[PATCH 1/2] ARM: cpu: common: skip R_ARM_NONE relocations

[PATCH 1/2] ARM: cpu: common: skip R_ARM_NONE relocations

[Ahmad Fatoum]

Relocations may be turned into no-op in place by strip running on an
executable by having their type set to 0 (R_ARM_NONE).

This can happen with the incoming ELF loading in PBL support, so teach
relocate_to_current_adr() to skip these no-op relocation entries.

Signed-off-by: Ahmad Fatoum <a.fatoum@barebox.org>
---
 arch/arm/cpu/common.c | 30 +++++++++++++++++++++---------
 1 file changed, 21 insertions(+), 9 deletions(-)

diff --git a/arch/arm/cpu/common.c b/arch/arm/cpu/common.c
index 339ef2db2534..5b65b0745b98 100644
--- a/arch/arm/cpu/common.c
+++ b/arch/arm/cpu/common.c
@@ -36,6 +36,7 @@ void sync_caches_for_execution(void)
 	arm_early_mmu_cache_flush();
 }
 
+#define R_ARM_NONE 0
 #define R_ARM_RELATIVE 23
 #define R_AARCH64_RELATIVE 1027
 
@@ -78,14 +79,19 @@ void __prereloc relocate_to_current_adr(void)
 #if defined(CONFIG_CPU_64)
 	while (dstart < dend) {
 		struct elf64_rela *rel = dstart;
+		unsigned long *fixup;
 
-		if (ELF64_R_TYPE(rel->r_info) == R_AARCH64_RELATIVE) {
-			unsigned long *fixup = (unsigned long *)(rel->r_offset + offset);
+		switch(ELF64_R_TYPE(rel->r_info)) {
+		case R_AARCH64_RELATIVE:
+			fixup = (unsigned long *)(rel->r_offset + offset);
 
 			*fixup = rel->r_addend + offset;
 			rel->r_addend += offset;
 			rel->r_offset += offset;
-		} else {
+			break;
+		case R_ARM_NONE:
+			break;
+		default:
 			putc_ll('>');
 			puthex_ll(rel->r_info);
 			putc_ll(' ');
@@ -104,20 +110,26 @@ void __prereloc relocate_to_current_adr(void)
 
 	while (dstart < dend) {
 		struct elf32_rel *rel = dstart;
+		unsigned long r, *fixup;
 
-		if (ELF32_R_TYPE(rel->r_info) == R_ARM_RELATIVE) {
-			unsigned long *fixup = (unsigned long *)(rel->r_offset + offset);
+		switch (ELF32_R_TYPE(rel->r_info)) {
+		case R_ARM_RELATIVE:
+			fixup = (unsigned long *)(rel->r_offset + offset);
 
 			*fixup = *fixup + offset;
 
 			rel->r_offset += offset;
-		} else if (ELF32_R_TYPE(rel->r_info) == R_ARM_ABS32) {
-			unsigned long r = dynsym[ELF32_R_SYM(rel->r_info) * 4 + 1];
-			unsigned long *fixup = (unsigned long *)(rel->r_offset + offset);
+			break;
+		case R_ARM_ABS32:
+			r = dynsym[ELF32_R_SYM(rel->r_info) * 4 + 1];
+			fixup = (unsigned long *)(rel->r_offset + offset);
 
 			*fixup = *fixup + r + offset;
 			rel->r_offset += offset;
-		} else {
+			break;
+		case R_ARM_NONE:
+			break;
+		default:
 			putc_ll('>');
 			puthex_ll(rel->r_info);
 			putc_ll(' ');
-- 
2.47.3

[PATCH 2/2] ARM: cpu: common: define generic relocate_image

[Ahmad Fatoum]

For use by the ELF loader in PBL to relocate barebox proper, export a
new relocate_image capable of relocating barebox and implement
relocate_to_current_adr() in terms of it.

When doing ELF loading, the PT_DYNAMIC segment will contain the info
needed to derive the arguments for relocate_image():

  - dstart: DT_REL  /DT_RELA
  - dend:   DT_RELSZ/DT_RELASZ
  - dynsym: DT_SYMTAB

dynend is optional and could in theory be generated by looking at
DT_HASH or DT_GNU_HASH, but it's not required. Best guess is that the
zeroing is there just to signify that we don't need this data anymore.

