From: Todd Kjos <tkjos@android.com>
To: gregkh@linuxfoundation.org, arve@android.com,
devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org,
maco@google.com, tkjos@google.com
Subject: [PATCH 12/37] binder: add log information for binder transaction failures
Date: Thu, 29 Jun 2017 12:01:46 -0700 [thread overview]
Message-ID: <20170629190211.16927-13-tkjos@google.com> (raw)
In-Reply-To: <20170629190211.16927-1-tkjos@google.com>
Add additional information to determine the cause of binder
failures. Adds the following to failed transaction log and
kernel messages:
return_error : value returned for transaction
return_error_param : errno returned by binder allocator
return_error_line : line number where error detected
Also, return BR_DEAD_REPLY if an allocation error indicates
a dead proc (-ESRCH)
Signed-off-by: Todd Kjos <tkjos@google.com>
---
drivers/android/binder.c | 87 +++++++++++++++++++++++++++++++++++++-----
drivers/android/binder_alloc.c | 20 +++++-----
2 files changed, 88 insertions(+), 19 deletions(-)
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 25f30d81c7d0..62ac0c41b8a6 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -196,6 +196,9 @@ struct binder_transaction_log_entry {
int to_node;
int data_size;
int offsets_size;
+ int return_error_line;
+ uint32_t return_error;
+ uint32_t return_error_param;
const char *context_name;
};
struct binder_transaction_log {
@@ -1142,7 +1145,7 @@ static int binder_translate_binder(struct flat_binder_object *fp,
ref = binder_get_ref_for_node(target_proc, node);
if (!ref)
- return -EINVAL;
+ return -ENOMEM;
if (fp->hdr.type == BINDER_TYPE_BINDER)
fp->hdr.type = BINDER_TYPE_HANDLE;
@@ -1199,7 +1202,7 @@ static int binder_translate_handle(struct flat_binder_object *fp,
new_ref = binder_get_ref_for_node(target_proc, ref->node);
if (!new_ref)
- return -EINVAL;
+ return -ENOMEM;
fp->binder = 0;
fp->handle = new_ref->desc;
@@ -1397,7 +1400,9 @@ static void binder_transaction(struct binder_proc *proc,
wait_queue_head_t *target_wait;
struct binder_transaction *in_reply_to = NULL;
struct binder_transaction_log_entry *e;
- uint32_t return_error;
+ uint32_t return_error = 0;
+ uint32_t return_error_param = 0;
+ uint32_t return_error_line = 0;
struct binder_buffer_object *last_fixup_obj = NULL;
binder_size_t last_fixup_min_off = 0;
struct binder_context *context = proc->context;
@@ -1417,6 +1422,8 @@ static void binder_transaction(struct binder_proc *proc,
binder_user_error("%d:%d got reply transaction with no transaction stack\n",
proc->pid, thread->pid);
return_error = BR_FAILED_REPLY;
+ return_error_param = -EPROTO;
+ return_error_line = __LINE__;
goto err_empty_call_stack;
}
binder_set_nice(in_reply_to->saved_priority);
@@ -1428,6 +1435,8 @@ static void binder_transaction(struct binder_proc *proc,
in_reply_to->to_thread ?
