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Re: [Xen-devel] [PATCH v4 03/15] xenctx: Add -m (--multiple_pages) option to output larger stack
On 03/19/14 11:34, George Dunlap wrote:
On 03/18/2014 10:15 PM, Don Slutz wrote:
From: Don Slutz <Don@xxxxxxxxxxxxxxx>
Important: This is the stack size to display not the configured
stack size.
Using pictures (for a 3 page configured system):
+------------------+
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+------------------+
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+------------------+
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SP --> | |
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+------------------+
Sorry, what is this a picture of? I can't make any sense out of it.
Shouldn't this have only one box, the next have two, and the bottom
one have three?
This is various pictures of a 3 page stack, and where the SP currently
is. Each box is a page. So here the "stack limit" is the end of 1
page. In the sense of how much stack is used, you are right it is 1, 2
and then 3. This tracks with the value passed for "-m" (see next line).
Display using "-m 1" since the used stack pages is 1.
+------------------+
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+------------------+
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SP --> | |
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+------------------+
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+------------------+
Here the stack limit is end of page + 1 full page.
Display using "-m 2" since the used stack pages is 2.
+------------------+
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SP --> | |
+------------------+
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+------------------+
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+------------------+
Display using "-m 3" since the used stack pages is 3.
Here the stack limit is end of page + 2 full pages.
Signed-off-by: Don Slutz <Don@xxxxxxxxxxxxxxx>
---
v4 Converted from xenctx: Add -2 (--two-pages) option to switch stack
size to 8KiB
tools/xentrace/xenctx.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/tools/xentrace/xenctx.c b/tools/xentrace/xenctx.c
index 42a47f3..6da38cc 100644
--- a/tools/xentrace/xenctx.c
+++ b/tools/xentrace/xenctx.c
@@ -35,6 +35,7 @@ static struct xenctx {
int frame_ptrs;
int stack_trace;
int disp_all;
+ int multiple_pages;
int all_vcpus;
int self_paused;
xc_dominfo_t dominfo;
@@ -664,6 +665,8 @@ static int print_stack(vcpu_guest_context_any_t
*ctx, int vcpu, int width)
stack_limit = ((stack_pointer(ctx) + XC_PAGE_SIZE)
& ~((guest_word_t) XC_PAGE_SIZE - 1));
+ if ( xenctx.multiple_pages > 1 )
+ stack_limit += (xenctx.multiple_pages - 1) * XC_PAGE_SIZE;
printf("\n");
printf("Stack:\n");
for (i=1; i<5 && stack < stack_limit; i++) {
@@ -834,18 +837,21 @@ static void usage(void)
kernel_start);
printf(" -a, --all display more registers\n");
printf(" -C, --all-vcpus print info for all vcpus\n");
+ printf(" -m PAGES, --multiple-pages=PAGES\n");
+ printf(" assume the kernel was compiled with
PAGES (default 1) of stacks.\n");
}
Opps, this needs fixing.
int main(int argc, char **argv)
{
int ch;
int ret;
- static const char *sopts = "fs:hak:SC";
+ static const char *sopts = "fs:hak:SCm:";
static const struct option lopts[] = {
{"stack-trace", 0, NULL, 'S'},
{"symbol-table", 1, NULL, 's'},
{"frame-pointers", 0, NULL, 'f'},
{"kernel-start", 1, NULL, 'k'},
+ {"multiple-pages", 0, NULL, 'm'},
I think I would call the long option "kernel-stack-pages" or something
like that. "Multiple pages" doesn't really convey much meaning. -m
is probably a fine short option, but -n might be more memorable.
The issue with "kernel-stack-pages" is that it leads to configured
kernel stack pages (which for the pictures above is 3). 3 is most
likely not the number to use here.
A big part of this is that how a "kernel" knows where it is in the stack
can be simple like for a 2 page stack, 1 page is odd, 2nd page is even.
(3 pages is most likely more complex, but fence page(s) may help here.)
Maybe stack-limit-in-pages is better?
-Don Slutz
-George
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