[RFC PATCH 15/15] selftests/rseq: x86-32: use %gs segment selector for accessing rseq thread area

From: Mathieu Desnoyers
Date: Mon Jan 24 2022 - 12:14:13 EST

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Rather than use rseq_get_abi() and pass its result through a register to
the inline assembler, directly access the per-thread rseq area through a
memory reference combining the %gs segment selector, the constant offset
of the field in struct rseq, and the rseq_offset value (in a register).

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
---
tools/testing/selftests/rseq/rseq-x86.h | 66 +++++++++++++------------
1 file changed, 34 insertions(+), 32 deletions(-)

diff --git a/tools/testing/selftests/rseq/rseq-x86.h b/tools/testing/selftests/rseq/rseq-x86.h
index 29769664edaa..f704d3664327 100644
--- a/tools/testing/selftests/rseq/rseq-x86.h
+++ b/tools/testing/selftests/rseq/rseq-x86.h
@@ -633,6 +633,8 @@ int rseq_cmpeqv_trymemcpy_storev_release(intptr_t *v, intptr_t expect,

#elif defined(__i386__)

+#define RSEQ_ASM_TP_SEGMENT %%gs
+
#define rseq_smp_mb() \
__asm__ __volatile__ ("lock; addl $0,-128(%%esp)" ::: "memory", "cc")
#define rseq_smp_rmb() \
@@ -732,14 +734,14 @@ int rseq_cmpeqv_storev(intptr_t *v, intptr_t expect, intptr_t newv, int cpu)
RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[error2])
#endif
/* Start rseq by storing table entry pointer into rseq_cs. */
- RSEQ_ASM_STORE_RSEQ_CS(1, 3b, RSEQ_CS_OFFSET(%[rseq_abi]))
- RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_CPU_ID_OFFSET(%[rseq_abi]), 4f)
+ RSEQ_ASM_STORE_RSEQ_CS(1, 3b, RSEQ_ASM_TP_SEGMENT:RSEQ_CS_OFFSET(%[rseq_offset]))
+ RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_ASM_TP_SEGMENT:RSEQ_CPU_ID_OFFSET(%[rseq_offset]), 4f)
RSEQ_INJECT_ASM(3)
"cmpl %[v], %[expect]\n\t"
"jnz %l[cmpfail]\n\t"
RSEQ_INJECT_ASM(4)
#ifdef RSEQ_COMPARE_TWICE
- RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_CPU_ID_OFFSET(%[rseq_abi]), %l[error1])
+ RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_ASM_TP_SEGMENT:RSEQ_CPU_ID_OFFSET(%[rseq_offset]), %l[error1])
"cmpl %[v], %[expect]\n\t"
"jnz %l[error2]\n\t"
#endif
@@ -750,7 +752,7 @@ int rseq_cmpeqv_storev(intptr_t *v, intptr_t expect, intptr_t newv, int cpu)
RSEQ_ASM_DEFINE_ABORT(4, "", abort)
: /* gcc asm goto does not allow outputs */
: [cpu_id] "r" (cpu),
- [rseq_abi] "r" (rseq_get_abi()),
+ [rseq_offset] "r" (rseq_offset),
[v] "m" (*v),
[expect] "r" (expect),
[newv] "r" (newv)
@@ -798,15 +800,15 @@ int rseq_cmpnev_storeoffp_load(intptr_t *v, intptr_t expectnot,
RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[error2])
#endif
/* Start rseq by storing table entry pointer into rseq_cs. */
- RSEQ_ASM_STORE_RSEQ_CS(1, 3b, RSEQ_CS_OFFSET(%[rseq_abi]))
- RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_CPU_ID_OFFSET(%[rseq_abi]), 4f)
