Commit da018f972619377e8c044c5c27ebf231be262bb3 | zig

author	Alex Rønne Petersen <alex@alexrp.com> 2024-11-04 18:30:36+01:00
committer	Alex Rønne Petersen <alex@alexrp.com> 2024-12-11 00:10:17+01:00
log	da018f972619377e8c044c5c27ebf231be262bb3
tree	00faa647aca74f648677b74828301ab0f8c14fc0
parent	7d0087707634028308d3a870883249bfa59d94b8
signature	Signed by SSH key SHA256:7B/LJ7bpR1eX8aCXSr4mtd5M45VMPKcx9zY8e95b5QM

std.os.linux: Add unwinding protection in clone() implementations.

Whatever was in the frame pointer register prior to clone() will no longer be
valid in the child process, so zero it to protect FP-based unwinders. Similarly,
mark the link register as undefined to protect DWARF-based unwinders.

This is only zeroing the frame pointer(s) on Arm/Thumb because of an LLVM
assembler bug: https://github.com/llvm/llvm-project/issues/115891

14 files changed, 98 insertions(+), 44 deletions(-)

lib
- std
  - os
    linux
    aarch64.zig
    arm.zig
    hexagon.zig
    loongarch64.zig
    mips.zig
    mips64.zig
    powerpc.zig
    powerpc64.zig
    riscv32.zig
    riscv64.zig
    s390x.zig
    sparc64.zig
    x86.zig
    x86_64.zig

lib/std/os/linux/aarch64.zig+6-1

...	...	@@ -120,8 +120,13 @@ pub fn clone() callconv(.Naked) usize {
120	120	\\ cbz x0,1f
121	121	\\ // parent
122	122	\\ ret
	123	\\
123	124	\\ // child
124		\\1: ldp x1,x0,[sp],#16
	125	\\1: .cfi_undefined lr
	126	\\ mov fp, 0
	127	\\ mov lr, 0
	128	\\
	129	\\ ldp x1,x0,[sp],#16
125	130	\\ blr x1
126	131	\\ mov x8,#93 // SYS_exit
127	132	\\ svc #0

lib/std/os/linux/arm.zig+8-3

...	...	@@ -120,11 +120,16 @@ pub fn clone() callconv(.Naked) usize {
120	120	\\ ldmfd sp!,{r4,r5,r6,r7}
121	121	\\ bx lr
122	122	\\
123		\\1: mov r0,r6
	123	\\ // https://github.com/llvm/llvm-project/issues/115891
	124	\\1: mov r7, #0
	125	\\ mov r11, #0
	126	\\ mov lr, #0
	127	\\
	128	\\ mov r0,r6
124	129	\\ bl 3f
125		\\2: mov r7,#1 // SYS_exit
	130	\\ mov r7,#1 // SYS_exit
126	131	\\ svc 0
127		\\ b 2b
	132	\\
128	133	\\3: bx r5
129	134	);
130	135	}

lib/std/os/linux/hexagon.zig+4

...	...	@@ -118,6 +118,10 @@ pub fn clone() callconv(.Naked) usize {
118	118	\\ p0 = cmp.eq(r0, #0)
119	119	\\ if (!p0) dealloc_return
120	120	\\
	121	\\ .cfi_undefined r31
	122	\\ r30 = #0
	123	\\ r31 = #0
	124	\\
121	125	\\ r0 = r10
122	126	\\ callr r11
123	127	\\

lib/std/os/linux/loongarch64.zig+4

...	...	@@ -121,6 +121,10 @@ pub fn clone() callconv(.Naked) usize {
121	121	\\ beqz $a0, 1f # whether child process
122	122	\\ jirl $zero, $ra, 0 # parent process return
123	123	\\1:
	124	\\ .cfi_undefined 1
	125	\\ move $fp, $zero
	126	\\ move $ra, $zero
	127	\\
124	128	\\ ld.d $t8, $sp, 0 # function pointer
125	129	\\ ld.d $a0, $sp, 8 # argument pointer
126	130	\\ jirl $ra, $t8, 0 # call the user's function

lib/std/os/linux/mips.zig+4

...	...	@@ -231,6 +231,10 @@ pub fn clone() callconv(.Naked) usize {
231	231	\\ jr $ra
232	232	\\ nop
233	233	\\1:
	234	\\ .cfi_undefined $ra
	235	\\ move $fp, $zero
	236	\\ move $ra, $zero
	237	\\
234	238	\\ lw $25, 0($sp)
235	239	\\ lw $4, 4($sp)
236	240	\\ jalr $25

