[U-Boot] [RFC PATCH] arm: lds: Remove libgcc eabi exception handling tables
Remove ARM eabi exception handling tables (for frame unwinding). AFAICT, u-boot stubs away the frame unwiding routines, so the tables will more or less just consume space. It should be OK to remove them.
Signed-off-by: Edgar E. Iglesias edgar.iglesias@xilinx.com Signed-off-by: Michal Simek michal.simek@xilinx.com --- Other options could be to complete u-boot/arch/arm/lib/* so that libgcc routines with exception handling dont get pulled in. Or to avoid user code (like the mentioned patch) which causes external libgcc functions to get pulled in...
--- arch/arm/cpu/u-boot.lds | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/arch/arm/cpu/u-boot.lds b/arch/arm/cpu/u-boot.lds index d9bbee3..e139b90 100644 --- a/arch/arm/cpu/u-boot.lds +++ b/arch/arm/cpu/u-boot.lds @@ -106,4 +106,6 @@ SECTIONS /DISCARD/ : { *(.plt*) } /DISCARD/ : { *(.interp*) } /DISCARD/ : { *(.gnu*) } + /DISCARD/ : { *(.ARM.exidx*) } + /DISCARD/ : { *(.gnu.linkonce.armexidx.*) } } -- 1.8.2.1
Hi Michal,
On Thu, 9 May 2013 11:35:33 +0200, Michal Simek michal.simek@xilinx.com wrote:
Remove ARM eabi exception handling tables (for frame unwinding). AFAICT, u-boot stubs away the frame unwiding routines, so the tables will more or less just consume space. It should be OK to remove them.
Signed-off-by: Edgar E. Iglesias edgar.iglesias@xilinx.com Signed-off-by: Michal Simek michal.simek@xilinx.com
Other options could be to complete u-boot/arch/arm/lib/* so that libgcc routines with exception handling dont get pulled in. Or to avoid user code (like the mentioned patch) which causes external libgcc functions to get pulled in...
Er... which mentioned patch?
Amicalement,
On 05/10/2013 09:07 PM, Albert ARIBAUD wrote:
Hi Michal,
On Thu, 9 May 2013 11:35:33 +0200, Michal Simek michal.simek@xilinx.com wrote:
Remove ARM eabi exception handling tables (for frame unwinding). AFAICT, u-boot stubs away the frame unwiding routines, so the tables will more or less just consume space. It should be OK to remove them.
Signed-off-by: Edgar E. Iglesias edgar.iglesias@xilinx.com Signed-off-by: Michal Simek michal.simek@xilinx.com
Other options could be to complete u-boot/arch/arm/lib/* so that libgcc routines with exception handling dont get pulled in. Or to avoid user code (like the mentioned patch) which causes external libgcc functions to get pulled in...
Er... which mentioned patch?
Ah yeah. Let me give you background. After adding: "arm: zynq: U-Boot udelay < 1000 FIX" (sha1: d54cc007878697a92e7f696b71a3eb203c0386e2)
we have found that new program header is added to u-boot for zynq.
Program Header: 0x70000001 off 0x000405fc vaddr 0x040385fc paddr 0x040385fc align 2**2 filesz 0x00000020 memsz 0x00000020 flags r-- LOAD off 0x00008000 vaddr 0x04000000 paddr 0x04000000 align 2**15 filesz 0x00041240 memsz 0x00041240 flags rwx STACK off 0x00000000 vaddr 0x00000000 paddr 0x00000000 align 2**2 filesz 0x00000000 memsz 0x00000000 flags rwx
Tracing down this we found that uldivmod is used 27: 00000000 0 NOTYPE GLOBAL DEFAULT UND __aeabi_uldivmod
Based on that Edgar proposed this patch.
After my experiment we can also use the patch below to fix it because external libgcc functions are not pulled it. But probably removing that ARM eabi exception handling tables is better solution then try to change code not to use it. But for me it is no problem to send the patch below to fix this problem.
Thanks, Michal
diff --git a/arch/arm/cpu/armv7/zynq/timer.c b/arch/arm/cpu/armv7/zynq/timer.c index 1b56373..4b26e96 100644 --- a/arch/arm/cpu/armv7/zynq/timer.c +++ b/arch/arm/cpu/armv7/zynq/timer.c @@ -118,12 +118,13 @@ void __udelay(unsigned long usec) u32 timeend; u32 timediff; u32 timenow; + u64 temp;
if (usec == 0) return;
- countticks = (u32) (((unsigned long long) TIMER_TICK_HZ * usec) / - 1000000); + temp = (TIMER_TICK_HZ * usec) / 1000000; + countticks = (u32)temp;
/* decrementing timer */ timeend = readl(&timer_base->counter) - countticks;
Hi Michal,
On Mon, 13 May 2013 09:45:12 +0200, Michal Simek monstr@monstr.eu wrote:
On 05/10/2013 09:07 PM, Albert ARIBAUD wrote:
Hi Michal,
On Thu, 9 May 2013 11:35:33 +0200, Michal Simek michal.simek@xilinx.com wrote:
Remove ARM eabi exception handling tables (for frame unwinding). AFAICT, u-boot stubs away the frame unwiding routines, so the tables will more or less just consume space. It should be OK to remove them.