+ RSEQ_ASM_STORE_RSEQ_CS(1, 3b, RSEQ_ASM_TP_SEGMENT:RSEQ_CS_OFFSET(%[rseq_offset]))
+ RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_ASM_TP_SEGMENT:RSEQ_CPU_ID_OFFSET(%[rseq_offset]), 4f)
RSEQ_INJECT_ASM(3)
"movl %[v], %%ebx\n\t"
"cmpl %%ebx, %[expectnot]\n\t"
"je %l[cmpfail]\n\t"
RSEQ_INJECT_ASM(4)
#ifdef RSEQ_COMPARE_TWICE
- RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_CPU_ID_OFFSET(%[rseq_abi]), %l[error1])
+ RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_ASM_TP_SEGMENT:RSEQ_CPU_ID_OFFSET(%[rseq_offset]), %l[error1])
"movl %[v], %%ebx\n\t"
"cmpl %%ebx, %[expectnot]\n\t"
"je %l[error2]\n\t"
@@ -821,7 +823,7 @@ int rseq_cmpnev_storeoffp_load(intptr_t *v, intptr_t expectnot,
RSEQ_ASM_DEFINE_ABORT(4, "", abort)
: /* gcc asm goto does not allow outputs */
: [cpu_id] "r" (cpu),
- [rseq_abi] "r" (rseq_get_abi()),
+ [rseq_offset] "r" (rseq_offset),
/* final store input */
[v] "m" (*v),
[expectnot] "r" (expectnot),
@@ -864,11 +866,11 @@ int rseq_addv(intptr_t *v, intptr_t count, int cpu)
RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[error1])
#endif
/* Start rseq by storing table entry pointer into rseq_cs. */
- RSEQ_ASM_STORE_RSEQ_CS(1, 3b, RSEQ_CS_OFFSET(%[rseq_abi]))
- RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_CPU_ID_OFFSET(%[rseq_abi]), 4f)
+ RSEQ_ASM_STORE_RSEQ_CS(1, 3b, RSEQ_ASM_TP_SEGMENT:RSEQ_CS_OFFSET(%[rseq_offset]))
+ RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_ASM_TP_SEGMENT:RSEQ_CPU_ID_OFFSET(%[rseq_offset]), 4f)
RSEQ_INJECT_ASM(3)
#ifdef RSEQ_COMPARE_TWICE
- RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_CPU_ID_OFFSET(%[rseq_abi]), %l[error1])
+ RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_ASM_TP_SEGMENT:RSEQ_CPU_ID_OFFSET(%[rseq_offset]), %l[error1])
#endif
/* final store */
"addl %[count], %[v]\n\t"
@@ -877,7 +879,7 @@ int rseq_addv(intptr_t *v, intptr_t count, int cpu)
RSEQ_ASM_DEFINE_ABORT(4, "", abort)
: /* gcc asm goto does not allow outputs */
: [cpu_id] "r" (cpu),
- [rseq_abi] "r" (rseq_get_abi()),
+ [rseq_offset] "r" (rseq_offset),
/* final store input */
[v] "m" (*v),
[count] "ir" (count)
@@ -916,14 +918,14 @@ int rseq_cmpeqv_trystorev_storev(intptr_t *v, intptr_t expect,
RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[error2])
#endif
/* Start rseq by storing table entry pointer into rseq_cs. */
- RSEQ_ASM_STORE_RSEQ_CS(1, 3b, RSEQ_CS_OFFSET(%[rseq_abi]))
- RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_CPU_ID_OFFSET(%[rseq_abi]), 4f)
+ RSEQ_ASM_STORE_RSEQ_CS(1, 3b, RSEQ_ASM_TP_SEGMENT:RSEQ_CS_OFFSET(%[rseq_offset]))
+ RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_ASM_TP_SEGMENT:RSEQ_CPU_ID_OFFSET(%[rseq_offset]), 4f)
RSEQ_INJECT_ASM(3)
"cmpl %[v], %[expect]\n\t"
"jnz %l[cmpfail]\n\t"
RSEQ_INJECT_ASM(4)
#ifdef RSEQ_COMPARE_TWICE
- RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_CPU_ID_OFFSET(%[rseq_abi]), %l[error1])
+ RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_ASM_TP_SEGMENT:RSEQ_CPU_ID_OFFSET(%[rseq_offset]), %l[error1])
"cmpl %[v], %[expect]\n\t"
"jnz %l[error2]\n\t"
#endif
@@ -938,7 +940,7 @@ int rseq_cmpeqv_trystorev_storev(intptr_t *v, intptr_t expect,
RSEQ_ASM_DEFINE_ABORT(4, "", abort)
: /* gcc asm goto does not allow outputs */
: [cpu_id] "r" (cpu),
- [rseq_abi] "r" (rseq_get_abi()),
+ [rseq_offset] "r" (rseq_offset),
/* try store input */
[v2] "m" (*v2),
[newv2] "m" (newv2),
@@ -987,15 +989,15 @@ int rseq_cmpeqv_trystorev_storev_release(intptr_t *v, intptr_t expect,
RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[error2])
#endif
/* Start rseq by storing table entry pointer into rseq_cs. */
- RSEQ_ASM_STORE_RSEQ_CS(1, 3b, RSEQ_CS_OFFSET(%[rseq_abi]))
- RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_CPU_ID_OFFSET(%[rseq_abi]), 4f)
+ RSEQ_ASM_STORE_RSEQ_CS(1, 3b, RSEQ_ASM_TP_SEGMENT:RSEQ_CS_OFFSET(%[rseq_offset]))
+ RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_ASM_TP_SEGMENT:RSEQ_CPU_ID_OFFSET(%[rseq_offset]), 4f)
RSEQ_INJECT_ASM(3)
"movl %[expect], %%eax\n\t"
"cmpl %[v], %%eax\n\t"
"jnz %l[cmpfail]\n\t"
RSEQ_INJECT_ASM(4)
#ifdef RSEQ_COMPARE_TWICE
- RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_CPU_ID_OFFSET(%[rseq_abi]), %l[error1])
+ RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_ASM_TP_SEGMENT:RSEQ_CPU_ID_OFFSET(%[rseq_offset]), %l[error1])
"movl %[expect], %%eax\n\t"
"cmpl %[v], %%eax\n\t"
"jnz %l[error2]\n\t"
@@ -1011,7 +1013,7 @@ int rseq_cmpeqv_trystorev_storev_release(intptr_t *v, intptr_t expect,
RSEQ_ASM_DEFINE_ABORT(4, "", abort)
: /* gcc asm goto does not allow outputs */
: [cpu_id] "r" (cpu),
- [rseq_abi] "r" (rseq_get_abi()),
+ [rseq_offset] "r" (rseq_offset),
/* try store input */
[v2] "m" (*v2),
[newv2] "r" (newv2),
@@ -1062,8 +1064,8 @@ int rseq_cmpeqv_cmpeqv_storev(intptr_t *v, intptr_t expect,
RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[error3])
#endif
/* Start rseq by storing table entry pointer into rseq_cs. */
- RSEQ_ASM_STORE_RSEQ_CS(1, 3b, RSEQ_CS_OFFSET(%[rseq_abi]))
- RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_CPU_ID_OFFSET(%[rseq_abi]), 4f)
+ RSEQ_ASM_STORE_RSEQ_CS(1, 3b, RSEQ_ASM_TP_SEGMENT:RSEQ_CS_OFFSET(%[rseq_offset]))
+ RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_ASM_TP_SEGMENT:RSEQ_CPU_ID_OFFSET(%[rseq_offset]), 4f)
RSEQ_INJECT_ASM(3)
"cmpl %[v], %[expect]\n\t"
"jnz %l[cmpfail]\n\t"
@@ -1072,7 +1074,7 @@ int rseq_cmpeqv_cmpeqv_storev(intptr_t *v, intptr_t expect,
"jnz %l[cmpfail]\n\t"
RSEQ_INJECT_ASM(5)
#ifdef RSEQ_COMPARE_TWICE
- RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_CPU_ID_OFFSET(%[rseq_abi]), %l[error1])
+ RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_ASM_TP_SEGMENT:RSEQ_CPU_ID_OFFSET(%[rseq_offset]), %l[error1])
"cmpl %[v], %[expect]\n\t"
"jnz %l[error2]\n\t"
"cmpl %[expect2], %[v2]\n\t"
