From eedf12d4758409c3c405f56edf3177a3955e1f67 Mon Sep 17 00:00:00 2001 From: Lianbo Jiang Date: Wed, 6 Mar 2024 14:31:27 +0800 Subject: [PATCH] gdb: fix "p" command to print module variables correctly 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 = { = {m_name = 0x349812f "test_no_static", value = {ivalue = 8, block = 0x8, bytes = 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} This causes a problem that the 'p' command cannot work well as expected, and emits an error or a bogus value: 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> The issue occurs with Linux 6.2 and later or kernels that have kernel commit 80e4c1cd42ff ("x86/retbleed: Add X86_FEATURE_CALL_DEPTH") and configured with CONFIG_CALL_DEPTH_TRACKING=y, including RHEL9.3 and later kernels. 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 --- gdb-10.2.patch | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/gdb-10.2.patch b/gdb-10.2.patch index 7416efed..3694b131 100644 --- a/gdb-10.2.patch +++ b/gdb-10.2.patch @@ -3237,3 +3237,27 @@ exit 0 for (compunit_symtab *cust : objfile->compunits ()) { +--- 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