From 02a2a705aa71646a47c955388491523a989516c5 Mon Sep 17 00:00:00 2001 From: Pierre Langlois Date: Thu, 9 Jul 2015 16:35:11 +0100 Subject: [PATCH] [AArch64] Teach stub unwinder to terminate gracefully The stub unwinder is used on AArch64 if the target's memory is not readable at the current PC. For example, the user could try to call at an invalid address such as 0x0, as covered in the gdb.base/signull.exp test case. Many GDB ports use a similar unwinder to handle this case too. If we purposely kill the inferior before examining the trace then we get the following issue: ~~~ ... (gdb) trace f Tracepoint 3 at 0x7fb7fc28c0 (gdb) tstart (gdb) continue ... (gdb) tstop (gdb) tsave /tmp/trace (gdb) kill ... (gdb) target tfile /tmp/trace ... (gdb) tfind Register 31 is not available. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Found trace frame 0, tracepoint 3 #-1 0x0000007fb7fc28c0 in f () ... ^^^ ~~~ This patch teaches the stub unwinder to report to the core frame code with UNWIND_UNAVAILABLE when either the stack pointer of the return address are unavailable to read from the target. gdb/ChangeLog: * aarch64-tdep.c (aarch64_make_stub_cache): Set available_p and swallow NOT_AVAILABLE_ERROR. (aarch64_stub_this_id): Call frame_id_build_unavailable_stack if available_p is not set. (aarch64_stub_frame_unwind_stop_reason): New function. (aarch64_stub_unwind): Install it. --- gdb/ChangeLog | 9 +++++++++ gdb/aarch64-tdep.c | 38 +++++++++++++++++++++++++++++++++----- 2 files changed, 42 insertions(+), 5 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index f715fcd275..5899173435 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,12 @@ +2015-07-09 Pierre Langlois + + * aarch64-tdep.c (aarch64_make_stub_cache): Set available_p and + swallow NOT_AVAILABLE_ERROR. + (aarch64_stub_this_id): Call frame_id_build_unavailable_stack if + available_p is not set. + (aarch64_stub_frame_unwind_stop_reason): New function. + (aarch64_stub_unwind): Install it. + 2015-07-09 Pierre Langlois * aarch64-tdep.c (aarch64_prologue_cache) : New diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c index 37d3eb31d6..db9ea76cb1 100644 --- a/gdb/aarch64-tdep.c +++ b/gdb/aarch64-tdep.c @@ -1119,13 +1119,38 @@ aarch64_make_stub_cache (struct frame_info *this_frame, void **this_cache) cache->saved_regs = trad_frame_alloc_saved_regs (this_frame); *this_cache = cache; - cache->prev_sp - = get_frame_register_unsigned (this_frame, AARCH64_SP_REGNUM); - cache->prev_pc = get_frame_pc (this_frame); + TRY + { + cache->prev_sp = get_frame_register_unsigned (this_frame, + AARCH64_SP_REGNUM); + cache->prev_pc = get_frame_pc (this_frame); + cache->available_p = 1; + } + CATCH (ex, RETURN_MASK_ERROR) + { + if (ex.error != NOT_AVAILABLE_ERROR) + throw_exception (ex); + } + END_CATCH return cache; } +/* Implement the "stop_reason" frame_unwind method. */ + +static enum unwind_stop_reason +aarch64_stub_frame_unwind_stop_reason (struct frame_info *this_frame, + void **this_cache) +{ + struct aarch64_prologue_cache *cache + = aarch64_make_stub_cache (this_frame, this_cache); + + if (!cache->available_p) + return UNWIND_UNAVAILABLE; + + return UNWIND_NO_REASON; +} + /* Our frame ID for a stub frame is the current SP and LR. */ static void @@ -1135,7 +1160,10 @@ aarch64_stub_this_id (struct frame_info *this_frame, struct aarch64_prologue_cache *cache = aarch64_make_stub_cache (this_frame, this_cache); - *this_id = frame_id_build (cache->prev_sp, cache->prev_pc); + if (cache->available_p) + *this_id = frame_id_build (cache->prev_sp, cache->prev_pc); + else + *this_id = frame_id_build_unavailable_stack (cache->prev_pc); } /* Implement the "sniffer" frame_unwind method. */ @@ -1162,7 +1190,7 @@ aarch64_stub_unwind_sniffer (const struct frame_unwind *self, struct frame_unwind aarch64_stub_unwind = { NORMAL_FRAME, - default_frame_unwind_stop_reason, + aarch64_stub_frame_unwind_stop_reason, aarch64_stub_this_id, aarch64_prologue_prev_register, NULL,