[Patch v2] mm/memblock: discard .text/.data if CONFIG_ARCH_KEEP_MEMBLOCK not set

[Patch v2] mm/memblock: discard .text/.data if CONFIG_ARCH_KEEP_MEMBLOCK not set

[Wei Yang]

When CONFIG_ARCH_KEEP_MEMBLOCK not set, we expect to discard related
code and data. But it doesn't until CONFIG_MEMORY_HOTPLUG not set
neither.

This patch puts memblock's .text/.data into its own section, so that it
only depends on CONFIG_ARCH_KEEP_MEMBLOCK to discard related code and
data.

After this, from the log message in mem_init_print_info(), init size
increase from 2420K to 2432K on arch x86.

Signed-off-by: Wei Yang <richard.weiyang@gmail.com>

---
v2: fix orphan section for powerpc
---
 arch/powerpc/kernel/vmlinux.lds.S |  1 +
 include/asm-generic/vmlinux.lds.h | 14 +++++++++++++-
 include/linux/memblock.h          |  8 ++++----
 3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index f420df7888a7..d6d33bec597a 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -125,6 +125,7 @@ SECTIONS
 		*(.text.asan.* .text.tsan.*)
 		MEM_KEEP(init.text)
 		MEM_KEEP(exit.text)
+		MEMBLOCK_KEEP(init.text)
 	} :text
 
 	. = ALIGN(PAGE_SIZE);
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index f7749d0f2562..775c5eedb9e6 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -147,6 +147,14 @@
 #define MEM_DISCARD(sec) *(.mem##sec)
 #endif
 
+#if defined(CONFIG_ARCH_KEEP_MEMBLOCK)
+#define MEMBLOCK_KEEP(sec)    *(.mb##sec)
+#define MEMBLOCK_DISCARD(sec)
+#else
+#define MEMBLOCK_KEEP(sec)
+#define MEMBLOCK_DISCARD(sec) *(.mb##sec)
+#endif
+
 #ifndef CONFIG_HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
 #define KEEP_PATCHABLE		KEEP(*(__patchable_function_entries))
 #define PATCHABLE_DISCARDS
@@ -356,6 +364,7 @@
 	*(.ref.data)							\
 	*(.data..shared_aligned) /* percpu related */			\
 	MEM_KEEP(init.data*)						\
+	MEMBLOCK_KEEP(init.data*)					\
 	*(.data.unlikely)						\
 	__start_once = .;						\
 	*(.data.once)							\
@@ -573,6 +582,7 @@
 		*(.ref.text)						\
 		*(.text.asan.* .text.tsan.*)				\
 	MEM_KEEP(init.text*)						\
+	MEMBLOCK_KEEP(init.text*)					\
 
 
 /* sched.text is aling to function alignment to secure we have same
@@ -680,6 +690,7 @@
 	KEEP(*(SORT(___kentry+*)))					\
 	*(.init.data .init.data.*)					\
 	MEM_DISCARD(init.data*)						\
+	MEMBLOCK_DISCARD(init.data*)					\
 	KERNEL_CTORS()							\
 	MCOUNT_REC()							\
 	*(.init.rodata .init.rodata.*)					\
@@ -706,7 +717,8 @@
 #define INIT_TEXT							\
 	*(.init.text .init.text.*)					\
 	*(.text.startup)						\
-	MEM_DISCARD(init.text*)
+	MEM_DISCARD(init.text*)						\
+	MEMBLOCK_DISCARD(init.text*)
 
 #define EXIT_DATA							\
 	*(.exit.data .exit.data.*)					\
diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index e2082240586d..3e1f1d42dde7 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -100,13 +100,13 @@ struct memblock {
 
 extern struct memblock memblock;
 
