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c18n: New {get,set}context APIs for libunwind #2123

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c18n: New {get,set}context APIs for libunwind #2123

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53f014c
c18n: Compare pointers by converting them to integers first
dpgao Aug 28, 2024
f0c2c5d
c18n: Expose unified unwinding APIs to setjmp/longjmp and libunwind
dpgao Jun 18, 2024
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47 changes: 24 additions & 23 deletions lib/libc/aarch64/gen/_setjmp.S
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Original file line number Diff line number Diff line change
Expand Up @@ -37,6 +37,13 @@ ENTRY(_setjmp)
ldr x8, .Lmagic
mov REG(9), REGN(sp)
stp REG(8), REG(9), [REG(0)], #(REG_WIDTH * 2)
#ifdef CHERI_LIB_C18N
/* Store the trusted stack pointer */
stp c0, c30, [csp, #-0x20]!
bl dl_c18n_get_trusted_stk
ldp c0, c30, [csp], #0x20
add c0, c0, #REG_WIDTH
#endif

/* Store the general purpose registers and lr */
stp REG(19), REG(20), [REG(0)], #(REG_WIDTH * 2)
Expand All @@ -55,18 +62,8 @@ ENTRY(_setjmp)
#endif

/* Return value */
#ifdef CHERI_LIB_C18N
mov c1, c0
#endif
mov x0, #0
#ifdef CHERI_LIB_C18N
/*
* Tail-call to save Executive mode state
*/
b _rtld_setjmp
#else
RETURN
#endif
.align 3
.Lmagic:
.quad _JB_MAGIC__SETJMP
Expand All @@ -79,12 +76,26 @@ ENTRY(_longjmp)
cmp x8, x9
b.ne botch

#ifdef CHERI_LIB_C18N
/*
* Preserve the arguments in callee-saved registers instead of pushing
* them onto the stack because stack unwinding will switch the stack.
*/
mov c19, c0
mov c20, c1
/* Pass the target untrusted stack pointer and trusted stack pointer */
ldp c0, c1, [c0]
bl dl_c18n_unwind_trusted_stk
mov c0, c19
mov c1, c20
#endif

/* Restore the stack pointer */
ldr REG(8), [REG(0)], #(REG_WIDTH)
#ifdef CHERI_LIB_C18N
mov c2, c8
#else
mov REGN(sp), REG(8)
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What's wrong with doing this for c18n? I'd like to see as much of libc etc de-ifdef'ed as eventually I'd like to see lib/c18n killed off, just as libunwind doesn't need two copies.

#ifdef CHERI_LIB_C18N
/* Skip the trusted stack pointer */
add c0, c0, #REG_WIDTH
#endif

/* Restore the general purpose registers and lr */
Expand All @@ -104,19 +115,9 @@ ENTRY(_longjmp)
#endif

/* Load the return value */
#ifdef CHERI_LIB_C18N
mov c3, c0
#endif
cmp x1, #0
csinc x0, x1, xzr, ne
#ifdef CHERI_LIB_C18N
/*
* Tail-call to restore Executive mode state
*/
b _rtld_longjmp
#else
RETURN
#endif

botch:
#ifdef _STANDALONE
Expand Down
52 changes: 24 additions & 28 deletions lib/libc/aarch64/gen/setjmp.S
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Original file line number Diff line number Diff line change
Expand Up @@ -32,11 +32,6 @@
#include <machine/setjmp.h>
#include <sys/elf_common.h>

#ifdef CHERI_LIB_C18N
.weak _rtld_setjmp
.weak _rtld_longjmp
#endif

ENTRY(setjmp)
sub REGN(sp), REGN(sp), #(REG_WIDTH * 2)
stp REG(0), REGN(lr), [REGN(sp)]
Expand All @@ -54,6 +49,13 @@ ENTRY(setjmp)
ldr x8, .Lmagic
mov REG(9), REGN(sp)
stp REG(8), REG(9), [REG(0)], #(REG_WIDTH * 2)
#ifdef CHERI_LIB_C18N
/* Store the trusted stack pointer */
stp c0, c30, [csp, #-0x20]!
bl dl_c18n_get_trusted_stk
ldp c0, c30, [csp], #0x20
add c0, c0, #REG_WIDTH
#endif

/* Store the general purpose registers and lr */
stp REG(19), REG(20), [REG(0)], #(REG_WIDTH * 2)
Expand All @@ -70,24 +72,28 @@ ENTRY(setjmp)
stp d14, d15, [REG(0)], #16

/* Return value */
#ifdef CHERI_LIB_C18N
mov c1, c0
#endif
mov x0, #0
#ifdef CHERI_LIB_C18N
/*
* Tail-call to save Executive mode state
*/
b _rtld_setjmp
#else
RETURN
#endif
.align 3
.Lmagic:
.quad _JB_MAGIC_SETJMP
END(setjmp)

