| Message ID | 4A527397.7060306@gmx.de (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
Helge, > but the unwind table when running the kernel with the attached patch > (see below) shows: > ... > unwind_init: start = 0x105fb3c0, end = 0x10634f30, entries = 14775 > unwind 1: 100ff900 - 100ffa80, len=385 > unwind 2: 100ffa84 - 100ffad4, len=81 > unwind 3: 100ffad8 - 100ffb2c, len=85 > unwind 4: 100ffb30 - 100ffbc8, len=153 > unwind 5: 100ffbcc - 100ffc38, len=109 > unwind 6: 100ffc3c - 100ffc9c, len=97 > unwind 7: 100ffca0 - 100ffd00, len=97 > unwind 8: 100ffd04 - 100ffd64, len=97 > unwind 9: 100ffd68 - 100ffdc8, len=97 > unwind 10: 100ffdcc - 100ffdec, len=33 > > From this table I don't even understand the values of the very first > entry (unwind 1: 100ff900 - 100ffa80). > This does not resolve to any entry in the assembly. I am a little fuzzy on the details, but the numbers printed above are what is stored in the unwind table. This does not correspond with the actual address in memory, which is adjusted by an offset. In the case of kernel symbols, this offset is KERNEL_START (this is a parameter passed to unwind_table_init() > My assumption: > When the linker creates the long-distance jump table, it does not adjusts > the values in the unwind table. this used to work..... > Second, when the linker discards attribute-weak functions, > it doesn't deletes/adjusts the unwind table entries of the deleted > functions either. can you try this with a userspace program? gdb uses this same unwind information to do backtraces. if the unwind info is wrong gdb will be very broken. On the other hand, the kernel does use a more complex linker script so it is possible that some options in the linker script is triggering some bug. randolph -- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 07/07/2009 04:57 AM, Randolph Chung wrote: > Helge, > >> but the unwind table when running the kernel with the attached patch >> (see below) shows: >> ... >> unwind_init: start = 0x105fb3c0, end = 0x10634f30, entries = 14775 >> unwind 1: 100ff900 - 100ffa80, len=385 >> unwind 2: 100ffa84 - 100ffad4, len=81 >> unwind 3: 100ffad8 - 100ffb2c, len=85 >> unwind 4: 100ffb30 - 100ffbc8, len=153 >> unwind 5: 100ffbcc - 100ffc38, len=109 >> unwind 6: 100ffc3c - 100ffc9c, len=97 >> unwind 7: 100ffca0 - 100ffd00, len=97 >> unwind 8: 100ffd04 - 100ffd64, len=97 >> unwind 9: 100ffd68 - 100ffdc8, len=97 >> unwind 10: 100ffdcc - 100ffdec, len=33 >> >> From this table I don't even understand the values of the very first >> entry (unwind 1: 100ff900 - 100ffa80). >> This does not resolve to any entry in the assembly. > I am a little fuzzy on the details, but the numbers printed above are > what is stored in the unwind table. This does not correspond with the > actual address in memory, which is adjusted by an offset. In the case of > kernel symbols, this offset is KERNEL_START (this is a parameter passed > to unwind_table_init() The addresses given above already got the offset added. They are wrong nevertheless. >> My assumption: >> When the linker creates the long-distance jump table, it does not adjusts >> the values in the unwind table. > this used to work..... Yes. Interestingly, this problem showed up to me now since I updated my 32- and 64bit crosscompilers to 4.3.3 (and binutils of course). I used (on 32bit) the gcc-3.3 before and this one doesn't exibited the problem of buggy unwind tables (with the existing/same kernel source code). >> Second, when the linker discards attribute-weak functions, >> it doesn't deletes/adjusts the unwind table entries of the deleted >> functions either. > can you try this with a userspace program? gdb uses this same unwind > information to do backtraces. if the unwind info is wrong gdb will be > very broken. I'll try, but I assume userspace is ok. If it wouldn't be, Dave probably won't be able to debug the other userspace issues (the segv-thread on debian's buildds). > On the other hand, the kernel does use a more complex linker script so > it is possible that some options in the linker script is triggering some > bug. Yes, maybe. But again, I think gcc-3.3 (and the old binutils) could handle this gracefully. Helge -- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Jul 7, 2009 at 2:33 PM, John David Anglin<dave@hiauly1.hia.nrc.ca> wrote: >> Interestingly, this problem showed up to me now since I updated my 32- and >> 64bit crosscompilers to 4.3.3 (and binutils of course). >> I used (on 32bit) the gcc-3.3 before and this one doesn't exibited the >> problem of buggy unwind tables (with the existing/same kernel source code). > > GCC doesn't know anything about PA-RISC unwind info. Â It's generated by the > assembler from assembler directives. Â So, I think it's unlikely that the > problem is in GCC. > > Your comments about dead-code elimination by the linker make me wonder > if that isn't the problem. Helge, Are you compiling with --gc-sections? Try without? I've seen at least one problem in the past on another target where garbage collection would not correctly update debug information. Cheers, Carlos. -- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/parisc/kernel/unwind.c b/arch/parisc/kernel/unwind.c index 69dad5a..d7c7241 100644 --- a/arch/parisc/kernel/unwind.c +++ b/arch/parisc/kernel/unwind.c @@ -94,6 +94,10 @@ unwind_table_init(struct unwind_table *table, const char *name, struct unwind_table_entry *start = table_start; struct unwind_table_entry *end = (struct unwind_table_entry *)table_end - 1; + int nr = 0; + + extern void stext(); + // base_addr += ((unsigned long)&stext) - KERNEL_START; // HELGE table->name = name; table->base_addr = base_addr; @@ -112,6 +116,15 @@ unwind_table_init(struct unwind_table *table, const char *name, start->region_start += base_addr; start->region_end += base_addr; + if (nr<10) { + nr++; + printk("unwind %d: %x - %x, len=%d\n", + nr, + start->region_start, + start->region_end, + start->region_end - start->region_start + 1); + + } } }
I started looking into why CONFIG_BACKTRACE_SELF_TEST=y shows uncomplete/wrong/broken backtraces. To me it seems, that the unwind tables are broken when using newer gcc/binutils versions. I'm running hppa-linux-gcc (GCC) 4.3.3, and GNU ld (GNU Binutils) 2.19.51.20090704. hppa-linux-objdump -d vmlinux gives: vmlinux: file format elf32-hppa-linux Disassembly of section .text: 10100000 <stext-0x700>: 10100000: 20 2f e2 06 ldil L%103df000,r1 10100004: e0 20 28 82 be,n 440(sr4,r1) 10100008: 20 38 42 02 ldil L%10170000,r1 1010000c: e0 20 23 da be,n 1ec(sr4,r1) 10100010: 20 32 62 02 ldil L%10165000,r1 10100014: e0 20 2a 0a be,n 504(sr4,r1) 10100018: 20 34 42 06 ldil L%10368000,r1 1010001c: e0 20 27 12 be,n 388(sr4,r1) 10100020: 20 33 f2 04 ldil L%102e7800,r1 10100024: e0 20 22 ea be,n 174(sr4,r1) 10100028: 20 35 22 06 ldil L%1032b000,r1 1010002c: e0 20 2e 2a be,n 714(sr4,r1) (and continuing) I assume this is a jump-table generated by the linker to resolve long-distance calls? and later: ... 10100700 <stext>: 10100700: 00 00 38 20 mtsp r0,sr4 10100704: 00 00 78 20 mtsp r0,sr5 10100708: 00 00 b8 20 mtsp r0,sr6 1010070c: 00 00 f8 20 mtsp r0,sr7 10100710: 20 69 80 0c ldil L%692000,r3 10100714: 34 63 00 00 ldo 0(r3),r3 10100718: 20 93 f0 0c ldil L%6e7800,r4 1010071c: 34 84 0f 58 ldo 7ac(r4),r4 10100720 <$bss_loop>: 10100720: 80 83 9f f7 cmpb,<<,n r3,r4,10100720 <$bss_loop> 10100724: 0c 60 12 a8 stw,ma r0,4(r3) .... but the unwind table when running the kernel with the attached patch (see below) shows: ... unwind_init: start = 0x105fb3c0, end = 0x10634f30, entries = 14775 unwind 1: 100ff900 - 100ffa80, len=385 unwind 2: 100ffa84 - 100ffad4, len=81 unwind 3: 100ffad8 - 100ffb2c, len=85 unwind 4: 100ffb30 - 100ffbc8, len=153 unwind 5: 100ffbcc - 100ffc38, len=109 unwind 6: 100ffc3c - 100ffc9c, len=97 unwind 7: 100ffca0 - 100ffd00, len=97 unwind 8: 100ffd04 - 100ffd64, len=97 unwind 9: 100ffd68 - 100ffdc8, len=97 unwind 10: 100ffdcc - 100ffdec, len=33 From this table I don't even understand the values of the very first entry (unwind 1: 100ff900 - 100ffa80). This does not resolve to any entry in the assembly. My assumption: When the linker creates the long-distance jump table, it does not adjusts the values in the unwind table. Second, when the linker discards attribute-weak functions, it doesn't deletes/adjusts the unwind table entries of the deleted functions either. Question: Might my analysis be correct? Helge