[2/2,gdb/tui] Only handle code sections in tui_find_backward_disassembly_start_address
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Commit Message
After adding a unit test in gdb/tui/tui-disasm.c excercising
tui_find_disassembly_address, I decided to try to extend it using addresses
around section borders.
The new test was very slow (when using gdb as inferior, as is done in
gdb.gdb/unittest.exp), due to disassembling entire non-code sections.
Fix this this by limiting tui_find_backward_disassembly_start_address to
SEC_CODE sections.
FWIW, compared to other self-tests it's still somewhat slow:
...
(gdb) maint selftest
...
Command execution time: 1.535391 (cpu), 1.571246 (wall)
(gdb) maint selftest tui-disasm
...
Command execution time: 0.482022 (cpu), 0.482028 (wall)
...
This is for calling gdb_print_insn ~550 times.
Tested on x86_64-linux.
---
gdb/tui/tui-disasm.c | 50 +++++++++++++++++++++++++++++++++++++-------
1 file changed, 43 insertions(+), 7 deletions(-)
Comments
On Tue, 5 Sep 2023 17:03:39 +0200
Tom de Vries via Gdb-patches <gdb-patches@sourceware.org> wrote:
> Fix this this by limiting tui_find_backward_disassembly_start_address to
> SEC_CODE sections.
What will happen when a user attempts to use the TUI to look at / debug
dynamically generated code?
Kevin
On 9/27/23 18:15, Kevin Buettner wrote:
> On Tue, 5 Sep 2023 17:03:39 +0200
> Tom de Vries via Gdb-patches <gdb-patches@sourceware.org> wrote:
>
>> Fix this this by limiting tui_find_backward_disassembly_start_address to
>> SEC_CODE sections.
>
> What will happen when a user attempts to use the TUI to look at / debug
> dynamically generated code?
>
Hi, and thanks for the review(s).
Hm, I don't know, good question.
Maybe it will be possible to detect these cases and expand the search,
and by default do a more narrow search.
I'm not familiar with the dynamically generated code scenarios and
support in gdb, so I'm dropping this for now.
Thanks,
- Tom
@@ -46,6 +46,8 @@
#include "gdb_curses.h"
+#include <unordered_set>
+
struct tui_asm_line
{
CORE_ADDR addr;
@@ -164,6 +166,15 @@ tui_disassemble (struct gdbarch *gdbarch,
static CORE_ADDR
tui_find_backward_disassembly_start_address (CORE_ADDR addr)
{
+ struct obj_section *section = find_pc_section (addr);
+ /* Don't handle addresses not in a known section. */
+ if (section == nullptr)
+ return addr;
+
+ /* Only handle sections with only code. */
+ if ((section->the_bfd_section->flags & SEC_CODE) == 0)
+ return addr;
+
struct bound_minimal_symbol msym, msym_prev;
msym = lookup_minimal_symbol_by_pc_section (addr - 1, nullptr,
@@ -174,13 +185,8 @@ tui_find_backward_disassembly_start_address (CORE_ADDR addr)
else if (msym_prev.minsym != nullptr)
return msym_prev.value_address ();
- /* Find the section that ADDR is in, and look for the start of the
- section. */
- struct obj_section *section = find_pc_section (addr);
- if (section != NULL)
- return section->addr ();
-
- return addr;
+ /* Use the start of the section. */
+ return section->addr ();
}
/* Find the disassembly address that corresponds to FROM lines above
@@ -545,6 +551,36 @@ run_tests ()
being passed a PC for which gdb_print_insn throws a MEMORY_ERROR. */
SELF_CHECK (tui_find_disassembly_address (gdbarch, 0, 1) == 0);
SELF_CHECK (tui_find_disassembly_address (gdbarch, 0, -1) == 0);
+
+ /* Poke around the edges of sections. */
+ gdbarch_iterate_over_objfiles_in_search_order
+ (target_gdbarch (),
+ [gdbarch] (objfile *obj)
+ {
+ std::unordered_set<CORE_ADDR> visited;
+
+ /* Already done above. */
+ visited.insert (0);
+
+ for (obj_section *osect : obj->sections ())
+ {
+ CORE_ADDR first_addr = osect->addr ();
+ CORE_ADDR last_addr = osect->endaddr () - 1;
+
+ for (auto addr_ : { first_addr, last_addr })
+ for (int offset = -1; offset <= 1; ++offset)
+ {
+ CORE_ADDR addr = addr_ + offset;
+ if (visited.find (addr) != visited.end ())
+ continue;
+
+ tui_find_disassembly_address (gdbarch, addr, 1);
+ tui_find_disassembly_address (gdbarch, addr, -1);
+ visited.insert (addr);
+ }
+ }
+ return false;
+ }, nullptr);
}
}