+#define __init_memblock        __section(".mbinit.text") __cold notrace \
+						  __latent_entropy
+#define __initdata_memblock    __section(".mbinit.data")
+
 #ifndef CONFIG_ARCH_KEEP_MEMBLOCK
-#define __init_memblock __meminit
-#define __initdata_memblock __meminitdata
 void memblock_discard(void);
 #else
-#define __init_memblock
-#define __initdata_memblock
 static inline void memblock_discard(void) {}
 #endif
 
-- 
2.34.1

Re: [Patch v2] mm/memblock: discard .text/.data if CONFIG_ARCH_KEEP_MEMBLOCK not set

[Mike Rapoport]

Hi,

On Fri, May 10, 2024 at 02:04:22AM +0000, Wei Yang wrote:
> When CONFIG_ARCH_KEEP_MEMBLOCK not set, we expect to discard related
> code and data. But it doesn't until CONFIG_MEMORY_HOTPLUG not set
> neither.
> 
> This patch puts memblock's .text/.data into its own section, so that it
> only depends on CONFIG_ARCH_KEEP_MEMBLOCK to discard related code and
> data.
> 
> After this, from the log message in mem_init_print_info(), init size
> increase from 2420K to 2432K on arch x86.
> 
> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
> 
> ---
> v2: fix orphan section for powerpc
> ---
>  arch/powerpc/kernel/vmlinux.lds.S |  1 +
>  include/asm-generic/vmlinux.lds.h | 14 +++++++++++++-
>  include/linux/memblock.h          |  8 ++++----
>  3 files changed, 18 insertions(+), 5 deletions(-)
>  
> +#define __init_memblock        __section(".mbinit.text") __cold notrace \
> +						  __latent_entropy
> +#define __initdata_memblock    __section(".mbinit.data")
> +

The new .mbinit.* sections should be added to scripts/mod/modpost.c
alongside .meminit.* sections and then I expect modpost to report a bunch
of section mismatches because many memblock functions are called on memory
hotplug even on architectures that don't select ARCH_KEEP_MEMBLOCK.

>  #ifndef CONFIG_ARCH_KEEP_MEMBLOCK
> -#define __init_memblock __meminit
> -#define __initdata_memblock __meminitdata
>  void memblock_discard(void);
>  #else
> -#define __init_memblock
> -#define __initdata_memblock
>  static inline void memblock_discard(void) {}
>  #endif
>  
> -- 
> 2.34.1
> 
> 

-- 
Sincerely yours,
Mike.

Re: [Patch v2] mm/memblock: discard .text/.data if CONFIG_ARCH_KEEP_MEMBLOCK not set

[Wei Yang]

On Tue, May 21, 2024 at 10:21:52AM +0300, Mike Rapoport wrote:
>Hi,
>
>On Fri, May 10, 2024 at 02:04:22AM +0000, Wei Yang wrote:
>> When CONFIG_ARCH_KEEP_MEMBLOCK not set, we expect to discard related
>> code and data. But it doesn't until CONFIG_MEMORY_HOTPLUG not set
>> neither.
>> 
>> This patch puts memblock's .text/.data into its own section, so that it
>> only depends on CONFIG_ARCH_KEEP_MEMBLOCK to discard related code and
>> data.
>> 
>> After this, from the log message in mem_init_print_info(), init size
>> increase from 2420K to 2432K on arch x86.
>> 
>> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
>> 
>> ---
>> v2: fix orphan section for powerpc
>> ---
>>  arch/powerpc/kernel/vmlinux.lds.S |  1 +
>>  include/asm-generic/vmlinux.lds.h | 14 +++++++++++++-
>>  include/linux/memblock.h          |  8 ++++----
>>  3 files changed, 18 insertions(+), 5 deletions(-)
>>  
>> +#define __init_memblock        __section(".mbinit.text") __cold notrace \
>> +						  __latent_entropy
>> +#define __initdata_memblock    __section(".mbinit.data")
>> +
>
>The new .mbinit.* sections should be added to scripts/mod/modpost.c
>alongside .meminit.* sections and then I expect modpost to report a bunch
>of section mismatches because many memblock functions are called on memory
>hotplug even on architectures that don't select ARCH_KEEP_MEMBLOCK.
>

I tried to add some code in modpost.c, "make all" looks good.