Signed-off-by: Ahmad Fatoum <a.fatoum@barebox.org>
---
 arch/arm/cpu/common.c        | 34 +++++++++++++++-------------------
 arch/arm/include/asm/reloc.h |  3 +++
 2 files changed, 18 insertions(+), 19 deletions(-)

diff --git a/arch/arm/cpu/common.c b/arch/arm/cpu/common.c
index 5b65b0745b98..f4f3f8f6325b 100644
--- a/arch/arm/cpu/common.c
+++ b/arch/arm/cpu/common.c
@@ -60,22 +60,10 @@ void pbl_barebox_break(void)
 /*
  * relocate binary to the currently running address
  */
-void __prereloc relocate_to_current_adr(void)
+void __prereloc relocate_image(unsigned long offset,
+			       void *dstart, void *dend,
+			       long *dynsym, long *dynend)
 {
-	unsigned long offset;
-	unsigned long __maybe_unused *dynsym, *dynend;
-	void *dstart, *dend;
-
-	/* Get offset between linked address and runtime address */
-	offset = get_runtime_offset();
-
-	/*
-	 * We have yet to relocate, so using runtime_address
-	 * to compute the relocated address
-	 */
-	dstart = runtime_address(__rel_dyn_start);
-	dend = runtime_address(__rel_dyn_end);
-
 #if defined(CONFIG_CPU_64)
 	while (dstart < dend) {
 		struct elf64_rela *rel = dstart;
@@ -105,8 +93,6 @@ void __prereloc relocate_to_current_adr(void)
 		dstart += sizeof(*rel);
 	}
 #elif defined(CONFIG_CPU_32)
-	dynsym = runtime_address(__dynsym_start);
-	dynend = runtime_address(__dynsym_end);
 
 	while (dstart < dend) {
 		struct elf32_rel *rel = dstart;
@@ -141,10 +127,21 @@ void __prereloc relocate_to_current_adr(void)
 		dstart += sizeof(*rel);
 	}
 
-	__memset(dynsym, 0, (unsigned long)dynend - (unsigned long)dynsym);
+	/* Optional: not required for correctness */
+	if (dynend)
+		__memset(dynsym, 0, (unsigned long)dynend - (unsigned long)dynsym);
 #else
 #error "Architecture not specified"
 #endif
+}
+
+void __prereloc relocate_to_current_adr(void)
+{
+	relocate_image(get_runtime_offset(),
+		       runtime_address(__rel_dyn_start),
+		       runtime_address(__rel_dyn_end),
+		       runtime_address(__dynsym_start),
+		       runtime_address(__dynsym_end));
 
 	sync_caches_for_execution();
 }
@@ -196,4 +193,3 @@ void print_pbl_mem_layout(ulong membase, ulong endmem, ulong barebox_base)
 	printf("membase               = 0x%08lx+0x%08lx\n",
 	       membase, endmem - membase);
 }
-
diff --git a/arch/arm/include/asm/reloc.h b/arch/arm/include/asm/reloc.h
index 2d7411ab5284..62c07932fad4 100644
--- a/arch/arm/include/asm/reloc.h
+++ b/arch/arm/include/asm/reloc.h
@@ -30,6 +30,9 @@ static inline __prereloc unsigned long global_variable_offset(void)
 }
 #define global_variable_offset() global_variable_offset()
 
+void relocate_image(unsigned long offset,
+		    void *dstart, void *dend,
+		    long *dynsym, long *dynend);
 void relocate_to_current_adr(void);
 void relocate_to_adr(unsigned long target);
 void relocate_to_adr_full(unsigned long target);
-- 
2.47.3

Re: [PATCH 2/2] ARM: cpu: common: define generic relocate_image

[Sascha Hauer]

On Tue, Jan 06, 2026 at 09:16:57AM +0100, Ahmad Fatoum wrote:
> For use by the ELF loader in PBL to relocate barebox proper, export a
> new relocate_image capable of relocating barebox and implement
> relocate_to_current_adr() in terms of it.
> 
> When doing ELF loading, the PT_DYNAMIC segment will contain the info
> needed to derive the arguments for relocate_image():
> 
>   - dstart: DT_REL  /DT_RELA
>   - dend:   DT_RELSZ/DT_RELASZ
>   - dynsym: DT_SYMTAB
> 
> dynend is optional and could in theory be generated by looking at
> DT_HASH or DT_GNU_HASH, but it's not required. Best guess is that the
> zeroing is there just to signify that we don't need this data anymore.
> 
> Signed-off-by: Ahmad Fatoum <a.fatoum@barebox.org>
> ---
>  arch/arm/cpu/common.c        | 34 +++++++++++++++-------------------
>  arch/arm/include/asm/reloc.h |  3 +++
>  2 files changed, 18 insertions(+), 19 deletions(-)
> 
> diff --git a/arch/arm/cpu/common.c b/arch/arm/cpu/common.c
> index 5b65b0745b98..f4f3f8f6325b 100644
> --- a/arch/arm/cpu/common.c
> +++ b/arch/arm/cpu/common.c
> @@ -60,22 +60,10 @@ void pbl_barebox_break(void)
>  /*
>   * relocate binary to the currently running address
>   */
> -void __prereloc relocate_to_current_adr(void)
> +void __prereloc relocate_image(unsigned long offset,
> +			       void *dstart, void *dend,
> +			       long *dynsym, long *dynend)

As relocate_image() now contains two entirely separate implementations
for ARM32 and ARM64, should we move it to arch/arm/lib[32|64]/ ?