in_reply_to->to_thread->pid : 0);
return_error = BR_FAILED_REPLY;
+ return_error_param = -EPROTO;
+ return_error_line = __LINE__;
in_reply_to = NULL;
goto err_bad_call_stack;
}
@@ -1435,6 +1444,7 @@ static void binder_transaction(struct binder_proc *proc,
target_thread = in_reply_to->from;
if (target_thread == NULL) {
return_error = BR_DEAD_REPLY;
+ return_error_line = __LINE__;
goto err_dead_binder;
}
if (target_thread->transaction_stack != in_reply_to) {
@@ -1444,6 +1454,8 @@ static void binder_transaction(struct binder_proc *proc,
target_thread->transaction_stack->debug_id : 0,
in_reply_to->debug_id);
return_error = BR_FAILED_REPLY;
+ return_error_param = -EPROTO;
+ return_error_line = __LINE__;
in_reply_to = NULL;
target_thread = NULL;
goto err_dead_binder;
@@ -1458,6 +1470,8 @@ static void binder_transaction(struct binder_proc *proc,
binder_user_error("%d:%d got transaction to invalid handle\n",
proc->pid, thread->pid);
return_error = BR_FAILED_REPLY;
+ return_error_param = -EINVAL;
+ return_error_line = __LINE__;
goto err_invalid_target_handle;
}
target_node = ref->node;
@@ -1467,6 +1481,7 @@ static void binder_transaction(struct binder_proc *proc,
if (target_node == NULL) {
return_error = BR_DEAD_REPLY;
mutex_unlock(&context->context_mgr_node_lock);
+ return_error_line = __LINE__;
goto err_no_context_mgr_node;
}
mutex_unlock(&context->context_mgr_node_lock);
@@ -1475,11 +1490,14 @@ static void binder_transaction(struct binder_proc *proc,
target_proc = target_node->proc;
if (target_proc == NULL) {
return_error = BR_DEAD_REPLY;
+ return_error_line = __LINE__;
goto err_dead_binder;
}
if (security_binder_transaction(proc->tsk,
target_proc->tsk) < 0) {
return_error = BR_FAILED_REPLY;
+ return_error_param = -EPERM;
+ return_error_line = __LINE__;
goto err_invalid_target_handle;
}
if (!(tr->flags & TF_ONE_WAY) && thread->transaction_stack) {
@@ -1493,6 +1511,8 @@ static void binder_transaction(struct binder_proc *proc,
tmp->to_thread ?
tmp->to_thread->pid : 0);
return_error = BR_FAILED_REPLY;
+ return_error_param = -EPROTO;
+ return_error_line = __LINE__;
goto err_bad_call_stack;
}
while (tmp) {
@@ -1516,6 +1536,8 @@ static void binder_transaction(struct binder_proc *proc,
t = kzalloc(sizeof(*t), GFP_KERNEL);
if (t == NULL) {
return_error = BR_FAILED_REPLY;
+ return_error_param = -ENOMEM;
+ return_error_line = __LINE__;
goto err_alloc_t_failed;
}
binder_stats_created(BINDER_STAT_TRANSACTION);
@@ -1523,6 +1545,8 @@ static void binder_transaction(struct binder_proc *proc,
tcomplete = kzalloc(sizeof(*tcomplete), GFP_KERNEL);
if (tcomplete == NULL) {
return_error = BR_FAILED_REPLY;
+ return_error_param = -ENOMEM;
+ return_error_line = __LINE__;
goto err_alloc_tcomplete_failed;
}
binder_stats_created(BINDER_STAT_TRANSACTION_COMPLETE);
@@ -1565,8 +1589,15 @@ static void binder_transaction(struct binder_proc *proc,
t->buffer = binder_alloc_new_buf(&target_proc->alloc, tr->data_size,
tr->offsets_size, extra_buffers_size,
!reply && (t->flags & TF_ONE_WAY));
- if (t->buffer == NULL) {
- return_error = BR_FAILED_REPLY;
+ if (IS_ERR(t->buffer)) {
+ /*
+ * -ESRCH indicates VMA cleared. The target is dying.
+ */
+ return_error_param = PTR_ERR(t->buffer);
+ return_error = return_error_param == -ESRCH ?
