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 <[email protected]>
Link: https://lore.kernel.org/all/[email protected]/
Signed-off-by: Palmer Dabbelt <[email protected]>
---
I'm not sure about a fixes here, the breakage comes from a binutils change
that's pretty much independent from the kernel.
Plumbing in through the RISC-V-specific switch is also a bit ugly, but I'm not
sure just dropping everyone's "$"-prefixed symbols is a good idea -- the rest
of this is sort of half-way arch-specific, though, so maybe that's the way to
go? I figure it's easier to delete stuff than add it, though.
---
include/linux/module_symbol.h | 12 +++++++++++-
kernel/module/kallsyms.c | 8 +++++++-
scripts/mod/modpost.c | 2 +-
3 files changed, 19 insertions(+), 3 deletions(-)
diff --git a/include/linux/module_symbol.h b/include/linux/module_symbol.h
index 7ace7ba30203..5b799942b243 100644
--- a/include/linux/module_symbol.h
+++ b/include/linux/module_symbol.h
@@ -3,12 +3,22 @@
#define _LINUX_MODULE_SYMBOL_H
/* This ignores the intensely annoying "mapping symbols" found in ELF files. */
-static inline int is_mapping_symbol(const char *str)
+static inline int is_mapping_symbol(const char *str, int is_riscv)
{
if (str[0] == '.' && str[1] == 'L')
return true;
if (str[0] == 'L' && str[1] == '0')
return true;
+ /*
+ * RISC-V defines various special symbols that start with "$". 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..1e988e542c5d 100644
--- a/kernel/module/kallsyms.c
+++ b/kernel/module/kallsyms.c
@@ -12,6 +12,12 @@
#include <linux/bsearch.h>
#include "internal.h"
+#ifdef CONFIG_RISCV
+#define IS_RISCV 1
+#else
+#define IS_RISCV 0
+#endif
+
/* Lookup exported symbol in given range of kernel_symbols */
static const struct kernel_symbol *lookup_exported_symbol(const char *name,
const struct kernel_symbol *start,
@@ -289,7 +295,7 @@ 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_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 */
--
2.41.0
On 2023-07-06 22:40:01-0700, 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.
> [..]
> diff --git a/kernel/module/kallsyms.c b/kernel/module/kallsyms.c
> index ef73ae7c8909..1e988e542c5d 100644
> --- a/kernel/module/kallsyms.c
> +++ b/kernel/module/kallsyms.c
> @@ -12,6 +12,12 @@
> #include <linux/bsearch.h>
> #include "internal.h"
>
> +#ifdef CONFIG_RISCV
> +#define IS_RISCV 1
> +#else
> +#define IS_RISCV 0
> +#endif
> +
> /* Lookup exported symbol in given range of kernel_symbols */
> static const struct kernel_symbol *lookup_exported_symbol(const char *name,
> const struct kernel_symbol *start,
> @@ -289,7 +295,7 @@ 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_RISCV))
IS_BUILTIN(CONFIG_RISCV) or IS_ENABLED(CONFIG_RISCV) ?
> continue;
>
> if (thisval <= addr && thisval > bestval) {
> [..]
On 7/6/23 22:40, 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 <[email protected]>
> Link: https://lore.kernel.org/all/[email protected]/
> Signed-off-by: Palmer Dabbelt <[email protected]>
Reviewed-by: Randy Dunlap <[email protected]>
Tested-by: Randy Dunlap <[email protected]> # build-tested
Thanks.
> ---
> I'm not sure about a fixes here, the breakage comes from a binutils change
> that's pretty much independent from the kernel.
>
> Plumbing in through the RISC-V-specific switch is also a bit ugly, but I'm not
> sure just dropping everyone's "$"-prefixed symbols is a good idea -- the rest
> of this is sort of half-way arch-specific, though, so maybe that's the way to
> go? I figure it's easier to delete stuff than add it, though.
> ---
> include/linux/module_symbol.h | 12 +++++++++++-
> kernel/module/kallsyms.c | 8 +++++++-
> scripts/mod/modpost.c | 2 +-
> 3 files changed, 19 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/module_symbol.h b/include/linux/module_symbol.h
> index 7ace7ba30203..5b799942b243 100644
> --- a/include/linux/module_symbol.h
> +++ b/include/linux/module_symbol.h
> @@ -3,12 +3,22 @@
> #define _LINUX_MODULE_SYMBOL_H
>
> /* This ignores the intensely annoying "mapping symbols" found in ELF files. */
> -static inline int is_mapping_symbol(const char *str)
> +static inline int is_mapping_symbol(const char *str, int is_riscv)
> {
> if (str[0] == '.' && str[1] == 'L')
> return true;
> if (str[0] == 'L' && str[1] == '0')
> return true;
> + /*
> + * RISC-V defines various special symbols that start with "$". 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..1e988e542c5d 100644
> --- a/kernel/module/kallsyms.c
> +++ b/kernel/module/kallsyms.c
> @@ -12,6 +12,12 @@
> #include <linux/bsearch.h>
> #include "internal.h"
>
> +#ifdef CONFIG_RISCV
> +#define IS_RISCV 1
> +#else
> +#define IS_RISCV 0
> +#endif
> +
> /* Lookup exported symbol in given range of kernel_symbols */
> static const struct kernel_symbol *lookup_exported_symbol(const char *name,
> const struct kernel_symbol *start,
> @@ -289,7 +295,7 @@ 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_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 */
--
~Randy
On Thu, 06 Jul 2023 23:06:19 PDT (-0700), [email protected] wrote:
> On 2023-07-06 22:40:01-0700, 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.
>
>> [..]
>
>> diff --git a/kernel/module/kallsyms.c b/kernel/module/kallsyms.c
>> index ef73ae7c8909..1e988e542c5d 100644
>> --- a/kernel/module/kallsyms.c
>> +++ b/kernel/module/kallsyms.c
>> @@ -12,6 +12,12 @@
>> #include <linux/bsearch.h>
>> #include "internal.h"
>>
>> +#ifdef CONFIG_RISCV
>> +#define IS_RISCV 1
>> +#else
>> +#define IS_RISCV 0
>> +#endif
>> +
>> /* Lookup exported symbol in given range of kernel_symbols */
>> static const struct kernel_symbol *lookup_exported_symbol(const char *name,
>> const struct kernel_symbol *start,
>> @@ -289,7 +295,7 @@ 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_RISCV))
>
> IS_BUILTIN(CONFIG_RISCV) or IS_ENABLED(CONFIG_RISCV) ?
Thanks, this is fixed in the v2.
>
>> continue;
>>
>> if (thisval <= addr && thisval > bestval) {
>
>> [..]