May I ask how can I trigger the "mismatch" warning?

BTW, if ARCH_KEEP_MEMBLOCK unset, we would discard memblock meta-data. If
hotplug would call memblock function, it would be dangerous?

The additional code I used is like below.

---
 scripts/mod/modpost.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 937294ff164f..c837e2882904 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -777,14 +777,14 @@ static void check_section(const char *modname, struct elf_info *elf,
 
 #define ALL_INIT_DATA_SECTIONS \
 	".init.setup", ".init.rodata", ".meminit.rodata", \
-	".init.data", ".meminit.data"
+	".init.data", ".meminit.data", "mbinit.data"
 
 #define ALL_PCI_INIT_SECTIONS	\
 	".pci_fixup_early", ".pci_fixup_header", ".pci_fixup_final", \
 	".pci_fixup_enable", ".pci_fixup_resume", \
 	".pci_fixup_resume_early", ".pci_fixup_suspend"
 
-#define ALL_XXXINIT_SECTIONS ".meminit.*"
+#define ALL_XXXINIT_SECTIONS ".meminit.*", "mbinit.*"
 
 #define ALL_INIT_SECTIONS INIT_SECTIONS, ALL_XXXINIT_SECTIONS
 #define ALL_EXIT_SECTIONS ".exit.*"
@@ -799,7 +799,7 @@ static void check_section(const char *modname, struct elf_info *elf,
 
 #define INIT_SECTIONS      ".init.*"
 
-#define ALL_TEXT_SECTIONS  ".init.text", ".meminit.text", ".exit.text", \
+#define ALL_TEXT_SECTIONS  ".init.text", ".meminit.text", ".mbinit.text", ".exit.text", \
 		TEXT_SECTIONS, OTHER_TEXT_SECTIONS
 
 enum mismatch {
-- 
2.34.1


>>  #ifndef CONFIG_ARCH_KEEP_MEMBLOCK
>> -#define __init_memblock __meminit
>> -#define __initdata_memblock __meminitdata
>>  void memblock_discard(void);
>>  #else
>> -#define __init_memblock
>> -#define __initdata_memblock
>>  static inline void memblock_discard(void) {}
>>  #endif
>>  
>> -- 
>> 2.34.1
>> 
>> 
>
>-- 
>Sincerely yours,
>Mike.

-- 
Wei Yang
Help you, Help me

Re: [Patch v2] mm/memblock: discard .text/.data if CONFIG_ARCH_KEEP_MEMBLOCK not set

[Mike Rapoport]