+ BR_DEAD_REPLY : BR_FAILED_REPLY;
+ return_error_line = __LINE__;
+ t->buffer = NULL;
goto err_binder_alloc_buf_failed;
}
t->buffer->allow_user_free = 0;
@@ -1586,6 +1617,8 @@ static void binder_transaction(struct binder_proc *proc,
binder_user_error("%d:%d got transaction with invalid data ptr\n",
proc->pid, thread->pid);
return_error = BR_FAILED_REPLY;
+ return_error_param = -EFAULT;
+ return_error_line = __LINE__;
goto err_copy_data_failed;
}
if (copy_from_user(offp, (const void __user *)(uintptr_t)
@@ -1593,12 +1626,16 @@ static void binder_transaction(struct binder_proc *proc,
binder_user_error("%d:%d got transaction with invalid offsets ptr\n",
proc->pid, thread->pid);
return_error = BR_FAILED_REPLY;
+ return_error_param = -EFAULT;
+ return_error_line = __LINE__;
goto err_copy_data_failed;
}
if (!IS_ALIGNED(tr->offsets_size, sizeof(binder_size_t))) {
binder_user_error("%d:%d got transaction with invalid offsets size, %lld\n",
proc->pid, thread->pid, (u64)tr->offsets_size);
return_error = BR_FAILED_REPLY;
+ return_error_param = -EINVAL;
+ return_error_line = __LINE__;
goto err_bad_offset;
}
if (!IS_ALIGNED(extra_buffers_size, sizeof(u64))) {
@@ -1606,6 +1643,8 @@ static void binder_transaction(struct binder_proc *proc,
proc->pid, thread->pid,
(u64)extra_buffers_size);
return_error = BR_FAILED_REPLY;
+ return_error_param = -EINVAL;
+ return_error_line = __LINE__;
goto err_bad_offset;
}
off_end = (void *)off_start + tr->offsets_size;
@@ -1622,6 +1661,8 @@ static void binder_transaction(struct binder_proc *proc,
(u64)off_min,
(u64)t->buffer->data_size);
return_error = BR_FAILED_REPLY;
+ return_error_param = -EINVAL;
+ return_error_line = __LINE__;
goto err_bad_offset;
}
@@ -1636,6 +1677,8 @@ static void binder_transaction(struct binder_proc *proc,
ret = binder_translate_binder(fp, t, thread);
if (ret < 0) {
return_error = BR_FAILED_REPLY;
+ return_error_param = ret;
+ return_error_line = __LINE__;
goto err_translate_failed;
}
} break;
@@ -1647,6 +1690,8 @@ static void binder_transaction(struct binder_proc *proc,
ret = binder_translate_handle(fp, t, thread);
if (ret < 0) {
return_error = BR_FAILED_REPLY;
+ return_error_param = ret;
+ return_error_line = __LINE__;
goto err_translate_failed;
}
} break;
@@ -1658,6 +1703,8 @@ static void binder_transaction(struct binder_proc *proc,
if (target_fd < 0) {
return_error = BR_FAILED_REPLY;
+ return_error_param = target_fd;
+ return_error_line = __LINE__;
goto err_translate_failed;
}
fp->pad_binder = 0;
@@ -1674,6 +1721,8 @@ static void binder_transaction(struct binder_proc *proc,
binder_user_error("%d:%d got transaction with invalid parent offset or type\n",
proc->pid, thread->pid);
return_error = BR_FAILED_REPLY;
+ return_error_param = -EINVAL;
+ return_error_line = __LINE__;
goto err_bad_parent;
}
if (!binder_validate_fixup(t->buffer, off_start,
@@ -1683,12 +1732,16 @@ static void binder_transaction(struct binder_proc *proc,
binder_user_error("%d:%d got transaction with out-of-order buffer fixup\n",
proc->pid, thread->pid);
return_error = BR_FAILED_REPLY;
+ return_error_param = -EINVAL;
+ return_error_line = __LINE__;
goto err_bad_parent;
}
ret = binder_translate_fd_array(fda, parent, t, thread,
in_reply_to);
if (ret < 0) {
return_error = BR_FAILED_REPLY;
+ return_error_param = ret;
+ return_error_line = __LINE__;
