libpayload: Cache copy of `cb_framebuffer` struct

Our AArch64 code supports dynamic framebuffer allocation which
makes it necessary to change the framebuffer information during
runtime. Having a pointer inside `libsysinfo` made a mess of it
as the pointer would either refer to the original struct inside
the coreboot table or to a new struct inside payload space. The
latter would be unaffected by a relocation of the payload.

Instead of the pointer, we'll always keep a copy of the whole
struct, which can be altered on demand without affecting the
coreboot table. To align the `video/graphics` driver with the
console driver, we also replace `fbaddr` with a macro `FB` that
calls phys_to_virt().

Change-Id: I3edc09cdb502a71516c1ee71457c1f8dcd01c119
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/43578
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Julius Werner <jwerner@chromium.org>

5 files changed, 15 insertions, 33 deletions

diff --git a/payloads/libpayload/arch/arm64/mmu.c b/payloads/libpayload/arch/arm64/mmu.c
index 1fa9ced1be..cb0081b789 100644
--- a/payloads/libpayload/arch/arm64/mmu.c
+++ b/payloads/libpayload/arch/arm64/mmu.c
@@ -625,14 +625,10 @@ static void mmu_extract_ranges(struct memrange *cb_ranges,
 static void mmu_add_fb_range(struct mmu_ranges *mmu_ranges)
 {
 	struct mmu_memrange *fb_range;
-	static struct cb_framebuffer modified_fb;
-	struct cb_framebuffer *framebuffer = lib_sysinfo.framebuffer;
+	struct cb_framebuffer *framebuffer = &lib_sysinfo.framebuffer;
 	uint32_t fb_size;
 
 	/* Check whether framebuffer is needed */
-	if (framebuffer == NULL)
-		return;
-
 	fb_size = framebuffer->bytes_per_line * framebuffer->y_resolution;
 	if (!fb_size)
 		return;
@@ -652,16 +648,7 @@ static void mmu_add_fb_range(struct mmu_ranges *mmu_ranges)
 	if (fb_range == NULL)
 		mmu_error();
 
-	/*
-	 * Set framebuffer address. However, one needs to use a freshly
-	 * allocated framebuffer structure because the one in the coreboot
-	 * table is part of a checksum calculation. Therefore, one cannot
-	 * modify a field without recomputing the necessary checksum
-	 * calcuation.
-	 */
-	modified_fb = *framebuffer;
-	modified_fb.physical_address = fb_range->base;
-	lib_sysinfo.framebuffer = &modified_fb;
+	framebuffer->physical_address = fb_range->base;
 }
 
 /*
diff --git a/payloads/libpayload/drivers/video/corebootfb.c b/payloads/libpayload/drivers/video/corebootfb.c
index c21665d0c0..1865ad37bf 100644
--- a/payloads/libpayload/drivers/video/corebootfb.c
+++ b/payloads/libpayload/drivers/video/corebootfb.c
@@ -60,7 +60,7 @@ static const u32 vga_colors[] = {
 	(0xFF << 16) | (0xFF << 8) | 0xFF,
 };
 
-struct cb_framebuffer fbinfo;
+static struct cb_framebuffer fbinfo;
 static unsigned short *chars;
 
 /* Shorthand for up-to-date virtual framebuffer address */
@@ -223,13 +223,10 @@ static void corebootfb_set_cursor(unsigned int x, unsigned int y)
 
 static int corebootfb_init(void)
 {
-	if (lib_sysinfo.framebuffer == NULL)
+	if (!lib_sysinfo.framebuffer.physical_address)
 		return -1;
 
