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authorJoel Brobecker <brobecker@gnat.com>2012-03-15 18:33:45 +0000
committerJoel Brobecker <brobecker@gnat.com>2012-03-15 18:33:45 +0000
commit35c63cd8ce5100859789b65ae76c6e5fe6ba47a4 (patch)
tree06b0067bd7fe07eb48b194b63dc353aab092ec9a /gdb/mem-break.c
parent7b8957f8c3b4054061363abdc38bbbf0a3b20635 (diff)
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Problem after hitting breakpoint on Windows (with GDBserver)
When debugging on Windows with GDBserver, the debugger starts failing after hitting a breakpoint. For instance: (gdb) b foo Breakpoint 1 at 0x40177e: file foo.adb, line 5. (gdb) cont Continuing. Breakpoint 1, foo () at foo.adb:5 5 Put_Line ("Hello World."); -- STOP (gdb) n Program received signal SIGSEGV, Segmentation fault. 0x00401782 in foo () at foo.adb:5 5 Put_Line ("Hello World."); -- STOP There are two issues: 1. While trying to re-insert a breakpoint that is still inserted in memory, insert_bp_location wipes out the breakpoint location's shadow_contents. As a consequence, we cannot restore the proper instruction when removing the breakpoint anymore. That's why the inferior's behavior changes when trying to resume after the breakpoint was hit. 2. mem-break.c:default_memory_insert_breakpoint passes a breakpoint location's shadow_contents as the buffer for a memory read. This reveals a limitation of the various memory-read target functions. This patch documents this limitation and adjust the two calls that seem to hit that limitation. gdb/ChangeLog: * breakpoint.c (breakpoint_xfer_memory): Add assertion. Update function description. (insert_bp_location): Do not wipe bl->target_info out. * mem-break.c: #include "gdb_string.h". (default_memory_insert_breakpoint): Do not call target_read_memory with a pointer to the breakpoint's shadow_contents buffer. Use a local buffer instead. * m32r-tdep.c (m32r_memory_insert_breakpoint): Ditto.
Diffstat (limited to 'gdb/mem-break.c')
-rw-r--r--gdb/mem-break.c17
1 files changed, 11 insertions, 6 deletions
diff --git a/gdb/mem-break.c b/gdb/mem-break.c
index 7d0e3f1..bd34fb2 100644
--- a/gdb/mem-break.c
+++ b/gdb/mem-break.c
@@ -29,6 +29,7 @@
#include "breakpoint.h"
#include "inferior.h"
#include "target.h"
+#include "gdb_string.h"
/* Insert a breakpoint on targets that don't have any better
@@ -46,6 +47,7 @@ default_memory_insert_breakpoint (struct gdbarch *gdbarch,
{
int val;
const unsigned char *bp;
+ gdb_byte *readbuf;
/* Determine appropriate breakpoint contents and size for this address. */
bp = gdbarch_breakpoint_from_pc
@@ -53,15 +55,18 @@ default_memory_insert_breakpoint (struct gdbarch *gdbarch,
if (bp == NULL)
error (_("Software breakpoints not implemented for this target."));
- /* Save the memory contents. */
+ /* Save the memory contents in the shadow_contents buffer and then
+ write the breakpoint instruction. */
bp_tgt->shadow_len = bp_tgt->placed_size;
- val = target_read_memory (bp_tgt->placed_address, bp_tgt->shadow_contents,
+ readbuf = alloca (bp_tgt->placed_size);
+ val = target_read_memory (bp_tgt->placed_address, readbuf,
bp_tgt->placed_size);
-
- /* Write the breakpoint. */
if (val == 0)
- val = target_write_raw_memory (bp_tgt->placed_address, bp,
- bp_tgt->placed_size);
+ {
+ memcpy (bp_tgt->shadow_contents, readbuf, bp_tgt->placed_size);
+ val = target_write_raw_memory (bp_tgt->placed_address, bp,
+ bp_tgt->placed_size);
+ }
return val;
}