goto err_translate_failed;
}
last_fixup_obj = parent;
@@ -1704,6 +1757,8 @@ static void binder_transaction(struct binder_proc *proc,
binder_user_error("%d:%d got transaction with too large buffer\n",
proc->pid, thread->pid);
return_error = BR_FAILED_REPLY;
+ return_error_param = -EINVAL;
+ return_error_line = __LINE__;
goto err_bad_offset;
}
if (copy_from_user(sg_bufp,
@@ -1711,7 +1766,9 @@ static void binder_transaction(struct binder_proc *proc,
bp->buffer, bp->length)) {
binder_user_error("%d:%d got transaction with invalid offsets ptr\n",
proc->pid, thread->pid);
+ return_error_param = -EFAULT;
return_error = BR_FAILED_REPLY;
+ return_error_line = __LINE__;
goto err_copy_data_failed;
}
/* Fixup buffer pointer to target proc address space */
@@ -1726,6 +1783,8 @@ static void binder_transaction(struct binder_proc *proc,
last_fixup_min_off);
if (ret < 0) {
return_error = BR_FAILED_REPLY;
+ return_error_param = ret;
+ return_error_line = __LINE__;
goto err_translate_failed;
}
last_fixup_obj = bp;
@@ -1735,6 +1794,8 @@ static void binder_transaction(struct binder_proc *proc,
binder_user_error("%d:%d got transaction with invalid object type, %x\n",
proc->pid, thread->pid, hdr->type);
return_error = BR_FAILED_REPLY;
+ return_error_param = -EINVAL;
+ return_error_line = __LINE__;
goto err_bad_object_type;
}
}
@@ -1789,13 +1850,17 @@ static void binder_transaction(struct binder_proc *proc,
err_invalid_target_handle:
err_no_context_mgr_node:
binder_debug(BINDER_DEBUG_FAILED_TRANSACTION,
- "%d:%d transaction failed %d, size %lld-%lld\n",
- proc->pid, thread->pid, return_error,
- (u64)tr->data_size, (u64)tr->offsets_size);
+ "%d:%d transaction failed %d/%d, size %lld-%lld line %d\n",
+ proc->pid, thread->pid, return_error, return_error_param,
+ (u64)tr->data_size, (u64)tr->offsets_size,
+ return_error_line);
{
struct binder_transaction_log_entry *fe;
+ e->return_error = return_error;
+ e->return_error_param = return_error_param;
+ e->return_error_line = return_error_line;
fe = binder_transaction_log_add(&binder_transaction_log_failed);
*fe = *e;
}
@@ -3622,11 +3687,13 @@ static void print_binder_transaction_log_entry(struct seq_file *m,
struct binder_transaction_log_entry *e)
{
seq_printf(m,
- "%d: %s from %d:%d to %d:%d context %s node %d handle %d size %d:%d\n",
+ "%d: %s from %d:%d to %d:%d context %s node %d handle %d size %d:%d ret %d/%d l=%d\n",
e->debug_id, (e->call_type == 2) ? "reply" :
((e->call_type == 1) ? "async" : "call "), e->from_proc,
e->from_thread, e->to_proc, e->to_thread, e->context_name,
- e->to_node, e->target_handle, e->data_size, e->offsets_size);
+ e->to_node, e->target_handle, e->data_size, e->offsets_size,
+ e->return_error, e->return_error_param,
+ e->return_error_line);
}
static int binder_transaction_log_show(struct seq_file *m, void *unused)
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 198d04c5d958..a0af1419cc79 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -262,7 +262,7 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
up_write(&mm->mmap_sem);
mmput(mm);
}
- return -ENOMEM;
+ return vma ? -ENOMEM : -ESRCH;
}
struct binder_buffer *binder_alloc_new_buf_locked(struct binder_alloc *alloc,
@@ -278,11 +278,12 @@ struct binder_buffer *binder_alloc_new_buf_locked(struct binder_alloc *alloc,
void *has_page_addr;
void *end_page_addr;