Signed-off-by: Edgar E. Iglesias edgar.iglesias@xilinx.com Signed-off-by: Michal Simek michal.simek@xilinx.com
Other options could be to complete u-boot/arch/arm/lib/* so that libgcc routines with exception handling dont get pulled in. Or to avoid user code (like the mentioned patch) which causes external libgcc functions to get pulled in...
Er... which mentioned patch?
Ah yeah. Let me give you background. After adding: "arm: zynq: U-Boot udelay < 1000 FIX" (sha1: d54cc007878697a92e7f696b71a3eb203c0386e2)
we have found that new program header is added to u-boot for zynq.
Program Header: 0x70000001 off 0x000405fc vaddr 0x040385fc paddr 0x040385fc align 2**2 filesz 0x00000020 memsz 0x00000020 flags r-- LOAD off 0x00008000 vaddr 0x04000000 paddr 0x04000000 align 2**15 filesz 0x00041240 memsz 0x00041240 flags rwx STACK off 0x00000000 vaddr 0x00000000 paddr 0x00000000 align 2**2 filesz 0x00000000 memsz 0x00000000 flags rwx
Tracing down this we found that uldivmod is used 27: 00000000 0 NOTYPE GLOBAL DEFAULT UND __aeabi_uldivmod
Based on that Edgar proposed this patch.
Ok, so Michal and I just did some fiddling with zynq builds and *exidx* sections.
By default the *exidx* sections are between rodata and data, so removing them causes many apparent changes at the binary level. However, builds of zynq based on ARM master with the patch above vs master with a patch mapping *exidx* sections after BSS gives identical binaries. Thus the RFC has no functional effect.
Also, ARM EHABI states that [exception] Tables are not required for ABI compliance at the C/Assembler level but are required for C++.
http://infocenter.arm.com/help/topic/com.arm.doc.ihi0038a/IHI0038A_ehabi.pdf
So as long as we don't put any C++ code in U-Boot (a prospect that I don't see happening any time soon), this RFC is safe and either is a no-op or removes useless bytes from the binary.
Amicalement,
Hi Albert,
On 05/14/2013 05:44 PM, Albert ARIBAUD wrote:
Hi Michal,
On Mon, 13 May 2013 09:45:12 +0200, Michal Simek monstr@monstr.eu wrote:
On 05/10/2013 09:07 PM, Albert ARIBAUD wrote:
Hi Michal,
On Thu, 9 May 2013 11:35:33 +0200, Michal Simek michal.simek@xilinx.com wrote:
Remove ARM eabi exception handling tables (for frame unwinding). AFAICT, u-boot stubs away the frame unwiding routines, so the tables will more or less just consume space. It should be OK to remove them.
Signed-off-by: Edgar E. Iglesias edgar.iglesias@xilinx.com Signed-off-by: Michal Simek michal.simek@xilinx.com
Other options could be to complete u-boot/arch/arm/lib/* so that libgcc routines with exception handling dont get pulled in. Or to avoid user code (like the mentioned patch) which causes external libgcc functions to get pulled in...
Er... which mentioned patch?
Ah yeah. Let me give you background. After adding: "arm: zynq: U-Boot udelay < 1000 FIX" (sha1: d54cc007878697a92e7f696b71a3eb203c0386e2)
we have found that new program header is added to u-boot for zynq.
Program Header: 0x70000001 off 0x000405fc vaddr 0x040385fc paddr 0x040385fc align 2**2 filesz 0x00000020 memsz 0x00000020 flags r-- LOAD off 0x00008000 vaddr 0x04000000 paddr 0x04000000 align 2**15 filesz 0x00041240 memsz 0x00041240 flags rwx STACK off 0x00000000 vaddr 0x00000000 paddr 0x00000000 align 2**2 filesz 0x00000000 memsz 0x00000000 flags rwx
Tracing down this we found that uldivmod is used 27: 00000000 0 NOTYPE GLOBAL DEFAULT UND __aeabi_uldivmod
Based on that Edgar proposed this patch.
Ok, so Michal and I just did some fiddling with zynq builds and *exidx* sections.
By default the *exidx* sections are between rodata and data, so removing them causes many apparent changes at the binary level. However, builds of zynq based on ARM master with the patch above vs master with a patch mapping *exidx* sections after BSS gives identical binaries. Thus the RFC has no functional effect.
Also, ARM EHABI states that [exception] Tables are not required for ABI compliance at the C/Assembler level but are required for C++.
http://infocenter.arm.com/help/topic/com.arm.doc.ihi0038a/IHI0038A_ehabi.pdf
So as long as we don't put any C++ code in U-Boot (a prospect that I don't see happening any time soon), this RFC is safe and either is a no-op or removes useless bytes from the binary.
Any update on this? Have you decided to add or not to add to this release? If you I need to fix zynq timer code do not use exception handling table.
Thanks, Michal
participants (3)
-
Albert ARIBAUD -
Michal Simek -
Michal Simek