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* [PATCH v2] module: Ignore RISC-V mapping symbols too
@ 2023-07-07 16:00 Palmer Dabbelt
  2023-07-07 22:41 ` Randy Dunlap
                   ` (2 more replies)
  0 siblings, 3 replies; 4+ messages in thread
From: Palmer Dabbelt @ 2023-07-07 16:00 UTC (permalink / raw)
  To: mcgrof, rdunlap, thomas; +Cc: linux-riscv, linux-kernel, Palmer Dabbelt

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@infradead.org>
Closes: https://lore.kernel.org/all/9d9e2902-5489-4bf0-d9cb-556c8e5d71c2@infradead.org/
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
---
Changes since v1 <20230707054007.32591-1-palmer@rivosinc.com/>:

* 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 */
-- 
2.41.0


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^ permalink raw reply related	[flat|nested] 4+ messages in thread

* Re: [PATCH v2] module: Ignore RISC-V mapping symbols too
  2023-07-07 16:00 [PATCH v2] module: Ignore RISC-V mapping symbols too Palmer Dabbelt
@ 2023-07-07 22:41 ` Randy Dunlap
  2023-07-10 19:45 ` Luis Chamberlain
  2023-07-21 13:19 ` Jon Hunter
  2 siblings, 0 replies; 4+ messages in thread
From: Randy Dunlap @ 2023-07-07 22:41 UTC (permalink / raw)
  To: Palmer Dabbelt, mcgrof, thomas; +Cc: linux-riscv, linux-kernel



On 7/7/23 09:00, 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@infradead.org>
> Closes: https://lore.kernel.org/all/9d9e2902-5489-4bf0-d9cb-556c8e5d71c2@infradead.org/
> Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>


Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org> # build-tested

Thanks.

> ---
> Changes since v1 <20230707054007.32591-1-palmer@rivosinc.com/>:
> 
> * 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 */

-- 
~Randy

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^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH v2] module: Ignore RISC-V mapping symbols too
  2023-07-07 16:00 [PATCH v2] module: Ignore RISC-V mapping symbols too Palmer Dabbelt
  2023-07-07 22:41 ` Randy Dunlap
@ 2023-07-10 19:45 ` Luis Chamberlain
  2023-07-21 13:19 ` Jon Hunter
  2 siblings, 0 replies; 4+ messages in thread
From: Luis Chamberlain @ 2023-07-10 19:45 UTC (permalink / raw)
  To: Palmer Dabbelt; +Cc: rdunlap, thomas, linux-riscv, linux-kernel

On Fri, Jul 07, 2023 at 09:00:51AM -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.
> 
> Reported-by: Randy Dunlap <rdunlap@infradead.org>
> Closes: https://lore.kernel.org/all/9d9e2902-5489-4bf0-d9cb-556c8e5d71c2@infradead.org/
> Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Thanks, applied and pushed!

  Luis

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^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH v2] module: Ignore RISC-V mapping symbols too
  2023-07-07 16:00 [PATCH v2] module: Ignore RISC-V mapping symbols too Palmer Dabbelt
  2023-07-07 22:41 ` Randy Dunlap
  2023-07-10 19:45 ` Luis Chamberlain
@ 2023-07-21 13:19 ` Jon Hunter
  2 siblings, 0 replies; 4+ messages in thread
From: Jon Hunter @ 2023-07-21 13:19 UTC (permalink / raw)
  To: Palmer Dabbelt, mcgrof, rdunlap, thomas
  Cc: linux-riscv, linux-kernel, linux-tegra

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@infradead.org>
> Closes: https://lore.kernel.org/all/9d9e2902-5489-4bf0-d9cb-556c8e5d71c2@infradead.org/
> Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
> ---
> Changes since v1 <20230707054007.32591-1-palmer@rivosinc.com/>:
> 
> * 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@linux-foundation.org/

-- 
nvpublic

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^ permalink raw reply	[flat|nested] 4+ messages in thread

end of thread, other threads:[~2023-07-21 13:19 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2023-07-07 16:00 [PATCH v2] module: Ignore RISC-V mapping symbols too Palmer Dabbelt
2023-07-07 22:41 ` Randy Dunlap
2023-07-10 19:45 ` Luis Chamberlain
2023-07-21 13:19 ` Jon Hunter

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