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Switch to using nolibc #9

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7501fae
Copy in nolibc from the linux kernel source tree
lukasstraub2 May 27, 2024
b45c1ed
Add a nolibc-style wrapper for the mprotect syscall
lukasstraub2 May 27, 2024
b36a331
Switch to using nolibc
lukasstraub2 May 27, 2024
fb42fef
Add a nolibc-style z_trampo implementation
lukasstraub2 May 27, 2024
fdb6b19
Remove now unused files
lukasstraub2 May 27, 2024
6bf46cf
Prevent fd leak
lukasstraub2 May 27, 2024
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10 changes: 2 additions & 8 deletions src/Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -6,9 +6,9 @@ ARCHS32 := i386
ARCHS64 := amd64 aarch64
ARCHS := $(ARCHS32) $(ARCHS64)

CFLAGS += -pipe -Wall -Wextra -fPIC -fno-ident -fno-stack-protector -U _FORTIFY_SOURCE
CFLAGS += -pipe -Wall -Wextra -fPIC -fno-ident -fno-stack-protector -U _FORTIFY_SOURCE -I include -I include/nolibc
LDFLAGS += -nostartfiles -nodefaultlibs -nostdlib
LDFLAGS += -pie -e z_start -Wl,-Bsymbolic,--no-undefined,--build-id=none
LDFLAGS += -pie -Wl,-Bsymbolic,--no-undefined,--build-id=none
TARGET := loader

ifeq "$(filter $(ARCH),$(ARCHS))" ""
Expand Down Expand Up @@ -36,12 +36,6 @@ endif
OBJS := $(patsubst %.c,%.o, $(wildcard *.c))
OBJS += $(patsubst %.S,%.o, $(wildcard $(ARCH)/*.S))

ifdef SMALL
OBJS := $(filter-out z_printf.%,$(OBJS))
OBJS := $(filter-out z_err.%,$(OBJS))
CFLAGS += -DZ_SMALL
endif

.PHONY: clean all

all: $(TARGET)
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11 changes: 11 additions & 0 deletions src/_start.c
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Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
void z_entry(unsigned long *sp, void (*fini)(void));

int main(int argc, char **argv) {
(void) argc;
(void) argv;
return 0;
}

void _start_c(unsigned long *sp) {
z_entry(sp, (void *) 0);
}
13 changes: 0 additions & 13 deletions src/aarch64/z_start.S
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16 changes: 0 additions & 16 deletions src/aarch64/z_syscall.S
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12 changes: 0 additions & 12 deletions src/aarch64/z_trampo.S
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11 changes: 0 additions & 11 deletions src/amd64/z_start.S
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17 changes: 0 additions & 17 deletions src/amd64/z_syscall.S
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10 changes: 0 additions & 10 deletions src/amd64/z_trampo.S
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11 changes: 0 additions & 11 deletions src/i386/z_start.S
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26 changes: 0 additions & 26 deletions src/i386/z_syscall.S
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12 changes: 0 additions & 12 deletions src/i386/z_trampo.S
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18 changes: 18 additions & 0 deletions src/include/mprotect.h
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Original file line number Diff line number Diff line change
@@ -0,0 +1,18 @@
#ifndef _MPROTECT_H
#define _MPROTECT_H

#include "nolibc.h"

static __attribute__((unused))
int sys_mprotect(void *addr, size_t length, int prot)
{
return my_syscall3(__NR_mprotect, addr, length, prot);
}

static __attribute__((unused))
int mprotect(void *addr, size_t length, int prot)
{
return __sysret(sys_mprotect(addr, length, prot));
}

#endif /* _MPROTECT_H */
154 changes: 154 additions & 0 deletions src/include/nolibc/arch-aarch64.h
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Original file line number Diff line number Diff line change
@@ -0,0 +1,154 @@
/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
/*
* AARCH64 specific definitions for NOLIBC
* Copyright (C) 2017-2022 Willy Tarreau <w@1wt.eu>
*/

#ifndef _NOLIBC_ARCH_AARCH64_H
#define _NOLIBC_ARCH_AARCH64_H

#include "compiler.h"
#include "crt.h"

/* Syscalls for AARCH64 :
* - registers are 64-bit
* - stack is 16-byte aligned
* - syscall number is passed in x8
* - arguments are in x0, x1, x2, x3, x4, x5
* - the system call is performed by calling svc 0
* - syscall return comes in x0.
* - the arguments are cast to long and assigned into the target registers
* which are then simply passed as registers to the asm code, so that we
* don't have to experience issues with register constraints.
*/