lib/std/os/linux/mips64.zig+4

...	...	@@ -210,6 +210,10 @@ pub fn clone() callconv(.Naked) usize {
210	210	\\ jr $ra
211	211	\\ nop
212	212	\\1:
	213	\\ .cfi_undefined $ra
	214	\\ move $fp, $zero
	215	\\ move $ra, $zero
	216	\\
213	217	\\ ld $25, 0($sp)
214	218	\\ ld $4, 8($sp)
215	219	\\ jalr $25

lib/std/os/linux/powerpc.zig+20-20

...	...	@@ -133,14 +133,14 @@ pub fn clone() callconv(.Naked) usize {
133	133	// syscall(SYS_clone, flags, stack, ptid, tls, ctid)
134	134	// 0 3, 4, 5, 6, 7
135	135	asm volatile (
136		\\ # store non-volatile regs r30, r31 on stack in order to put our
	136	\\ # store non-volatile regs r29, r30 on stack in order to put our
137	137	\\ # start func and its arg there
138		\\ stwu 30, -16(1)
139		\\ stw 31, 4(1)
	138	\\ stwu 29, -16(1)
	139	\\ stw 30, 4(1)
140	140	\\
141		\\ # save r3 (func) into r30, and r6(arg) into r31
142		\\ mr 30, 3
143		\\ mr 31, 6
	141	\\ # save r3 (func) into r29, and r6(arg) into r30
	142	\\ mr 29, 3
	143	\\ mr 30, 6
144	144	\\
145	145	\\ # create initial stack frame for new thread
146	146	\\ clrrwi 4, 4, 4
...	...	@@ -167,28 +167,28 @@ pub fn clone() callconv(.Naked) usize {
167	167	\\ # compare sc result with 0
168	168	\\ cmpwi cr7, 3, 0
169	169	\\
170		\\ # if not 0, jump to end
171		\\ bne cr7, 2f
	170	\\ # if not 0, restore stack and return
	171	\\ beq cr7, 2f
	172	\\ lwz 29, 0(1)
	173	\\ lwz 30, 4(1)
	174	\\ addi 1, 1, 16
	175	\\ blr
172	176	\\
173	177	\\ #else: we're the child
	178	\\ 2:
	179	\\ .cfi_undefined lr
	180	\\ li 31, 0
	181	\\ mtlr 0
	182	\\
174	183	\\ #call funcptr: move arg (d) into r3
175		\\ mr 3, 31
176		\\ #move r30 (funcptr) into CTR reg
177		\\ mtctr 30
	184	\\ mr 3, 30
	185	\\ #move r29 (funcptr) into CTR reg
	186	\\ mtctr 29
178	187	\\ # call CTR reg
179	188	\\ bctrl
180	189	\\ # mov SYS_exit into r0 (the exit param is already in r3)
181	190	\\ li 0, 1
182	191	\\ sc
183		\\
184		\\ 2:
185		\\
186		\\ # restore stack
187		\\ lwz 30, 0(1)
188		\\ lwz 31, 4(1)
189		\\ addi 1, 1, 16
190		\\
191		\\ blr
192	192	);
193	193	}
194	194

lib/std/os/linux/powerpc64.zig+6-1

...	...	@@ -160,7 +160,12 @@ pub fn clone() callconv(.Naked) usize {
160	160	\\ cmpwi cr7, 3, 0
161	161	\\ bnelr cr7
162	162	\\
163		\\ # we're the child. call fn(arg)
	163	\\ # we're the child
	164	\\ .cfi_undefined lr
	165	\\ li 31, 0
	166	\\ mtlr 0
	167	\\
	168	\\ # call fn(arg)
164	169	\\ ld 3, 16(1)
165	170	\\ ld 12, 8(1)
166	171	\\ mtctr 12

lib/std/os/linux/riscv32.zig+5-1

...	...	@@ -120,7 +120,11 @@ pub fn clone() callconv(.Naked) usize {
120	120	\\ ret
121	121	\\
122	122	\\ # Child
123		\\1: lw a1, 0(sp)
	123	\\1: .cfi_undefined ra
	124	\\ mv fp, zero
	125	\\ mv ra, zero
	126	\\
	127	\\ lw a1, 0(sp)
124	128	\\ lw a0, 4(sp)
125	129	\\ jalr a1
126	130	\\