-	fbinfo = *lib_sysinfo.framebuffer;
-
-	if (fbinfo.physical_address == 0)
-		return -1;
+	fbinfo = lib_sysinfo.framebuffer;
 
 	font_init(fbinfo.x_resolution);
 
diff --git a/payloads/libpayload/drivers/video/graphics.c b/payloads/libpayload/drivers/video/graphics.c
index 21f520c290..2d2ea030ba 100644
--- a/payloads/libpayload/drivers/video/graphics.c
+++ b/payloads/libpayload/drivers/video/graphics.c
@@ -45,8 +45,10 @@ static struct rect screen;
  * Framebuffer is assumed to assign a higher coordinate (larger x, y) to
  * a higher address
  */
-static struct cb_framebuffer *fbinfo;
-static uint8_t *fbaddr;
+static const struct cb_framebuffer *fbinfo;
+
+/* Shorthand for up-to-date virtual framebuffer address */
+#define FB ((unsigned char *)phys_to_virt(fbinfo->physical_address))
 
 #define LOG(x...)	printf("CBGFX: " x)
 #define PIVOT_H_MASK	(PIVOT_H_LEFT|PIVOT_H_CENTER|PIVOT_H_RIGHT)
@@ -296,7 +298,7 @@ static inline void set_pixel(struct vector *coord, uint32_t color)
 		break;
 	}
 
-	uint8_t * const pixel = fbaddr + rcoord.y * bpl + rcoord.x * bpp / 8;
+	uint8_t * const pixel = FB + rcoord.y * bpl + rcoord.x * bpp / 8;
 	for (i = 0; i < bpp / 8; i++)
 		pixel[i] = (color >> (i * 8));
 }
@@ -310,12 +312,9 @@ static int cbgfx_init(void)
 	if (initialized)
 		return 0;
 
-	fbinfo = lib_sysinfo.framebuffer;
-	if (!fbinfo)
-		return CBGFX_ERROR_FRAMEBUFFER_INFO;
+	fbinfo = &lib_sysinfo.framebuffer;
 
-	fbaddr = phys_to_virt((uint8_t *)(uintptr_t)(fbinfo->physical_address));
-	if (!fbaddr)
+	if (!fbinfo->physical_address)
 		return CBGFX_ERROR_FRAMEBUFFER_ADDR;
 
 	switch (fbinfo->orientation) {
@@ -627,7 +626,7 @@ int clear_screen(const struct rgb_color *rgb)
 	 * We assume that for 32bpp the high byte gets ignored anyway. */
 	if ((((color >> 8) & 0xff) == (color & 0xff)) && (bpp == 16 ||
 	    (((color >> 16) & 0xff) == (color & 0xff)))) {
-		memset(fbaddr, color & 0xff, fbinfo->y_resolution * bpl);
+		memset(FB, color & 0xff, fbinfo->y_resolution * bpl);
 	} else {
 		for (p.y = 0; p.y < screen.size.height; p.y++)
 			for (p.x = 0; p.x < screen.size.width; p.x++)
diff --git a/payloads/libpayload/include/sysinfo.h b/payloads/libpayload/include/sysinfo.h
index 188b2c3ecf..303e08e311 100644
--- a/payloads/libpayload/include/sysinfo.h
+++ b/payloads/libpayload/include/sysinfo.h
@@ -81,7 +81,7 @@ struct sysinfo_t {
 
 	char *cb_version;
 
-	struct cb_framebuffer *framebuffer;
+	struct cb_framebuffer framebuffer;
 
 	int num_gpios;
 	struct cb_gpio gpios[SYSINFO_MAX_GPIOS];
diff --git a/payloads/libpayload/libc/coreboot.c b/payloads/libpayload/libc/coreboot.c
index 5ecdd51fab..43d9df4147 100644
--- a/payloads/libpayload/libc/coreboot.c
+++ b/payloads/libpayload/libc/coreboot.c
@@ -186,8 +186,7 @@ static void cb_parse_checksum(void *ptr, struct sysinfo_t *info)
 #if CONFIG(LP_COREBOOT_VIDEO_CONSOLE)
 static void cb_parse_framebuffer(void *ptr, struct sysinfo_t *info)
 {
-	/* ptr points to a coreboot table entry and is already virtual */
-	info->framebuffer = ptr;
+	info->framebuffer = *(struct cb_framebuffer *)ptr;
 }
 #endif