xen-console: Optimize console_display_thrd #66
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xen-console-srv/src/xen_console.c
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| if (read) { | ||
| shell_fprintf(shell, SHELL_NORMAL, "%s", buf); | ||
| } | ||
| buf_pos = (console->int_cons++) & |
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Increment should be removed
| size = (console->int_prod - console->int_cons) & | ||
| (XEN_CONSOLE_BUFFER_SZ - 1); | ||
| shell_fprintf(shell, SHELL_NORMAL, "%.*s", size + 1, | ||
| &console->int_buf[buf_pos]); |
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fprintf may overrun the end of int_buf if buf_pos is closer than size+1 bytes to end of array. This will cause access to foreign memory, so this should be normalized and divided into 2 parts in this corner case.
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Yep. This is a circular buffer so wrap around should be handled gracefully.
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Fixed logic to prevent buffer overruns. |
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With last small comment:
Reviewed-by: Dmytro Firsov <[email protected]>
| (XEN_CONSOLE_BUFFER_SZ - 1); | ||
| prod_buf_pos = (console->int_prod) & | ||
| (XEN_CONSOLE_BUFFER_SZ - 1); | ||
| if (buf_pos < prod_buf_pos) { |
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Please, comment that this condition means no buffer wrap around and in other case we print only part before buffer end
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With @firscity comment addressed:
Reviewed-by: Volodymyr Babchuk <[email protected]>
Optimize console_display_thrd by removing the inner loop that copies data from the console buffer to the output buffer. Instead, calculate the size of the data to be copied and print it in one go. Signed-off-by: Mykyta Poturai <[email protected]> Reviewed-by: Dmytro Firsov <[email protected]> Reviewed-by: Volodymyr Babchuk <[email protected]>
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Optimize console_display_thrd by removing the inner loop that copies data from the console buffer to the output buffer. Instead, calculate the size of the data to be copied and print it in one go.