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GH-146128: Remove the buggy AArch64 "33rx" relocation (#146263)

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Brandt Bucher 2026-04-06 21:52:59 -07:00 • committed by GitHub
parent 132abfd135
commit 6bb7b33e8f
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4 changed files with 10 additions and 116 deletions
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73
Python/jit.c
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@ -355,18 +355,6 @@ patch_aarch64_12(unsigned char *location, uint64_t value)
set_bits(loc32, 10, value, shift, 12);
}
// Relaxable 12-bit low part of an absolute address. Pairs nicely with
// patch_aarch64_21rx (below).
void
patch_aarch64_12x(unsigned char *location, uint64_t value)
{
// This can *only* be relaxed if it occurs immediately before a matching
// patch_aarch64_21rx. If that happens, the JIT build step will replace both
// calls with a single call to patch_aarch64_33rx. Otherwise, we end up
// here, and the instruction is patched normally:
patch_aarch64_12(location, value);
}
// 16-bit low part of an absolute address.
void
patch_aarch64_16a(unsigned char *location, uint64_t value)
@ -427,18 +415,6 @@ patch_aarch64_21r(unsigned char *location, uint64_t value)
set_bits(loc32, 5, value, 2, 19);
}
// Relaxable 21-bit count of pages between this page and an absolute address's
// page. Pairs nicely with patch_aarch64_12x (above).
void
patch_aarch64_21rx(unsigned char *location, uint64_t value)
{
// This can *only* be relaxed if it occurs immediately before a matching
// patch_aarch64_12x. If that happens, the JIT build step will replace both
// calls with a single call to patch_aarch64_33rx. Otherwise, we end up
// here, and the instruction is patched normally:
patch_aarch64_21r(location, value);
}
// 21-bit relative branch.
void
patch_aarch64_19r(unsigned char *location, uint64_t value)
@ -469,55 +445,6 @@ patch_aarch64_26r(unsigned char *location, uint64_t value)
set_bits(loc32, 0, value, 2, 26);
}
// A pair of patch_aarch64_21rx and patch_aarch64_12x.
void
patch_aarch64_33rx(unsigned char *location, uint64_t value)
{
uint32_t *loc32 = (uint32_t *)location;
// Try to relax the pair of GOT loads into an immediate value:
assert(IS_AARCH64_ADRP(*loc32));
unsigned char reg = get_bits(loc32[0], 0, 5);
assert(IS_AARCH64_LDR_OR_STR(loc32[1]));
// There should be only one register involved:
assert(reg == get_bits(loc32[1], 0, 5)); // ldr's output register.
assert(reg == get_bits(loc32[1], 5, 5)); // ldr's input register.
uint64_t relaxed = *(uint64_t *)value;
if (relaxed < (1UL << 16)) {
// adrp reg, AAA; ldr reg, [reg + BBB] -> movz reg, XXX; nop
loc32[0] = 0xD2800000 | (get_bits(relaxed, 0, 16) << 5) | reg;
loc32[1] = 0xD503201F;
return;
}
if (relaxed < (1ULL << 32)) {
// adrp reg, AAA; ldr reg, [reg + BBB] -> movz reg, XXX; movk reg, YYY
loc32[0] = 0xD2800000 | (get_bits(relaxed, 0, 16) << 5) | reg;
loc32[1] = 0xF2A00000 | (get_bits(relaxed, 16, 16) << 5) | reg;
return;
}
int64_t page_delta = (relaxed >> 12) - ((uintptr_t)location >> 12);
if (page_delta >= -(1L << 20) &&
page_delta < (1L << 20))
{
// adrp reg, AAA; ldr reg, [reg + BBB] -> adrp reg, AAA; add reg, reg, BBB
patch_aarch64_21rx(location, relaxed);
loc32[1] = 0x91000000 | get_bits(relaxed, 0, 12) << 10 | reg << 5 | reg;
return;
}
relaxed = value - (uintptr_t)location;
if ((relaxed & 0x3) == 0 &&
(int64_t)relaxed >= -(1L << 19) &&
(int64_t)relaxed < (1L << 19))
{
// adrp reg, AAA; ldr reg, [reg + BBB] -> ldr reg, XXX; nop
loc32[0] = 0x58000000 | (get_bits(relaxed, 2, 19) << 5) | reg;
loc32[1] = 0xD503201F;
return;
}
// Couldn't do it. Just patch the two instructions normally:
patch_aarch64_21rx(location, value);
patch_aarch64_12x(location + 4, value);
}
// Relaxable 32-bit relative address.
void
patch_x86_64_32rx(unsigned char *location, uint64_t value)