Re: [Crash-utility] [PATCH] ARM: fix unwinding on recent kernels

On Mon, Feb 13, 2012 at 11:59:04AM -0500, Dave Anderson wrote: > > Maybe add some comment explaining why we do this check (a reference to the > > kernel commit perhaps)? > > I agree about the comment -- and then some... > > This seems to be a fairly signficant piece of information to be hidden > in a static variable: > > +static int index_in_prel31; > > Can you put it in the ARM machine_specific data structure? And then > display it in arm_dump_machdep_table() for "help -m". Here's a v2 of the patch. Rabin

diff --git a/arm.c b/arm.c index 4ca2fcd..4be224e 100644 --- a/arm.c +++ b/arm.c @@ -406,6 +406,7 @@ arm_dump_machdep_table(ulong arg) fprintf(fp, "exception_text_start: %lx\n", ms->exception_text_start); fprintf(fp, " exception_text_end: %lx\n", ms->exception_text_end); fprintf(fp, " crash_task_regs: %lx\n", (ulong)ms->crash_task_regs); + fprintf(fp, "unwind_index_prel31: %d\n", ms->unwind_index_prel31); } /* diff --git a/defs.h b/defs.h index 82d51e5..2e7f6bd 100755 --- a/defs.h +++ b/defs.h @@ -4241,6 +4241,7 @@ struct machine_specific { ulong exception_text_start; ulong exception_text_end; struct arm_pt_regs *crash_task_regs; + int unwind_index_prel31; }; int init_unwind_tables(void); diff --git a/unwind_arm.c b/unwind_arm.c index d86ec63..640d6c9 100644 --- a/unwind_arm.c +++ b/unwind_arm.c @@ -104,6 +104,7 @@ static int is_core_kernel_text(ulong); static struct unwind_table *search_table(ulong); static struct unwind_idx *search_index(const struct unwind_table *, ulong); static ulong prel31_to_addr(ulong, ulong); +static void index_prel31_to_addr(struct unwind_table *); static int unwind_frame(struct stackframe *, ulong); /* @@ -187,6 +188,19 @@ init_kernel_unwind_table(void) goto fail; } + /* + * Kernel versions before v3.2 (specifically, before commit + * de66a979012db "ARM: 7187/1: fix unwinding for XIP kernels") + * converted the prel31 offsets in the unwind index table to absolute + * addresses on startup. Newer kernels don't perform this conversion, + * and have a slightly more involved search algorithm. + * + * We always just use the older search method (a straightforward binary + * search) and convert the index table offsets ourselves if we detect + * that the kernel didn't do it. + */ + machdep->machspec->unwind_index_prel31 = !is_kernel_text(kernel_unwind_table->idx[0].addr); + kernel_unwind_table->start = kernel_unwind_table->idx; kernel_unwind_table->end = (struct unwind_idx *) ((char *)kernel_unwind_table->idx + idx_size); @@ -194,6 +208,9 @@ init_kernel_unwind_table(void) kernel_unwind_table->end_addr = (kernel_unwind_table->end - 1)->addr; kernel_unwind_table->kv_base = idx_start; + if (machdep->machspec->unwind_index_prel31) + index_prel31_to_addr(kernel_unwind_table); + if (CRASHDEBUG(1)) { fprintf(fp, "UNWIND: master kernel table start\n"); fprintf(fp, "UNWIND: size : %ld\n", idx_size); @@ -260,6 +277,9 @@ read_module_unwind_table(struct unwind_table *tbl, ulong addr) tbl->end_addr = TABLE_VALUE(buf, unwind_table_end_addr); tbl->kv_base = idx_start; + if (machdep->machspec->unwind_index_prel31) + index_prel31_to_addr(tbl); + if (CRASHDEBUG(1)) { fprintf(fp, "UNWIND: module table start\n"); fprintf(fp, "UNWIND: start : %p\n", tbl->start); @@ -571,6 +591,16 @@ prel31_to_addr(ulong addr, ulong insn) return addr + offset; } +static void +index_prel31_to_addr(struct unwind_table *tbl) +{ + struct unwind_idx *idx = tbl->start; + ulong kvaddr = tbl->kv_base; + + for (; idx < tbl->end; idx++, kvaddr += sizeof(struct unwind_idx)) + idx->addr = prel31_to_addr(kvaddr, idx->addr); +} + static int unwind_frame(struct stackframe *frame, ulong stacktop) {