size_t size, data_offsets_size;
+ int ret;
if (alloc->vma == NULL) {
pr_err("%d: binder_alloc_buf, no vma\n",
alloc->pid);
- return NULL;
+ return ERR_PTR(-ESRCH);
}
data_offsets_size = ALIGN(data_size, sizeof(void *)) +
@@ -292,21 +293,21 @@ struct binder_buffer *binder_alloc_new_buf_locked(struct binder_alloc *alloc,
binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
"%d: got transaction with invalid size %zd-%zd\n",
alloc->pid, data_size, offsets_size);
- return NULL;
+ return ERR_PTR(-EINVAL);
}
size = data_offsets_size + ALIGN(extra_buffers_size, sizeof(void *));
if (size < data_offsets_size || size < extra_buffers_size) {
binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
"%d: got transaction with invalid extra_buffers_size %zd\n",
alloc->pid, extra_buffers_size);
- return NULL;
+ return ERR_PTR(-EINVAL);
}
if (is_async &&
alloc->free_async_space < size + sizeof(struct binder_buffer)) {
binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
"%d: binder_alloc_buf size %zd failed, no async space left\n",
alloc->pid, size);
- return NULL;
+ return ERR_PTR(-ENOSPC);
}
while (n) {
@@ -327,7 +328,7 @@ struct binder_buffer *binder_alloc_new_buf_locked(struct binder_alloc *alloc,
if (best_fit == NULL) {
pr_err("%d: binder_alloc_buf size %zd failed, no address space\n",
alloc->pid, size);
- return NULL;
+ return ERR_PTR(-ENOSPC);
}
if (n == NULL) {
buffer = rb_entry(best_fit, struct binder_buffer, rb_node);
@@ -350,9 +351,10 @@ struct binder_buffer *binder_alloc_new_buf_locked(struct binder_alloc *alloc,
(void *)PAGE_ALIGN((uintptr_t)buffer->data + buffer_size);
if (end_page_addr > has_page_addr)
end_page_addr = has_page_addr;
- if (binder_update_page_range(alloc, 1,
- (void *)PAGE_ALIGN((uintptr_t)buffer->data), end_page_addr, NULL))
- return NULL;
+ ret = binder_update_page_range(alloc, 1,
+ (void *)PAGE_ALIGN((uintptr_t)buffer->data), end_page_addr, NULL);
+ if (ret)
+ return ERR_PTR(ret);
rb_erase(best_fit, &alloc->free_buffers);
buffer->free = 0;
--
2.13.2.725.g09c95d1e9-goog
next prev parent reply other threads:[~2017-06-29 19:03 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-29 19:01 [PATCH 00/37] fine-grained locking in binder driver Todd Kjos
2017-06-29 19:01 ` [PATCH 01/37] Revert "android: binder: Sanity check at binder ioctl" Todd Kjos
2017-07-03 9:17 ` Greg KH
[not found] ` <CAHRSSExh9JX5xiSRig55DSei31C_BPSasOKB+BTC6jjjuZ+ZpA@mail.gmail.com>
2017-07-05 18:47 ` Greg KH
2017-06-29 19:01 ` [PATCH 02/37] binder: use group leader instead of open thread Todd Kjos
2017-07-03 9:17 ` Greg KH
[not found] ` <CAHRSSEyH3t0igLJqcC4e-HR68RH0bg4T310jnRHZzrMChoOeOg@mail.gmail.com>
2017-07-05 18:47 ` Greg KH
2017-07-07 18:23 ` Todd Kjos
2017-07-07 18:29 ` Greg KH
2017-07-24 21:00 ` John Stultz
2017-07-24 21:07 ` John Stultz
2017-07-25 9:13 ` Martijn Coenen
2017-07-27 9:08 ` Amit Pundir
2017-07-27 13:23 ` Greg Kroah-Hartman
2017-07-27 13:40 ` Martijn Coenen
2017-07-27 13:42 ` Amit Pundir
2017-07-28 11:58 ` Martijn Coenen
2017-07-24 21:23 ` Greg Kroah-Hartman
2017-07-24 21:53 ` John Stultz
2017-06-29 19:01 ` [PATCH 03/37] binder: Use wake up hint for synchronous transactions Todd Kjos
2017-07-03 9:18 ` Greg KH
2017-06-29 19:01 ` [PATCH 04/37] binder: separate binder allocator structure from binder proc Todd Kjos
2017-06-29 19:01 ` [PATCH 05/37] binder: remove unneeded cleanup code Todd Kjos