@@ -1086,7 +1088,7 @@ int rseq_cmpeqv_cmpeqv_storev(intptr_t *v, intptr_t expect,
RSEQ_ASM_DEFINE_ABORT(4, "", abort)
: /* gcc asm goto does not allow outputs */
: [cpu_id] "r" (cpu),
- [rseq_abi] "r" (rseq_get_abi()),
+ [rseq_offset] "r" (rseq_offset),
/* cmp2 input */
[v2] "m" (*v2),
[expect2] "r" (expect2),
@@ -1144,15 +1146,15 @@ int rseq_cmpeqv_trymemcpy_storev(intptr_t *v, intptr_t expect,
"movl %[dst], %[rseq_scratch1]\n\t"
"movl %[len], %[rseq_scratch2]\n\t"
/* Start rseq by storing table entry pointer into rseq_cs. */
- RSEQ_ASM_STORE_RSEQ_CS(1, 3b, RSEQ_CS_OFFSET(%[rseq_abi]))
- RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_CPU_ID_OFFSET(%[rseq_abi]), 4f)
+ RSEQ_ASM_STORE_RSEQ_CS(1, 3b, RSEQ_ASM_TP_SEGMENT:RSEQ_CS_OFFSET(%[rseq_offset]))
+ RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_ASM_TP_SEGMENT:RSEQ_CPU_ID_OFFSET(%[rseq_offset]), 4f)
RSEQ_INJECT_ASM(3)
"movl %[expect], %%eax\n\t"
"cmpl %%eax, %[v]\n\t"
"jnz 5f\n\t"
RSEQ_INJECT_ASM(4)
#ifdef RSEQ_COMPARE_TWICE
- RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_CPU_ID_OFFSET(%[rseq_abi]), 6f)
+ RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_ASM_TP_SEGMENT:RSEQ_CPU_ID_OFFSET(%[rseq_offset]), 6f)
"movl %[expect], %%eax\n\t"
"cmpl %%eax, %[v]\n\t"
"jnz 7f\n\t"
@@ -1202,7 +1204,7 @@ int rseq_cmpeqv_trymemcpy_storev(intptr_t *v, intptr_t expect,
#endif
: /* gcc asm goto does not allow outputs */
: [cpu_id] "r" (cpu),
- [rseq_abi] "r" (rseq_get_abi()),
+ [rseq_offset] "r" (rseq_offset),
/* final store input */
[v] "m" (*v),
[expect] "m" (expect),
@@ -1261,15 +1263,15 @@ int rseq_cmpeqv_trymemcpy_storev_release(intptr_t *v, intptr_t expect,
"movl %[dst], %[rseq_scratch1]\n\t"
"movl %[len], %[rseq_scratch2]\n\t"
/* Start rseq by storing table entry pointer into rseq_cs. */
- RSEQ_ASM_STORE_RSEQ_CS(1, 3b, RSEQ_CS_OFFSET(%[rseq_abi]))
- RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_CPU_ID_OFFSET(%[rseq_abi]), 4f)
+ RSEQ_ASM_STORE_RSEQ_CS(1, 3b, RSEQ_ASM_TP_SEGMENT:RSEQ_CS_OFFSET(%[rseq_offset]))
+ RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_ASM_TP_SEGMENT:RSEQ_CPU_ID_OFFSET(%[rseq_offset]), 4f)
RSEQ_INJECT_ASM(3)
"movl %[expect], %%eax\n\t"
"cmpl %%eax, %[v]\n\t"
"jnz 5f\n\t"
RSEQ_INJECT_ASM(4)
#ifdef RSEQ_COMPARE_TWICE
- RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_CPU_ID_OFFSET(%[rseq_abi]), 6f)
+ RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_ASM_TP_SEGMENT:RSEQ_CPU_ID_OFFSET(%[rseq_offset]), 6f)
"movl %[expect], %%eax\n\t"
"cmpl %%eax, %[v]\n\t"
"jnz 7f\n\t"
@@ -1320,7 +1322,7 @@ int rseq_cmpeqv_trymemcpy_storev_release(intptr_t *v, intptr_t expect,
#endif
: /* gcc asm goto does not allow outputs */
: [cpu_id] "r" (cpu),
- [rseq_abi] "r" (rseq_get_abi()),
+ [rseq_offset] "r" (rseq_offset),
/* final store input */
[v] "m" (*v),
[expect] "m" (expect),
--
2.17.1

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