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Fix register mapping to avoid volatile registers and issues with R12 #78

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merged 3 commits into from
Jun 16, 2021
Merged

Fix register mapping to avoid volatile registers and issues with R12 #78

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86a5001
Fix register mapping to avoid volatile registers and issues with R12
Jun 1, 2021
e2b41e2
Tweak register mapping
Jun 2, 2021
955e51c
PR feedback
Jun 7, 2021
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18 changes: 12 additions & 6 deletions vm/ubpf_jit_x86_64.c
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Original file line number Diff line number Diff line change
Expand Up @@ -51,18 +51,24 @@ static int platform_nonvolatile_registers[] = {
static int platform_parameter_registers[] = {
RCX, RDX, R8, R9
};
#define RCX_ALT R15
#define RCX_ALT R10
// Register assignments:
// BPF R0-R4 are "volatile"
// BPF R5-R10 are "non-volatile"
// Map BPF volatile registers to x64 volatile and map BPF non-volatile to
// x64 non-volatile.
// Avoid R12 as we don't support encoding modrm modifier for using R12.
static int register_map[REGISTER_MAP_SIZE] = {
RAX,
R15,
R10,
RDX,
R8,
R9,
R10,
R11,
R12,
R13,
R14,
R15,
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RDI,
RSI,
RBX,
RBP,
};
#else
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