffffffffc1082000 16384 /home/test_sanity.ko
> crash> p test_no_static
> p: gdb request failed: p test_no_static
> crash>
>
> With the patch:
> crash> mod -s test_sanity /home/test_sanity.ko
> MODULE NAME BASE SIZE OBJECT FILE
> ffffffffc1084040 test_sanity ffffffffc1082000 16384 /home/test_sanity.ko
> crash> p test_no_static
> test_no_static = $1 = 5
> crash>
>
> Signed-off-by: Lianbo Jiang <lijiang@xxxxxxxxxx>
> ---
> Here is the test case:
> #include <linux/kernel.h>
> #include <linux/module.h>
>
> int test_no = 0;
> static int test_no_static = 0;
>
> static int test_init(void)
> {
> test_no += 5;
> test_no_static += 5;
> printk(KERN_INFO "%d static=%d\n", test_no, test_no_static);
> return 0;
> }
> static void test_exit(void)
>
> {
> test_no += 7;
> test_no_static += 7;
> printk(KERN_INFO "%d static=%d\n", test_no, test_no_static);
> }
> module_init(test_init);
> module_exit(test_exit);
> MODULE_LICENSE("GPL");
>
>
> gdb-10.2.patch | 24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
>
> diff --git a/gdb-10.2.patch b/gdb-10.2.patch
> index a7018a249118..35388ba03e25 100644
> --- a/gdb-10.2.patch
> +++ b/gdb-10.2.patch
> @@ -16057,3 +16057,27 @@ exit 0
> m10200-dis.c
> m10200-opc.c
> m10300-dis.c
> +--- gdb-10.2/gdb/minsyms.c.orig
> ++++ gdb-10.2/gdb/minsyms.c
> +@@ -535,7 +535,9 @@ lookup_minimal_symbol_linkage (const char *name, struct objfile *objf)
> + {
> + if (strcmp (msymbol->linkage_name (), name) == 0
> + && (MSYMBOL_TYPE (msymbol) == mst_data
> +- || MSYMBOL_TYPE (msymbol) == mst_bss))
> ++ || MSYMBOL_TYPE (msymbol) == mst_bss
> ++ || MSYMBOL_TYPE (msymbol) == mst_file_bss
> ++ || MSYMBOL_TYPE (msymbol) == mst_file_data))
> + return {msymbol, objfile};
> + }
> + }
> +--- gdb-10.2/gdb/symtab.h.orig
> ++++ gdb-10.2/gdb/symtab.h
> +@@ -1110,7 +1110,7 @@ struct symbol : public general_symbol_info, public allocate_on_obstack
> + is_objfile_owned (1),
> + is_argument (0),
> + is_inlined (0),
> +- maybe_copied (0),
> ++ maybe_copied (1),/* The objfile potentially supports copy relocations. */
> + subclass (SYMBOL_NONE)
> + {
> + /* We can't use an initializer list for members of a base class, and
> --
> 2.41.0
> --
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