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banner stub: preserve lr, pop-return to caller

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SashegDev
2026-09-11 07:15:31 +00:00
parent 61ddf9de6b
commit e473826732
2 changed files with 10 additions and 12 deletions
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qemu/banner.S
+5 -3
View File
@@ -1,11 +1,13 @@
.syntax unified .syntax unified
.cpu cortex-a7 .cpu cortex-a7
.thumb .thumb
@ Banner stub for SBL1 logger call at 0x802f690 (blx r3 patched to bl here). @ Banner stub for SBL1 logger call at 0x802f690 (patched to bl here).
@ r0 = string. Print raw bytes via UARTDM until NUL (cap 256), return 0. @ r0 = string. Print raw bytes via UARTDM until NUL (cap 256).
@ Preserve lr (set by bl) and return to caller with r0=0.
.text .text
.global banner_stub .global banner_stub
banner_stub: banner_stub:
push {r4, lr}
movw r3, #0xf000 movw r3, #0xf000
movt r3, #0x78a movt r3, #0x78a
bn_loop: bn_loop:
@@ -15,4 +17,4 @@ bn_loop:
b bn_loop b bn_loop
bn_done: bn_done:
movs r0, #0 movs r0, #0
bx lr pop {r4, pc}
qemu/saimaa.c
+5 -9
View File
@@ -440,17 +440,13 @@ static void saimaa_machine_init(MachineState *machine)
} }
} }
/* Banner stub at 0x08062150: print r0 string via UARTDM /* Banner stub at 0x08062150: print r0 string via UARTDM
* (b16 redirects 0x802f690 blx here). Built from qemu/banner.S */ * (b16 redirects 0x802f690 blx here). Built from qemu/banner.S:
* push/pop frame, preserves lr, returns r0=0 to caller. */
{ {
static const uint8_t bn[] = { static const uint8_t bn[] = {
0x4f, 0xf2, 0x00, 0x03, /* movw r3,#0xf000 */ 0x10, 0xb5, 0x4f, 0xf2, 0x00, 0x03, 0xc0, 0xf2,
0xc0, 0xf2, 0x8a, 0x73, /* movt r3,#0x78a */ 0x8a, 0x73, 0x10, 0xf8, 0x01, 0x1b, 0x09, 0xb1,
0x10, 0xf8, 0x01, 0x1b, /* ldrb r1,[r0],#1 */ 0x19, 0x67, 0xfa, 0xe7, 0x00, 0x20, 0x10, 0xbd,
0x09, 0xb1, /* cbz r1,done */
0x19, 0x67, /* str r1,[r3,#0x70] */
0xfa, 0xe7, /* b loop */
0x00, 0x20, /* movs r0,#0 */
0x70, 0x47, /* bx lr */
}; };
size_t k; size_t k;
for (k = 0; k < sizeof(bn); k += 4) { for (k = 0; k < sizeof(bn); k += 4) {