On Fri, May 24, 2024 at 01:46:56AM +0000, Wei Yang wrote:
> On Tue, May 21, 2024 at 10:21:52AM +0300, Mike Rapoport wrote:
> >Hi,
> >
> >On Fri, May 10, 2024 at 02:04:22AM +0000, Wei Yang wrote:
> >> When CONFIG_ARCH_KEEP_MEMBLOCK not set, we expect to discard related
> >> code and data. But it doesn't until CONFIG_MEMORY_HOTPLUG not set
> >> neither.
> >> 
> >> This patch puts memblock's .text/.data into its own section, so that it
> >> only depends on CONFIG_ARCH_KEEP_MEMBLOCK to discard related code and
> >> data.
> >> 
> >> After this, from the log message in mem_init_print_info(), init size
> >> increase from 2420K to 2432K on arch x86.
> >> 
> >> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
> >> 
> >> ---
> >> v2: fix orphan section for powerpc
> >> ---
> >>  arch/powerpc/kernel/vmlinux.lds.S |  1 +
> >>  include/asm-generic/vmlinux.lds.h | 14 +++++++++++++-
> >>  include/linux/memblock.h          |  8 ++++----
> >>  3 files changed, 18 insertions(+), 5 deletions(-)
> >>  
> >> +#define __init_memblock        __section(".mbinit.text") __cold notrace \
> >> +						  __latent_entropy
> >> +#define __initdata_memblock    __section(".mbinit.data")
> >> +
> >
> >The new .mbinit.* sections should be added to scripts/mod/modpost.c
> >alongside .meminit.* sections and then I expect modpost to report a bunch
> >of section mismatches because many memblock functions are called on memory
> >hotplug even on architectures that don't select ARCH_KEEP_MEMBLOCK.
> >
> 
> I tried to add some code in modpost.c, "make all" looks good.
> 
> May I ask how can I trigger the "mismatch" warning?
> 
> BTW, if ARCH_KEEP_MEMBLOCK unset, we would discard memblock meta-data. If
> hotplug would call memblock function, it would be dangerous?
> 
> The additional code I used is like below.
> 
> ---
>  scripts/mod/modpost.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index 937294ff164f..c837e2882904 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -777,14 +777,14 @@ static void check_section(const char *modname, struct elf_info *elf,
>  
>  #define ALL_INIT_DATA_SECTIONS \
>  	".init.setup", ".init.rodata", ".meminit.rodata", \
> -	".init.data", ".meminit.data"
> +	".init.data", ".meminit.data", "mbinit.data"

should be ".mbinit.data"
>  
>  #define ALL_PCI_INIT_SECTIONS	\
>  	".pci_fixup_early", ".pci_fixup_header", ".pci_fixup_final", \
>  	".pci_fixup_enable", ".pci_fixup_resume", \
>  	".pci_fixup_resume_early", ".pci_fixup_suspend"
>  
> -#define ALL_XXXINIT_SECTIONS ".meminit.*"
> +#define ALL_XXXINIT_SECTIONS ".meminit.*", "mbinit.*"

and ".mbinit.*"

But regardless of typos, when ARCH_KEEP_MEMBLOCK=n the .mbinit is equivalent
to .init and it should not be referenced from .meminit, so I don't think
adding it here is correct.

If I simply alias __init_memblock to __init then with
CONFIG_MEMORY_HOTPLUG=y I get

WARNING: modpost: vmlinux: section mismatch in reference: early_pfn_to_nid+0x42 (section: .meminit.text) -> memblock_search_pfn_nid (section: .init.text)
WARNING: modpost: vmlinux: section mismatch in reference: memmap_init_range+0x142 (section: .meminit.text) -> mirrored_kernelcore (section: .init.data)
WARNING: modpost: vmlinux: section mismatch in reference: memmap_init_range+0x1e1 (section: .meminit.text) -> memblock (section: .init.data)
WARNING: modpost: vmlinux: section mismatch in reference: memmap_init_range+0x1e8 (section: .meminit.text) -> memblock (section: .init.data)
WARNING: modpost: vmlinux: section mismatch in reference: sparse_buffer_alloc+0x3b (section: .meminit.text) -> memblock_free (section: .init.text)

>  #define ALL_INIT_SECTIONS INIT_SECTIONS, ALL_XXXINIT_SECTIONS
>  #define ALL_EXIT_SECTIONS ".exit.*"
> @@ -799,7 +799,7 @@ static void check_section(const char *modname, struct elf_info *elf,
>  
>  #define INIT_SECTIONS      ".init.*"
>  
> -#define ALL_TEXT_SECTIONS  ".init.text", ".meminit.text", ".exit.text", \
> +#define ALL_TEXT_SECTIONS  ".init.text", ".meminit.text", ".mbinit.text", ".exit.text", \
>  		TEXT_SECTIONS, OTHER_TEXT_SECTIONS
>  
>  enum mismatch {
> 
> -- 
> Wei Yang
> Help you, Help me
> 

-- 
Sincerely yours,
Mike.