Hello!
On 07/07/2023 17:00, Palmer Dabbelt wrote:
RISC-V has an extended form of mapping symbols that we use to encode
the ISA when it changes in the middle of an ELF. This trips up modpost
as a build failure, I haven't yet verified it yet but I believe the
kallsyms difference should result in stacks looking sane again.
Reported-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Closes: https://lore.kernel.org/all/9d9e2902-5489-4bf0-d9cb-556c8e5d71c2@xxxxxxxxxxxxx/
Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
---
Changes since v1 <20230707054007.32591-1-palmer@xxxxxxxxxxxx/>:
* Drop the unnecessary IS_RISCV define and just inline it.
---
include/linux/module_symbol.h | 12 +++++++++++-
kernel/module/kallsyms.c | 2 +-
scripts/mod/modpost.c | 2 +-
3 files changed, 13 insertions(+), 3 deletions(-)
diff --git a/include/linux/module_symbol.h b/include/linux/module_symbol.h
index 7ace7ba30203..5b799942b243 100644
--- a/include/linux/module_symbol.h
+++ b/include/linux/module_symbol.h
@@ -3,12 +3,22 @@
#define _LINUX_MODULE_SYMBOL_H
/* This ignores the intensely annoying "mapping symbols" found in ELF files. */
-static inline int is_mapping_symbol(const char *str)
+static inline int is_mapping_symbol(const char *str, int is_riscv)
{
if (str[0] == '.' && str[1] == 'L')
return true;
if (str[0] == 'L' && str[1] == '0')
return true;
+ /*
+ * RISC-V defines various special symbols that start with "$". The
+ * mapping symbols, which exist to differentiate between incompatible
+ * instruction encodings when disassembling, show up all over the place
+ * and are generally not meant to be treated like other symbols. So
+ * just ignore any of the special symbols.
+ */
+ if (is_riscv)
+ return str[0] == '$';
+
return str[0] == '$' &&
(str[1] == 'a' || str[1] == 'd' || str[1] == 't' || str[1] == 'x')
&& (str[2] == '\0' || str[2] == '.');
diff --git a/kernel/module/kallsyms.c b/kernel/module/kallsyms.c
index ef73ae7c8909..78a1ffc399d9 100644
--- a/kernel/module/kallsyms.c
+++ b/kernel/module/kallsyms.c
@@ -289,7 +289,7 @@ static const char *find_kallsyms_symbol(struct module *mod,
* and inserted at a whim.
*/
if (*kallsyms_symbol_name(kallsyms, i) == '\0' ||
- is_mapping_symbol(kallsyms_symbol_name(kallsyms, i)))
+ is_mapping_symbol(kallsyms_symbol_name(kallsyms, i), IS_ENABLED(CONFIG_RISCV)))
continue;
if (thisval <= addr && thisval > bestval) {
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index b29b29707f10..7c71429d6502 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -1052,7 +1052,7 @@ static inline int is_valid_name(struct elf_info *elf, Elf_Sym *sym)
if (!name || !strlen(name))
return 0;
- return !is_mapping_symbol(name);
+ return !is_mapping_symbol(name, elf->hdr->e_machine == EM_RISCV);
}
/* Look up the nearest symbol based on the section and the address */
Since this commit was added, our builders are failing with the following
error ...
kernel/scripts/mod/modpost.c: In function ‘is_valid_name’:
kernel/scripts/mod/modpost.c:1055:57: error: ‘EM_RISCV’ undeclared
(first use in this function)
return !is_mapping_symbol(name, elf->hdr->e_machine == EM_RISCV);
^
We have had some cases of this before [0] and was fixed by ensuring this
is defined if it is not.
Thanks
Jon
[0]
https://patchwork.kernel.org/project/linux-mm/patch/20210924224338.8vuOlQPWr%25akpm@xxxxxxxxxxxxxxxxxxxx/
--
nvpublic