#define my_syscall0(num) \
({ \
register long _num __asm__ ("x8") = (num); \
register long _arg1 __asm__ ("x0"); \
\
__asm__ volatile ( \
"svc #0\n" \
: "=r"(_arg1) \
: "r"(_num) \
: "memory", "cc" \
); \
_arg1; \
})

#define my_syscall1(num, arg1) \
({ \
register long _num __asm__ ("x8") = (num); \
register long _arg1 __asm__ ("x0") = (long)(arg1); \
\
__asm__ volatile ( \
"svc #0\n" \
: "=r"(_arg1) \
: "r"(_arg1), \
"r"(_num) \
: "memory", "cc" \
); \
_arg1; \
})

#define my_syscall2(num, arg1, arg2) \
({ \
register long _num __asm__ ("x8") = (num); \
register long _arg1 __asm__ ("x0") = (long)(arg1); \
register long _arg2 __asm__ ("x1") = (long)(arg2); \
\
__asm__ volatile ( \
"svc #0\n" \
: "=r"(_arg1) \
: "r"(_arg1), "r"(_arg2), \
"r"(_num) \
: "memory", "cc" \
); \
_arg1; \
})

#define my_syscall3(num, arg1, arg2, arg3) \
({ \
register long _num __asm__ ("x8") = (num); \
register long _arg1 __asm__ ("x0") = (long)(arg1); \
register long _arg2 __asm__ ("x1") = (long)(arg2); \
register long _arg3 __asm__ ("x2") = (long)(arg3); \
\
__asm__ volatile ( \
"svc #0\n" \
: "=r"(_arg1) \
: "r"(_arg1), "r"(_arg2), "r"(_arg3), \
"r"(_num) \
: "memory", "cc" \
); \
_arg1; \
})

#define my_syscall4(num, arg1, arg2, arg3, arg4) \
({ \
register long _num __asm__ ("x8") = (num); \
register long _arg1 __asm__ ("x0") = (long)(arg1); \
register long _arg2 __asm__ ("x1") = (long)(arg2); \
register long _arg3 __asm__ ("x2") = (long)(arg3); \
register long _arg4 __asm__ ("x3") = (long)(arg4); \
\
__asm__ volatile ( \
"svc #0\n" \
: "=r"(_arg1) \
: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), \
"r"(_num) \
: "memory", "cc" \
); \
_arg1; \
})

#define my_syscall5(num, arg1, arg2, arg3, arg4, arg5) \
({ \
register long _num __asm__ ("x8") = (num); \
register long _arg1 __asm__ ("x0") = (long)(arg1); \
register long _arg2 __asm__ ("x1") = (long)(arg2); \
register long _arg3 __asm__ ("x2") = (long)(arg3); \
register long _arg4 __asm__ ("x3") = (long)(arg4); \
register long _arg5 __asm__ ("x4") = (long)(arg5); \
\
__asm__ volatile ( \
"svc #0\n" \
: "=r" (_arg1) \
: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
"r"(_num) \
: "memory", "cc" \
); \
_arg1; \
})

#define my_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6) \
({ \
register long _num __asm__ ("x8") = (num); \
register long _arg1 __asm__ ("x0") = (long)(arg1); \
register long _arg2 __asm__ ("x1") = (long)(arg2); \
register long _arg3 __asm__ ("x2") = (long)(arg3); \
register long _arg4 __asm__ ("x3") = (long)(arg4); \
register long _arg5 __asm__ ("x4") = (long)(arg5); \
register long _arg6 __asm__ ("x5") = (long)(arg6); \
\
__asm__ volatile ( \
"svc #0\n" \
: "=r" (_arg1) \
: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
"r"(_arg6), "r"(_num) \
: "memory", "cc" \
); \
_arg1; \
})

/* startup code */
void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_stack_protector _start(void)
{
__asm__ volatile (
"mov x0, sp\n" /* save stack pointer to x0, as arg1 of _start_c */
"and sp, x0, -16\n" /* sp must be 16-byte aligned in the callee */
"bl _start_c\n" /* transfer to c runtime */
);
__builtin_unreachable();
}
#endif /* _NOLIBC_ARCH_AARCH64_H */
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