ENTRY(longjmp)
#ifdef CHERI_LIB_C18N
/*
* Preserve the arguments in callee-saved registers instead of pushing
* them onto the stack because stack unwinding will switch the stack.
*/
mov c19, c0
mov c20, c1
/* Pass the target untrusted stack pointer and trusted stack pointer */
ldp c0, c1, [c0, #(REG_WIDTH * 1)]
bl dl_c18n_unwind_trusted_stk
mov c0, c19
mov c1, c20
#endif

sub REGN(sp), REGN(sp), #(REG_WIDTH * 4)
stp REG(0), REGN(lr), [REGN(sp)]
str REG(1), [REGN(sp), #(REG_WIDTH * 2)]
Expand All @@ -110,10 +116,10 @@ ENTRY(longjmp)

/* Restore the stack pointer */
ldr REG(8), [REG(0)], #(REG_WIDTH)
#ifdef CHERI_LIB_C18N
mov c2, c8
#else
mov REGN(sp), REG(8)
#ifdef CHERI_LIB_C18N
/* Skip the trusted stack pointer */
add c0, c0, #REG_WIDTH
#endif

/* Restore the general purpose registers and lr */
Expand All @@ -131,19 +137,9 @@ ENTRY(longjmp)
ldp d14, d15, [REG(0)], #16

/* Load the return value */
#ifdef CHERI_LIB_C18N
mov c3, c0
#endif
cmp x1, #0
csinc x0, x1, xzr, ne
#ifdef CHERI_LIB_C18N
/*
* Tail-call to restore Executive mode state
*/
b _rtld_longjmp
#else
RETURN
#endif

botch:
bl _C_LABEL(longjmperror)
Expand Down
3 changes: 1 addition & 2 deletions lib/libgcc_s/Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -53,10 +53,9 @@ SRCS+= s_logbl.c
SRCS+= s_scalbnl.c
.endif

# LIBUNWIND_SANDBOX_OTYPES is only supported on aarch64 (Morello).
# c18n is only supported on Morello.
.if ${MACHINE_ABI:Mpurecap} && ${MACHINE_CPUARCH} == "aarch64"
SYMBOL_MAPS+= ${.CURDIR}/Symbol-c18n.map
CFLAGS+= -D_LIBUNWIND_CHERI_C18N_SUPPORT
.endif

.include <bsd.lib.mk>
7 changes: 4 additions & 3 deletions lib/libgcc_s/Symbol-c18n.map
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Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
FBSDprivate_1.0 {
_rtld_unw_getcontext;
_rtld_unw_setcontext;
_rtld_unw_getsealer;
dl_c18n_get_trusted_stk;
dl_c18n_unwind_trusted_stk;
dl_c18n_is_tramp;
dl_c18n_pop_trusted_stk;
};
8 changes: 4 additions & 4 deletions libexec/rtld-elf/Symbol-c18n.map
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Original file line number Diff line number Diff line change
Expand Up @@ -11,10 +11,10 @@ FBSDprivate_1.0 {
_rtld_setjmp;
_rtld_longjmp;
_rtld_unw_getcontext;
_rtld_unw_getcontext_unsealed;
_rtld_unw_setcontext;
_rtld_unw_setcontext_unsealed;
_rtld_unw_getsealer;
_rtld_safebox_code;
_rtld_sandbox_code;
dl_c18n_get_trusted_stk;
dl_c18n_unwind_trusted_stk;
dl_c18n_is_tramp;
dl_c18n_pop_trusted_stk;
};
3 changes: 3 additions & 0 deletions libexec/rtld-elf/aarch64/rtld_c18n_asm.S
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Expand Up @@ -34,6 +34,9 @@
* See rtld_c18n.h for an overview of the design.
*/

/*
* XXX: These assembly stubs are kept here for compatibility with old libunwind.
*/
/*
* The _rtld_unw_{get,set}context_epilogue functions are stack unwinding
* helpers. See the 'Stack unwinding' section in rtld_c18n.c.
Expand Down
34 changes: 1 addition & 33 deletions libexec/rtld-elf/aarch64/rtld_c18n_machdep.h
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Expand Up @@ -133,7 +133,7 @@ set_untrusted_stk(const void *sp)
}
#endif

struct trusted_frame {
struct dl_c18n_compart_state {
void *fp;
void *pc;
/*
Expand All @@ -145,38 +145,6 @@ struct trusted_frame {
* caller made the call.
*/
void *sp;
/*
* INVARIANT: This field contains the top of the caller's stack when the
* caller was last entered.
*/
void *osp;
/*
* Address of the previous trusted frame
*/
struct trusted_frame *previous;
/*
* Compartment ID of the caller
*/
stk_table_index caller;
/*
* Zeros
*/
uint16_t zeros;
/*
* Compartment ID of the callee
*/
stk_table_index callee;
/*
* Number of return value registers, encoded in enum tramp_ret_args
*/
uint8_t ret_args : 2;
uint16_t reserved : 14;
/*
* This field contains the code address in the trampoline that the
* callee should return to. This is used by trampolines to detect cross-
* compartment tail-calls.
*/
ptraddr_t landing;
};
#endif
#endif
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