lib/std/os/linux/riscv64.zig+5-1

...	...	@@ -120,7 +120,11 @@ pub fn clone() callconv(.Naked) usize {
120	120	\\ ret
121	121	\\
122	122	\\ # Child
123		\\1: ld a1, 0(sp)
	123	\\1: .cfi_undefined ra
	124	\\ mv fp, zero
	125	\\ mv ra, zero
	126	\\
	127	\\ ld a1, 0(sp)
124	128	\\ ld a0, 8(sp)
125	129	\\ jalr a1
126	130	\\

lib/std/os/linux/s390x.zig+6-1

...	...	@@ -133,7 +133,12 @@ pub fn clone() callconv(.Naked) usize {
133	133	\\ltgr %%r2, %%r2
134	134	\\bnzr %%r14
135	135	\\
136		\\# we're the child. call fn(arg)
	136	\\# we're the child
	137	\\.cfi_undefined %%r14
	138	\\lghi %%r11, 0
	139	\\lghi %%r14, 0
	140	\\
	141	\\# call fn(arg)
137	142	\\lg %%r1, 8(%%r15)
138	143	\\lg %%r2, 16(%%r15)
139	144	\\basr %%r14, %%r1

lib/std/os/linux/sparc64.zig+13-8

...	...	@@ -198,29 +198,34 @@ pub fn clone() callconv(.Naked) usize {
198	198	\\ mov %%i5, %%o3
199	199	\\ ldx [%%fp + 0x8af], %%o4
200	200	\\ t 0x6d
201		\\ bcs,pn %%xcc, 2f
	201	\\ bcs,pn %%xcc, 1f
202	202	\\ nop
203	203	\\ # The child pid is returned in o0 while o1 tells if this
204	204	\\ # process is # the child (=1) or the parent (=0).
205		\\ brnz %%o1, 1f
	205	\\ brnz %%o1, 2f
206	206	\\ nop
207	207	\\ # Parent process, return the child pid
208	208	\\ mov %%o0, %%i0
209	209	\\ ret
210	210	\\ restore
211	211	\\1:
212		\\ # Child process, call func(arg)
	212	\\ # The syscall failed
	213	\\ sub %%g0, %%o0, %%i0
	214	\\ ret
	215	\\ restore
	216	\\2:
	217	\\ # Child process
	218	\\ .cfi_undefined %%i7
	219	\\ mov %%g0, %%fp
	220	\\ mov %%g0, %%i7
	221	\\
	222	\\ # call func(arg)
213	223	\\ mov %%g0, %%fp
214	224	\\ call %%g2
215	225	\\ mov %%g3, %%o0
216	226	\\ # Exit
217	227	\\ mov 1, %%g1 // SYS_exit
218	228	\\ t 0x6d
219		\\2:
220		\\ # The syscall failed
221		\\ sub %%g0, %%o0, %%i0
222		\\ ret
223		\\ restore
224	229	);
225	230	}
226	231

lib/std/os/linux/x86.zig+11-8

...	...	@@ -148,19 +148,22 @@ pub fn clone() callconv(.Naked) usize {
148	148	\\ movl $120,%%eax // SYS_clone
149	149	\\ int $128
150	150	\\ testl %%eax,%%eax
151		\\ jnz 1f
152		\\ popl %%eax
153		\\ xorl %%ebp,%%ebp
154		\\ calll *%%eax
155		\\ movl %%eax,%%ebx
156		\\ movl $1,%%eax // SYS_exit
157		\\ int $128
158		\\1:
	151	\\ jz 1f
159	152	\\ popl %%edi
160	153	\\ popl %%esi
161	154	\\ popl %%ebx
162	155	\\ popl %%ebp
163	156	\\ retl
	157	\\
	158	\\1:
	159	\\ .cfi_undefined %%eip
	160	\\ xorl %%ebp,%%ebp
	161	\\
	162	\\ popl %%eax
	163	\\ calll *%%eax
	164	\\ movl %%eax,%%ebx
	165	\\ movl $1,%%eax // SYS_exit
	166	\\ int $128
164	167	);
165	168	}
166	169

lib/std/os/linux/x86_64.zig+2

...	...	@@ -116,8 +116,10 @@ pub fn clone() callconv(.Naked) usize {
116	116	\\ testq %%rax,%%rax
117	117	\\ jz 1f
118	118	\\ retq
	119	\\
119	120	\\1: .cfi_undefined %%rip
120	121	\\ xorl %%ebp,%%ebp
	122	\\
121	123	\\ popq %%rdi
122	124	\\ callq *%%r9
123	125	\\ movl %%eax,%%edi