[gdb/riscv-tdep] Avoid scan invalid prologue
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Commit Message
When running gdb connect to openocd, I run into:
(gdb) set debug remote 1
(gdb) set *0x40000000=0
[remote] Sending packet: $m0,2#fb
[remote] Packet received: 7310
[remote] Sending packet: $m2,2#fd
[remote] Packet received: 4030
[remote] Sending packet: $X40000000,0:#72
[remote] Packet received: OK
[remote] check_binary_download: binary downloading supported by target
[remote] Sending packet: $X40000000,4:\000\000\000\000#76
[remote] Packet received: OK
[remote] Sending packet: $g#67
[remote] Packet received: 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 [16 bytes omitted]
[remote] Sending packet: $m0,2#fb
[remote] Packet received: 7310
[remote] Sending packet: $m2,2#fd
[remote] Packet received: 4030
It means that this operation has performed some invalid operations, and in some cases it will cause the system to slow down.
When I file and load xxx.elf into, run again:
(gdb) set *0x40000000=0
[remote] Sending packet: $X40000000,4:\000\000\000\000#76
[remote] Packet received: OK
[remote] Sending packet: $g#67
[remote] Packet received: 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 [16 bytes omitted]
When I debug gdb hit in riscv_frame_cache:
{
...
/* Scan the prologue, filling in the cache. */
start_addr = get_frame_func (this_frame);
pc = get_frame_pc (this_frame);
riscv_scan_prologue (gdbarch, start_addr, pc, cache);
start_addr -> get_frame_func -> get_frame_func_if_available -> get_pc_function_start (pc = 0x40000000) -> return 0
So that scan invalid prologue, filling in the cache.
---
gdb/riscv-tdep.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--•
2.25.1
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@@ -3723,6 +3723,8 @@ riscv_frame_cache (frame_info_ptr this_frame, void **this_cache)
•
/* Scan the prologue, filling in the cache. */
start_addr = get_frame_func (this_frame);
+ if (start_addr == 0)
+ return NULL;
pc = get_frame_pc (this_frame);
riscv_scan_prologue (gdbarch, start_addr, pc, cache);
•
@@ -3776,7 +3778,8 @@ riscv_frame_this_id (frame_info_ptr this_frame,
try
{
cache = riscv_frame_cache (this_frame, prologue_cache);
- *this_id = cache->this_id;
+ if (cache)
+--> *this_id = cache->this_id;
}
catch (const gdb_exception_error &ex)
{