File gdb-tdep-fix-gdb.base-watchpoint-running-on-arm... of Package gdb

Overview Repositories Revisions Requests Users Attributes Meta

File gdb-tdep-fix-gdb.base-watchpoint-running-on-arm-ppc6.patch of Package gdb (Revision e118954a7b5ee9a56c9e519ce0b644b1)

Currently displaying revision e118954a7b5ee9a56c9e519ce0b644b1 , Show latest

From 1e64a66f72c79874016e78a4672b85cdeb506b9f Mon Sep 17 00:00:00 2001
From: Tom de Vries <tdevries@suse.de>
Date: Tue, 4 Jun 2024 09:30:03 +0000
Subject: [PATCH] [gdb/tdep] Fix gdb.base/watchpoint-running on
 {arm,ppc64le}-linux

When running test-case gdb.base/watchpoint-running on ppc64le-linux, we get:
...
(gdb) watch global_var^M
warning: Error when detecting the debug register interface. \
  Debug registers will be unavailable.^M
Watchpoint 2: global_var^M
(gdb) FAIL: $exp: all-stop: hardware: watch global_var
FAIL: $exp: all-stop: hardware: watchpoint hit (timeout)
...

The problem is that ppc_linux_dreg_interface::detect fails to detect the
hardware watchpoint interface, because the calls to ptrace return with errno
set to ESRCH.

This is a feature of ptrace: if a call is done while the tracee is not
ptrace-stopped, it returns ESRCH.

Indeed, in the test-case "watch global_var" is executed while the inferior is
running, and that triggers the first call to ppc_linux_dreg_interface::detect.

And because the detection failure is cached, subsequent attempts at setting
hardware watchpoints will also fail, even if the tracee is ptrace-stopped.

Fix this by calling target_can_use_hardware_watchpoint from
linux_init_ptrace_procfs, which is called from both:
- linux_nat_target::post_attach, and
- linux_nat_target::post_startup_inferior.

By fixing this here, we also fix the same problem for arm-linux.

Tested on ppc64le-linux and arm-linux.

PR tdep/31834
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31834
PR tdep/31705
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31705

(cherry picked from commit bbc92bfbf25ad42548100e31e491ed3c32fbfa3e)
---
 gdb/linux-nat.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index c8991cc3da4..47d74d27e11 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -385,6 +385,18 @@ linux_init_ptrace_procfs (pid_t pid, int attached)
   linux_ptrace_init_warnings ();
   linux_proc_init_warnings ();
   proc_mem_file_is_writable ();
+
+  /* Some targets (for instance ppc and arm) may call ptrace to answer a
+     target_can_use_hardware_watchpoint query, and cache the result.  However,
+     the ptrace call will fail with errno ESRCH if the tracee is not
+     ptrace-stopped, making the query fail.  And if the caching mechanism does
+     not disregard an ESRCH result, all subsequent queries will also fail.
+     Call it now, where we known the tracee is ptrace-stopped.
+
+     Other targets (for instance aarch64) do the relevant ptrace call and
+     caching in their implementation of post_attach and post_startup_inferior,
+     in which case this call is expected to have no effect.  */
+  target_can_use_hardware_watchpoint (bp_hardware_watchpoint, 1, 0);
 }
 
 linux_nat_target::~linux_nat_target ()

base-commit: a6800d9c8145f25001dd39afc3571e3350573e81
-- 
2.35.3

Places

File gdb-tdep-fix-gdb.base-watchpoint-running-on-arm-ppc6.patch of Package gdb (Revision e118954a7b5ee9a56c9e519ce0b644b1)

Places