efi/libstub: Buffer output of efi_puts (fd0528a2) · Commits · 戴 / test

Use a buffer to convert the string to UTF-16. This will reduce the number of firmware calls required to print the string from one per character to one per string in most cases. Cast the input char to unsigned char before converting to efi_char16_t to avoid sign-extension in case there are any non-ASCII characters in the input. Signed-off-by:

Arvind Sankar <nivedita@alum.mit.edu> Link: https://lore.kernel.org/r/20200518190716.751506-4-nivedita@alum.mit.edu Signed-off-by:

Ard Biesheuvel <ardb@kernel.org>

drivers/firmware/efi/libstub/efi-stub-helper.c

+13 −6

Original line number	Diff line number	Diff line
		@@ -8,6 +8,7 @@
		*/

		#include <linux/efi.h>
		#include <linux/kernel.h>
		#include <asm/efi.h>

		#include "efistub.h"
		@@ -34,13 +35,19 @@ void efi_char16_puts(efi_char16_t *str)

		void efi_puts(const char *str)
		{
		while (*str) {
		efi_char16_t ch[] = { *str++, L'\0' };
		efi_char16_t buf[128];
		size_t pos = 0, lim = ARRAY_SIZE(buf);

		if (ch[0] == L'\n')
		efi_char16_puts(L"\r\n");
		else
		efi_char16_puts(ch);
		while (*str) {
		if (*str == '\n')
		buf[pos++] = L'\r';
		/* Cast to unsigned char to avoid sign-extension */
		buf[pos++] = (unsigned char)(*str++);
		if (*str == '\0' \|\| pos >= lim - 2) {
		buf[pos] = L'\0';
		efi_char16_puts(buf);
		pos = 0;
		}
		}
		}

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