gdbserver ignores page protection by virtue of using /proc/$pid/mem.
Teach qemu gdbstub to do this too. This will not work if /proc is not
mounted; accept this limitation.
One alternative is to temporarily grant the missing PROT_* bit, but
this is inherently racy. Another alternative is self-debugging with
ptrace(POKE), which will break if QEMU itself is being debugged - a
much more severe limitation.
Signed-off-by: Ilya Leoshkevich <i...@linux.ibm.com>
---
cpu-target.c | 55 ++++++++++++++++++++++++++++++++++++++--------------
1 file changed, 40 insertions(+), 15 deletions(-)
diff --git a/cpu-target.c b/cpu-target.c
index 5eecd7ea2d7..69e97f78980 100644
--- a/cpu-target.c
+++ b/cpu-target.c
@@ -406,6 +406,15 @@ int cpu_memory_rw_debug(CPUState *cpu, vaddr addr,
vaddr l, page;
void * p;
uint8_t *buf = ptr;
+ int ret = -1;
+ int mem_fd;
+
+ /*
+ * Try ptrace first. If /proc is not mounted or if there is a different
+ * problem, fall back to the manual page access. Note that, unlike ptrace,
+ * it will not be able to ignore the protection bits.
+ */
+ mem_fd = open("/proc/self/mem", is_write ? O_WRONLY : O_RDONLY);
while (len > 0) {
page = addr & TARGET_PAGE_MASK;
@@ -413,22 +422,33 @@ int cpu_memory_rw_debug(CPUState *cpu, vaddr addr,
if (l > len)
l = len;
flags = page_get_flags(page);
- if (!(flags & PAGE_VALID))
- return -1;
+ if (!(flags & PAGE_VALID)) {
+ goto out_close;
+ }
if (is_write) {
- if (!(flags & PAGE_WRITE))
- return -1;
+ if (mem_fd == -1 ||
+ pwrite(mem_fd, ptr, len, (off_t)g2h_untagged(addr)) != len) {
+ if (!(flags & PAGE_WRITE)) {
+ goto out_close;
+ }
+ /* XXX: this code should not depend on lock_user */
+ p = lock_user(VERIFY_WRITE, addr, l, 0);
+ if (!p) {
+ goto out_close;
+ }
+ memcpy(p, buf, l);
+ unlock_user(p, addr, l);
+ }
+ } else if (mem_fd == -1 ||
+ pread(mem_fd, ptr, len, (off_t)g2h_untagged(addr)) != len) {
+ if (!(flags & PAGE_READ)) {
+ goto out_close;
+ }
/* XXX: this code should not depend on lock_user */
- if (!(p = lock_user(VERIFY_WRITE, addr, l, 0)))
- return -1;
- memcpy(p, buf, l);
- unlock_user(p, addr, l);
- } else {
- if (!(flags & PAGE_READ))
- return -1;
- /* XXX: this code should not depend on lock_user */
- if (!(p = lock_user(VERIFY_READ, addr, l, 1)))
- return -1;
+ p = lock_user(VERIFY_READ, addr, l, 1);
+ if (!p) {
+ goto out_close;
+ }
memcpy(buf, p, l);
unlock_user(p, addr, 0);
}
@@ -436,7 +456,12 @@ int cpu_memory_rw_debug(CPUState *cpu, vaddr addr,
buf += l;
addr += l;
}
- return 0;
+ ret = 0;
+out_close:
+ if (mem_fd != -1) {
+ close(mem_fd);
+ }
+ return ret;
}
#endif
--
2.43.0
