From 35c63cd8ce5100859789b65ae76c6e5fe6ba47a4 Mon Sep 17 00:00:00 2001 From: Joel Brobecker Date: Thu, 15 Mar 2012 18:33:45 +0000 Subject: 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. --- gdb/mem-break.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) (limited to 'gdb/mem-break.c') 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; } -- cgit v1.1