>  {
> -	unsigned long offset;
> -	unsigned long __maybe_unused *dynsym, *dynend;
> -	void *dstart, *dend;
> -
> -	/* Get offset between linked address and runtime address */
> -	offset = get_runtime_offset();
> -
> -	/*
> -	 * We have yet to relocate, so using runtime_address
> -	 * to compute the relocated address
> -	 */
> -	dstart = runtime_address(__rel_dyn_start);
> -	dend = runtime_address(__rel_dyn_end);
> -
>  #if defined(CONFIG_CPU_64)
>  	while (dstart < dend) {
>  		struct elf64_rela *rel = dstart;
> @@ -105,8 +93,6 @@ void __prereloc relocate_to_current_adr(void)
>  		dstart += sizeof(*rel);
>  	}
>  #elif defined(CONFIG_CPU_32)
> -	dynsym = runtime_address(__dynsym_start);
> -	dynend = runtime_address(__dynsym_end);
>  
>  	while (dstart < dend) {
>  		struct elf32_rel *rel = dstart;
> @@ -141,10 +127,21 @@ void __prereloc relocate_to_current_adr(void)
>  		dstart += sizeof(*rel);
>  	}
>  
> -	__memset(dynsym, 0, (unsigned long)dynend - (unsigned long)dynsym);
> +	/* Optional: not required for correctness */
> +	if (dynend)
> +		__memset(dynsym, 0, (unsigned long)dynend - (unsigned long)dynsym);

The purpose of this memset is that we can call relocate_to_current_adr()
multiple times on the same binary. This happens when relocate_to_current_adr()
is called in the board code and then again in uncompress.c. I think in
this particular case we could just early return above when offset == 0,
but I think there are (were?) some cases where the same binary is moved multiple
times.

Sascha

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

Re: [PATCH 2/2] ARM: cpu: common: define generic relocate_image

[Ahmad Fatoum]

Hi,

On 1/6/26 9:16 AM, Ahmad Fatoum wrote:
> -	__memset(dynsym, 0, (unsigned long)dynend - (unsigned long)dynsym);
> +	/* Optional: not required for correctness */
> +	if (dynend)
> +		__memset(dynsym, 0, (unsigned long)dynend - (unsigned long)dynsym);

Unexpected revelation: We don't have any R_ARM_ABS32 relocations any
longer. Maybe because ARM32 is now always relocatable?

This will allow us to simplify some things.

Cheers,
Ahmad

>  #else
>  #error "Architecture not specified"
>  #endif
> +}
> +
> +void __prereloc relocate_to_current_adr(void)
> +{
> +	relocate_image(get_runtime_offset(),
> +		       runtime_address(__rel_dyn_start),
> +		       runtime_address(__rel_dyn_end),
> +		       runtime_address(__dynsym_start),
> +		       runtime_address(__dynsym_end));
>  
>  	sync_caches_for_execution();
>  }
> @@ -196,4 +193,3 @@ void print_pbl_mem_layout(ulong membase, ulong endmem, ulong barebox_base)
>  	printf("membase               = 0x%08lx+0x%08lx\n",
>  	       membase, endmem - membase);
>  }
> -
> diff --git a/arch/arm/include/asm/reloc.h b/arch/arm/include/asm/reloc.h
> index 2d7411ab5284..62c07932fad4 100644
> --- a/arch/arm/include/asm/reloc.h
> +++ b/arch/arm/include/asm/reloc.h
> @@ -30,6 +30,9 @@ static inline __prereloc unsigned long global_variable_offset(void)
>  }
>  #define global_variable_offset() global_variable_offset()
>  
> +void relocate_image(unsigned long offset,
> +		    void *dstart, void *dend,
> +		    long *dynsym, long *dynend);
>  void relocate_to_current_adr(void);
>  void relocate_to_adr(unsigned long target);
>  void relocate_to_adr_full(unsigned long target);

-- 
Pengutronix e.K.                  |                             |
Steuerwalder Str. 21              | http://www.pengutronix.de/  |
31137 Hildesheim, Germany         | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686  | Fax:   +49-5121-206917-5555 |

Re: [PATCH 1/2] ARM: cpu: common: skip R_ARM_NONE relocations

[Sascha Hauer]

On Tue, 06 Jan 2026 09:16:56 +0100, Ahmad Fatoum wrote:
> Relocations may be turned into no-op in place by strip running on an
> executable by having their type set to 0 (R_ARM_NONE).
> 
> This can happen with the incoming ELF loading in PBL support, so teach
> relocate_to_current_adr() to skip these no-op relocation entries.
> 
> 
> [...]

Applied, thanks!

[1/2] ARM: cpu: common: skip R_ARM_NONE relocations
      https://git.pengutronix.de/cgit/barebox/commit/?id=9ef816e176d9 (link may not be stable)
[2/2] ARM: cpu: common: define generic relocate_image
      https://git.pengutronix.de/cgit/barebox/commit/?id=d7ee5518c5cc (link may not be stable)

Best regards,
-- 
Sascha Hauer <s.hauer@pengutronix.de>