2017-06-29 19:01 ` [PATCH 06/37] binder: separate out binder_alloc functions Todd Kjos
2017-06-29 19:01 ` [PATCH 07/37] binder: move binder_alloc to separate file Todd Kjos
2017-06-29 19:01 ` [PATCH 08/37] binder: remove binder_debug_no_lock mechanism Todd Kjos
2017-06-29 19:01 ` [PATCH 09/37] binder: add protection for non-perf cases Todd Kjos
2017-06-29 19:01 ` [PATCH 10/37] binder: change binder_stats to atomics Todd Kjos
2017-06-29 19:01 ` [PATCH 11/37] binder: make binder_last_id an atomic Todd Kjos
2017-06-29 19:01 ` Todd Kjos [this message]
2017-06-29 19:01 ` [PATCH 13/37] binder: refactor queue management in binder_thread_read Todd Kjos
2017-06-29 19:01 ` [PATCH 14/37] binder: avoid race conditions when enqueuing txn Todd Kjos
2017-06-29 19:01 ` [PATCH 15/37] binder: don't modify thread->looper from other threads Todd Kjos
2017-06-29 19:01 ` [PATCH 16/37] binder: remove dead code in binder_get_ref_for_node Todd Kjos
2017-06-29 19:01 ` [PATCH 17/37] binder: protect against two threads freeing buffer Todd Kjos
2017-06-29 19:01 ` [PATCH 18/37] binder: add more debug info when allocation fails Todd Kjos
2017-06-29 19:01 ` [PATCH 19/37] binder: use atomic for transaction_log index Todd Kjos
2017-06-29 19:01 ` [PATCH 20/37] binder: refactor binder_pop_transaction Todd Kjos
2017-06-29 19:01 ` [PATCH 21/37] binder: guarantee txn complete / errors delivered in-order Todd Kjos
2017-06-29 19:01 ` [PATCH 22/37] binder: make sure target_node has strong ref Todd Kjos
2017-06-29 19:01 ` [PATCH 23/37] binder: make sure accesses to proc/thread are safe Todd Kjos
2017-06-29 19:01 ` [PATCH 24/37] binder: refactor binder ref inc/dec for thread safety Todd Kjos
2017-06-29 19:01 ` [PATCH 25/37] binder: use node->tmp_refs to ensure node safety Todd Kjos
2017-06-29 19:02 ` [PATCH 26/37] binder: introduce locking helper functions Todd Kjos
2017-06-29 19:02 ` [PATCH 27/37] binder: use inner lock to sync work dq and node counts Todd Kjos
2017-06-29 19:02 ` [PATCH 28/37] binder: add spinlocks to protect todo lists Todd Kjos
2017-06-29 19:02 ` [PATCH 29/37] binder: add spinlock to protect binder_node Todd Kjos
2017-06-29 19:02 ` [PATCH 30/37] binder: protect proc->nodes with inner lock Todd Kjos
2017-06-29 19:02 ` [PATCH 31/37] binder: protect proc->threads with inner_lock Todd Kjos
2017-06-29 19:02 ` [PATCH 32/37] binder: protect transaction_stack with inner lock Todd Kjos
2017-06-29 19:02 ` [PATCH 33/37] binder: use inner lock to protect thread accounting Todd Kjos
2017-06-29 19:02 ` [PATCH 34/37] binder: protect binder_ref with outer lock Todd Kjos
2017-06-29 19:02 ` [PATCH 35/37] binder: protect against stale pointers in print_binder_transaction Todd Kjos
2017-06-29 19:02 ` [PATCH 36/37] binder: fix death race conditions Todd Kjos
2017-06-30 6:05 ` Greg KH
2017-06-29 19:02 ` [PATCH 37/37] binder: remove global binder lock Todd Kjos
2017-06-30 6:04 ` [PATCH 00/37] fine-grained locking in binder driver Greg KH
2017-07-17 12:49 ` Greg KH
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170629190211.16927-13-tkjos@google.com \
--to=tkjos@android.com \
--cc=arve@android.com \
--cc=devel@driverdev.osuosl.org \
--cc=gregkh@linuxfoundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=maco@google.com \
--cc=tkjos@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).