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Footprint record #38

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Merged
retrage merged 2 commits into from
Sep 29, 2025
Merged

Footprint record #38

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9da21d7
main: Add SUPPLEMENTAL__FOOTPRINT_RECORD
retrage Sep 11, 2025
1492110
main: Report size of each trampoline stage
retrage Sep 11, 2025
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2 changes: 2 additions & 0 deletions Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@ PROGS = libsvchook.so
CLANG_FORMAT ?= clang-format

SYSCALL_RECORD ?= 0
FOOTPRINT_RECORD ?= 0

CLEANFILES = $(PROGS) *.o *.d

Expand All @@ -19,6 +20,7 @@ CFLAGS += -Wunused-function
CFLAGS += -Wextra
CFLAGS += -fPIC
CFLAGS += -DSUPPLEMENTAL__SYSCALL_RECORD=$(SYSCALL_RECORD)
CFLAGS += -DSUPPLEMENTAL__FOOTPRINT_RECORD=$(FOOTPRINT_RECORD)

LIBDL ?= -ldl
LDFLAGS += -shared
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42 changes: 40 additions & 2 deletions main.c
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Original file line number Diff line number Diff line change
Expand Up @@ -58,10 +58,21 @@ static void bm_increment(size_t syscall_nr) {
}
#endif /* SUPPLEMENTAL__SYSCALL_RECORD */

#if SUPPLEMENTAL__FOOTPRINT_RECORD
/*
* SUPPLEMENTAL: trampoline memory footprint record
*/
static size_t stage1_size = 0;
static size_t stage2_size = 0;
static size_t stage3_size = 0;
#endif /* SUPPLEMENTAL__FOOTPRINT_RECORD */

extern void do_rt_sigreturn(void);
extern long enter_syscall(int64_t, int64_t, int64_t, int64_t, int64_t, int64_t,
int64_t, int64_t);
extern void enter_syscall_end(void);
extern void asm_syscall_hook(void);
extern void asm_syscall_hook_end(void);

#define CONTEXT_SIZE 256
// clang-format off
Expand Down Expand Up @@ -121,7 +132,9 @@ void ____asm_impl(void) {
"ldr x6, [x6, #:got_lo12:syscall_table] \n\t"
"ldr x6, [x6] \n\t"
"add x6, x6, xzr, lsl #3 \n\t"
"br x6 \n\t");
"br x6 \n\t"
".globl enter_syscall_end \n\t"
"enter_syscall_end: \n\t");

/*
* asm_syscall_hook is the address where the
Expand Down Expand Up @@ -203,7 +216,10 @@ void ____asm_impl(void) {
".globl do_rt_sigreturn \n\t"
"do_rt_sigreturn: \n\t"
"svc #0 \n\t"
"b do_return \n\t");
"b do_return \n\t"

".globl asm_syscall_hook_end \n\t"
"asm_syscall_hook_end: \n\t");
}

static long (*hook_fn)(int64_t a1, int64_t a2, int64_t a3, int64_t a4,
Expand Down Expand Up @@ -792,6 +808,10 @@ static void setup_trampoline(void) {
code[off++] = gen_br(15);
assert(off == jump_code_size);

#if SUPPLEMENTAL__FOOTPRINT_RECORD
stage2_size += off * sizeof(uint32_t);
#endif /* SUPPLEMENTAL__FOOTPRINT_RECORD */

for (size_t i = 0; i < entry->count; i++) {
/*
* put 'gate' code for each svc instruction
Expand Down Expand Up @@ -824,6 +844,10 @@ static void setup_trampoline(void) {
code[off++] = gen_b(current_pc, do_jump_addr);

assert(off - gate_off == gate_size);

#if SUPPLEMENTAL__FOOTPRINT_RECORD
stage1_size += (off - gate_off) * sizeof(uint32_t);
#endif /* SUPPLEMENTAL__FOOTPRINT_RECORD */
}
}

Expand Down Expand Up @@ -870,12 +894,26 @@ static void load_hook_lib(void) {
assert(hook_init);
assert(hook_init(0, &hook_fn) == 0);
}

#if SUPPLEMENTAL__FOOTPRINT_RECORD
fprintf(stderr, "trampoline memory footprint summary:\n");
fprintf(stderr, "stage1: %zu\n", stage1_size);
fprintf(stderr, "stage2: %zu\n", stage2_size);
fprintf(stderr, "stage3: %zu\n", stage3_size);
fprintf(stderr, "total: %zu\n", stage1_size + stage2_size + stage3_size);
#endif /* SUPPLEMENTAL__FOOTPRINT_RECORD */
}

__attribute__((constructor(0xffff))) static void __svc_hook_init(void) {
#if SUPPLEMENTAL__SYSCALL_RECORD
bm_init();
#endif /* SUPPLEMENTAL__SYSCALL_RECORD */

#if SUPPLEMENTAL__FOOTPRINT_RECORD
stage3_size += (uintptr_t)enter_syscall_end - (uintptr_t)enter_syscall;
stage3_size += (uintptr_t)asm_syscall_hook_end - (uintptr_t)asm_syscall_hook;
#endif /* SUPPLEMENTAL__FOOTPRINT_RECORD */

scan_code();
setup_syscall_table();
setup_trampoline();
Expand Down