Hi Anthony,
On Tue, Sep 20, 2011 at 7:22 AM, GROYER, Anthony Anthony.GROYER@airliquide.com wrote:
Hello,
I came back on a discussion started on April 2011.
The use of the initial patches for the CONFIG_SYS_SKIP_ARM_RELOCATION features has revealed two issues.
First issue: the calculation of the relocation offset was done only if the relocation is actually done. So we could reach a point where r9 has a wrong value, since it has never been used before (in my case, this bug happens without JTAG). The first diff moves the relocation offset calculation before the test of a relocation need.
Second issue: board_init_r was thinking the memory area for the malloc is just below the code, whereas the board_init_f had allocated some space for the malloc at the end of the SDRAM. If the code is located at the base of the SDRAM with CONFIG_SYS_SKIP_ARM_RELOCATION defined, the malloc area does not point to a correct memory address. The 2 other diff store the calculated malloc start address in a global data member so that it can be used in board_init_r().
Thanks for coming back to this. Hopefully you can do patches for the other CPU types also as Albert requests - and I can test armv7 when you do that. This feature is one that I use a lot with an ICE and I would like to see it in U-Boot.
Regards, Simon
Index: arch/arm/cpu/arm926ejs/start.S
--- arch/arm/cpu/arm926ejs/start.S (révision 1083) +++ arch/arm/cpu/arm926ejs/start.S (révision 1113) @@ -196,6 +196,10 @@ mov r4, r0 /* save addr_sp */ mov r5, r1 /* save addr of gd */ mov r6, r2 /* save addr of destination */
- /* set relocation offset here for all cases:
- relocation or not */
- ldr r0, _TEXT_BASE /* r0 <- Text base */
- sub r9, r6, r0 /* r9 <- relocation offset */
/* Set up the stack */ stack_setup: @@ -218,8 +222,6 @@ /* * fix .rel.dyn relocations */
- ldr r0, _TEXT_BASE /* r0 <- Text base */
- sub r9, r6, r0 /* r9 <- relocation offset */
ldr r10, _dynsym_start_ofs /* r10 <- sym table ofs */ add r10, r10, r0 /* r10 <- sym table in FLASH */ ldr r2, _rel_dyn_start_ofs /* r2 <- rel dyn start ofs */ Index: arch/arm/include/asm/global_data.h =================================================================== --- arch/arm/include/asm/global_data.h (révision 1083) +++ arch/arm/include/asm/global_data.h (copie de travail) @@ -69,6 +69,7 @@ unsigned long mon_len; /* monitor len */ unsigned long irq_sp; /* irq stack pointer */ unsigned long start_addr_sp; /* start_addr_stackpointer */
- unsigned long start_addr_malloc; /* start_addr_malloc */
unsigned long reloc_off; #if !(defined(CONFIG_SYS_NO_ICACHE) && defined(CONFIG_SYS_NO_DCACHE)) unsigned long tlb_addr; Index: arch/arm/lib/board.c =================================================================== --- arch/arm/lib/board.c (révision 1138) +++ arch/arm/lib/board.c (copie de travail) @@ -367,6 +367,7 @@ * reserve memory for malloc() arena */ addr_sp = addr - TOTAL_MALLOC_LEN;
- gd->start_addr_malloc = addr_sp;
debug ("Reserving %dk for malloc() at: %08lx\n", TOTAL_MALLOC_LEN >> 10, addr_sp); /* @@ -445,7 +446,6 @@ { char *s; bd_t *bd;
- ulong malloc_start;
#if !defined(CONFIG_SYS_NO_FLASH) ulong flash_size; #endif @@ -473,9 +473,7 @@ post_output_backlog (); #endif
- /* The Malloc area is immediately below the monitor copy in DRAM */
- malloc_start = dest_addr - TOTAL_MALLOC_LEN;
- mem_malloc_init (malloc_start, TOTAL_MALLOC_LEN);
- mem_malloc_init (gd->start_addr_malloc, TOTAL_MALLOC_LEN);
#if !defined(CONFIG_SYS_NO_FLASH) puts ("Flash: ");
Regards, Anthony Groyer
On Wed, Apr 20, 2011 at 11:56 PM, Aneesh V ane...@ti.com wrote:
Hi Simon, Wolfgang,
On Thursday 21 April 2011 12:04 AM, Simon Glass wrote:
On Fri, Mar 25, 2011 at 11:35 AM, Albert ARIBAUDalbert.arib...@free.fr wrote:
Le 25/03/2011 17:12, Aneesh V a écrit :
Another problem I have with relocation is that it makes debugging with JTAG debugers more difficult. The addresses of symbols in the ELF target are no longer valid. Of course, you can load the symbols at an offset from the original location. But one has to first enable debug prints, find the relocation offset, use it while loading the symbols before you can do source level debugging.
Actually you don't need recompiling: simply set a breakpoint at the entry of relocate_code and once you hit the bp, look up r2: it contains the destination. If you want the offset rather than the absolute address, set the breakpoint right after the 'sub r9, r6, r0' round line 222: r9 will then give you the offset. Unload the current symbols, reload the symbols with the relevant offset, and there you go.
I would like to revisit this thread. I'm not sure how other people do development in U-Boot but I like to use an ICE and a source-level debugger for any significant effort. I think it should be possible to use a JTAG debugging just by loading the u-boot ELF file and running.
With this patch (or something similar) this is possible. Without it, it is painful.
To be clear, we are not talking here about creating a platform that doesn't use relocation, just that for development purposes it is convenient to be able to disable it.
Actually, I am not even sure why relocation shouldn't be disabled in my platform for good. It may be useful to have things such as the frame buffer at the end of available memory. But, IMHO, that can still be done without relocating u-boot. That's what the patch does.Am I missing something?
Well relocation does remove a lot of this ad-hoc positioning of things at compile time. I think it is desirable. My point is that it is not engineer-friendly during development, and we should have an easy way to disable it for debugging / JTAG purposes.
Regards, Simon
Looking at the December thread http://thread.gmane.org/gmane.comp.boot-loaders.u-boot/88067/focus=88262
Aneesh:
Shouldn't we provide a CONFIG option by which users can disable Elf relocation?
Wolfgang:
Why should we? It would just make the code even more complicated, and require a lot of additional test cases.
From what I can see this is a new CONFIG option, two ifdefs in the board.c file, and optionally disabling the -pie position-independent executable option to reduce size. It is pretty trivial:
arch/arm/config.mk | 2 ++ arch/arm/lib/board.c | 5 +++++ 2 files changed, 7 insertions(+), 0 deletions(-)
Regards, Simon
Amicalement,
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